Abstract
Neurological diseases affect the functions of the central nervous system (CNS) and the neuromuscular system. Preexisting CNS diseases have important implications regarding the selection of anesthetic drugs, techniques, monitoring, cerebral protection and resuscitation of the patients. Neurological patients are more sensitive to anesthetic drugs, and are at risk of perioperative cardiac and respiratory complications. This chapter will include the present recommendations for anesthetic management in patients with various neurological diseases.
Keywords
Anesthesia, Brain tumor, Epilepsy, Head injury, Neurologic diseases, Neuromuscular disease, Nonneurologic procedures
Outline
Neurodegenerative Diseases 784
Alzheimer Disease 784
Anesthetic Considerations 784
Effect of Disease on Anesthesia 785
Effect of Anesthetic Agents on Disease Progression 785
Parkinson Disease 785
Anesthetic Considerations 785
Effect of the Disease on Anesthetic Agents 785
Effect of Anesthetic Agents on the Disease 786
Huntington Disease 787
Anesthetic Considerations 787
Amyotrophic Lateral Sclerosis 788
Anesthetic Consideration 788
Demyelinating Disease 788
Guillain-Barré Syndrome 788
Anesthetic Considerations 789
Multiple Sclerosis 789
Anesthetic Consideration 789
Neuromuscular Disease: Myasthenia Gravis 791
Anesthetic Consideration 791
Epilepsy 793
Anesthetic Considerations 793
Intracranial Tumors 794
Traumatic Brain Injury 797
Anesthetic Considerations 797
Goals of Anesthesia 797
Anesthetic Management of Patients With Head Injury for Associated Life-Threatening Extracranial Injury 798
Anesthetic Management of Patients With Head Injury for Non-Life Threatening Extracranial Injury 799
Management of Patient for Elective Surgery Following Recovery From Acute Brain Injury 800
References 800
Neurological diseases affect the functions of the central nervous system (CNS) and the neuromuscular system. Preexisting CNS diseases have important implications regarding the selection of anesthetic drugs, techniques, monitoring, cerebral protection, and resuscitation of the patients. Neurological patients are more sensitive to the anesthetic drugs, and are at risk of perioperative cardiac and respiratory complications. This chapter will include the present recommendations for anesthetic management in patients with various neurological diseases ( Box 47.1 ).
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Neurodegenerative Diseases
Alzheimer Disease
Alzheimer disease (AD) is characterized by an insidious onset and gradually progressive neurodegenerative disease, leading to decline in the intellectual functions. It affects about 4.5 million Americans and remains a major public health problem. It begins initially with forgetfulness and progresses to loss of judgment, complex visual perception defects, language problems, and inability to generate abstract concepts. The major anesthesiologist’s concern during the perioperative period is dealing with a patient who is unable to comprehend and cooperate with those providing medical care.
Anesthetic Considerations ( Table 47.1 )
A few issues must be addressed in the patients with AD. Patients with severe cognitive dysfunction are incapable of giving proper history and consent, so caregivers should be involved in preoperative assessment and preparation. In advanced stage, patients with AD might be disoriented and uncooperative, and make regional anesthesia more difficult. Anesthesia becomes even more challenging in these patients due to interactions of the drugs used for its treatment with the anesthetic agents and the adverse effects of anesthetic agents on the disease progression.
