The word "shared airway" evokes a subtle anxiety in the most experienced anesthesiologist. As a specialty, we are known for our skills to secure, maintain, and control the airway. Any activity that threatens a secure airway is a source of concern, if not annoyance. All aspects of throat surgery involve sharing the airway with another airway expert. Like any relationship, it requires communication, understanding, and trust.
Abnormal Airway Disorders
Surgery to correct the abnormal airway will exercise all of the anesthesiologist's skills. Myriad disorders affect the airway, and patients can be of any age and present under any circumstances. The potential combinations of patient and airway are too numerous to allow detailed consideration of each possible scenario. This overview focuses on the most common disorders associated directly with the supraglottic, glottic, and subglottic structures.
As a conceptual approach, consider that the abnormal airway is any airway compromised by an acquired disorder, such as an infection, mass lesion, FB, and therapy (radiation), or by an anatomic disorder, such as congenital malformations, the malacias, and stenoses. These definitions are not strict because it is apparent that some lesions share features of both disorders. They are characterized in this manner only for ease of understanding. Yellon23 has summarized an excellent approach to management of pediatric patients with abnormal airways. The guiding principles include a thorough preoperative evaluation of the patient and careful planning between the surgical and anesthesia teams. Physical examination may include endoscopy, laryngoscopy, and bronchoscopy to identify both dynamic and fixed lesions before performing any definitive surgical procedure. Safe, successful surgical and anesthetic outcomes depend on these efforts. Many of the same considerations apply to adult patients as well (Fig. 67-3).
Conceptual approach to the abnormal airway. [Illustration by Daniel Muller, Haderer & Muller Biomedical Art, LLC.]
Acquired Airway Disorders
Epiglottitis is an acute bacterial infection that untreated can become a life-threatening disease. Most commonly, it affects pediatric patients in the 2- to 7-year age range. Haemophilus influenzae (type B) usually is the causative organism. With the use of H. influenzae vaccine in children, epiglottitis is becoming a disease of adults. Age notwithstanding, epiglottitis is a serious condition that must be treated aggressively.
In the classic presentation, the patient arrives with an abrupt high fever, sore throat, stridor, dysphagia, and drooling. Physical examination reveals an anxious, pale patient sitting in the sniffing position. Epiglottitis can be distinguished from croup by the lack of a spontaneous cough. A lateral neck film will show a thickened, flat epiglottitis akin to a "thumbprint." Supraglottitis is a newer term suggested for this condition because the inflammation involves all supraglottic structures.
Adult patients are admitted and treated conservatively. Rarely do they require intubation. In the pediatric population, total airway obstruction can occur at any time. These patients cannot be left unattended until the airway is secured. In a controlled setting with an ENT surgeon and anesthesiologist present, an inhalational induction is done in the sitting position. Muscle relaxation is to be avoided. Laryngoscopy confirms the diagnosis, and endotracheal intubation immediately follows. It is suggested that the endotracheal tube be 0.5 to 1 size smaller than usual. If the airway obstructs and intubation becomes impossible, rigid bronchoscopy or tracheotomy must be performed immediately. Patients with epiglottitis usually respond to cephalosporin therapy after several days.
Croup is a benign disease typically affecting pediatric patients in the 3-month to 3-year-age range. It follows 2 to 3 days after a respiratory tract infection (RTI), and parainfluenza virus is the most common cause. The subglottic structures are involved, and the patient presents with stridor, dyspnea, and the classic "barking cough." Croup can be distinguished from epiglottitis on clinical grounds, and lateral neck radiographs are rarely needed. If obtained, they should reveal a normal epiglottis. Treatment is conservative with oxygen, nebulized racemic epinephrine, and IV dexamethasone. Endotracheal intubation is indicated only for respiratory fatigue, progressive intercostals retractions, and cyanosis. As with epiglottis, endotracheal intubation should be done in the OR under similar controlled conditions and with surgical expertise immediately available.
Pediatric and Preoperative Concerns
A tonsillectomy probably is the most frequently performed airway surgical procedure. It is estimated that more than 300,000 tonsillectomies are done annually in North America alone. Indications for surgery include obstructive tonsillar hyperplasia, recurrent or chronic tonsillitis, and peritonsillar abscess. Often, a combined procedure including the adenoids is performed. Adenoidectomy is done to relieve nasopharyngeal obstruction caused by adenoid hyperplasia. Frequently, these patients also have reflux.
The majority (but not all) of these patients are in the pediatric age range, and children have unique physiologic responses and psychological needs. The anesthetist's primary focus is the child, but one must address the concerns of the parents as well.
The relationship between the parent and child in the perioperative setting has been the subject of much research. Not surprisingly, Kain et al24 confirmed that whereas a relaxed parental presence at induction had a calming effect on an anxious child, a stressed parent was of no benefit to an anxious child. Arai et al25 found that induction and emergence behavior of children closely correlated with the maternal serum amylase activity during the preoperative period. The children of mothers who were experiencing more stress exhibited more anxiety than the children of calm mothers. These factors can contribute greatly to an uneventful anesthetic.
On the day of operation, parents should be queried regarding a current or recent RTI. These infections are frequent in this population, and a concurrent illness can affect the anesthetic management. In the past, the presence of an RTI would result in immediate cancellation of an elective procedure. In current practice, a decision is determined on a case-by-case basis. Most practitioners agree that children with a concurrent RTI have more respiratory complications. Most studies suggest that factors associated with these adverse events include endotracheal intubations, age younger than 6 years, and an RTI within 2 weeks before planned surgery.26 According to Tait and Malviya,27 children with RTIs have more respiratory complications, but they are not associated with serious morbidity. The child who presents with an uncomplicated RTI can be managed safely as long as the practitioner understands and anticipates likely adverse events, such as laryngospasm or bronchospasm. This view is further maintained in a review article by Mamie et al.28
Another preoperative issue is the anxiety or agitation level of the child. Although a thorough preoperative consultation can relieve much concern, some patients are still inconsolable. Should the child be premedicated? Any premedication will sedate the patient and can contribute to both preoperative and postoperative respiratory complications. Premedication also will delay emergence and the return of protective airway reflexes. It can also delay discharge from the recovery unit. Conversely, any child who has a very frightening experience will be difficult to bring back to the OR, and this may contribute to a lifelong fear of the health care profession. Sedative premedication should not be given on a routine basis. Only very anxious and agitated children should be treated. When required, orally administered midazolam (0.5 mg/kg; maximum, 10 mg) given at least 20 minutes before operation is the most common sedative. Alternatives include rectal ketamine, oral fentanyl, nasal fentanyl, clonidine, diazepam with midazolam, and dexmedetomidine. Oral dexmedetomidine was found to be especially effective in patients with neurobehavioral disorders resistant to previous sedative attempts.
Obstructive Sleep Apnea Syndrome
Pediatric patients with obstructive sleep apnea syndrome (OSAS) present additional challenges because these obese children have a greater incidence of perioperative complications than normal-weight children.29 Furthermore, these patients may have cardiovascular involvement, with altered right ventricular diastolic function, pulmonary hypertension, arrhythmias, and silent carditis. This diagnosis increases the risk of postoperative respiratory complications from approximately 1% to 20%. Granzotto et al30 found a correlation between the palatine tonsil size and pulmonary artery pressure. This may prove to be a useful predictor of cardiac complications in children with OSAS. It is suggested that a polysomnography (PSG) be obtained in these patients before operation. Yellon31 reported that preoperative PSG is indicated for patients younger than 3 years of age, with medical comorbidities, small tonsils and adenoids, and physical findings inconsistent with the extent of obstruction. Other significant risk factors include carbon dioxide (CO2) tension greater than 50 mm Hg during rest while awake, witnessed severe upper airway obstruction, and nocturnal oxygen desaturation (<90%). These patients are not candidates for outpatient procedures and should be admitted for overnight observation.
Tonsillectomy can be performed in adults with obstructive sleep apnea, but the more common procedure for treatment of adult OSAS is uvulopalatopharyngoplasty (UPPP). This is a partial resection of the soft palate and is not a lengthy procedure. Extensive preoperative evaluation of the patient's airway is required. If the patient reports that nightly continuous positive airway pressure (CPAP) use relieves the symptoms, it is a good indication that the patient will be able to be ventilated with a face mask. However, when in doubt, awake fiberoptic intubation remains the technique of choice for airway management. Of interest, Kim and Lee32 found that the preoperative apnea-hypopnea index was a reliable indicator of difficult intubation in UPPP patients. It is also suggested that intraoperative narcotics be kept to a minimum, if used at all, and that the trachea be extubated when the patient is awake. These patients are likely to be sensitive to sedatives. Moreover, they will be admitted for observation. Postoperatively, the UPPP procedure is known to be the most painful of ENT procedures. Pain control is a challenge because of the desire to limit the use of narcotics. Monitoring and careful observation are required to manage patient discomfort. For a more detailed discussion, see the review article by Isono33 and the American Society of Anesthesiologists "Practice Guidelines for the Perioperative Management of Patients With Obstructive Sleep Apnea."34
Adenotonsillectomy Anesthesia Induction
Pediatric anesthesia induction requires 2 persons. Both must be skilled in airway management and IV catheter placement. To perform a mask induction in a child by oneself is to invite disaster. Apart from the usual concerns of pediatric induction (laryngospasm, bradycardia-hypotension, lack of IV access), significant numbers of these patients have OSAS. Several investigators have looked at different airway maneuvers to improve mask ventilation in this situation. Reber et al35 compared chin lift with CPAP versus jaw thrust with CPAP and the found the latter to be superior. Young-Chang et al demonstrated that a lateral position with jaw thrust returned heart rate variability to baseline in children with OSAS.36 Regardless of one's preferred technique, it is apparent that jaw thrust and CPAP are effective in partially obstructed children.
