The time-honored statement that "an ounce of prevention is worth a pound of cure" is essential to remember2 when considering the management of adverse outcomes in regional anesthesia practice. It is most effective to prevent and minimize the risk of regional anesthesia complications. Neurologic injury is one of the most dreaded complications associated with all anesthesia techniques, including regional anesthesia, and it is important to realize that once a serious neurologic injury occurs, the chances of full recovery are unlikely.
Safe regional anesthesia begins with the first encounter with the patient. The first task at hand is to perform a thorough preoperative assessment of the patient. Good outcomes are obtained when a skilled anesthesiologist uses appropriate equipment and technique and sound judgment. Skilled intraoperative sedation and monitoring are vital to the practice of regional anesthesia. To this end, we advocate for specialized regional anesthesia areas in the operating room space where the appropriate equipment, monitoring, and assistance are readily available. Resuscitation drugs and equipment must always be immediately available in the event of a problem, and one must always be ready to convert to general anesthesia if required. Patients must be carefully observed during the postoperative period by appropriately trained postanesthetic care team when most of the serious complications become evident. Early identification and intervention are of the utmost importance in preventing neurologic injury.
Poor outcomes and serious complications are not prima facie evidence of negligence. However, the risk of litigation in contemporary anesthesia practice is closely associated with the severity of patient injury rather than the occurrence of negligence; this is particularly true of regional anesthesia injuries. The American Society of Anesthesiologists (ASA) Closed Claims study in the United States reported a high incidence of successful suits against anesthesiologists involved in regional anesthesia cases, even though the standard of care was met.3 The importance of effective communication and truthful disclosure with the patient and the patient's family cannot be overemphasized. Litigation is more frequent with the combination of an adverse event and a poor physician–patient relationship. A patient who feels that the physician has the patient's best interests at heart is less likely to pursue litigation than is a patient who does not respect or trust the physician; thus the anesthesiologist should pay particular attention to developing a good rapport with the patient in the limited time allotted. Table 50-1 summarizes basic recommendations for maintaining a standard of care in regional anesthesia practice. Maintaining a standard of care at all times does not guarantee against legal action, but it certainly will minimize the risk and is to be encouraged at all times.4
Table 50-1 Maintaining a Standard of Care during Regional Anesthetic Practice ||Download (.pdf)
Table 50-1 Maintaining a Standard of Care during Regional Anesthetic Practice
Preoperative patient selection
Appropriate use of equipment and technique
Monitoring regional anesthesia practice
Accurate and meticulous anesthesia documentation
Appropriate and timely postoperative follow-up
Proper patient selection is a critical consideration for the safe and successful performance of regional anesthesia, as not all patients are suitable candidates for regional anesthesia (Fig. 50-1).5 Some patients are not psychologically suitable for regional anesthesia. A number of patients suffer from needle phobias and faint at the least provocation. In general, patients with severe mental illness are not suitable candidates for regional anesthesia unless it is combined with general anesthesia. Gross anatomic distortion may hinder the performance of regional anesthesia in some patients. Neuraxial techniques may be associated with hemodynamic disturbances such as bradycardia and hypotension; therefore, they are contraindicated in hemodynamically unstable patients and in those with fixed cardiac outputs. Regional anesthesia should be used cautiously in patients with preexisting neurologic disease, and if regional techniques are used in these patients, neurologic deficits must be clearly documented before the performance of regional anesthesia. Some patients are rigidly opposed to regional anesthesia, and it is important not to sell them on it. If it is clearly evident that a patient will benefit from regional anesthesia, it is reasonable to explain in detail the rationale behind the procedure; however, the decision to undergo regional anesthesia must be finally left to the discretion of the patient. It is very important to discuss the options of anesthesia with patients even if they are undergoing minor operative procedures. It is imperative to follow national and international guidelines pertaining to regional anesthesia practice (eg, ASA monitoring, American Society of Regional Anesthesia and Pain Medicine [ASRA] guidelines for anticoagulated patients, etc.), and if there is any deviation, it is important to specify the reasons and to document them. Table 50-2 summarizes the important factors involved in selecting suitable patients for regional anesthesia.