| Derangements | Management | ||
|---|---|---|---|
| Special concerns | Cognitive dysfunctions | Unable to cooperate and give consent or history | Caregivers should be involved |
| High risk for postoperative confusion | Predispose to postoperative delirium | Sedative premedications should be carefully prescribed | |
| Avoid the drugs and conditions causing delirium | |||
| Increased sensitivity to anesthetic agents | Smaller doses for sedative–hypnotic drugs are needed | ||
| Drug interactions | Cholinesterase inhibitors
| Side effects: nausea, vomiting, diarrhea, and hepatotoxicity | |
| Vagotonic effects of SA and AV node: bradycardia and syncope | |||
| Bronchoconstriction | |||
| Cholinergic crisis | |||
| Prolonged response to succinylcholine | |||
| Resistance to nondepolarizing NMBs | |||
| MAOIs | Profound pressor effect after administration of both indirectly and directly acting sympathomimetic drugs | ||
| Antidepressant and psychotomimetic drugs | Excessive sedation with concomitant use of anxiolytic and sedative drugs | ||
| Regional anesthesia | Lesser dose is required to achieve the same sensory level as in patients without AD | ||
Effect of Disease on Anesthesia
These patients are at high risk for postoperative confusion and delirium due to preexisting cognitive impairment. Sedative premedications should be carefully prescribed as these patients are more sensitive to sedative drugs and further increment in mental confusion can occur. Increased sensitivity is attributed to age-related changes in body composition and physiology, causing altered pharmacokinetics and pharmacodynamics of the drugs. There is smaller initial volume of distribution, relative increase in body fat, lower serum albumin, and age-related decline in renal function, which necessitate smaller doses for sedative–hypnotic agents. Other factors that can precipitate delirium; including cerebral hypoxia or hypoperfusion, endocrine or ionic imbalances, postoperative pain, sepsis, and bowel or bladder distention, should be avoided. Use of certain medications such as high-dose steroids, neuroleptics, benzodiazepines, ketamine, tertiary anticholinergics, opioids, histamine H 2 blockers, and droperidol can also precipitate delirium.
Various medications used for the treatment of AD interact with the anesthetic agents. Cholinesterase inhibitors have been reported to prolong the action of succinylcholine and remifentanil, and may cause resistance to nondepolarizing neuromuscular blockers (NMBs). The patients taking monoamine oxidase inhibitors can develop profound pressor effect after administration of both indirectly and directly acting sympathomimetic drugs. If the patient is receiving antidepressants and psychotomimetic drugs preoperatively, there can be exaggerated effect of anxiolytic and sedative agents. So, the patient’s drug chart must be reviewed to avoid severe drug interactions due to polypharmacy.
The requirements for both volatile and intravenous anesthetic agents decline progressively with age. Elderly patients have altered responses to regional anesthesia. The dose of local anesthetic for subarachnoid block, to achieve the same level of sensory blockade, is lesser than the healthy indiviuals. The sensitivity of CNS to the depressant effects of general anesthetic agents is aggravated by severe cortical atrophy and synaptic loss. Hence, lower dosages of sedative and hypnotic agents are required, and the emergence from general anesthesia may be slow.
Effect of Anesthetic Agents on Disease Progression
In the same manner, anesthetic agents also affect the course of this disease. The experimental and animal studies showed that the general anesthetic agents and some perioperative events enhance the molecular mechanisms associated with AD. The use volatile anesthetic agents and hyperventilation increase the amyloid beta levels, and hypothermia leads to profound phosphorylation of tau (τ) protein. The clinical significance of such experimental studies is unclear. The data from retrospective studies fail provide any convincing evidence for an association between anesthetic exposure and the subsequent risk for development of AD. There is no single “best” anesthetic agent or technique for the patients with AD.
To summarize, the goals of anesthetic management of patients with AD are to avoid drug interactions, postoperative delirium, and the drugs and physiological conditions that can aggravate the disease and careful selection of anesthesia technique to maintain hemodynamic stability.
Parkinson Disease
After AD, Parkinson disease (PD) is considered the second most common neurodegenerative disease afflicting about 1 million Americans. In India the crude prevalence of PD ranges from 7 to 328 per 100,000. PD is characterized by unopposed actions of acetylcholine due to decreased levels of dopamine. This disease affects the multiple systems of body and remains a challenge for anesthesiologists.
