CHAPTER 16 Anesthesia for Central Nervous Diseases


Patients with diseases of the central nervous system (CNS) may require diagnostic, therapeutic as well as a surgical intervention under anesthesia. The pharmacodynamic effects of anesthetic agents are mediated through their action on various proteins in the CNS. These agents may cause long-term neurological sequelae in patients with underlying pathology of CNS. The patients with CNS disorders may have cognitive, sensory, motor, and autonomic deficit that make preoperative assessment difficult and in addition make intraoperative and postoperative care challenging. This chapter highlights salient anesthetic considerations of common CNS disorders.

Parkinson’s Disease

Parkinson’s disease (PD) is characterized by the loss of dopaminergic neurons in the substantia nigra. The common clinical manifestations include:

  • Resting tremors—characteristic pill-rolling tremor in hands.

  • Bradykinesia.

  • Limb rigidity.

  • Gait and balance problems.

Drugs such as phenothiazines, butyrophenones, and metoclopramide can inhibit dopaminergic receptors and result in Parkinsonism.

Anesthetic Considerations

  • Interruption of anti-Parkinson’s drug therapy should be as brief as possible and should be continued on the day of surgery with a sip of water.

  • Avoid dopaminergic drugs like metoclopramide as premedication. Prokinetic agents such as cisapride or domperidone do not interact with dopaminergic receptors and are an acceptable alternative to metoclopramide.

  • The autonomic function should be evaluated preoperatively, as these patients are at the risk of orthostatic hypotension and altered response to vasopressors.

  • Regional anesthesia is preferred over general anesthesia because general anesthetics and muscle relaxants can mask tremors.

  • The patients taking levodopa are at increased risk of tachyarrhythmias, especially with halothane and ketamine.

  • Propofol has the potential to produce dyskinesias and ablation of resting tremor, suggesting that it may have both excitatory and inhibitory effects in this patient population.

  • Opioids like alfentanil and fentanyl can cause exacerbation of muscle rigidity, while morphine has a dose-related effect on dyskinesia (dyskinesia decreases at low dose and increases at a higher dose).

  • Nondepolarizing muscle relaxants do not affect the symptoms of PD. However, suxamethonium has been reported to cause hyperkalemia in PD.

  • The glycopyrrolate bromide is the anticholinergic agent of choice, as it does not cross the blood–brain barrier (BBB).

  • Adequacy of ventilation and return of airway reflexes should be ensured prior to extubation.

The patient’s anti-Parkinson’s drugs should be resumed as soon as possible in the postoperative period to avoid exacerbation of symptoms.

Alzheimer’s Disease

Alzheimer’s disease (AD) is the most common neurodegenerative disorder among the elderly. It is characterized by profound memory disturbances and irreversible impairment of cognitive function.

Anesthetic Considerations

  • Loss of memory and cognitive dysfunction makes the patient disoriented, uncooperative, confused, and at times violent. Besides, the clinical history and examination may remain incomplete, and obtaining consent is difficult.

  • Perioperative sedation may aggravate mental confusion, and hence attention should be paid before prescribing them. Benzodiazepines often result in worsening of acute confusion and delirium.

  • Regional anesthesia is potentially challenging because of poor cooperation and disorientation.

  • Fragile skin, weak bones, bradykinesia, and stiff joints with limited range of motion demand careful and gentle intraoperative positioning and adequate padding.

  • Prolonged immobilization increases the incidence of deep venous thrombosis (DVT) and pulmonary embolism (PE).

  • The recovery of mental status to the preoperative level is delayed due to slow metabolism and excretion of drugs.

  • Glycopyrrolate is preferred over atropine or scopolamine as antisialagogue because it is impermeable to the BBB.

  • The dose of intravenous (IV) anesthetics and minimum alveolar concentration (MAC) of inhaled anesthetics should be kept low and titrated to achieve an adequate balance between the anesthetic effect and the harmful effects.

  • Postoperative cognitive dysfunction (POCD) and delirium are possible consequences of anesthetic agents interacting with acetylcholine receptors (AChRs) to produce inhibition of central cholinergic transmission already impaired by age-related changes.


The burden of epilepsy in the general population ranges from 0.5 to 1.0%. Epilepsy is the paroxysmal, abnormal cerebral electrical discharge associated with a clinical change. It can be either generalized or focal.

Anesthetic Considerations

  • The preoperative assessment should focus on duration, frequency, and control of seizure symptoms with medications.