Patient selection factors for the prevention of complications of regional anesthesia techniques.
Table 50-2 Patient Selection Factors ||Download (.pdf)
Table 50-2 Patient Selection Factors
|Factors Involved in Patient Selection||Relative Contraindications||Absolute Contraindications|
|Patient cooperation||Anxiety states; needle phobias; poorly controlled psychiatric disease; language barriers; pediatric patients||Patient refusal|
|Anatomic and physiologic considerations||Anatomical anomalies; technical challenges: obesity, severe arthritis, degenerative joint disease|
|Anesthetic considerations||Lack of experience and skills; lack of appropriate equipment for performing the block (eg, nerve stimulator, ultrasonogram); lack of appropriate equipment for resuscitation and monitoring (eg, oxygen, mask, drugs)|
|Coexisting diseases||Preexisting progressive neurologic disease; comatose states; sepsis; coagulopathy||Infection at the site of injection; allergy to local anesthetics; coagulopathy (although an international normalized ratio [INR] of <2 is acceptable for ophthalmic procedures)|
|Surgical procedures||Lengthy procedures that outlast the duration of action of the local anesthetic (single-injection techniques; uncomfortable positioning for an extended period of time)|
Informed consent and an explanation of the risks and alternatives to regional anesthesia must be provided to the patient (the anesthesiologist should never coerce a patient to accept or reject any anesthetic plan). Potentially serious complications associated with regional anesthesia should be disclosed to patients, including convulsions and the risk of cardiac toxicity from systemic injections of local anesthetics, spinal cord/nerve injury leading to paralysis or neurologic deficit, pneumothorax, hematoma, infection, cardiac arrest, and death. Interestingly, a recent study revealed that fewer than half of anesthetists disclose the risks of seizures, respiratory failure, and cardiac arrest before the administration of either neuraxial blocks or peripheral nerve blocks.6 Any common side effects specific to certain procedures such as the failure to achieve surgical anesthesia, patient awareness during conscious sedation, nausea, pruritus, headache, shivering, backache, dizziness, and urinary retention should also be discussed. However, anesthesiologists should bear in mind that even with informed consent, proper disclosure, effective communication, and an appropriate ethical approach, there is no guarantee that they will be legally protected.7
Use of Appropriate Equipment and Technique
As advances in regional anesthesia continue, techniques used must be continuously revised in light of any new, clinically relevant information and developments. For years, we have been percutaneously inserting needles toward neural targets and have relied solely on our knowledge of anatomy and techniques of paresthesia and the loss of resistance (LOR). The introduction of nerve stimulation was an important advance in regional anesthesia because it provided some objective evidence that the needle tip was close to the neural target. One of the most exciting recent advances has been the introduction of ultrasonography as a method to accurately place needles in close proximity to neural targets. Ultrasonography allows real-time visualization of anatomical structures and offers the potential to guide needle and catheter placement in regional anesthesia. This section highlights recent advances in nerve stimulation and ultrasonography that may play an important role in preventing complications during regional anesthesia practice.