After the patient is anesthetized and IV access obtained, the airway must be secured by endotracheal intubation. Tonsillar hypertrophy can be extensive, and the challenge of laryngoscopy should not be underestimated. What may appear to be a routine intubation can quickly manifest as a difficult airway. Another source of difficulty is the presence of lingual tonsillar hypertrophy. Furthermore, trauma to fragile inflamed tonsils during laryngoscopy can cause bleeding.
There is no uniformity of opinion regarding the use of muscle relaxants during these procedures. An uncomplicated tonsillectomy will last anywhere from 15 to 30 minutes with an experienced surgeon. Relaxants, if used, should be of the short-acting type. These patients also require narcotics for postoperative analgesia, and these drugs affect the child's ability to breathe. In a related issue, Khan and Memon37 compared spontaneous with controlled ventilation for tonsillectomy. Their results suggest that controlled ventilation offers more hemodynamic stability and rapid recovery. It is the author's practice to give morphine immediately after IV access has been obtained and to intubate the trachea under the effects of both morphine and the inhaled anesthetic sevoflurane, thus avoiding muscle relaxants altogether.
Several techniques and drugs have been evaluated to facilitate tracheal intubation without the use of neuromuscular blockade. Woods and Allam38 have provided an excellent review. Of the inhaled anesthetics, sevoflurane has emerged as the best choice, especially when combined with remifentanil. Of the IV agents, remifentanil followed by propofol seems to provide the best intubating conditions. Whatever approach is used, the avoidance of muscle relaxants allows the rapid return of spontaneous ventilation and protective airway reflexes (Fig. 67-4).
Twelve-year-old girl prepared for tonsillectomy. The endotracheal tube is secured midline on the mandible, and the mouth gag is in position with the handle placed on the operating room tray. [Courtesy of Michael Cunningham, MD, and Bil Ragan, MD, Massachusetts Eye and Ear Infirmary).]
As an alternative, LMAs have been used successfully on healthy patients having ambulatory procedures. Although by definition an endotracheal tube provides a more secure airway than an LMA, adverse events have been quite rare. In a study Gravningsbraten et al39 used LMAs in 1126 patients and converted 6 patients from an LMA to an endotracheal tube (0.5%). A concern with the use of a classic LMA in this setting is its displacement by the mouth gag. On occasion, the straight, solid blade of a traditional mouth gag will compress the tube of an LMA and move the tip posterior. To alleviate this problem, a new open channel mouth gag is being investigated and it appears promising (Fig. 67-5). By not compressing the LMA tube, it allows it to maintain its normal curvature and glottic seal. Use of an LMA is less invasive and easier and requires less recovery time than endotracheal tubes.
The open channel mouth gag, which allows the laryngeal mask airway to maintain its curve without displacement. [Courtesy of Samir Bhatt, MD, and Bil Ragan, MD, Massachusetts Eye and Ear Infirmary.]
After the airway is secured, the surgeon places a mouth gag in the oral cavity to better expose the tonsils. This is a stimulating event with the potential for complications. Some surgeons disconnect the anesthesia circuit before placing the mouth gag. Others work around the endotracheal tube. During this manipulation, the endotracheal tube can be compressed, kinked, or displaced. Rarely, an unexpected extubation occurs. After the mouth gag is in place, one should recheck to verify bilateral breath sounds. The endotracheal tube is secured to the midline mandible; any extension can result in the tube moving several centimeters. When the mouth gag is in position, the surgeon places the inferior handle of the mouth gag on the OR instrument tray. If the child is lightly anesthetized and moves, potential cervical injury can occur. The other option is to place the handle on a stack of towels placed on the patient's sternum. This places pressure on the patient's chest, which can affect spontaneous ventilation. Before incision, the surgeon usually requests that an antibiotic and anti-inflammatory steroid be given.
Surgical techniques for tonsillectomy include guillotine resection (rare), cold dissection, bipolar dissection, and cold ablation (coblation) dissection. Each has its particular merits. Blood loss is greater, but pain is less with the first 2 techniques. Bipolar dissection allows immediate coagulation and less blood loss. However, thermal injury to the surrounding healthy tissue is responsible for greater postoperative discomfort. Coblation passes a radiofrequency bipolar current through a saline medium to produce a plasma field of sodium ions. Using a much lower frequency than standard bipolar diathermy, these ions essentially vaporize soft tissue at only 140°F (60°C). It also requires no electrical ground, and irrigating saline reduces thermal injury to adjacent tissue. Coblation offers the advantages of both cold dissection and bipolar diathermy with less postoperative pain and blood loss.
At the end of the procedure, the patient should be breathing spontaneously. In addition to morphine, the author also gives ondansetron for emesis control. After hemostasis has been achieved, the patient's stomach and oral cavity are suctioned. An awake extubation can be performed to ensure that the protective airway reflexes have returned. These children are at high risk for laryngospasm secondary to blood and secretions in the oral cavity. Tsui et al40 explored a "no touch" extubation technique. The patients were turned to a head-down lateral recovery position while still anesthetized. If the nondependent hip is flexed, the patient will easily stay in this position. The importance of the head-down position cannot be overemphasized. This arrangement allows pooling of blood and secretions to occur on the side of the mouth rather than midline. In addition, the upper airway of a child widens in the lateral position and is less likely to obstruct. Aside from oximetry monitoring, no additional stimulation was allowed with the technique. After the patient emerged from anesthesia, confirmed by eye opening, extubation of the trachea was performed. No incidences of laryngospasm, oxygen desaturation, or coughing were observed.
Complications of tonsillectomy include hemorrhage (discussed in Posttonsillectomy Hemorrhage), postoperative airway obstruction secondary to laryngeal edema, and dental trauma. In a study of 864 children, Isaacson41 was able to reduce postoperative airway obstructive events by using a protocol that included (1) rapid bloodless tonsillectomy, (2) repeated release of the tonsillar retractor, (3) avoidance of uvular edema, (4) intranasal oxymetazoline with nasal airway placement, and (5) extended postanesthesia care unit stay. Raghavendran et al42 have shown a reduction in respiratory events by the administration of dexamethasone and reduced need for opioids.
Postoperative analgesia of some type is required after this procedure. Local anesthetic infiltration before incision has provided satisfactory results. However, bupivacaine infiltration has been implicated in short-term vocal cord paralysis, and large quantities of local anesthetic can suppress protective airway reflexes for several hours. As an alternative, peritonsillar infiltration with ketamine43,44 or tramadol45 has produced good results.
Of the IV agents, ketamine, morphine, and meperidine all are proven potent analgesics. However, each has its own undesired side effects. Ketamine can cause an extreme dysphoric reaction if the patient is not pretreated with a benzodiazepine. It can also cause increased oral secretions, which is undesired in this patient group. The narcotics morphine and meperidine are very effective, but they provoke nausea. They also have sedative effects, can cause pruritus, and are respiratory depressants. Alhashemi and Daghistani46 found IV acetaminophen as effective as intramuscular meperidine in the treatment of posttonsillectomy pain. White and Nolan47 used fentanyl but not morphine and noted a significant decrease in the incidence of PONV; analgesia remained excellent.
Tramadol is a synthetic codeine derivative that behaves as a centrally acting atypical opioid. It lacks many of the opioid side effects while exhibiting both opioid and monoaminergic mechanisms of action. For adenotonsillectomy procedures, tramadol has been favorably compared with ketamine, morphine, and meperidine. Tramadol has been shown to have analgesic properties that are similar to those of morphine but without the associated respiratory depression. It is well tolerated with less nausea. Good results have been obtained when tramadol was combined with acetaminophen. However, a study by Arcioni et al48 noted that ondansetron has an inhibitory effect when used simultaneously with tramadol. Despite this concern, tramadol remains a promising analgesic agent.
Nonsteroidal anti-inflammatory drugs (NSAIDs) have also been considered for postoperative analgesia. They provide excellent pain relief without the side effects of narcotics. NSAIDs also cause platelet dysfunction and prolonged bleeding time. Their use in adenotonsillectomies remains controversial. Moiniche et al49 did a quantitative review of 25 studies to examine the relationship between NSAID use and postoperative bleeding. They concluded that NSAIDs offer similar analgesia and significantly less emesis than opioids, but they also contribute to more reoperations for hemostasis. A review by Marret et al50 went even further and suggested that NSAIDs should not be used after tonsillectomy. Both of these reports contrast with a review by Cardwell et al,51 which found no increase in bleeding requiring a return to the OR. Overall, the weight of the evidence appears to support avoidance of NSAIDs in adenotonsillectomy patients.