Anesthetic Considerations
Perioperative challenges of the patient with PD include maintenance of perioperative drug therapy that leads to potential adverse drug interactions, and various other systemic derangements associated with the disease ( Table 47.2 ). Our goal is to prevent the aggravation of symptoms and to maintain the hemodynamics. Perioperative stress can also worsen the disease.
| Systemic Derangements | Management | |
|---|---|---|
| Special concerns | Upper airway dysfunction Involuntary movements of glottis and supraglottic structures leads to:
| Continue or increase the antiparkinsonian drugs perioperatively |
| Succinylcholine might be required to relieve the laryngospasm | ||
Respiratory system
| Antiaspiration prophylaxis and rapid sequence induction | |
| Postoperative need of mechanical ventilation | ||
Autonomic nervous system
| Unable to respond to hypovolemia and vasodilation | |
| Potential for perioperative hemodynamic instability | ||
| Altered responses to vasopressors such as noradrenaline | ||
Gastrointestinal system
| Antacids and Prokinetic drugs should be used | |
| Metoclopramide must be avoided | ||
| Domperidone and cisapride are safe | ||
Cardiovascular system
| Vasodilators should be used with caution | |
Central nervous system
| Benzodiazepines for anxiety and antipsychotics for psychosis can have severe side effects, such as oversedation and acute exacerbation of motor symptoms | |
| Drug interactions | Malignant syndrome | Avoid the withdrawal of antiparkinsonian drugs |
| “ On-off ” phenomenon with levodopa | Can be controlled with carbidopa | |
| Regional anesthesia | Advantage : side effects of anesthetic agents can be avoided Disadvantage : patient’s cooperation is a limiting factor | |
Effect of the Disease on Anesthetic Agents
The short half-life of levodopa (about 90 min) makes its even brief interruption undesirable. Drug interactions might lead to malignant syndrome, characterized by hyperthermia, akinesia, altered consciousness, muscle rigidity, and autonomic dysfunction. Hence, the drug interruption should be brief, and if patients are not able to take oral drugs then intravenous levodopa with carbidopa should be used. Bioavailability of levodopa decreases significantly in patients with gastroparesis as it undergoes first-pass metabolism after absorption from stomach.
Effect of Anesthetic Agents on the Disease
Various agents being used perioperatively can affect the disease course of PD. Volatile anesthetic agents affect dopaminergic circuitry in the brain, but their effect on PD is not known. These agents have been successfully used during deep brain stimulation with intraoperative electrophysiological monitoring. Propofol has both excitatory and inhibitory effects and produces both dyskinesias and ablation of resting tremor, and has also been used successfully during deep brain stimulation surgery. Dexmedetomidine does not interfere with motor symptoms and appears to be safe. Ketamine has a potential of interactions with levodopa due to its sympathomimetic effects. Drugs acting on dopamine receptors (butyrophenones and phenothiazines) can exacerbate PD and should be avoided. In patients with deep brain stimulation coil implanted, the neurostimulator should be switched off during magnetic resonance imaging. In these patients if cautery is required intraoperatively then bipolar mode should be used, and the leads and generator should not be placed in the path from surgical site to the ground plate.
Regional anesthesia is advantageous over general anesthesia, as the side effects of general anesthetic agents can be avoided. Besides this, oral levodopa can be continued preoperatively, during surgery and in early postoperative period, if required. During regional anesthesia the pharyngeal and laryngeal reflexes are intact or at least same as baseline, so chances of aspiration are lesser. The major disadvantage of regional anesthesia is the difficulty in positioning the patient.
To summarize, the patients with PD are associated with multisystem derangements that leads to increased risk of perioperative morbidity and mortality. Our anesthetic goal should be to avoid any drug that can decrease the level of dopamine, and the drugs that interact with anesthetic agents.
Huntington Disease
Huntington disease (HD) is a rare hereditary neurodegenerative disorder. Even if it is genetically transmitted, it usually manifests between 30 and 40 years of age. In 10% of patients there can be juvenile onset of the disease (symptoms beginning before 20 years of age) and death usually occurs 10–30 years after the disease manifestations. HD is characterized by a triad of progressive cognitive deterioration, dementia, and involuntary choreiform movements. This disease affects 5 to 7 persons per 100,000 population.
