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Regional Anesthesia in the Patient with Preexisting Neurologic Disease

Steven Deschner, MD

        INTRODUCTION

Patients with preexisting neurologic disease present a unique challenge to the anesthesiologist. Knowledge of the pathophysiology of the disease and the effect of anesthetic drug therapy on the disease process is essential for the safe management of anesthesia for these patients. Both active and dormant neurologic diseases may worsen in the perioperative period, independent of the chosen anesthetic method. However when regional techniques are used, the cause of postoperative neurologic deficits may be difficult to evaluate as neural injury can be related to a wide variety of reasons, ie, surgical trauma, tourniquet pressure, improper positioning, or anesthetic technique.¹ The possibility of needle-induced trauma, local anesthetic toxicity, or neural tissue ischemia or damage during regional anesthesia has led many anesthesiologists to avoid regional techniques in patients with underlying neurologic diseases.

        Many of these patients can benefit from regional techniques. Greater autonomic stability, the ability to provide selective anesthesia and analgesia, greater hemodynamic stability (especially with peripheral nerve block anesthesia in patients with concurrent cardiomyopathy), and the avoidance of side effects related to general anesthetics and opioids are a few of the advantages.^2,3 Careful preoperative neurologic evaluation, evaluation of the risk/benefit ratio, and a comprehensive discussion with the patient about the anesthetic plan and the possibility of worsening neurologic signs and symptoms unrelated to the anesthetic technique is important for successful implementation of regional techniques in this patient population.

        INCIDENCE OF NEUROLOGIC COMPLICATIONS RELATED TO REGIONAL ANESTHESIA

Although perioperative nerve injuries have been well recognized as a complication of spinal and epidural anesthesia, severe or disabling neurologic complications occur relatively rarely. In 1999, Cheney and colleagues examined the American Society of Anesthesiologists Closed Claims database to determine what percentage of the claims were related to nerve damage in malpractice cases.⁴ Of the 4183 claims reviewed, 670 (16%) were anesthesia-related nerve injuries. Ulnar neuropathies were the most frequently reported, followed by other injuries to the brachial plexus, lumbosacral nerve roots, and spinal cord. The injuries were bilateral in 14% of the ulnar injuries and in 12% of the brachial plexus injuries. The important factor in this analysis is that the incidence of ulnar and brachial plexus injuries was greater with general anesthesia than with regional anesthesia.^5,6 Horlocker and coworkers examined the cause of perioperative nerve injury in a review of 607 patients undergoing 1614 axillary blocks for upper extremity surgery. Various surgical variables (direct trauma, stretch, hematoma, vascular compromise, case or tourniquet ischemia) were thought to be the cause of neurologic complications in the majority of the cases (89%).⁷

        In the Closed Claims Analysis 189 (4%) involved either the lumbosacral root or the spinal cord. Injuries to these areas were more frequently associated with regional anesthesia. The lumbosacral root injuries were thought to be related to paresthesias during needle or catheter placement or pain on injection of local anesthetic. The spinal cord injuries were related to blocks for chronic pain or neuraxial blocks on patients receiving systemic anticoagulation. These injuries were not related to the presence of preexisting neurologic disease. In another review of over 50,000 spinal and epidural anesthetics, the incidence of persistent peripheral neuropathy, including paresthesia and sensory or motor dysfunction ranged from 0% to 0.16% for spinal anesthetics and 0% to 0.06% for epidural anesthetics, still appreciably lower than the incidence of nerve injuries reported with general anesthetic cases.^8–11

        Although the reported incidence of nerve injuries with regional anesthesia is very low, the use of regional techniques in patients with preexisting neuropathies is often considered controversial. The possibility of needle- or catheter-induced nerve trauma, neural ischemia, or local anesthetic toxicity placing the patient with an underlying neurologic deficit at greater risk has limited the use of regional techniques in this patient population. In a retrospective study of over 300 patients with preexisting ulnar neuropathy undergoing ulnar nerve transposition, it was demonstrated that anesthetic technique did not affect neurologic outcome in the immediate postoperative period or up to 6 weeks after surgery.⁶ The authors did not find any evidence that the use of a peripheral nerve block increased the risk of new or worsening neurologic symptoms in patients with preexisting ulnar nerve neuropathy. They concluded that regional anesthesia is as safe as general anesthesia in these patients with mononeuropathy.

        In patients with other serious neurologic diseases, regional anesthesia is often avoided for a variety of reasons, including lack of understanding of the disease process, the risk of unknown or unpredicted effects of local anesthetics in abnormal nervous tissue, concerns regarding possibly worsening preexisting symptoms, limited experience using regional techniques, and limited data to support its utilization.