In addition to pain, PONV must be expected and treated. Even if narcotics are not used, swallowed blood can cause nausea. Several studies demonstrated the antiemetic effects of dexamethasone and it is often requested by the surgeon to reduce postoperative swelling and pain. Aouad et al52 found dexamethasone significantly better than placebo for both decreasing vomiting and promoting postoperative oral intake. Elhakim et al53 confirmed these findings and noted an analgesic benefit as well. Dexamethasone was also found to act synergistically when combined with serotonin (5-HT3) antagonists.54 Karaman et al55 found that a dexamethasone dose of 0.7 mg/kg was optimal in preventing PONV. In a systematic review and meta-analysis, Bolton et al56 determined that the most effective antiemetics were a serotonergic antagonist and dexamethasone.
Posttonsillectomy hemorrhage remains the most serious complication of this procedure. Posttonsillectomy hemorrhage occurs in about 5% of all cases and most often within 24 hours (primary hemorrhage). Secondary hemorrhage can occur anytime thereafter. A study by Brown et al57 noted that nearly half of posttonsillectomy hemorrhage cases occurred in patients with previously undiagnosed coagulation disorders. Typically, posttonsillectomy hemorrhage is characterized by slow oozing. These patients can be hypovolemic and tachycardic before the complication is recognized. Bleeding can be quite brisk; a clot may dislodge upon intubation, and in a matter of seconds, the entire oral cavity can be filled with blood. These patients also may demonstrate orthostatic hypotension and may have swallowed a large volume of blood. They should be considered as having a "full stomach" regardless of their actual NPO (nothing by mouth) status.
Posttonsillectomy hemorrhage is a surgical emergency that requires immediate treatment. Windfuhr58,59 has concluded that immediate surgical intervention prevented mortality in most cases. Before anesthesia induction, intravascular fluid expansion should be accomplished using either crystalloids or blood products if indicated. Failure to do so can result in fatal outcomes. As already mentioned, these patients should be considered as having full stomachs, and the airway should be secured immediately after a rapid-sequence induction. Large-bore, high-volume suction should be available, and the patient's stomach should be emptied after the airway is secured.
Windfuhr60 also described treatment of excessive posttonsillectomy hemorrhage by ligature of the external carotid artery. He reported in follow-up studies that an age younger than 8 years and repeated episodes of secondary bleeding were risk factors for massive hemorrhage.
Pharyngeal Abscesses (Peritonsillar, Retropharyngeal)
Patients who present with a pharyngeal abscess can have significant coexisting morbidity. For example, the author treated an elderly man who arrived with progressive quadriplegia and somnolence. The underlying etiology was a retropharyngeal abscess compressing the patient's brainstem. Thus, although of infectious origin, pharyngeal abscesses are "mass lesions."
The majority of these cases occur in children or young adults. Incision and drainage of the abscess usually are performed under general anesthesia, with the airway secured by endotracheal intubation. Conversely, if the abscess is relatively small and not compressing the airway, some surgeons perform the procedure in the emergency department under local anesthesia alone. This requires a cooperative patient with a high pain tolerance. Under this condition, the patient is at risk for aspiration and additional complications. For patient care and comfort reasons, these cases are best handled in the OR.
After a general anesthetic has been decided upon, a thorough examination of the airway is required. This includes reviewing the relevant computed tomographic (CT) scans with the surgeon. Airway obstruction can occur, and intubation can be difficult. Depending on its extent, a retropharyngeal abscess can cause atlantoaxial subluxation. Furthermore, the underlying tissue may be quite friable, and the goal is to prevent any abscess contents from entering the trachea before securing the airway. This step should be a gentle intubation, attempting to not disturb the abscess. After the abscess is drained, the surgeon irrigates and suctions the oral cavity multiple times. These cases are not lengthy, and an awake extubation is indicated.
In a related scenario, patients with deep neck infections should be considered to have compromised airways despite their appearance. The classic example is Ludwig angina, which is a severe cellulitis involving the sublingual and submental spaces. Symptoms include tongue elevation, rapid breathing, difficulty swallowing, glottic edema, leukocytosis, and fever. Airway assessment is similar to that described above. An analysis and review by Ovassapian et al61 concluded that an awake fiberoptic intubation is the safest approach. If an awake fiberoptic intubation is not feasible, an awake tracheostomy under local anesthesia should be pursued.
Benign or Malignant Tumors
In addition to infectious masses, a wide variety of benign or malignant tumors may affect the throat and related structures. Hemangiomas can be found anywhere in the oral cavity. They are not treated unless they compromise the airway or interfere with function. Lasers are frequently used in the surgical management of these hemangiomas. Other benign masses include lymphangiomas of cavernous or cystic hygroma origin and papillomas. Malignant tumors are no less diverse and can be ulcerative, exophytic, or infiltrative lesions. Patients may present before diagnosis or after multiple excisions and chemotherapy or radiation therapy.
These cases must be thoroughly reviewed with the surgeon before bringing the patient to the OR. This includes discussing the surgical plan, the airway issues and a review of relevant CT and magnetic resonance imaging (MRI) scans. Previous anesthesia records should be located and reviewed, especially if prior diagnostic or therapeutic procedures have been performed, because the experience of others can be helpful in guiding the anesthetic plan.
Finally, careful evaluation of the patient is mandatory. One must determine the extent of mouth opening and attempt to visualize the mass lesion. An awake fiberoptic intubation is suggested if any sign of obstruction, limited neck extension, or any other factor is encountered that can interfere with direct laryngoscopy. Conversely, a small lesion in an otherwise normal appearing airway is reassuring. When managing a mass lesion, regardless of origin, one must be prepared with multiple approaches that can be invoked to secure the airway, including emergent surgical intervention, and the spectrum of options must be well rehearsed to prevent serious consequences.
Foreign body aspiration is a life-threatening emergency and a leading cause of death in 1- to 3-year-old children. The variety of possible FBs is limited only by the imagination and seemingly, local culture. If an object can be picked up and placed in the mouth, it will be by some children. Where it may travel becomes the challenge for the ENT surgeon and anesthesiologist. Most commonly, FB ingestion or aspiration is encountered in pediatric patients in the age range from 6 months to 5 years. Occasionally, one meets the young adult attempting to do a "party trick" while under the influence of alcohol or drugs. Alternatively, trauma to the neck can result in bone, cartilage, or soft tissue occupying previously open space akin to a FB. Whatever, the source, airway assessment and management are similar.
Complete airway obstruction is rarely seen by the tertiary care team. Primary intervention by a Heimlich maneuver is the therapy of first choice, followed by digital extraction. Be aware that digital manipulation can push an obstructing FB further into the airway. If the patient has become hypoxic, cyanotic, and moribund, the only lifesaving option is emergent tracheotomy.
Partial airway obstruction is the clinical entity most frequently encountered. The guiding principle of management should be, "Do not convert a partial airway obstruction into a complete airway obstruction." The patient and family will arrive in an emotionally charged state. The child may be dyspneic, drooling, sitting forward, and frightened. Prominent, stridorous breathing may be noted and is indicative of supraglottic or glottic involvement. Wheezing is heard more often with subglottic obstruction. The nature of the FB and the context of its ingestion must be determined. Nonmetallic objects are difficult to visualize on plain radiographs. Secondary radiographic findings, such as a hyperinflated lung or lobe, can help localize the object. If the patient is stable and the FB is fixed in position, one can wait and allow the stomach to empty before going to the OR. However, this is not often the case.
Bronchoscopy and Foreign Body Management
After the FB has been identified and located, a definitive management plan can be made. If the object lies near or within the trachea, the patient will require a laryngoscopy and bronchoscopy. If the patient is cooperative, it is possible to perform a bronchoscopy under topical anesthesia, but most patients require general anesthesia. Most practitioners advocate an inhalation induction for the patient with a partially obstructed airway to avoid positive pressure that might displace the FB and convert a partial obstruction to a total obstruction or cause the FB to migrate more distally in the airway. After induction, a rigid ventilating bronchoscope allows maintenance gases and oxygenation to continue, but hypoxemia remains a risk. Chen et al62 identified the following risk factors for hypoxemia: patient age (younger more likely), FB type (plant seed), surgical duration, preexisting pneumonia, and spontaneous ventilation (jet ventilation or JV, decreased risk). Be aware that there is a significant leak around the end of the bronchoscope, and the entrained air often dilutes the inhaled anesthetic gases. Inhalation anesthesia may be supplemented by IV drugs given as a continuous infusion or intermittent boluses. Either alone or in combination, propofol, remifentanil, and fentanyl have been studied in this scenario. It appears that remifentanil provides greater hemodynamic stability and rapid recovery.
Bronchoscopy under general anesthesia is a delicate procedure. Complications arise from poor ventilation (hypercapnia, hypoxemia) and inadequate anesthesia (bronchospasm, bucking).
