Chapter 30. Management of a Patient Admitted to the ICU with Impending Respiratory Failure Due to a Suspected Infectious Etiology

A 47-year-old previously healthy male physician presented to hospital with the acute onset of fever, nonproductive cough, dyspnea, and malaise. As an intensive care unit (ICU) physician, he had intubated the trachea of a known Severe Acute Respiratory syndrome (SARS) patient in the emergency department 2 weeks earlier. He began to have respiratory symptoms 1 week later. He was admitted and placed in an isolation room. Both sputum and blood cultures were negative. In spite of empiric treatment with broad-spectrum antibiotics, his respiratory status progressively worsened over the next 24 hours, necessitating ICU admission. His vitals on admission to the ICU were respiratory rate (RR) 24 breaths per minute, heart rate (HR) 100 beats per minute (bpm), BP 130/90 mm Hg, and temperature 38.6°C. Oxygen saturation was 95% on an FiO2 of 60%, and arterial blood gases (ABGs) revealed the following: pH 7.45, PCO2 30, PO2 60. With the PO2 to FiO2 ratio (PF ratio) determined to be 100, respiratory failure was diagnosed. The chest x-ray (CXR) showed progressive bilateral basal infiltrates. A complete blood count, electrolytes, creatinine, and liver function tests were all normal, but LDH was elevated. Neurological and cardiovascular systems were intact on examination.

Anesthesia was consulted regarding possible tracheal intubation for respiratory failure with an ARDS picture. The patient was agreeable to intubation. On airway examination he was noted to be of average body habitus (5 ft 10 in [176 cm] and 154 lb [70 kg]) with no obvious dysmorphic facial features. He had no beard and no history of obstructive sleep apnea. Although he was dyspneic, there was no evidence of stridor. With full dentition, the patient was able to open his mouth 5 cm, had a 4 cm thyromental distance, and had a Mallampati Class III pharyngeal view. He exhibited good jaw protrusion, and head and neck mobility was unrestricted. The cricothyroid membrane was easily palpable in the midline.

30.2.1 What Airborne Pathogens May Pose Serious Danger to Health Care Workers? What Is the Likely Pathogen that Caused the Illness of the Presented Patient?

Health care workers (HCW) are at risk of coming in contact with respiratory secretions from patients with febrile respiratory illness of unknown etiology. There are a number of airborne viruses or bacteria that can pose a risk to HCW. For instance, active pulmonary tuberculosis carries a high risk of transmission to HCW. Similarly, active anthrax pulmonary infection may also pose a significant risk to HCW.

In general, most airborne viruses which can potentially infect HCW are not associated with high morbidity or mortality. In 2009, a new influenza A H1N1 virus (also known as swine flu) caused a worldwide pandemic affecting millions of patients. At the time of writing this chapter, there were over 375,000 confirmed cases with over 4500 deaths.1 Fortunately, most infected patients ran a benign course. Rarely, patients presented to the hospital with a rapidly progressive severe pneumonia/ARDS picture.

The clinical picture presented in this patient is compatible with the diagnosis of Severe Acute Respiratory syndrome or SARS which is not transmitted through airborne pathogens.

30.2.2 What Is the Epidemiology of SARS? How Did SARS Come out Of Nowhere to Affect Thousands of People Worldwide?

In November 2002, a cluster of atypical pneumonia cases of unknown etiology was discovered in Guangdong Province, China. In late February 2003, a symptomatic Chinese physician traveled to Hong Kong and transmitted the illness to others staying in the same hotel, initiating a worldwide epidemic. On March 12, 2003, the World Health Organization (WHO) issued a global alert warning of a wave of severe atypical pneumonia of unknown etiology.2-4 On April 13, 2003, the causative agent for SARS was identified as a new coronavirus (SARS-CoV). By the end of July 2003, there were over 8000 cases of SARS worldwide with over 700 deaths.5 Countries and regions with the highest case loads were China, Hong Kong, Taiwan, and Canada.

30.2.3 How Is the SARS Virus Transmitted?

SARS is thought to be transmitted by respiratory droplets or by direct/indirect contact.3 It is a moderately transmissible virus with a secondary infection rate of approximately 2.7 per case. The majority of SARS patients do not infect others while a small number of super-spreaders may be highly infectious.6,7 There is no evidence of airborne transmission.