        The following paragraphs discuss many of the neurologic conditions the anesthesiologist may encounter. The approach to the management of anesthesia is included with a discussion of various regional techniques that can be safely used in these patients. When information in the literature is sparse, suggestions for anesthetic techniques are included based on available neurologic research, case reports, and experience of clinicians in institutions performing large volume regional anesthesia techniques.

        CENTRAL NERVOUS SYSTEM DISEASE

Degenerative Diseases

Parkinson’s Disease

Parkinsons disease is a disabling neurologic disease affecting 3% of the population older than age 65 years. The peak onset is in the sixth decade, but the disease can begin to manifest from age 20 to age 80 with the male to female ratio of 3:2. Parkinson’s disease is caused by loss of dopamine-containing nerve cells in the substantia nigra.¹³ The presence of Lewy bodies, eosinophilic cytoplasmic inclusions in pigmented neurons, are a characteristic feature. The cause of the disease is unknown although multiple theories have been proposed, including a defect in the gene for a-synuclein, mitochondrial dysfunction, excitotoxicity secondary to persistent activation of iV-methyl-D-aspartate (NMDA) receptors, and oxidative stress secondary to catabolism of dopamine.^12,13

        Four clinical features are characteristic of Parkinson’s disease: rigidity “cogwheel,” bradykinesia, resting tremor, and postural instability.

        These patients may have depression and dysautonomia. Patients with Parkinson’s disease may suffer from orthostatic hypotension and urinary dysfunction. Clinical assessment should include an evaluation of these systems to identify potential problems. Measurements of blood pressure in the lying and standing position should be obtained to assess the degree of autonomic dysfunction as evidenced by orthostatic hypotension.

        Treatment is directed at increasing dopamine levels in the brain.¹² The mainstay of treatment is levodopa or dopamine receptor agonists. Monoamine oxide inhibitors are used to prolong the action of dopamine in the striatum. Catechol-O-methyl transferase (COMT) inhibitors are used to inhibit the breakdown of dopamine in the periphery and increase its bioavailability. Anticholinergics are effective in treating tremor, but because of many side effects (worsening dementia, psychosis, dry mouth, constipation), they are reserved for younger patients in the early phase of disease.

Anesthetic Considerations

Patients with Parkinson disease most commonly present for urologie, ophthalmologic, or orthopedic procedures. In addition to the routine history, physical examination, and preoperative testing, assessment of systems specifically affected by Parkinson disease should be evaluated. See Table 59-1 for specific systems affected.

Regional Anesthesia in Parkinson’s Disease

Autonomic dysfunction is exacerbated by inhalational anesthetics, resulting in more hemodynamic instability.¹⁴ Halothane, although less commonly used today, sensitizes the heart to catecholamines and should be avoided in patients on levodopa.¹⁴ Isoflurane and sevoflurane are less arrhythmo- genic; however, hypotension from catecholamine depletion, autonomic dysfunction, and the coadministration of other medications remains a concern.¹⁴ Muscle relaxants and positive pressure ventilation can lead to prolonged postoperative ventilatory support in a patient with respiratory impairment, common in the Parkinson patient.¹⁵ There are numerous reports of opioid-induced muscle rigidity in patients with an established diagnosis of Parkinson’s disease.¹⁵ Postoperative nausea and vomiting related to opioids, reversal agents, and inhalation anesthetics may be more common.¹⁷ Patients with Parkinson’s disease are more prone to postoperative confusion and hallucinations.¹⁷

        Regional anesthesia may have advantages over general anesthesia as the effects of inhalation anesthetics, muscle relaxants, high-dose opioids, and anesthetic medications that may exacerbate the symptoms of Parkinson’s disease are eliminated. By utilizing peripheral nerve block anesthesia or appropriate segmental epidural anesthesia with limited sedation, the autonomic instability can be controlled, the incidence of nausea and vomiting limited, and muscle rigidity resulting from doses of narcotics used for general anesthesia can be avoided. Careful titration of sedation with limited use of opioids is suggested in this patient population.