Bronchoscopy and Foreign Body Management
Any FB ingestion posterior to the glottis is managed by esophagoscopy. If the airway is not compromised, a rapid-sequence induction with cricoid pressure can be performed. After the airway has been secured, there is no fear of aspiration. Rigid esophagoscopy is used for diagnostic purposes, FB removal, and tumor localization. The most serious complication is esophageal perforation, which frequently occurs in the hypopharynx. The consequences are significant; resulting mortality can range from 34% to 84%. Appropriate muscle relaxation can reduce the incidence by preventing unwanted movement or "bucking" during the procedure. In addition to perforation, other complications are compression of the endotracheal tube, dysrhythmias, and aspiration.
Flexible esophagoscopy is more of a diagnostic procedure and can be done as a monitored anesthesia care (MAC) anesthetic with sedation. It is not indicated for FB management.
Surgery and Radiation Therapy
Acquired airway disorders may result from other therapeutic activities that permanently alter the airway. Many otolaryngologic malignancies are treatable, and patients do survive. They will return to the OR for additional biopsies and surveillance endoscopies, but their airways may be significantly deformed.
Common surgical procedures include wide intraoral excisions, laryngectomies, and radical neck dissections with free flap reconstruction. Many of these patients present with a preexisting tracheotomy that makes their management straightforward. Others present with an intact airway that is greatly altered. As emphasized earlier, these cases must be discussed well in advance with the surgeon, previous anesthesia records must be reviewed, and the patient must be examined carefully.
These patients understand their postsurgical condition. Most are cooperative after the anesthesia concerns are explained. Unless the patient has a near-normal airway (unlikely), an awake fiberoptic intubation is the approach of choice. During laryngoscopy, the glottis is rarely found in the midline position; it is typically displaced laterally and the surrounding structures may be unrecognizable.
Radiation therapy often results in airway abnormalities. Radiation, which can be imagined as a form of burn, leads to fibrosis and shrinkage of the affected tissues. Schmitt et al63 described factors that better identify potential difficult fiberoptic intubations in patients after radiotherapy. These include laryngeal edema, hoarseness, and stridor. The patient may appear to have a normal neck and mouth, but the difficulty of laryngoscopy should not be underestimated. After radiation, muscle tissue becomes very firm and fixed. The patient likely will not be able to extend the neck and may not be able to open the mouth more than a few millimeters. Muscle relaxants are of little or no benefit in this scenario. Similar to scar contractures caused by burn injuries, these patients have small, fixed upper airways. Laryngoscopies are extraordinarily difficult, if not impossible. Awake fiberoptic intubation is frequently the technique of choice.
Disorders of the vocal cords can be of infectious origin, such as papillomas; they can be benign masses, such as hemangiomas and granulomas; or they can be neoplastic masses. Besides mechanical mass effects, mobility can be affected by fibrosis, inflammation, and nerve injury. Whereas some diagnostic procedures can be accomplished by flexible endoscopy, most surgical procedures are done by laryngoscopy and microlaryngoscopy. Medialization or voice restoration operations (phonosurgery) typically are conducted under MAC. The patient must be able to phonate (eg, say "EEE …") to guide the repair. If the lesion is well defined, general anesthesia can be used. Special techniques, such as apneic oxygenation and jet ventilation, may be necessary. Frequently, the surgeon requests profound muscle relaxation for a relatively brief procedure. Vocal cord surgery often uses lasers as the primary surgical instrument.
Using a combination of local and topical anesthesia can prepare the airway for laryngoscopy and some minor procedures. This requires blocking both superior laryngeal nerves and the glossopharyngeal nerves and injecting the trachea with local anesthetic. More commonly, these procedures are done under general anesthesia. Laryngoscopy is a stimulating event. It can elicit hypertension and tachycardia, which can lead to myocardial ischemia or even infarction in vulnerable patients. Conversely, laryngeal stimulation in a lightly anesthetized patient can cause bradycardia and dysrhythmias. The mechanism is a reflex pathway between the superior laryngeal nerve afferent fibers and vagal cardioinhibitory fibers. As with any general anesthetic, the patient must be sufficiently anesthetized before laryngoscopy begins. Giving β-blockers or opioids (ie, remifentanil) may blunt the hemodynamic effects (Fig. 67-6).
A. Vocal cord cyst. B. Bilateral vocal cord hemangiomas. [Courtesy of Christopher Hartnick, MD, Massachusetts Eye and Ear Infirmary.]
Microlaryngoscopy with suspension is a technique that uses both a surgical laryngoscope and an OR microscope. The surgical laryngoscope is attached to either an instrument tray or the OR table by extension, and the patient's upper torso is practically suspended for the duration of the procedure. A small-diameter, laser-compatible endotracheal tube with a large cuff volume is used. The head and neck are padded and braced; if the patient moves, injury can occur. Muscle relaxation is required for these procedures. The arrangement provides excellent exposure of the vocal cords, and the combination of microscope and laser allows the surgeon to make precise excisions. Prolonged suspension can cause glottic edema, resulting in airway obstruction in the recovery room. IV steroids can reduce this risk (Fig. 67-7).
Patient positioned for microlaryngoscopy under suspension. Note that the patient's head is covered in a damp cloth. The microscope and laser are in the upper left, and the suspension laryngoscope is in the center. [Courtesy of Phillip Song, MD, and Bil Ragan, MD, Massachusetts Eye and Ear Infirmary.]
Ventilation during this procedure is a challenge. Unless a cuffed endotracheal tube is used, all volatile anesthetics will be diluted by entrainment of air. Pollution of the OR also may occur. Induction and maintenance of anesthesia are best accomplished using IV techniques. Some anesthesiologists have used apneic oxygenation for brief procedures. Others have advocated an intermittent ventilation technique whereby an endotracheal tube is placed and removed multiple times until the operation is complete. This places the airway at risk and prolongs the time needed to finish the procedure. It can also lead to additional vocal cord irritation and trauma.
Other practitioners have used jet ventilation to good effect. Essentially, a volume of gas is compressed and delivered under high pressure through a small tube or catheter. In a tubeless technique, this gas can be given through a side port in the laryngoscope. Depending on the situation, jet ventilation may be administered above, at, or below the glottis. Various devices are available to provide jet ventilation, and all have at least 3 common components. A compressor provides a blend of oxygen and N2O (or nitrogen, helium, and so on) under high pressure. This mixture then passes through a pressure regulator before patient exposure. For adults, the initial jet pressure should be 20 pounds per square inch (psi) or less and for children should be 10 psi or less. Actual gas delivery is controlled by a hand-operated valve.
Jet ventilation is advantageous because it provides an unobstructed operating field to the surgeon and increases safety during laser procedures. However, there are some significant concerns. Jet ventilation requires additional time, effort, and skill to set up and operate. Because ambient air is being entrained along with high-pressure gas via the Venturi principle, the patient receives a diluted mixture that results in inadequate anesthetic depth. Furthermore, in the absence of a sealed airway, this can lead to OR pollution. Furthermore, Buczkowski et al64 have shown that when using high-frequency jet ventilation (HFJV) above the stenosis, air entrainment occurs resulting in higher distal airway pressures. This complication is avoided if HFJV is given below the stenotic lesion. General anesthesia must be supplemented or maintained by IV agents when jet ventilation is used. Respiratory gas monitoring is inaccurate, and one must rely upon chest movement and pulse oximetry to assess ventilation. Air trapping can lead to barotrauma if a mass blocks expiration in a "ball-valve" phenomenon. Carbon dioxide can accumulate, leading to respiratory acidosis and its unwanted effects (tachycardia, arrhythmias). Moreover, the exit opening for the high-pressure gas, whether it is a needle, tube, or catheter, should not lie near the mucosa. The Hunsaker tube has extensions to keep it away from the airway surface and is a proven device in microlaryngeal surgery.65 Barotrauma associated with jet ventilation can result in subcutaneous emphysema, pneumothorax, and pneumomediastinum. Jet ventilation is a sophisticated technique and complications are related to practitioner experience.66
Most recent research on jet ventilation has focused on ventilatory frequency. Whereas hand-operated valves allow delivery of low-frequency jet ventilation, newer, automated devices allow delivery of up to 600-Hz, HFJV. First described in 1976, this mode of jet ventilation is advantageous with certain types of airway pathology and in patients with severe pulmonary failure. High-frequency jet ventilation allows easy positioning in airway stenosis, decreases risks in laser surgery (no tube), decreases aspiration risk because of continuous outflow of gas, provides continuous ventilation, and allows cricothyroid rescue ventilation (see Unzueta et al67). In the latest variation, superimposed HFJV (SHFJV) has been shown to be quite useful in cases of severe stenosis.68 This technique simultaneously uses 2 jet streams of different frequencies.