30.2.4 What Are the Risk Factors for SARS Viral Transmission?

SARS patients develop nonspecific viral symptoms in the first week of their illness and respiratory symptoms in the second week, during which they are most infectious. Fowler et al assessed the risk factors for SARS transmission among 122 health care workers in a critical care setting.8 They found that performing endotracheal intubation and caring for patients receiving noninvasive positive pressure ventilation were associated with 13 and 2.3 times the risk of acquiring infection compared to those who did not. Loeb et al studied risk factors for SARS transmission among 43 critical care nurses.9 They found that assisting with intubation, suctioning prior to intubation, and manipulation of the oxygen mask were high-risk activities. In a third report, bag-mask-ventilation (BMV), endotracheal intubation, airway suctioning, noninvasive ventilation, and high-frequency oscillation were identified as high-risk procedures for SARS transmission in the ICU.10

30.2.5 What Is the Definition of SARS?

The WHO definition11 of a suspect SARS patient is a person presenting after November 1, 2002 with a history of:

1. Fever >38°C

2. Cough and respiratory difficulty

3. Known exposure to a SARS patient or traveling in endemic area within 10 days of presenting illness

The WHO definition of a probable SARS patient is a suspect person with

1. Radiologic evidence of infiltrates consistent with pneumonia or respiratory distress syndrome or

2. One or more assays positive for SARS coronavirus or

3. Autopsy findings consistent with the pathology of respiratory distress syndrome without an identifiable cause

30.2.6 What Is the Typical Clinical Course of a SARS Patient?

The incubation period is 2 to 5 days but can be up to 10 days.12 The most common symptoms at admission to hospital are fever, nonproductive cough, myalgia, dyspnea, headache, malaise, chills, and diarrhea (Table 30-1). The majority of patients have unilateral or bilateral infiltrates on the chest radiograph. The overall death rate is 10% to 13%, but is as high as 50% in the 23% to 26% of patients requiring intensive care admission.12-14 Risk factors for death include age, comorbidities, and APACHE II scores.14

30.3.1 What Are the Major Considerations in This Patient?

This patient fulfills the WHO definition of probable SARS and clinical criteria for ARDS (bilateral lung infiltrate with PF ratio ≤200 mm Hg). The patient has increased pulmonary shunting due to fluid-filled alveoli and atelectasis, leading to a high A-a gradient and a low PF ratio. He has little pulmonary reserve and is prone to the development of hypoxemia during intubation. He is also at risk of barotrauma (eg, pneumothorax) with positive pressure ventilation.

The patient is likely to have a depleted extracellular fluid volume due to his fasting status and large amounts of fluid loss from his respiratory system. This volume depletion, coupled with institution of positive pressure ventilation and removal of sympathetic drive puts him at risk of hypotension during and immediately following intubation.

30.3.2 What Is the Differential Diagnosis of a Patient with Bilateral Pulmonary Infiltrates of Unknown Etiology?

The patient may be suffering from bacterial, viral, fungal, or parasitic pneumonia. Tuberculosis, Pneumocystis carinii, and atypical pneumonia such as mycoplasma and legionella are possibilities. In addition, bilateral lung infiltrates may be due to leaky pulmonary capillaries caused by diverse causes such as sepsis or pancreatitis. Of these causes, tuberculosis and SARS pose the highest risk of transmission to the health care workers and appropriate personal protection precautions should be exercised (see later).

30.4.1 Is This Patient Predicted to Have a Difficult Airway?

Airway examination should focus on the ability to provide ventilation and oxygenation through a bag-mask, an endotracheal tube, an extraglottic device, and a surgical airway. The mnemonics MOANS, RODS, LEMON, and SHORT described in Chapter 1 provide a useful framework to assess these aspects of the patient's airway. It should be emphasized that while the ASA task force on management of the difficult airway outlined 11 criteria for preoperative airway assessment for laryngoscopy and intubation,15 no single airway test has perfect sensitivity or specificity in predicting difficult laryngoscopic intubation. In general, all single airway predictors share a common set of characteristics: low sensitivity, high specificity, and low positive predictive value. The combination of several airway predictors tends to improve the positive predictive value for difficult laryngoscopic intubation.