Alzheimer’s Disease

Alzheimer’s disease is the major cause of dementia in the United States.¹⁶ If affects 10% of people older than age 65 with the female to male ratio of 2:1. Risk factors include female sex, advanced age, family history, Down syndrome, and African American or Hispanic descent. Patients with a history of brain trauma may have an increased risk of developing the disease.¹⁶

        The cause is unknown. Pathologic changes in the brain include the accumulation of tau protein with formation of neurofibrillary tangles, deposition of β-amyloid with formation of neuritic plaques, and selective loss of cholinergic neurons, leading to cortical atrophy. It is theorized that these changes may arise as a result of excitotoxicity involving the NMDA receptor. Current drug therapy is directed at increasing the levels of acetylcholine, cholinesterase inhibition, cholinergic receptor stimulation, and blocking NMDA receptors with the intent of reducing excitotoxicity.¹⁶

        The clinical features of the patient with Alzheimer’s disease are a gradual decline of intellectual function, progressive loss of short-term memory, disorientation, language and speech problems, and seizures in 10% of the patients. Paranoid delusions with hallucinations and personality changes are common.¹⁶

Anesthetic Considerations

The choice of anesthetic technique for patients with Alzheimer’s disease should be guided by the patient’s general physiologic condition, the degree of neurologic deterioration, and the potential for drug interactions between the anesthetics and the patient’s treatment. Detection of early symptoms may be difficult. Administration of sedatives or anticholinergics could precipitate delirium. Inhalation agents must be administered with care as the elderly patient is more sensitive to the depressant cerebral and cardiovascular effects of these agents.¹⁷ Anesthetics with short durations of action and rapid recovery are advantageous.

Regional Anesthesia in Alzheimer Disease

Regional anesthesia can be a challenge because these patients are often uncooperative preoperatively. The advantage of regional techniques is the ability to selectively anesthetize the area of interest without subjecting the patient to systemic effects of general anesthetic agents. For block placement, a short-acting sedative/hypnotic, such as propofol or midazolam, at a low dose is effective. Depending on the type of block, a short-acting narcotic (eg, alfentanil) may be administered just before the block placement. Avoiding postoperative confusion and delirium caused by inhalation agents, narcotics, muscle relaxants, and reversal agents may be beneficial to this patient population.¹⁷ Postoperative pain control without narcotics may be an even greater benefit of peripheral nerve blocks. Educating the staff and the caregivers about protection of the insensate extremity, requiring assistance with mobilization, and the duration of the block is a necessary part of the anesthetic management. Although these patients can be challenging to treat without general anesthesia, they can benefit from regional techniques.

Amyotrophic Lateral Sclerosis (Lou Gehrig Disease)

Amyotrophic lateral sclerosis (ALS) is a progressive degenerative disease of motor cells throughout the central nervous system (CNS). It involves destruction of cortical, brainstem, and spinal motor neurons. Progression of the disease is relentless. Death occurs within 3 to 5 years of the diagnosis, most commonly precipitated by aspiration. The onset is usually after the age of 50 with a male to female ration of 2:1. The cause is unknown, but theories include glutamate excitotoxicity, oxidative stress, mitochondrial dysfunction, paraneoplastic tumors, autoimmune disease, and viral infection.¹⁸ The prevalence of the disease is 6:100,000, making it a rare but profound disease.

        Initially, the disease presents as atrophy, weakness, and fasciculations in the intrinsic hand muscles. As the disease progresses, atrophy and weakness develop in all skeletal muscles including those of the tongue, pharynx, larynx, and respiratory muscles of the chest. Patients lose the ability to cough, increasing the risk of aspiration. Eventually, respiratory failure ensues, requiring mechanical ventilation. Autonomic dysfunction may be evident and is manifested by orthostatic hypotension and an increased resting heart rate. The cause of death is usually related to respiratory failure.¹⁸

Anesthetic Considerations

Patients with ALS present a challenge to the anesthesiologist. Neuromuscular transmission is markedly abnormal leading to the up-regulation of nicotinic acetylcholine receptors (nAChRs).¹⁹ The up-regulation makes these patients vulnerable to hyperkalemia in response to succinylcholine.²⁰ They have presynaptic impairment of neuromuscular transmission, making them hypersensitive to nondepolarizing muscle relaxants.²¹ If general anesthesia is used, intubation with a deep inhalation agent without the administration of muscle relaxants is recommended.²² As the disease progresses, respiratory muscles weaken, placing these patients at high risk for respiratory depression and aspiration. They can be exquisitely sensitive to sedatives and anesthetic drugs. Postoperative ventilatory support after general anesthesia is usually necessary.²³

Regional Anesthesia in ALS

Regional anesthesia has been used on patients with ALS. There have been several case reports of successful epidural anesthesia for abdominal surgeries, ie, hysterectomy, bowel obstruction, and orthopedic procedures.^24–26 Case studies and reports of the use of peripheral nerve blocks in patients with ALS are not available, probably because the condition is so rare. Given the importance of preserving the laryngeal reflexes and respiratory failure due to the weakness of the respiratory muscles, the judicious use of selective peripheral nerve blocks may be beneficial for these patients. In patients with advanced weakness of the respiratory muscles, interscalene nerve block should be used with caution due to the resultant diaphragmatic paralysis.