High-frequency jet ventilation has disadvantages. Hautman et al69 identified that complications of HFJV included hypertension, hypotension, bronchospasm, hypercarbia, and hypoxia. Insufficient humidification is another concern. Histologic injury correlates with frequency of jet pulses and manifests as mucosal edema, congestion, and epithelial cell flattening, all of which can contribute to necrotizing tracheobronchitis. In addition to barotraumas, other complications include dysrhythmias, pneumoperitoneum, and gastric rupture secondary to misdirected gas flows. Some studies have suggested that preterm infants receiving HFJV have a greater incidence of necrotizing enterocolitis. With these concerns in mind, other investigators have examined the benefits of using combined-frequency jet ventilation. These techniques use both low-frequency jet ventilation and HFJV in differing ratios and have given satisfactory results. Regardless of the approach used, jet ventilation remains a useful but specialized anesthetic technique. It requires experience and should not be attempted by unaccompanied novices.
Schawlow and Townes first theoretically proposed lasers (light amplification by stimulated emission of radiation) in 1958, and development followed rapidly. In 1960, Maimon produced a laser, and since that time, lasers have become common in multiple applications, including medical and surgical practice. Anesthesia providers should have a basic understanding of how lasers function and of the benefits and hazards associated with their use.
A laser beam can be described as monochromatic (same wavelength), coherent (in phase), and collimated (parallel waves) light. Most lasers are 1 of 4 types. Dye lasers use an active material (usually an organic dye) in a liquid suspension as the lasing medium. By changing the chemical composition of the dye, the laser can be "tuned" to different wavelengths. Diode lasers use an optical cavity to amplify light emitted from the energy-based gap that exists in semiconductors. Gas lasers consist of a gas-filled tube upon which a voltage is applied to excite molecules to a state of population inversion. Free electron lasers function by having an electron beam in an optical cavity pass through a magnetic undulator. Free electron lasers can produce a wide variety of wavelengths (Fig. 67-8).
Schematic diagrams illustrating the components and types of common medical lasers. A. Dye laser. B. Diode laser. C. Gas laser. D. Free electron laser. [Illustration by Daniel Muller, Haderer & Muller Biomedical Art, LLC.]
Lasers focus a large amount of energy on a discrete area to exert their effects. In biologic tissue, this can manifest as thermal effects via energy absorption, photochemical effects by the reaction of radiant energy with specific molecules, and mechanical effects by disruption secondary to propagation of photo acoustic shock waves. In addition, the smoke, or laser "plume" can contain known carcinogens, toxic gases, and viable microorganisms (Table 67-1).70
Table 67-1 Laser Effects ||Download (.pdf)
Table 67-1 Laser Effects
|Thermal injury: Burns secondary to energy absorption|
|Photochemical reactions: Secondary to interaction between specific molecules and radiant energy|
|Mechanical effects: Tissue disruption secondary to photoacoustic shock waves|
|Toxin release: Toxic gases, carcinogens, and viable microorganisms within the laser "plume"|
Every facility that uses medical lasers should have a laser safety officer or committee. The responsibilities should include education of health care providers, protocol formulation, and implementation of safety policies. When a laser is in use, signs and appropriate safety glasses must be available at all entrances. All persons in the OR should wear safety glasses, and the patient's eyes should be taped closed and covered with soaked gauze.
As with any medical device, national standards have been established to ensure the safe use of lasers. In the United States, these can be found in the industry publication American National Standards Institute (ANSI) Z136.3-2005, Safe Use of Lasers in Health Care Facilities.71 Two important concepts are emphasized in this handbook. One is the nominal hazard zone. This is the minimal distance in which lasers beams can have effects. For the majority of medical lasers, this distance varies between 0.46 and 178 m. The other concept is borrowed from radiation safety studies and is the maximum permissible exposure. This represents the maximal laser energy that can be absorbed without resulting in harm. Most laser injuries result from reflected beams, and the eyes are most vulnerable. Eye injuries include photokeratitis, photochemical cataracts, thermal retinal injuries, and corneal burns. Within the eye, the retina is vulnerable to laser wavelengths of 400 to 1400 nm (argon, neodymium:yttrium-aluminum-garnet [Nd:YAG] lasers). Wavelengths of 1400 nm or above can damage the cornea. Aside from wavelength, the extent of eye injury is determined by pupil size, degree of pigmentation, size of retinal image, pulse duration, and pulse repetition rate (Table 67-2).
Table 67-2 Determinants of Eye Injury ||Download (.pdf)
Table 67-2 Determinants of Eye Injury
1. Pupil size
2. Degree of pigmentation
3. Size of retinal image
4. Pulse duration
5. Pulse repetition rate
The safety glasses needed are wavelength specific and depend on the laser being used. Argon (514-nm) pulse lasers exhibit a green beam and cause thermal effects. They require orange glasses. The potassium titanyl phosphate (KTP; 532 nm) diode pulse laser also has thermal effects and requires orange glasses. Dye pulse lasers have both mechanical and thermal effects and require blue glasses. Nd:YAG (1064 nm) and CO2 (10,600 nm) pulse lasers cause thermal effects, and clear glasses are needed for protection (Table 67-3).
Table 67-3 Commonly Used Medical Lasers (Pulse Mode) ||Download (.pdf)
Table 67-3 Commonly Used Medical Lasers (Pulse Mode)
|Type of Laser||Wavelength (nm)||Primary Effect||Protective Eyewear|
|Dye||583-587||Thermal/Mechanical||Blue (dye specific)|
|Argon||514||Thermal||Orange (argon specific)|
Laser Fire and Laser Endotracheal Tubes
The greatest danger caused by a laser is an endotracheal tube airway fire. Although rare, the results of an endotracheal tube airway fire can be catastrophic and fatal. If the endotracheal tube is penetrated by the laser beam, the oxygen-rich environment within the tube can produce a vivid, intense flame. Every practitioner should have the image of a "blow torch" in his or her mind to appreciate the danger. All of the elements to support a fire are found in this setting: oxygen (supports combustion along with N2O), combustible material (endotracheal tube), and an ignition source (laser). Much effort has been expended to develop a laser-safe endotracheal tube, but as of yet, there are no "perfect" laser endotracheal tubes.
Metal endotracheal tubes are laser resistant but have other disadvantages. They are not as pliable or as easy to handle as conventional polyvinyl chloride (PVC) tubes. This characteristic can lead to unnecessary manipulation and potential vocal cord trauma. Metal endotracheal tubes do not have a cuff, and one cannot seal the trachea. Furthermore, the laser beam can reflect off the tube and damage healthy adjacent tissue. Metal tubes can transmit heat to surrounding tissue. A Mallinckrodt Laser-Flex is a metal tube containing an inner PVC endotracheal tube fitted with tandem cuffs. If one cuff is damaged, the remaining cuff can still maintain a seal. Despite its other advantages, the PVC cuff still conveys a risk of laser ignition.
The Xomed Laser Shield II is a silicone endotracheal tube covered with metallic particles. Its cuff also has a metallic covering to improve its survivability. This is the endotracheal tube used at the author's institution, with safe, reliable results obtained. However, under certain circumstances, this tube can burn. Typically, a cool saline-blue dye mixture is used to inflate the cuff. This allows easy visualization of any cuff damage and provides a "heat sink" to slow potential ignition of the cuff. (Fig. 67-9)
A Xomed Laser Shield II endotracheal tube. Note that the cuff has been test filled with saline and blue dye. [Courtesy of Bil Ragan, MD, Massachusetts Eye and Ear Infirmary.]
A Sheridan 2 is a polyvinyl acetate (Merocel), copper foil–wrapped endotracheal tube. Red rubber tubes wrapped with a metallic tape have been used safely for many years. One advantage is that ignited rubber tends to char rather than melt. In addition, more energy is required to ignite rubber than PVC. Great care must be taken when applying the metallic tape. Any exposed areas are liable to ignition. Rough or loose edges can injure the patient's airway. Similar to a metal tube, certain metallic tapes can reflect the metal beam onto healthy tissue.
Airway Fire Precautions and Management
To reduce the risk of an airway fire, certain precautions should be observed:
Consider a tubeless technique using spontaneous ventilation, apneic techniques, or jet ventilation.
Use an appropriate laser endotracheal tube, such as metal, Mallinckrodt, Xomed, Sheridan, or Red Rusch.
Reduce inspired oxygen as tolerated by the patient to less than 30% but ideally 21%.
Use either air or helium to dilute the oxygen; N2O supports combustion.
Fill the endotracheal tube cuff with a saline–dye mixture or lidocaine jelly.
Completely soaked gauze should be placed within and around the airway to reduce ignition risk.
Use H2O-based ointments; petroleum-based ointments are flammable.
Limit the duration and intensity of laser exposure; continuous mode allows heat buildup.
Maintain a ready source of water in case of fire (multiple 60-mL filled syringes).
These steps will not eliminate the risk of an airway fire, but they will reduce it.
Despite these precautions, what should the anesthesiologist do in the event of an airway fire? The ANSI has developed the following protocol:
Disconnect the oxygen source and flood the airway with water.
Remove the burned endotracheal tube and examine the airway.
Mask ventilate the patient and reintubate.
Survey the extent of injury using a flexible bronchoscope.
Monitor the patient for 24 hours.