With reference to the airway examination presented in Section 30.1 earlier, it is apparent that this patient has several predictors of a difficult laryngoscopic intubation: borderline mouth opening, a reduced thyromental distance, and a Mallampati III classification. In combination, these characteristics place this patient at a moderately high risk for difficult laryngoscopy. However, alternative intubation devices, such as the intubating LMA (ILMA) or lighted stylet should be successful, and with adequate control of secretions, so should flexible or rigid fiberoptic devices or videolaryngoscopes. Bag-mask-ventilation if needed should be possible, although not optimal. Should extraglottic device placement and use be required, decreased pulmonary compliance due to ARDS may present a problem with pop-off leak developing at higher airway pressures: availability of an LMA Pro-Seal or LMA Supreme might be advisable. Cricothyrotomy should be possible. Note that although some of these techniques are not desirable in the patient with SARS, their predicted success must still be assessed, particularly in the patient with predictors of difficulty.

30.4.2 What Do You Do Differently When Establishing an Airway in a SARS Patient?

A SARS patient poses a unique risk to health care workers due to its highly infectious nature and a high mortality rate for those infected. In developed countries such as Canada and Singapore, approximately 50% of SARS cases were health care workers involved in caring for SARS patients. The processes of tracheal intubation, bag-mask-ventilation, and suctioning were associated with the highest risk of acquiring SARS.8-10 A cluster of nine health care workers who cared for a single SARS patient around the time of intubation in the ICU themselves developed SARS.16

In order to minimize the risk of SARS cross-transmission to health care workers, guidelines have been developed to reduce the risk of aerosolization of SARS droplets during the process of intubation.3,17,18 It is critical that the health care worker apply and remove personal protection equipment (see Section 30.5.5) prior to and after intubation. In addition, bag-mask-ventilation, nebulization, and application of topical airway anesthesia are to be avoided. The patient should thus be sedated and paralyzed unless contraindicated. However, if a high potential for difficult laryngoscopy exists, there may be a conflict of priorities.

30.4.3 How Are You Going to Approach This Patient's Airway?

This patient's situation presents us with a real dilemma. On the one hand, an awake intubation following application of topical airway anesthesia is generally considered to be the safest method of securing the airway in the patient presenting with potential difficult laryngoscopic intubation. On the other hand, to minimize the risk to health care personnel of SARS transmission, avoiding BMV is preferred, and paralysis of the patient will help avoid the potential for coughing. Protecting the patient and the health care worker are both important priorities.

Ultimately the method chosen for intubation is determined by how likely one is to encounter a failed airway situation (see Chapter 2). The possibility for such a situation will become evident as the patient is assessed for predictors of difficulty in all aspects of airway management. If the patient presents with evidence that airway control will be difficult using various techniques of endotracheal tube placement, bag-mask-ventilation, an extraglottic device, or cricothyrotomy, the practitioner should accept the risk of disease transmission and perform an awake intubation. However, in this case, as outlined in Section 30.4.1 earlier, the patient presents predictors of only moderate difficulty with laryngoscopy and no predictors of difficulty with alternative intubation (eg, ILMA, lighted stylet, flexible bronchoscope) equipment use. Bag-mask and extraglottic device ventilation, if needed, will most likely be successful in spite of reduced pulmonary compliance. Cricothyrotomy should pose few problems.

Thus, a reasonable Plan A approach in this patient is to attempt tracheal intubation by direct laryngoscopy after induction using short-acting anesthetic and paralytic agents. The intubation should be undertaken by an experienced airway practitioner, wearing full protection, and with a full complement of alternative intubating devices. In addition, an extraglottic rescue device and cricothyrotomy equipment should be readily available in the room.

If direct laryngoscopy fails after one or two attempts, and oxygenation remains acceptable, Plan B calls for an alternative device to be used, in this case a video laryngoscope (eg, Glidescope) or a flexible bronchoscope. If intubation is not successful after three attempts, the patient should be awakened with the intention of proceeding with an awake intubation. If at any time between attempts oxygenation cannot be maintained with bag-mask-ventilation, Plan C calls for the immediate use of an EGD, such as an LMA ProSeal or LMA Fastrach™, while concurrently preparing to perform a cricothyrotomy in this cannot intubate cannot oxygenate situation.

30.5.1 Where in the ICU Should the Patient Be Placed?

In order to minimize the spread of SARS virus, the patient should be placed in an isolation room, equipped with negative pressure ventilation.3,17,18 The room should have a preentry room (anteroom) to allow application and removal of personal protection equipment.

30.5.2 Who Should Perform and Who Should Assist with Tracheal Intubation?

Only those persons required to carry out the intubation should be permitted in the immediate vicinity of the patient. This team may consist of an experienced airway practitioner, respiratory therapist, and an ICU nurse. Students should be excluded. Additional personnel should stand by outside the room in the event that help or equipment is required during the airway management procedure. In this situation, this may include another individual with airway management expertise.