Nerve Stimulation in Regional Anesthesia: Peripheral Nerve Blockade
Despite years of clinical use, the electrophysiologic effect of injectates on nerve stimulation has never been fully explained. The classic unanswered question concerning electrical stimulation is why is it that one may not be able to consistently stimulate a nerve with a current of less than 0.5 mA, even after eliciting a paresthesia in that nerve? Another phenomenon that is poorly understood is the "Raj test." The Raj test is when nerve stimulation is used to locate a nerve and a twitch is observed when the needle tip is close to the neural target. Ideally, the twitch is required to persist at a current of 0.5 mA. The clinician then injects a small volume of local anesthetic or normal saline through the needle. If the needle tip is in the correct location, the muscle twitch disappears immediately.8 Until very recently, the disappearance of the twitch was thought to be caused by physical displacement of the nerve by the injectate.9 We recently learned that this mechanism is best explained in electrical terms and is not entirely a result of the physical displacement of the nerve.10 In a porcine model, the injection of 0.9% sodium chloride solution (NaCl) abolished the motor response, and a subsequent injection of 5% dextrose reestablished a motor response during peripheral nerve stimulation.10 Simulation and in vitro experiments show that injections of 0.9% NaCl and 5% dextrose alter the electrical field in different ways.11 It was concluded that the injection of electrically conducting solutions (saline or local anesthetic) increases the conductive area surrounding the stimulating needle tip, leading to a decrease in the current density surrounding the target nerve (Fig. 50-2). The current density surrounding the needle tip is then no longer sufficient to stimulate the desired nerve.10 This observation suggests that effective nerve stimulation is sensitive to changes that occur at the needle–tissue interface, such as the angle of the needle or the injection of the local anesthetic. The net effect of these changes is to alter the current density at the tip of the needle or the path of the electric current, ultimately resulting in a change in the quality of the motor response.12 This phenomenon has also been reported in a clinical setting.13,14 In a clinical study, the mean current required to stimulate the supraclavicular, axillary, femoral, and sciatic nerves when using an insulated needle was significantly higher (up to 6 times) after the injection of normal saline.15 This effect has also been verified by others in the femoral and sciatic nerves.16 The clinical implications are as follows:
- One may use a nonconducting solution, such as 5% dextrose in water (D5W), rather than saline to open up the perineural space.10
- Reports of the use of nonconducting injectates (eg, D5W) in peripheral nerve block are promising and appear to provide stability when using electrical stimulation techniques.13,14,16
- The motor response resulting from electrical stimulation is augmented after an injection of D5W in a very high percentage of cases (96%). This allows one to increase the accuracy of placement of continuous catheters.14,16
Gel electrophoresis: changes in the electrical field with uninsulated and insulated needles after 5% dextrose in water (D5W) and saline injection. Arrows show the margin of the clear zone/electric field. Far left: Diffuse electric field with an uninsulated needle; center left: narrow electric field with an uninsulated needle; center right: electric field with an insulated needle after D5W injection remains narrow; far right: diffuse electric field with an insulated needle after normal saline injection. [Adapted from Tsui BC, Wagner A, Finucane B. Electrophysiologic effect of injectates on peripheral nerve stimulation. Reg Anesth Pain Med. 2004;29(3):189-193. Copyright May 2004, with permission from American Society of Regional Anesthesia and Pain Medicine.]
Nerve Stimulation in Regional Anesthesia: Neuraxial Blockade
Epidural stimulation has been used to confirm and guide catheter placement in the epidural space. The epidural stimulation test confirms catheter placement through stimulation of the spinal nerve roots (not the spinal cord) with a low-amplitude electrical current conducted through normal saline via an electrically conducting catheter.17 Correct placement of the epidural catheter tip (1-2 cm from the nerve roots) is indicated by a motor response elicited with a current between 1 and 10 mA.17,18 There has been 1 case report of a current response indicating epidural placement with radiologic evidence of subdural placement.19 Any motor response observed with a significantly lower threshold current (<1 mA) suggests that the catheter is in the subarachnoid or subdural space or is in close proximity to a nerve root20-22; in these rare cases, a motor response is elicited with a significantly lower threshold current because the stimulating catheter may be very close (<1 cm) to the nerve roots or because it may be in direct contact with highly conductive cerebrospinal fluid (CSF) (Table 50-3).