Administer steroids to reduce inflammation and edema.
Provide antibiotics and ventilatory support if indicated.
It is common practice at the author's institution not to tape or secure the endotracheal tube to the patient's face. This will allow rapid removal of the tube in the event of an airway fire; however, this raises a controversial point. In the author's own research (unpublished observations), it appears that the first step is to remove the endotracheal tube as rapidly as possible even if gas flows and ventilation are still occurring. After being ignited, even without gas flow, the endotracheal tube will continue to burn and cause injury. By the time an endotracheal tube fire is recognized, approximately 3 to 4 seconds have passed. It will take another 3 to 4 seconds to stop ventilation, stop gas flows, and flood the airway before removing the endotracheal tube. In contrast, simply removing an untaped endotracheal tube will take approximately 1 second, thus potentially reducing the amount of injury to the patient.
Besides endotracheal tubes, lasers can ignite surgical drapes and other flammable items within the OR. Electrocautery can be a source of surgical fires. Under the right conditions, drapes, towels, ointments, and gowns can be combustible. Only by taking all possible precautions and practicing due diligence are surgical fires prevented. Every member of the OR team must be aware and prepared to intervene if necessary (Tables 67-4 and 67-5).
Table 67-4 Airway Fire Precautions ||Download (.pdf)
Table 67-4 Airway Fire Precautions
1. Use a laser endotracheal tube or consider tubeless technique, apnea, or jet ventilation.
2. Reduce inspired O2 to less than 30%.
3. Avoid N2O; use air or helium.
4. Fill the endotracheal tube cuff with saline dye or lidocaine jelly.
5. Place a soaked gauze around the airway.
6. Use only H2O-based solvents.
7. Limit laser exposure.
8. Maintain a ready source of H2O.
Table 67-5 Airway Fire Protocol ||Download (.pdf)
Table 67-5 Airway Fire Protocol
1. Stop ventilation.
2. Stop O2 flow and flood the airway with water.
3. Remove the endotracheal tube and examine the airway.
4. Mask ventilate the patient and reintubate.
5. Determine injury via bronchoscopy.
6. Monitor the patient for 24 h
7. Consider steroid administration.
8. Provide antibiotics and ventilator support as needed (Fig. 67-10).
A standard polyvinyl chloride 7.0 endotracheal tube on fire. A. Approximately 3 seconds after ignition while receiving 1 L of oxygen and 2 L of nitrous oxide, note the "blow torch." B. Approximately 10 seconds after ignition; the flame intensifies and is accompanied by a large volume of combustible products. C. Gas flows have been stopped, but the tube continues to burn vigorously. [Courtesy of Bil Ragan, MD, and Artem Grush, MD, Massachusetts Eye and Ear Infirmary.]
Anatomic Airway Disorders
These malformations were alluded to in the discussion of choanal atresia. In contemporary obstetric practice, it is now possible to identify and diagnose many airway lesions in the prenatal period. Polyhydramnios can be associated with atresia, webs, gastrointestinal obstruction, and neurologic disorders. Mass lesions include teratomas, cystic hygromas, and hemangiomas. If an airway lesion is undetected and the delivery unexpected, securing the airway may be difficult or impossible. Fatal outcomes can be prevented with advance planning.
Farrell72 examined this problem. After a diagnosis has been established, elective cesarean section is the preferred technique for delivering the fetus; it is usually scheduled early enough to avoid spontaneous labor and yet late enough to allow pulmonary maturation to occur. Such a complicated delivery requires 2 surgical teams, an obstetric team and a neonatal team. The neonatal team should include a pediatrician, pediatric anesthesiologist, and pediatric otorhinolaryngologist. Each team will have its own setup and equipment. Careful planning and practice are necessary before delivery. When the infant's head emerges, the neonatal team secures the airway as planned. This often occurs before umbilical separation.
Craniofacial abnormalities range from an incomplete cleft lip to complete centrofacial dysgenesia. Congenital malformations include Beckwith-Wiedemann syndrome; cleft lip and palate; craniocarpotarsal dysplasia/Freeman-Sheldon/whistling face syndrome; craniofacial dyostosis; fibrodysplasia ossificans progressive; hemifacial microsomia; Klippel-Feil syndrome; mandibulofacial dyostosis or Treacher-Collins syndrome; mucopolysaccharidosis; Pierre-Robin syndrome; trisomy 21 or Down syndrome; and vascular malformations. Nargozian73 has described an approach to airway management in these special patients. Pediatric Anesthesia published a special supplement in July 2009 titled "The Pediatric Airway."74 It contains a series of comprehensive review articles covering all aspects of the pediatric airway. This overview briefly discusses cleft lip and palate repair.
Cleft malformations may be an isolated finding or associated with other syndromes. These infants have difficulty feeding and fail to gain weight. Aspiration may lead to pulmonary problems. Aside from feeding issues, cleft malformations are associated with chronic serous otitis, which can lead to hearing deficits and speech delay. Parents will desire a timely repair for functional as well as cosmetic reasons. Initial lip repair may be done as a "lip adhesion" at approximately 6 weeks of age. This is simply a sutured approximation of the cleft edges that will promote better feeding and weight gain before later procedures. The definitive repair is done at approximately 12 weeks of age, with revisions after that as needed.
Similar to lips, cleft palates may be unilateral or bilateral, and they may be complete or incomplete (only soft palate involved). There is a strong association between an incomplete cleft palate, micrognathia, and various syndromes. A submucous cleft only involves the muscles beneath the mucous membranes and cannot be seen on visual examination. Some surgeons repair the soft palate with the lip at 12 weeks of age. Hard palate repair is accomplished between 9 and 18 months; most surgeons prefer approximately 1 year of age. The maxillae have better growth with later repair, but the infant will develop better speech with early repair. These procedures are managed with general anesthesia and endotracheal tube intubation. Securing the airway is not difficult if no other syndromic abnormalities are present. Mesnil et al75 have shown that bilateral suprazygomatic maxillary nerve blocks provide excellent analgesia and decrease opioid use after repair.
Malacias refer to conditions caused by cartilage softness that leads to airway collapse and obstruction. With the exception of reactive airway disease, the malacias are unique among the airway disorders in exerting their effects by dynamic processes. These disorders can lead to significant morbidity and mortality and are a rare condition characterized by softness of the airway structures. A review article by Austin and Ali76 fully describes the assessment, treatment, and management of tracheomalacia and bronchomalacia in children. Laryngomalacia can produce similar symptoms.
Excessive intrathoracic pressure during expiration creates narrowing and airway collapse. The patient will have wheezing unresponsive to bronchodilators. Less commonly, extrathoracic pressure causes produce collapse during inspiration demonstrated by stridor. Most patients with airway malacia are neonates who have aortopulmonary malformations, bronchopulmonary dysplasia, or tracheoesophageal malformations. Congenital airway malacia may be an isolated finding or part of a syndrome. Acquired airway malacia results from chronic compression that limits cartilage growth. Thus, even after a "pexy procedure," airway collapse may still occur.
Being a dynamic airway disorder, malacia assessment is best accomplished by flexible bronchoscopy in a spontaneous breathing patient. Typically, this is accomplished by performing a mask induction on the neonate. After the patient is under anesthesia, a bronchoscope is introduced to observe and record airway structures while the child is breathing. The patient receives 100% oxygen under insufflation and supplemental IV anesthesia during the study. Combinations of propofol and remifentanil, when titrated to effect, work very well. The goal of the anesthetic is to prevent airway collapse by using positive end-expiratory pressure or CPAP and to avert coughing. Videofluoroscopy with or without contrast can be useful. CT and MRI scans cannot show the dynamic processes but can reveal which anatomic structures may be compressing the airway. Spirometry data allow one to assess the functional impact of the disorder. As discussed by Austin and Ali, treatment can be (1) long-term ventilation or CPAP, (2) resection of the affected segment, (3) external splinting, (4) pexy procedures, and (5) stenting. At present, the last 2 modalities appear to offer the most promising results (Figs. 67-11 and 67-12).
Tracheomalacia as seen in an 11-month-old girl. Note that the posterior wall has collapsed into the tracheal lumen. [Courtesy of Christopher Hartnick, MD, Massachusetts Eye and Ear Infirmary.]
Laryngomalacia as seen in a 1-day-old neonate presenting with stridor. [Courtesy of Christopher Hartnick, MD, Massachusetts Eye and Ear Infirmary.]
Subglottic stenosis refers to any condition in which the trachea is narrowed by a fixed lesion that compromises air flow. Pediatric subglottic stenosis can result from congenital causes, such as abnormal cartilage, or acquired causes, such as prolonged intubation, trauma, burns (thermal and chemical), gastroesophageal reflux disease, and mass compression. Adult subglottic stenosis is almost entirely of the acquired variety. There are few experiences as frustrating to the anesthesiologist as an inability to advance an endotracheal tube beyond the vocal cords following what appeared to be a routine laryngoscopy.