  • All the current medications and their dosage should be reviewed.

  • Patients should continue their medications on the day of the surgery.

  • The potent anticonvulsant action of thiopentone makes it the drug of choice for refractory status epilepticus.

  • Propofol decreases cortical activity during both anesthesia and status epilepticus. However, it has been reported to cause excitation of the CNS in a 10% population.

  • Ketamine produces a state of dissociative anesthesia. It should normally be avoided in epileptics.

  • The myoclonus due to etomidate should not be misdiagnosed as an epileptiform activity.

  • Inhalational anesthetics cause burst suppression on the electroencephalogram (EEG) and are safe for use in epileptics, except enflurane, which causes epileptiform activity.

  • All of the commonly used anticonvulsants cause enzyme induction in the liver. This can lead to markedly reduced duration of activity of the aminosteroidal muscle relaxants, particularly those which are excreted via the liver (vecuronium and pancuronium).

  • The extrapyramidal effects and dystonic reactions due to dopamine antagonists may be confused with epileptic activity and should be avoided.

  • Metabolic disturbances due to prolonged fasting should be avoided as they may precipitate seizures.

  • Hypocarbia and hypoventilation should be avoided.

  • The shivering and confusion in the postoperative period should not be confused with seizure activity.


Acute stroke is the second leading cause of death worldwide and the leading cause of long-term disability, of which ischemic stroke accounts for 87% of cases.

Anesthetic Considerations

  • The preoperative assessment should focus on the level of consciousness, fasting status, allergies, airway assessment, comorbidities, and hemodynamic stability.

  • The neurological deficit should be evaluated and documented during the preoperative evaluation. The risk of perioperative stroke and exacerbation of neurological deficit should be explained to patients, and consent for the same must be obtained.

  • General anesthesia is advantageous over local anesthesia or sedation in terms of better immobility, pain control, and airway protection but at the cost of hemodynamic changes with intubation.

  • On the other hand, local anesthesia or sedation provides smooth hemodynamics and allows intraprocedural clinical neurological evaluation. However, it has
    disadvantages like lack of airway protection, continued patient movement, uncontrolled pain and agitation, and prolonged procedure time.

  • Patients can also present for other surgeries poststroke, and they may be in different stages of recovery.

  • Patients with a recent history of stroke < 3 months should be taken up only for emergency surgeries. The anesthetic concerns for such patients include:

    • Perioperative recurrence of stroke.

    • Re-emergence of neurological deficits postoperatively.

  • Perioperative stroke increases risk of mortality by eightfold compared with patients without stroke.

  • Exacerbation of prior unrecognized or unreported neurological deficits can occur following both neuraxial and general anesthesia due to compromised cerebral perfusion.

  • Antihypertensive medications and statins should be continued preoperatively, and adequate hydration should be ensured.

  • Sedative premedication should be avoided or used in minimal dosages.

  • Apart from standard American Society of Anesthesiologists (ASA) monitoring, invasive arterial blood pressure, central venous pressure, urine output, and neuromuscular monitoring on the unaffected side may be required.

  • Cerebral electrophysiological monitoring and transcranial Doppler (TCD) are restricted to patients at high-risk repeat stroke. Cerebral oximetry is useful to detect ischemia during high-risk cardiac or major vascular surgery and surgeries in the beach chair position.

  • IV anesthetic agents offer cerebral protection by decreasing cerebral metabolism. Inhalational agents are vasodilators and, therefore, may be beneficial.

  • Addition of intermediate- or short-acting opioids reduce the dose of induction agents, thereby reducing hemodynamic instability during induction.

  • Succinylcholine can cause life-threatening hyperkalemia in patients of stroke with loss of significant muscle function.

  • Avoid hypotension as it can reduce the focal cerebral blood flow and predispose the patient to postoperative stroke. Intraoperative blood pressure should be maintained at baseline or slightly elevated levels.

  • Avoid hypoxia, hypercarbia and hypocarbia, and acidosis.

  • Avoid hypoglycemia and hyperglycemia. Tight glucose control is beneficial in stroke patients.

  • Ascertain protective airway reflexes prior to tracheal extubation. The neurological function should be assessed at the earliest after recovery from anesthesia.

  • High-dependency unit care is required for patients with major neurological deficits.

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Dec 11, 2022 | Posted by in ANESTHESIA | Comments Off on CHAPTER 16 Anesthesia for Central Nervous Diseases

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