Central Nervous System Diseases

• Multiple Sclerosis-overview

  • Acquired CNS disease-Characteristics:

    •  CNS inflammation

    •  Multiple sites of brain and spinal cord demyelination

    •  Demyelination plaques along spinal fluid pathways (e.g. optic tracts and periventricular regions)

  • Causes:

    •  Immunological events in genetically-susceptible individuals

    •  Geographical correlations suggest possible environmental factors (triggers), e.g. toxins, viruses

  • Symptoms:

    • Depends on demyelination sites, i.e.:

      • Optic tract demyelination causes visual disturbances

      • Oculomotor pathway demyelination causes nystagmus

      • Spinal cord lesions result in paresthesias & limb weakness (legs more than arms)

      • Brain stem demyelination sites:cardiac arrhythmias, autonomic dysfunction, apnea/respiratory failure, trigeminal neuralgia, diplopia

    • Disease Progression

      •  exacerbation of symptoms that variable, unpredictable intervals over a time frame of years

      •  residual effects following remission may be debilitating

  • Therapies: non-curative

    •  Corticosteroids

    •  Cyclophosphamide (Cytoxan), cyclosporine (Sandimmune, Neoral), azathioprine (Imuran), interferon

    •  Plasmapheresis

    •  Symptomatic management of muscle spasticity:

      •  Diazepam (Valium)

      •  Dantrolene (Dantrium)

      •  Baclofen (Lioresal)

    •  Management of dysthesias, dysarthria, ataxia, tonic seizures: carbamazepine (Tegretol)

  • Management of anesthesia: multiple sclerosis

    • Concerns: surgery may induce a relapse

    • Post-surgical neurological examination should be compared to pre-surgical neurologic findings to document possible changes

    • Even slight increases in temperature during surgery must be aggressively managed

    • Selection of anesthetic agents:

      • Should consider medications patient is taking for multiple sclerosis

        • e.g., Carbamazepine (Tegretol) may cause resistance to nondepolarizing neuromuscular-blocking drugs

        • Perioperative corticosteroid supplementation may be required for patients using corticosteroids to control MS.

      • Autonomic dysfunction associated with multiple sclerosis could potentiate hypotensive action of volatile agents

        • Careful cardiovascular system monitoring is recommended

      • Weakness of respiratory muscles may make postoperative mechanical ventilation more likely.

return to main menu

• Epilepsy-Review:

  • Grand Mal Seizure

    •  Generalized tonic-clonic seizure

    • Respiratory activity suspended (leading to arterial hypoxemia)

    • Tonic phase: 20-40 seconds; followed by clonic phase

    • Initial treatment objectives:

      •  management of hypoxemia

      •  arresting the seizure

    •  Pharmacological management of the acute seizure:

      •  diazepam (Valium)

      •  thiopental (Pentothal)

    •  Pharmacological management for seizure control/prevention

      •  phenytoin (Dilantin), valproic acid (Depakene, Depakote), felbamate (Felbatol), carbamazepine (Tegretol)

  • Focal Cortical Seizure (Jacksonian epilepsy)

    • sensory or motor, depending on focus; no loss of consciousness; may spread to produce a grand mal seizure

  • Absence Seizure (Petit mal)

    •  Brief loss of awareness; 30 seconds

    •  Manifestations also include: staring, rolling the eyes, and blinking

    •  Immediate resumption of consciousness

    •  Population group at risk: young adults & children

    •  Pharmacological management:

      •  absence seizures without other seizure activity: ethosuximide (Zarontin)

      •  absence seizures with other seizure activity: valproic acid (Depakene, Depakote)

  • Status epilepticus

    • Definition:

      • two consecutive tonic-clonic seizures without regained consciousness

      • or continual seizure activity for > 30 minutes

      • Typical duration: 48 hours with seizure frequencies of 4-5/hour

    •  Mortality frequency:

      • Grand Mal status epilepticus may reach 20%

    • Symptoms:

      •  impaired respiration (inhibition of respiratory centers)

      •  impaired ventilation (secondary to uncoordinated skeletal muscle contractions)

      •  bronchoconstriction (secondary to abnormal autonomic activity)

    • Some consequences:

      •  arterial hypoxemia

      •  possible permanent role damage

    • Pharmacological management: (acute)

      •  Drugs of choice

        •  diazepam (Valium)

        •  lorazepam (Ativan)

        •  thiopental (Pentothal) (effective but not first choice)

        •  halothane (Fluothane), isoflurane (Forane)-rarely used, but effective

      •  Other effective agents:

        •  clonazepam (Klonopin)

      •  Skeletal muscle relaxation: (to allow tracheal intubation if needed): muscle relaxants

      •  Longer acting agents

        •  e.g.,phenytoin (Dilantin), phenobarbital (Luminal)

   

  • Anesthesia management: epilepsy

    • Preoperative: maintain normal anticonvulsant regimen

    • Postoperative: provide parenteral anticonvulsant agents until oral intake can be resumed

    • Most inhaled anesthetics may produce seizure activity; rare with halothane (Fluothane) are isoflurane (Forane)

    •  Enflurane (Ethrane): Spike & wave activity (EEG), particularly with hypercarbia presence

      • Children: especially susceptible

    • Halothane (Fluothane),isoflurane (Forane), desflurane (Suprane): preferable to enflurane (Ethrane) for patients with seizure disorder

    •  Ketamine (Ketalar): controversial; probably reasonable to avoid ketamine (Ketalar) for patients with seizure disorders because alternative agent such as barbiturates, propofol (Diprivan), & benzodiazepines may be used.

    •  Methohexital (Brevital): may induce seizures in children; thiopental (Pentothal) better alternative

    •  Seizure activity may be associated with opioids (controversial, more likely with high doses)

      •  High-does fentanyl (Sublimaze) (200-400 ug/kg) or sufentanil (Sufenta) (40-160 ug/kg): cautious use in patients with seizure disorder

      •  Patients receding chronic anticonvulsants: higher intraoperative fentanyl (Sublimaze) doses needed (probably due to enhanced metabolism following hepatic microsomal enzyme induction)

return to main menu

• Parkinson's Disease- Review

  • Frequency: affects about 2.5% of the population > 65 years of age

  • Degenerative, neurological disorder

    • Cause: loss of dopaminergic fibers in the basal ganglia, secondary to nerve cell body destruction in the substantia nigra.

  • Clinical presentations:

    •  Cog-wheel rigidity (extremities)

    •  Flat facial affect (facial immobility)

    •  Shuffling gate

    •  Stooped posture

    •  Increase in spontaneous movements

    •  Resting, rhythmic tremor

  • Other clinical presentations frequently associated with Parkinson's disease: sialorrhea, seborrhea, orthostatic hypotension, pupillary abnormalities, diaphragmatic spasm, oculogyric crisis, mental depression {may require antidepressant treatment}

  • Some Drugs used in management of Parkinson's disease:

    •  L-DOPA: dopamine precursor; often given in combination with carbidopa (Lodosyn), a peripheral decarboxylase inhibitor

    •  Direct dopamine (Intropin) receptor agonists: bromocriptine (Parlodel), pergolide (Permax)

    •  monoamine oxidase-B inhibitor: selegiline (Eldepryl)

  • Anesthesia Management: Parkinson's disease

    • Maintain normal Parkinson's disease medication through the morning of surgery

    • Avoid drugs that antagonize dopamine (Intropin) effects in the basal ganglia, e.g. phenothiazines & butyrophenones (droperidol (Inapsine))

    •  Alfentanil (Alfenta): may cause acute dystonic reactions in patients with untreated Parkinson's disease.

    •  In elderly patients with coronary vascular disease & Parkinson's disease: ketamine (Ketalar) should be use with caution as it may induce tachycardia to & hypertension.

    •  Parkinson's disease patients may be a greater risk for aspiration pneumonitis because of autonomic dysfunction leading to excessive salivation, dysphagia, and esophageal abnormalities.

    • The most common cardiovascular abnormality in Parkinson's disease patients is orthostatic hypotension:

      • Parkinson's disease patients are more likely to exhibit hypotensive reactions in response to inhaled halogenated anesthetics

    • Postoperative: more susceptible to mental confusion & hallucinations-unknown mechanism.

return to main menu