Seizures, Tonic-Clonic (Grand Mal)

Incidence in USA: 500,000–1,000,000 with recurrent tonic-clonic seizures.

10–20 million at risk to have one tonic-clonic seizure secondary to alcohol withdrawal, febrile convulsions (in children), CNS pathology, and/or metabolic disturbances.

Prevalence of epilepsy is 0.5–1% of the population.

Seizures:

• Periop seizures: Incidence is 3.1:10,000 pts; incidence related to LA toxicity is 120:10,000; in pts with known seizures undergoing RA, frequency is 5.8%.

• SE

Seizure-induced sequelae:

• Physical injuries

• Tachycardia, hypertension, hypoxia, metabolic acidosis

• Pulmonary aspiration

• Elevated ICP, cerebral edema, postictal paralysis (Todd paralysis)

Seizure induction with periop drugs: Local anesthetics, sevoflurane, etomidate, ketamine.

Altered pharmacokinetics and dynamics with anticonvulsants: Resistance to neuromuscular blockers and opioids with chronic therapy.

Routine preop monitoring of serum anticonvulsant levels is indicated only in pts with poor seizure control or those who are critically ill.

Caution with intraop IV phenytoin or fosphenytoin (hypotension, rate of 50 and 150 μg/min, respectively).

Delayed emergence.

Periop seizures: First episode or with known seizure disorder.

Often self-limiting, trauma to head or extremities is common if precautions are not taken (padded hospital bed). May progress to SE, a life-threatening condition requiring rapid and emergent intervention to terminate attack before cerebral damage results (30–60 min). Subtherapeutic anticonvulsant serum levels and alcohol withdrawal most commonly provoke SE.

During seizures and postictally, airway reflexes are typically preserved; intubation is not indicated unless aspiration is strongly suspected.

Postictally, enhancement of a previous neurologic motor deficit is common (Todd paralysis) for hours after seizure.

Idiopathic; Leading cause (30%).

Acquired: Secondary to congenital syndromes, perinatal asphyxia, developmental disorders, trauma, CNS infection, cerebrovascular disease, intracranial tumor, drug withdrawal (commonly alcohol), metabolic (glucose, Na ⁺ , Ca ²⁺ , Mg ²⁺ ), renal or hepatic failure.

Periop factors that might precipitate seizure in a pt with a known seizure disorder include NPO status, noncompliance with anticonvulsants, sleep deprivation, fatigue, stress, surgical pain, adverse drug reactions, and interactions between anticonvulsants and anesthetic agents.