Table 50-3 Comparison of the Standard Test Dose with the Epidural Stimulation (Tsui) Test for Confirming Epidural Catheter Location ||Download (.pdf)
Table 50-3 Comparison of the Standard Test Dose with the Epidural Stimulation (Tsui) Test for Confirming Epidural Catheter Location
|Catheter Location||Test Dose||Epidural Stimulation Test|
|Subarachnoid||Hypotension/total spinal||Positive unilateral/bilateral motor response (<1 mA)|
|Subdural||Diffuse motor response in many segments (<1 mA)|
|Epidural space close to the nerve root||Unilateral motor response (<1 mA)|
|Positive motor response (1-10 mA); threshold current increased after local anesthetic injection|
|Not intravascular||↑ Heart rate||Remain or return to baseline positive motor response (1-10 mA) even after local anesthetic injection|
|Intravascular||↑ Blood pressure||Electrocardiogram changes|
Electrical stimulation has been applied to neural structures for neurophysiologic evaluation and pain control for many years23-26 and has proven to be safe. Although no known complication or patient discomfort has resulted from the epidural stimulation test, it has been recommended to keep the current below 15 mA and the stimulation time as brief (less than a few minutes) as possible.17,18,27,28 In particular, the current output must be carefully increased from zero and stopped once motor activity is visible to ensure that all motor responses, even those elicited with a low current (<1 mA), are detected. The nerve stimulator must allow a gradual increase in current output to at least 10 mA.
Table 50-3 compares features of the epidural "test dose" (lidocaine with 1:200 000 epinephrine) and the epidural stimulation test. Epidural stimulation is a tool for clinician use that may have a significant impact on 3 of the most significant complications associated with epidural anesthesia: systemic toxicity, accidental subarachnoid or subdural injections of local anesthetics, and neural damage.
Ultrasound Imaging in Regional Anesthesia
The application of ultrasound in regional anesthesia was first published in 1989 by Ting and Sivagnanratnam.29 Since then there has been an increasing number of reports in the world literature on this exciting application in regional anesthesia. With the widespread availability of highly portable ultrasound machines, ultrasound techniques have taken hold as a mainstay in the practice of regional anesthesia.
Ultrasound-Guided Peripheral Nerve Blockade
With the use of ultrasonography, one can observe neural targets, vascular structures, the advancing needle, and the actual spread of the local anesthetic solution after the injection of the local anesthetic in real time. Brachial plexus anesthesia is one of the most challenging techniques in regional anesthesia; therefore, ultrasound has potential to improve success rates with this technique. The application of ultrasound in regional anesthesia has renewed interest in the classic supraclavicular brachial plexus block (Fig. 50-3).30,31 Advances in this technology and, more importantly, familiarity with it (via appropriate training programs)32 continue to facilitate better imaging of nerve trunks, blood vessels, pleura, and the approaching needle.33,34 The safety advantages to ultrasound have been studied with great fervor.35 It seems that ultrasound convincingly can decrease the amount of local anesthetic used, it can decrease the incidence of unintentional vascular punctures, and it can significantly decrease the number of needle passes to perform a block.36-40 One can draw all sorts of conclusions regarding the positive effects that ultrasound-guided blocks will have on patient outcomes, but this has not yet been proven.41 Ultrasonographic technology is an undeniable advance in regional anesthesia; however, it does not completely eliminate difficulty in accurately identifying structures and observing the advancing needle in detail in all cases.
Ultrasonogram of supraclavicular region. The trunks of the brachial plexus can be identified as a cluster of circles (ie, a honeycomb shape) positioned lateral and superior to the subclavian artery. If the identity of the hollow structure was in doubt, the color flow Doppler provided further verification (left bottom).