Spinal Cord Injury

Spinal cord injury after trauma affects over 10,000 Americans each year. Of these, approximately one half occur at the cervical level. Complete neurologic deficit occurs in about 3500 patients per year, and partial deficits in another 4500 patients per year.²⁷ The majority of the injuries are secondary to blunt trauma, with a smaller percentage the result of penetrating injuries. Advances in the care of patients with acute spinal cord injury have reduced the mortality rate to less than 7% per year.²⁸

        The clinical presentation varies depending on the chronicity, the magnitude, and the level of the injury. Acutely, the patient appears flaccid with spinal shock. Hypotension, bradycardia, dysrhythmias, hypoxemia, and alveolar hypoventilation are common presenting symptoms. There is high risk of aspiration. When the injury becomes chronic, as manifested by the return of spinal reflexes, multiple complications arise including involuntary skeletal muscle spasms, overactivity of the sympathetic nervous system, chronic respiratory and genitourinary infections, altered thermoregulation, and pain.²⁹

        A major problem that appears after the resolution of spinal shock is autonomic dysreflexia. It is a life-threatening syndrome resulting from cutaneous or visceral stimulation below the level of the spinal cord injury and leading to extreme vascular instability. The syndrome has been shown to develop if the level of injury is at T7 or above, although some cases have been reported in patients with lesions below T7.¹¹ The trigger for the syndrome is a cutaneous, proprioceptive, or visceral stimulus below the level of the spinal cord injury lesion, ie, a full bladder or bowel. Activation of sympathetic nerves cause vasoconstriction and subsequent hypertension. The increase in the blood pressure is sensed in the aortic bodies and carotid sinus, resulting in vagal hyperactivity. Exaggerated vagal stimulation causes bradycardia, heart block, and ventricular dysrhythmias. Reflex vasodilation can be observed above the level of the lesion causing flushing in the head and neck. Hypertension can be so severe that subarachnoid hemorrhage, seizures, and acute left ventricular failure can occur.²⁹ In the obstetric patient, it can result in significant maternal-fetal morbidity including hypertensive encephalopathy, stroke, intraventricular hemorrhage, and death. It may occur in up to 85% of pregnant women with spinal cord lesions at or above T6 to T7.³¹

        Other abnormalities occur with spinal cord injury. Retention of urine and feces are common. Abdominal distension can be severe enough to impair respiration. Acute spinal cord injury is associated with the highest risk of venous thromboembolism among all hospital admissions. If there is no DVT prophylaxis or the patient is noncompliant with prophylactic therapy, DVTs will occur in more than half (40-100%) of the patients within the first 3 months after injury.³²

Anesthetic Considerations

The care of the patient with spinal cord injury depends on the timing, the location, and any associated injuries the patient may have. In the acute phase, the spinal cord is vulnerable to secondary injury from hypotension and hypoxia. Thermoregulation is impaired. Prompt recognition and treatment with early intubation and oxygenation, vasopressor therapy, and warming measures is indicated. During the acute phase, well-controlled general anesthesia is usually the best option as an anesthetic plan if there is any indication of respiratory compromise. Because of the high risk of deep venous thrombosis in the acute injury phase, most patients will be on prophylactic medication, either low-molecular-weight heparin or unfractionated heparin subcutaneously, which serves as a potential contraindication to neuraxial anesthesia. Most urgent orthopedic trauma cases are often performed under general anesthesia because the majority of these patients are already intubated, the mental status is altered by the trauma, or multiple procedures are going to be performed at one time involving multiple areas of the body. The use of succinly- choline should be avoided after the first 24 h of injury to avoid the massive hyperkalemic response that has been well documented.³³

        Patients with either quadriplegia or paraplegia may be hemodynamically unstable acutely as a result of initial spinal shock or occult injury. Computed tomographic scans, radiographs, and laboratory studies should be reviewed prior to surgery and blood samples drawn for either type and screen or type and cross match. Invasive monitoring, such as arterial lines, may be necessary to manage blood pressure changes. Vasopressors may be necessary to stabilize the blood pressure. Complicating the hemodynamic picture at this time with neuraxial anesthesia may not be the best option.