It is critically important that all team members are aware of Plan A, Plan B, and Plan C and have had the chance to rehearse the sequence of events prior to securing the airway.

30.5.3 What Airway Equipment Should Be Available in the Patient's Room?

• General equipment: The room should contain a ventilator with hydrophobic filters (eg, PALL®) on the inspiratory and expiratory limbs, suction, capnography, oximetry, ventilation bag with expiratory filter, and oropharyngeal airway.3
• Plan A equipment: A laryngoscope handle, an appropriately sized curved and straight blade, a tracheal tube introducer (eg, Eschmann introducer), several sizes of endotracheal tubes, and endotracheal tube stylets.
• Alternative (Plan B) rescue airway equipment: The LMA, and at least two alternative intubation devices such as a flexible bronchoscope, lighted stylet, intubating laryngeal mask, or video laryngoscope, such as the Glidescope®.
• Plan C equipment: The equipment necessary to perform a surgical airway, as Plan C stipulates, ought to be immediately available and open.

30.5.4 What Other Equipment Is Considered Essential?

Two functioning intravenous lines should be placed. Induction and emergency drugs should be prepared. Induction drugs consist of midazolam, fentanyl, propofol, succinylcholine, and a nondepolarizing muscle relaxant. Emergency drugs consist of atropine, ephedrine, phenylephrine, and epinephrine.

30.5.5 How Should Health Care Workers Dress in Order to Minimize SARS Transmission?

All health care workers in direct contact with SARS patients should be wearing basic personal protection equipment (PPE). Enhanced PPE should be worn by all health care workers involved in high-risk procedures such as intubation3,18 (Table 30-2).

Basic personal protection strategy consists of airborne precautions, contact precautions, and eye protection.

30.5.5.1 Basic PPE: Airborne Precautions

An N-95 mask or equivalent is used for airborne precaution. N-95 masks offer 8 hours of protection while PCM-2000 masks provide 4 hours. Touching the mask or lifting the mask to wipe the face with gloved fingers immediately contaminates the mask and it must be replaced. It is crucial that all staff who may be involved in the care of such patients be tested and trained for proper mask fitting well before they are needed. An improper mask fit may not provide airborne protection. A properly fitted N-95 mask can be a very uncomfortable experience for users who may need to wear them for a prolonged period of time.

30.5.5.2 Basic PPE: Contact and Eye Precautions

Contact precautions include double gloves, double gown, disposable hats, and shoe covers.3 Following contact with each patient and removing gloves, an alcohol-based skin disinfectant should be used to wash hands. Eyes should be protected against contamination using disposable goggles or face shields.

30.5.5.3 Enhanced PPE

Enhanced PPE consists of basic PPE plus powered air purification respirator (PAPR) systems.18 They should be worn by all health care workers involved in high-risk procedures for these patients. One example of a commonly used PAPR system is the Air-Mate® (3M, St. Paul, MN). The Air-Mate® PAPR system consists of a belt-mounted powered air purifier (Figure 30-1, right) with a HEPA filter, connected via a tube to a light-weight head-piece (Figure 30-1, left). The HEPA filter removes particles of 0.3 to 15 μm with an efficiency of 98% to 100%.5 Experience of several years' duration using the PAPR system in the bronchoscopy suite has revealed no documented disease transmission to health care workers. Chee et al reported their experience in Singapore among health care workers caring for SARS patients undergoing 41 surgical procedures.19 With rigid adherence to basic and enhanced PPE, none of 124 health care workers directly exposed to SARS patients was infected.

It takes time to properly set up the room and apply PPE.18 Therefore, it is crucial to be advised well in advance of patients requiring tracheal intubation. Furthermore, staff involved in the intubation must be trained and familiar with the personal protection equipment so that it can be applied properly and expeditiously, and removed properly to avoid contamination.

30.5.6 What Conditions Must Be Satisfied before Proceeding with Intubation?

Just before performing intubation, a checklist should be completed and Plans A, B, and C rehearsed so that all parties involved are absolutely clear as to each person's responsibilities and course of action until the airway is secured (Table 30-2).

The ventilator, monitors, airway equipment, suction, intravenous access, induction, and emergency drugs should be in the room. All equipment for Plans A, B, and C should be ready. The primary intubation team members apply basic and enhanced PPE including PAPR system and enter the patient's room. A second, parallel team is dressed and ready to enter the room if needed. A practitioner experienced in securing a surgical airway should be part of the second team on standby.