Anesthetic Considerations ( Table 47.3 )
The literature on anesthetic management for a patient with HD is derived mostly through the case reports and by theoretical complications as per patient’s symptoms.
| Systemic Involvement | Management | |
|---|---|---|
| Special concerns | Central nervous system
| Increased sensitivity to anesthetic agents especially benzodiazepines (midazolam) |
Motor system
| Pulmonary aspiration risk: antiaspiration prophylaxis and RSI are used | |
| Drug interactions | Hypnotic drugs | Prolonged apnea after thiopentone |
| Succinylcholine | Abnormal levels of plasma psuedo-cholinesterase | |
| Prolonged paralysis | ||
| No evidence of hyperkalemia | ||
| Polypharmacy | Beware of side effects | |
| Caution about drug interactions | ||
| Neurolept malignant syndrome seen with droperidol and metoclopramide in patients receiving tetrabenazine | ||
| Regional anesthesia | Technically difficult but not contraindicated | |
Effect of the Disease on Anesthetic Agents
Patients with HD are at risk of pulmonary aspiration due to dysphagia, so antiaspiration prophylaxis and precautions should be taken. These patients can develop prolonged respiratory depression and delayed awakening after general anesthesia, necessitating the use of lower dosage of sedatives and hypnotic agents. This increased sensitivity might be related to altered pharmacokinetics due to nutritional depletion or increased CNS sensitivity due to neurodegeneration. In a few case reports patients with HD experienced a normal anesthetic and postanesthetic course. Use of thiopentone has been reported to cause prolonged apnea in these patients. Tertiary ammonium compounds, such as atropine, should be avoided as these can aggravate the movement disorders. The response to muscle relaxants in patients with HD also varies. These patients might have a high incidence of abnormal plasma cholinesterase that leads to prolonged the muscle relaxation following the use of succinylcholine, but it has been used uneventfully in a few patients. There are no case reports of succinylcholine-induced hyperkalemia. Similarly, both abnormal and normal responses have been reported with nondepolarizing NMBs. A few authors have reported generalized tonic muscle spasms related to shivering during emergence from anesthesia and suggested to maintain normothermia and avoid inhalational agents to prevent shivering. Regional anesthesia is technically difficult because of the continuous uncontrollable movements, but there is no contraindication.
Amyotrophic Lateral Sclerosis
Amyotrophic lateral sclerosis (ALS) is a progressive and debilitating degenerative disease of the CNS that affects 1–2.5 persons per 100,000 population and presents between 50 and 70 years of age. It is marked by loss of both upper and lower motor neurons in the anterior horn of the spinal cord and brainstem nuclei of cranial nerves.
Anesthetic Consideration ( Table 47.4 )
The response of various anesthetic agents is altered due to clinical manifestations of the disease, such as muscle weakness, respiratory impairment, bulbar dysfunction, and malnourishment. Motor neuron palsy–induced denervation causes proliferation of fetal neuromuscular receptors, which predisposed these patients to succinylcholine induced hyperkalemia. These patients also have increased sensitivity to nondepolarizing NMBs hence, the relaxants should be used cautiously and under neuromuscular monitoring. Deranged respiratory functions pose a significant risk of perioperative pulmonary complications and need of postoperative mechanical ventilation. If feasible, regional anesthesia is preferable to general anesthesia in these high-risk patients, but such practice is not established. Antiaspiration prophylaxis should be considered in patients with bulbar dysfunction and dysphagia. Regional anesthesia does not facilitate progression ALS. Also, there is no evidence in the literature to prove that general anesthesia is responsible for progression of ALS.