To minimize risks of regional anesthesia, potential exists to combine ultrasound and nerve stimulation techniques when performing regional anesthesia. Ultrasonography allows the clinician to see the advancing needle approaching what appears to be the target nerve or trunk. Nerve stimulation allows one to identify which nerve is being approached and, if indeed, what is being approached is a neural structure. Needle/catheter-tip visibility is enhanced using D5W as a preinjectate. Moreover, by using ultrasonography, one can observe the pattern of spread of D5W before committing to the injection of local anesthetic. Individually, ultrasonography (anatomic locating tool) and nerve stimulation techniques (physiologic response aid) have their limitations, but, when used in combination, these techniques may serve to compensate for each other's weaknesses and may facilitate optimal needle placement for peripheral nerve blocks, although this remains to be proven.35
Ultrasound Imaging for Neuraxial Blockade
Ultrasonography is useful for guiding peripheral nerve block placement in adult patients42,43; however, its application for guiding neuraxial blockade in adults and children remains limited, despite increasing interest.44
- Real-time ultrasound imaging of the lumbar spine is a simple procedure. Ultrasound aids the placement of lumbar epidural catheters and enhances the performance of combined spinal–epidural anesthesia.45,46
- Ultrasonography use improves the learning curve of obstetric lumbar epidural catheter placement for anesthesia trainees.47
- In patients with anticipated difficult epidural localization, this technology is helpful for estimating lumbar epidural depth; it also facilitates ease of placement.48,49
- Although ultrasound imaging has been used to guide lumbar epidural needle placement, it may be of limited value in the thoracic region, particularly in older children and adults, when visualization of the spinal cord and relevant structures is sought.50,51 Calcification of the posterior vertebral bodies in children older than 6 months of age prevents reliable imaging of the spinal cord.50
At the present time, ultrasonography guidance is helpful for viewing the lumbar region of selected patients, although its use for thoracic epidural placement is of value only in infants and small children, as their vertebrae are not fully ossified.
Monitoring Regional Anesthesia
We believe it is important to have an assistant observe and aid the patient at all times during the performance of regional anesthesia. As many as 15% of patients have a fear of needles and vasovagal episodes occur when performing regional anesthesia.52
- Standard electrocardiogram and pulse oximetry are essential monitors while performing regional anesthesia.
- Before performing the neural block, a baseline blood pressure reading should be obtained. Once the regional anesthesia procedure is complete, the monitors should remain attached. In conscious patients, end-tidal carbon dioxide monitoring is not used; however, there are special nasal prongs available for monitoring spontaneously ventilating patients.
- Evidence of regressing sensory and motor blockade and stable vital signs must be present to fulfill the criteria for discharge from the recovery area.
- Local anesthetic infusions are now routinely used in many medical centers. Patients receiving local anesthetic infusions should be visited regularly by a qualified physician postoperatively (ie, Acute Pain Service).
Accurate and meticulous recording of anesthesia information is essential for maintaining the quality of care in regional anesthesia. When determining the true nature and extent of complications, an accurately documented preoperative examination is important.
- Detailed documentation of patient consent and the clinical procedure is very important.
- Open and honest communication with the patient is essential for providing good quality patient care.
Effective communication with each patient is essential for the prevention and early diagnosis of any potential complications. Patients undergoing regional anesthesia may report anxiety, and appropriate preoperative education for the patient can help mitigate this.53 Discussing the procedures, including their benefits and any significant risks involved, is the legal and professional responsibility of all anesthesiologists. It is equally important to maintain good rapport with the patient during the postoperative period.
- A telephone call to the patient on the first postoperative day is a reasonable and practical alternative to a visit.
- Specific common risks for certain blocks should be discussed with the patient before discharge. For example, patients undergoing supraclavicular blocks should be warned about the risk of pneumothorax and be informed about potential symptoms and what to do if they develop.
- Caution patients about the risk of burns (ie, from radiators) or the consequences of applying pressure to desensitized areas when sensory anesthesia continues after discharge.
- Warn patients about lying on paralyzed extremities for any length of time or letting them become dependent.
- Patients should receive written instructions and information about when to seek medical attention before discharge from the hospital.
- As per hospital policy in local practice areas, ambulatory patients should be discharged to the care of a family member or guardian. The consequences of being left unmonitored must be made clear to patients.