A full-term infant has a subglottic diameter of approximately 5 to 6 mm. Congenital subglottic stenosis is defined as a subglottic diameter smaller than 4 mm or the inability to pass a 3-mm endotracheal tube. For premature neonates weighing less than 1500 g, consider a smaller diameter, for example, the inability to pass a 2.5-mm endotracheal tube. A simple grading system is used to classify the severity of subglottic stenosis. Grade I lesions exhibit 0% to 50% obstruction. Grade II lesions exhibit 51% to 70% obstruction, and grade III lesions exhibit 71% to 99% obstruction. Grade IV lesions exhibit no detectable lumen and are incompatible with life unless a fistula or cleft is present, permitting air exchange. Typically, grade I and II lesions are mildly symptomatic. Patients with grade III and IV lesions require surgical repair (Fig. 67-13).
A. Type II subglottic stenosis in a neonate caused by a hemangioma. B. Type III subglottic stenosis secondary to trauma in an otherwise healthy 4-year-old boy. [Courtesy of Christopher Hartnick, MD, Massachusetts Eye and Ear Infirmary.]
The short-term solution is to intubate the patient's trachea. Long-term treatment options include observation (only for grade I and II lesions), endoscopic dilation, CO2 laser ablation, tracheostomy, an anterior cricoid split, laryngotracheal reconstruction, and cricotracheal resection. Endoscopic dilation may be of benefit in early stenosis but is ineffective in treating firm stenosis. CO2 laser has been used for circumferential soft stenosis but is limited in other conditions. A tracheostomy often is the initial step in management. It provides a safe airway, allows the infant to grow, optimizes the patient's pulmonary status, and allows for treatment of gastroesophageal reflux disease. Tracheostomy is not a benign procedure. Aside from quality-of-life issues, complications can result in significant morbidity and mortality. For these reasons, early airway reconstruction is desired.
The anterior cricoid split is a procedure that can be used with or without a cartilage graft. Duration of stenting is based on the infant's weight. If the infant weighs less than 2000 g, the stent will remain in place for at least 2 weeks. For infants weighing more than 2000 g, the stent will be removed after 1 week. Indications for an anterior cricoid split include 2 or more previous extubation failures because of subglottic stenosis, weaned from the ventilator for at least 10 days, supplemental oxygen less than 30%, normotensive for at least 10 days, and no acute upper respiratory tract infection or congestive heart failure within the previous month. Ultimate decannulation success rates are approximately 75% to 80%.
Tracheal Reconstruction or Resection
Laryngotracheal reconstruction is considered when an infant reaches a weight of 10 kg. A laryngotracheal reconstruction can be an anterior, posterior, or lateral repair, and the graft may be of rib, thyroid ala, or auricular origin. Single-stage laryngotracheal reconstruction procedures are indicated for older children with minimal glottic involvement and no pulmonary pathology. Usually only a single graft is involved. Indications for 2-stage laryngotracheal reconstruction procedures include extensive grafting, concomitant glottic pathology, and significant tracheomalacia. Decannulation rates for grade II and III lesions vary from 91% to 97%. For grade IV lesions, the rate declines to 71% (see Walner77).
Cricotracheal resection is an alternative in select patients with discrete grade III or IV lesions. The stenosis should be at least 4 mm distal to the vocal cords. This location will ensure later voice quality. Some investigators suggest that these patients have less speech pathology compared with laryngotracheal reconstruction patients. Triglia et al78 have provided an extensive review of the technique. The duration of postoperative stenting remains controversial, and there is a greater risk of recurrent laryngeal nerve injury with this procedure. Various studies have demonstrated decannulation rates of 85% to 100% for grade III and IV lesions.
At the author's institution, anterior cricoids split, single-stage, and 2-stage laryngotracheal reconstructions are frequently performed. The patient typically arrives with a tracheostomy. After an inhalation induction and establishment of IV access, the tracheostomy cannula is removed and replaced with an appropriately size reinforced endotracheal tube. The graft is harvested next; this is the source of most postoperative discomfort. After the graft is obtained and shaped, the resection and reconstruction begin. Depending on the location of the lesion, the endotracheal tube may be advanced or withdrawn small distances to provide better surgical access. After the reconstruction is complete, a nasal intubation is performed. The patient is then taken to the intensive care unit and kept intubated for 7 to 10 days. The entire operation takes 4 to 6 hours to complete.
Tracheotomy and Tracheostomy
A tracheotomy is an incision or opening into the trachea. A tracheostomy is the creation of a permanent opening in the trachea such that the mucous membrane becomes continuous with the external epithelium. Tracheostomies are common surgical procedures that are performed for a variety of reasons, ranging from emergent care to chronic care. Anesthesia care varies depending on the specific condition. For example, if urgent surgical airway access is required, tracheostomy can be performed using only local anesthesia with sedation.
Most patients who require tracheostomy are brought to the OR and placed in the supine position with the back slightly elevated. This position promotes respiratory effort and provides better surgical access. An inflatable shoulder roll or stack of towels is placed under the shoulders to extend the head and further expose the neck. If the patient is already intubated, the surgeon proceeds directly to the tracheotomy. This procedure is not without its complications. Rarely, the surgeon pierces the endotracheal tube cuff and produces a large leak. If ventilation becomes compromised, a throat pack can be placed or the endotracheal tube replaced. The surgeon can also approximate the wound to reduce the leak. Airway fires are known to occur, particularly if 100% oxygen or high concentrations of N2O are used in the presence of electrocautery. After the trachea is fully exposed, the surgeon requests that the endotracheal cuff be deflated and the tube slowly retracted cephalad but with the tube tip still below the glottis so it can be advanced again if necessary. After electrocautery is completed, ventilation with 100% oxygen is performed for at least 60 seconds before withdrawal of the endotracheal tube and insertion of the tracheostomy cannula. After the tube is withdrawn cephalad, the surgeon inserts the tracheostomy cannula and passes the new circuit to the anesthesiologist. Great resistance to ventilation should immediately alert the practitioner to incorrect cannula placement. The presence of CO2 via capnography, the presence of bilateral breath sounds, and the ability to ventilate the patient all indicate a successful tracheostomy. Only after ventilation is verified should the endotracheal tube be removed entirely.
The approach to pediatric tracheostomy is similar to that for adults except that children will not cooperate for this procedure under local anesthesia. Indications for pediatric tracheostomy include prolonged ventilation, laryngotracheal malacia, subglottic stenosis, respiratory papillomatosis, alkali ingestion, and craniofacial syndromes. Pediatric tracheostomy may present airway challenges for anesthetists; Wrightson et al79 reviewed 100 pediatric tracheostomies and noted that 26% were difficult to intubate. When intubation proved impossible, ventilation was accomplished by LMA or facemask until the surgical airway was established. A common surgical technique is the percutaneous dilational tracheostomy first described by Ciaglia in 1985. Used both in adult and pediatric patients, it is associated with a low complication rate.80 A modified percutaneous dilational tracheostomy set called the Ciaglia Blue Rhino® has been introduced and used with good results. Other tracheostomy sets include the Percu-Twist®, Fanconi translaryngeal tracheostomy, and the Portex Ultraperc®. Pediatric tracheostomies frequently are accomplished using bronchoscopic guidance.
Maxillofacial surgery is performed to repair facial trauma or correct facial deformity. Midface fractures are described using the Le Fort classification. Class I involves the lower third of the nasal septum and maxilla above the nasal floor and mobilizes the maxillary alveolar process, palate, part of the palatine bone, and lower third of the pterygoid plates. Oral or nasal intubation can be established, and the airway usually is intact. Nasal intubation is contraindicated in a Le Fort class II fracture, which involves the upper nasal bone, under the zygomaticomaxillary suture and through the pterygoid plate. A Le Fort class III fracture separates the base of the skull from the midface, and nasal intubation is contraindicated here as well. Before surgery, the patient must be fully evaluated for any airway compromise, other traumatic injury, and other preexisting medical problems. Depending on the nature of the injuries, a facial fracture repair may be delayed to stabilize the patient's condition.
Often, a nasal intubation is requested to provide better surgical access. As mentioned, nasal intubations are contraindicated in Le Fort class II and class III fractures and in the presence of a CSF leak. Nasal intubations are not entirely benign. They can lead to bleeding, damage turbinates, increase the risk of sinusitis and otitis, and may be difficult to perform in the presence of a traumatized airway. It is unwise to blindly pass a nasal endotracheal tube into a potentially disrupted nasopharynx. The tube can be directed into a sinus, the orbit, the hypopharynx, and even intracranially. Nasal intubations are discussed in a separate section. A tracheostomy can be performed if facial trauma is too severe or in the presence of a basal skull fracture.
Other options for securing the airway are available. Kannan et al81 described using an intubating LMA to facilitate an awake fiberoptic intubation in a severe facial trauma case. In another approach, Altemir described placing a submental intubation (SMI). An SMI is a secure surgical airway that gives open access to the oral cavity and does not elicit the complications of a nasal intubation or tracheostomy. Essentially, an SMI is an oral intubation with the proximal end of the endotracheal tube passing through an incision in the floor of the mouth and connected externally to the anesthesia circuit. It is a useful airway technique for maxillofacial surgery in patients with severe oral, nasal, and neck trauma. In a study of 13 patients with panfacial fractures, Anwer et al82 found SMIs safe and effective. In a modification of this technique, Biswas et al83 have used a percutaneous dilational tracheostomy set to create the passage for the endotracheal tube. SMI is also appropriate for patients undergoing elective procedures who are not expected to need prolonged postoperative ventilation. SMIs are used in European practice but have yet to be fully accepted in North American practice (Fig. 67-14).