| Systemic Involvements | ALS | GBS | |
|---|---|---|---|
| Special concerns | Cardiovascular system | − | Myocardial denervation predisposes these patients to arrhythmia |
| Autonomic nervous system | − | Both sympathetic or parasympathetic hyperactivity | |
| Sensitive to vasodilators | |||
| Sensitive to sudden positional change | |||
| Respiratory weakness | + | + (During acute phase) | |
| Bulbar weakness | + | + (During acute phase) | |
| Drug interactions | Succinylcholine | Hyperkalemia | Hyperkalemia |
| Nondepolarizing NMBs | Increased sensitivity | In early phase: resistance | |
| In late phase: sensitivity | |||
| Regional anesthesia | Does not facilitate progression | Does not facilitate progression | |
| Not contraindicated | Not contraindicated | ||
| Sudden cardiovascular collapse in the presence of autonomic dysfunction | |||
Demyelinating Disease
Guillain-Barré Syndrome
Guillain-Barré syndrome (GBS) is a demyelinating paralytic disease affecting 1 in 100,000 population younger than 30 years and about 4 in 100,000 population older than 70 years. GBS results from antibody-mediated segmental demyelination of peripheral nerves and varying degrees of secondary axonal degeneration. Patients present with acute or subacute condition (weeks), progressive, ascending, symmetrical paralysis beginning from the lower limbs to upper limbs and finally, involving the trunk and cranial nerves. GBS is also associated with dysautonomia, paresthesias, numbness, pain, and impaired brainstem functions.
Anesthetic Considerations ( Table 47.4 )
Anesthetic challenges in patients with GBS are related to pathophysiological involvement, such as dysautonomia, pulmonary insufficiency, and cranial nerve dysfunction. Autonomic dysfunction in GBS affects both the sympathetic and parasympathetic nervous systems. These can present as both underactivity and overactivity of sympathetic and parasympathetic nervous systems. This imbalance leads to sweating, gastrointestinal dysfunction, hypotension, hypertension, abnormal hemodynamic responses to drugs, abnormal thermoregulation, arrhythmias, and even death. In the presence of dysautonomia, patients are unable to compensate for vasodilation leading to severe hemodynamic instability and circulatory collapse. Myocardial denervation predisposes these patients to arrhythmias. Muscle denervation leads to an abnormal response to the muscle relaxants and increases the risk for hyperkalemia after succinylcholine use. The response to nondepolarizing muscle relaxants is also variable. In early phase patients are resistant to nondepolarizing agents, while in late phase (up to 4 years) there is increased sensitivity to the blockade. Respiratory muscle weakness gives a restrictive pattern on flow volume loops study. In severe disease, there might be impaired cough and type-2 respiratory failure. Cranial nerve dysfunction leads to bulbar weakness and increases the risk of aspiration pneumonitis and airway obstruction. Antiaspiration prophylaxis and definitive airway protection using endotracheal tube or early tracheostomy should be considered in the presence of bulbar muscles weakness. Regional anesthesia is not contraindicated, but these patients are more sensitivity to the local anesthetics, and sudden cardiovascular collapse can occur in patients with autonomic dysfunction. Epidural anesthesia can be used safely.
Multiple Sclerosis
Multiple sclerosis (MS) is an acquired immune-mediated disease of the CNS characterized by multiple demyelinating plaques within the brain and spinal cord. The incidence varies between 6 and 80 per 100,000 in the United States, involving the urban dwellers and population of higher socioeconomic groups. MS usually presents at 20–30 years of age with a female preponderance. Clinical features vary according to the nerve fibers affected. Multiple drug therapy might complicate anesthesia management.
Anesthetic Consideration
The goal of anesthesia in patients with MS is to prevent the relapse, to avoid drug interactions, and to prevent further neuronal damage. Perioperative concerns regarding drug therapy in MS are described in Table 47.5 . The decision of anesthesia technique demands a detailed history and clinical examination to recognize the type and severity of MS, presence of acute exacerbation, current medications, and degree of neurological deficits, especially when planning for regional anesthesia.