Regional Anesthesia in Patients with Spinal Cord Injuries

Regional anesthesia techniques can be a valuable tool in the treatment of patients with chronic spinal cord injury. Central neuraxial anesthesia has been used successfully for extracor- poreal shockwave lithotripsy, for gynecologic procedures to prevent autonomic hyperreflexia, and in obstetrics for labor and delivery.^34–36 Peripheral nerve blocks have been used successfully to facilitate lithotomy positioning required for gynecologic or urologie examinations in spastic paraplegics.³⁷

LESIONS BELOW T7. For patients with lesions below T7, the risk of hemodynamic instability from autonomic dysreflexia is reduced, but not eliminated. The incidence has been reported for lesions as low as T10.³⁸ In obstetrics, spinal or epidural anesthesia for labor, delivery, and cesarean section is preferred after the period of spinal shock has passed to attempt to avoid the complications associated with autonomic dysreflexia, as the occurrence is reduced with regional techniques.^35,36

        Pulmonary dysfunction, although more prevalent in lesions above T7, is still a concern with the paraplegic patient.³⁹

        Peripheral nerve blocks on the lower extremities may be an excellent anesthetic choice in these patients, providing adequate anesthesia while avoiding the known effects of general anesthesia, ie, respiratory compromise, overall muscle relaxation, nausea, and sedation from narcotics. Because of the uncertain risk of autonomic hyperreflexia in lesions below T7, peripheral nerve block or central neuraxial blocks reduce the risk of its occurrence by blocking the sensory limb of the reflex. An added advantage to peripheral nerve blocks is prevention of chronic pain, common in patients with spinal cord injuries.⁴⁰ Patients with spinal cord injury are prone to the development of spasticity. In the dysreflexive spinal cord of a paraplegic patient, pain has been shown to increase the level of spasticity.⁴⁰ Pain from surgical procedures may, therefore, precipitate spasticity. Utilizing peripheral nerve block anesthesia may prevent this from occurring. Nerve blocks must be performed with a nerve stimulator or ultrasound rather than paresthesia techniques as the patient with paraplegia may not have sensory (paresthesia) perception.

        Upper extremity blocks can be performed safely in the paraplegic patient, as spinal cord functions above the lesion is intact and normal. Careful evaluation of the patient for coexisting medical problems or to ascertain the absolute level of the lesion is recommended. The development of syringomyelia has been reported in these patients, creating deficits above the established lesion which can cause unforeseen problems for the anesthesiologist.

LESIONS ABOVE T7. The risk of autonomic hyperreflexia has been reported to be 85% or higher in this patient population.⁴¹ Light general anesthesia does not offer protection against its occurrence. Deep general anesthesia is effective, but the associated hemodynamic instability associated may not be tolerated in many of these patients. Pulmonary dysfunction is common and accounts for the largest percentage of morbidity in this population. General anesthesia with intubation may result in prolonged mechanical ventilation with increased risk of pulmonary infection. These patients are prone to the development of neurogenic pulmonary edema. It has been reported that certain anesthetic agents, ie, barbiturates, can provoke its occurrence.⁴² General anesthesia- induced bowel and bladder dysfunction can compound the preexisting dysfunction associated with the disease.

        Regional anesthesia, eg, spinal and epidural blockade, are effective in preventing autonomic hyperreflexia and have been used successfully in obstetrics for spinal cord-injured patients, even with high cord lesions.^36,43 However, concerns about the ability to determine the anesthetic level, exaggerated hypotension, and difficulties with placing the block secondary to spinal deformities from injury or prior surgery make many clinicians reluctant to use neuraxial anesthesia in this setting.

        Peripheral nerve blocks, especially on the lower extremities, are a theoretically acceptable form of anesthesia for the properly evaluated patient with a high-level spinal cord injury. Selective nerve blocks on the lower extremities, ie, femoral- sciatic or ankle blocks, are an effective alternative to exposing the patient to general anesthesia. Providing adequate anesthesia is even more important with a high spinal cord lesion to avoid the stimulus for autonomic hyperreflexia. Avoiding systemic hypotension with general anesthesia or an exaggerated hypotensive response with neuraxial anesthesia is possible with selective nerve blocks. Again, paresthesia techniques cannot be used; nerve stimulation or ultrasound-guided technique are required for proper localization of the nerve(s) to be blocked.

Related posts:

Introduction to Ultrasound-Assisted Regional Anesthesia Techniques. Preemptive Analgesia, Regional Anesthesia, & the Prevention of Chronic Postoperative Pain. Newer Amide Anesthetics & Sustained-Release Local Anesthetics1. Diagnosis & Management of Intraspinal, Epidural, & Peripheral Nerve Hematoma. Histology of Peripheral Nerves. Supraclavicular Brachial Plexus Block.