Submental intubation. Note that the proximal end of the endotracheal tube emerges just medial to the mandible. [Illustration by Daniel Muller, Haderer & Muller Biomedical Art, LLC.]
An uncommon surgical procedure is facial bipartition. This is done to correct severe deformities or malformations. Mallory et al84 reviewed a series of 22 cases and noted that the most significant complication was hemorrhage. Every patient required an intraoperative blood transfusion. Four of the 22 patients required postoperative ventilation, which was associated with younger age and major blood loss. Recently, Stricker et al85 reviewed 159 cases, and it was noted that the intraoperative administration of fresh-frozen plasma resulted in fewer postoperative coagulation disorders and complications.
Orthognathic reconstructions are elective procedures to correct malocclusion or facial deformity. These cases are performed by oral or maxillofacial surgeons. Typically, a sagittal split osteotomy of the mandible is done to advance or retract the lower jaw. The maxilla can also be moved forward or in a transverse direction. Care must be taken with the intubation. These patients may present with semipermanent orthodontic devices in place. In addition, they may have anatomic abnormalities, such as prominent incisors, retrognathia, or small mouths.
Orthognathic surgery is an oral procedure, and the patient requires a nasotracheal intubation. As mentioned in the Maxillofacial Reconstruction section, nasal intubations are more traumatic than oral intubations and have their own complications. Hall and Shutt86 have provided a complete and excellent review of nasotracheal intubations. Epistaxis, bacteremia, and possible posterior pharyngeal wall laceration are possible. It is also possible to enter the hypopharynx and create a false passage. Rarely, the tube becomes obstructed with avulsed tissue from the inferior turbinate. Other problems include maxillary sinusitis, otitis, and possible cuff rupture from passage through the turbinates or by use of the MacGill forceps.
Contraindications to nasal intubation include the presence of a CSF leak, basal skull fracture (Le Fort III), Le Fort II fracture, the presence of a nasal FB, or a traumatized nasopharynx. Relative contraindications include bleeding coagulopathy, cardiac valve disease, and an immunocompromised condition.
Before anesthesia and nasotracheal intubation, the patient should assist the practitioner by identifying the more patent nasal passage. If the patient is uncooperative, a steel blade or mirror can be placed beneath the nostrils, and the side that steams greater is more open. It is helpful to administer vasoconstrictors to both sides and to use a local anesthetic lubricant. Other techniques are available to assist the anesthesiologist. Use of a soft red rubber nasal tube to expand the nostril and spread the lubricant is helpful.
After induction and before laryngoscopy, the anesthesiologist should gently place the endotracheal tube in the selected nostril and advance the tube parallel to the palate. Ideally, one advances the tube along the floor of the nose under the inferior turbinate. This is referred to as the "lower pathway."87 The endotracheal tube should not be advanced in a superior direction toward the nasal bridge. There will be resistance in the nasal passage until deep posterior, where a sudden "give" is felt as the nasotracheal tube passes the inferior turbinate. If laryngoscopy is planned, advancement should stop when the tube is in the pharynx.
Upon laryngoscopy, bloody secretions may be present in the oral cavity. Various devices, agents, and techniques have been used to reduce epistaxis. Among the newer endotracheal tubes, both the Parker Flex-Tip and the Endoflex endotracheal tubes have shown good results with reduced trauma to the nasal mucosa. If the tube bevel is inserted on the turbinate mucosa, it is likely to cause more bleeding.
Suctioning should reveal the tip of the endotracheal tube lying on the posterior pharyngeal wall. Examination of its location and the glottis will determine if the tube can be advanced into the trachea without the MacGill forceps. This will lessen the chances of a torn cuff or more trauma from airway instruments. After the trachea has been intubated, the practitioner should inflate the cuff, ventilate, and observe for CO2 and condensation, and listen for bilateral breath sounds. When the tube is being secured, it should not pull on the nose or pressure necrosis may occur. The author prefers to place a band of tape completely around the patient's head just above the ears. This becomes the foundation on which the tube tape is secured. The circuit is brought down from the forehead and underneath the OR table. The endotracheal tube and circuit should be secured in a manner that will allow flexion and extension of the head without jeopardizing their position.
Other problems may arise after surgery begins. During maxillary osteotomy, the osteotome may slice through the endotracheal tube and pilot tube. When this occurs, a secure airway must be quickly reestablished to prevent a life-threatening event. In a brief communication, Davies and Dyer88 reported the successful use of an Obwegieser nasal septal osteotome. This instrument has 2 blunt horns that prevent direct contact with the endotracheal tube. The author is familiar with a case in which extubation of a trachea became impossible after a palate expansion. CT scan revealed surgical wires passing through the nasotracheal tube, preventing its removal. These complications do occur, and one should be prepared.
Hemorrhage may be significant with orthognathic surgery, especially when maxillary procedures are involved. Blood loss can vary between 300 and greater than 2000 mL. Depending on the procedure, autologous blood transfusion may be considered. Moreover, controlled hypotension with isoflurane or other agents may be helpful. These patients are generally young and otherwise healthy and will tolerate such techniques.
At the conclusion of surgery, the pharyngeal packs are removed and the stomach suctioned. As with nasal or sinus procedures, swallowed blood can provoke nausea. Appropriate antiemetics should be administered well in advance of the expected extubation. Only after the patient is fully awake with airway reflexes intact should the endotracheal tube be removed. Rigid internal fixation is beginning to replace intermaxillary fixation and provides more postoperative comfort. Intermaxillary fixation will still be encountered and will result in the patient's jaws being "wired shut" using elastic bands or wires. This obviously blocks access to the airway, restricts suctioning, and makes reintubation practically impossible until the mandible is free. When intermaxillary fixation is used, without exception, the patient must be fully awake before extubation. As long as the patient has intermaxillary fixation in place, cutting instruments to free the airway must be immediately available at the bedside.
Pain management begins early. Narcotics are supplemented by the surgeon providing local anesthetic infiltration directly into the wound. Besides the usual narcotics, other analgesic classes have been investigated. Moller et al89 obtained good results with IV propacetamol. These results were supported by Van Aken et al,90 who found the analgesic qualities of propacetamol similar to those of morphine and better tolerated.
In recent years, dentists have reduced the use of N2O in the office setting. This was prompted by a number of unfortunate events resulting in patient harm and subsequent increased legal liability. Most office procedures are now performed using topical anesthetic supplemented by local anesthetic injections. If needed, a preoperative oral sedative (usually a benzodiazepam) can be prescribed.91
Because of this trend, it is becoming more common to provide general anesthesia to certain dental patients in an OR. The vast majority are pediatric patients who are uncooperative and have behavioral problems or who need an extensive amount of repair that is easier to accomplish in one OR visit than multiple office visits.
All of the concerns regarding pediatric anesthesia and oral surgery apply here. Some have used flexible LMAs for these cases, but the dentist may request a nasal intubation to provide better access to a small oral cavity. These patients may not have seen a pediatrician before arrival, and the preoperative physical examination may yield unexpected findings.92 As noted earlier, preoperative anxiety may be an issue with any pediatric patient. Appropriate doses of midazolam can be quite effective in this situation.
In older patients, these procedures are possible with conscious sedation as MAC anesthetics. Certainly the elderly patient needing total extractions before a cardiac valve replacement is a candidate for MAC. (See Chapter 69 for a description of monitored anesthetic care.)
Plastic surgery is a broad surgical field; this brief discussion focuses only on rhytidoplasty, commonly known as a "facelift." One may encounter both young and healthy patients as well as older patients who present for this procedure. Whereas some procedures can be done under local anesthesia with sedation, rhytidoplasty is often performed using general anesthesia with endotracheal intubation. When the procedure is complete, the surgeon will be especially concerned about bleeding and edema in the subcutaneous tissues. The anesthetic goals include prevention of patient "coughing" and "bucking" during tracheal extubation and avoidance of retching associated with PONV. Both coughing and vomiting contribute to facial and orbital ecchymoses. Rama-Maceiras et al93 reported less PONV using propofol with remifentanil compared with propofol and fentanyl. Pretreatment with metoclopramide and ondansetron can decrease this risk. Others have successfully used combinations of haloperidol and dexamethasone.94 In addition, the patient should be fluid loaded and carefully suctioned before extubation. When ventilation has been well established and with the patient's upper torso slightly elevated, the trachea should be extubated during a moderately deep plane of anesthesia. The face is commonly wrapped in soft gauze, and the eyes are covered with ice packs. Occasionally, the dressing may be wrapped tight enough to constrict the patient's airway, a matter that should receive special attention from the anesthesia provider.