| Drug | Important Side Effects | Anesthetic Implications |
|---|---|---|
| Interferon β | Flulike syndrome | Rule out other causes of fever |
| Abnormal hemogram including thrombocytopenia | Evaluate complete blood counts | |
| Caution should be taken while considering neuraxial blocks | ||
| Raised hepatic enzymes or autoimmune hepatitis Autoimmune Thyroiditis | Evaluate hepatic and thyroid functions before surgery and modify drug therapy accordingly | |
| Glatiramer acetate | Hepatotoxicity | Modify drug therapy |
| Progressive multifocal leukoencephalopathy | Vulnerable for opportunistic infections | |
| Natalizumab | Bradycardia | Avoid drug therapy aggravating bradycardia |
| Bronchitis, bronchospasm | Care, preoperative evaluation, and optimization | |
| Hepatotoxicity | Modify drug therapy | |
| Progressive multifocal leukoencephalopathy | Vulnerable for opportunistic infections | |
| Fingolimod | Cardiac conduction changes, cardiomyopathy, bradycardia, AV block | Careful cardiac evaluation and optimization |
| Elevated liver enzymes | Careful anesthetic drug therapy | |
| Tecfidera | Albuminuria Decreased blood counts Elevated liver enzymes Gastroenteritis Abdominal cramps | Altered drug binding |
| Evaluate complete blood counts | ||
| Careful anesthetic drug therapy | ||
| Antacids and take drugs with food | ||
| Cyclophosphamide | Myelosuppression Myocarditis Pulmonary fibrosis Elevated liver enzymes | Evaluate complete blood counts |
| Evaluate and optimize cardiac and pulmonary systems | ||
| Careful anesthetic drug therapy | ||
| High-dose corticosteroids | Adrenal suppression | Replace intraoperative steroids |
| Baclofen | Muscle weakness | Extremely sensitive to the nondepolarizing NMBs |
| Agitation, delirium, and convulsions on abrupt stoppage | Avoid abrupt stoppage |
Effect of Disease on Anesthesia ( Table 47.6 )
Respiratory muscle weakness or incoordination and cranial nerve dysfunction can occur in MS. Preoperative assessment should include ability to clear respiratory secretions and strength of cough, and in few cases pulmonary function tests. Sleep disorders, such as central sleep apnea, Ondine curse, insomnia, nocturnal movement disorders, and narcolepsy might be associated with MS and localizes lesions in the higher centers regulating motor control of respiratory and airway muscles. These patients might develop autonomic nervous system dysfunction that leads to altered hemodynamic responses. There might be limitation of movements secondary to spasticity and contractures that makes the surgical positioning difficult and interferes with airway management. Cardiac functions and liver functions tests are affected by drug treatments and must be evaluated. Patients on steroid therapy or who have taken steroids recently must receive perioperative steroid replacement.
| Systemic Involvement | Anesthetic Considerations | |
|---|---|---|
| Specific concerns | Central nervous system Depression, fatigue, painful seizures, pain syndromes, sensory deficits | |
| Interaction due to polypharmacy | ||
| Upper motor neuron type of paralysis with spasticity | Upregulation of acetylcholine receptors, altered response to NMBs | |
| Brainstem and cranial nerves involvement | Risk of aspiration | |
| Interaction with pain medications used for trigeminal neuralgia | ||
| Brainstem and spinal cord | ||
| Autonomic dysfunction | Cardiac dysfunction | |
| Impaired control of ventilation and response to raised PaCO 2 | Exaggerated hypotension with vasodilation and regional techniques | |
| Diaphragmatic paralysis | Poor response to fluid loading and pressor agents | |
| Respiratory muscle weakness | Hypoventilation, hypoxemia, apnea, and respiratory failure | |
| Limb weakness, paresthesias and sensory deficits | Resistance/sensitivity to NMBs | |
| Pain medications/drugs for spasticity | Cardiovascular, respiratory, and NM monitoring essential | |
| Thermoregulation | Even 0.5 degrees rise in body temperature can cause exacerbation | Core and surface temperature monitoring is recommended |
| Regional anesthesia | Controversial but not contraindicated | |
| It is recommended to use the lowest possible doses of local anesthetics for neuraxial blockade | ||
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