30.6.1 Describe the Actual Steps of Tracheal Intubation in This Patient

The patient was denitrogenated while spontaneously breathing with FiO2 of 1.0 for 5 minutes. At no time was positive pressure ventilation applied prior to intubation. Topicalization of the airway and nebulization of drugs were likewise avoided. The ventilator was set on volume control mode.

Once the patient was adequately denitrogenated, fentanyl 50 μg and midazolam 1 mg were given intravenously. A sleep dose of propofol was given followed by succinylcholine 1.5 mg·kg−1.

After the patient was anesthetized and paralyzed, laryngoscopy was attempted with a MAC 3 blade. A Grade 3 laryngeal view was observed despite external laryngeal pressure and a head lift. The decision was made not to attempt blind intubation with direct laryngoscopy. Flexible bronchoscope-guided intubation was elected as the next option.

A propofol infusion was administered using a syringe pump at 100 μg·kg−1·min−1. Additional succinylcholine of 40 mg was given. The patient's vital signs were stable with a SpO2 of 100%. Gentle tongue traction was performed by an ICU nurse. A 5.1 mm OD fiberscope was introduced orally and guided successfully through the larynx into the trachea under indirect visualization. A 7.5 mm ID endotracheal tube was advanced easily over the bronchoscope into the trachea. The endotracheal tube was positioned 3 cm above the carina and taped 22 cm at the teeth. The endotracheal tube pilot balloon was inflated and a ventilation bag was used to ventilate the patient. A colorimetric CO2 indicator further confirmed endotracheal placement of endotracheal tube.

30.7.1 Outline Your Postintubation Management

The patient's endotracheal tube was connected to the ventilator, and mechanical ventilation in a volume-control mode was begun.20 As the patient's blood pressure and heart rate remained stable, the infusion of propofol was continued for patient sedation.

The airway management team proceeded to remove their PPE. Utmost care was taken to remove the gloves, gown, PAPR head gear, goggles, cap, and shoe covers in the proper sequence so that the health care workers' bodies were not contaminated.3 Disposable equipment was discarded while reusable equipment such as the PAPR head gear was carefully wiped down using a disinfectant agent (eg, Virox®).

Any health care workers who participated in the care of the SARS patient were advised to be on high alert for the subsequent development of any symptoms or signs of SARS.21

30.7.2 Would Precautions for Other Airborne Pathogens Differ in Any Way from SARS Patients?

In general, HCW at risk of coming in contact with respiratory secretions from patients with febrile respiratory illness of unknown etiology should wear personal protection equipment including gloves, goggle, gown, and N-95 face mask.

As indicated earlier, the influenza A H1N1 virus (also known as swine flu) caused a worldwide pandemic with over 375,000 confirmed cases and over 4500 deaths in 2009.21 The case-fatality ratio is significantly lower than SARS. Because it is a new virus, people have no immunity and can be infected upon exposure. The spectrum of clinical manifestation includes fever, cough, sore throat, malaise, myalgia, headache, and, occasionally, gastrointestinal symptoms. Fortunately, most patients diagnosed with H1N1 run a benign course, and rarely present with a severe pneumonia/ARDS picture.

The WHO recommends the following infection control measures1:

1. Before any contact with a patient with suspected H1N1 infection, basic PPE including surgical face mask gloves, goggle, and gown should be used.

2. For high-risk aerosol-generating procedures such as intubation or bronchoscopy, in addition to basic PPE, a N-95 face mask should be used.

Two antiviral drugs for influenza, oseltamivir and zanamivir, are available for treatment of pandemic influenza. Their efficacy in H1N1 infections is unknown as there are insufficient clinical data. An H1N1 vaccine has recently become available.

In summary, the SARS epidemic and the recent H1N1 pandemic illustrate the rapidity and severity with which a new virus can strike worldwide. A global surveillance system for new infections and a national coordinated response must be in place should future viral infection alerts occur. There is a need in our health care system for emphasis on and compliance with ordinary infection-control measures such as hand washing, and the use of gloves, masks, and eye protection. Health care workers should be familiar, and hospitals must be equipped, with enhanced personal protection equipment should the need arise to care for suspected SARS patients. In order to minimize the risk of contamination and SARS transmission, they should be aware of the modifications of techniques for intubation. Much of what we have learned from the SARS epidemic can be used to improve our management of patients affected by viral or infectious outbreaks in the future.