Seizure

Antiepileptic drugs - Keep them on schedule through the morning of surgery. Noncompliance is one of the most common causes of breakthrough seizures, and one emergency department series found sub-therapeutic levels in roughly two-thirds of patients who presented with a seizure complaint.

Preop labs that change the plan - Antiepileptic drug levels, serum sodium and glucose, and a basic metabolic panel. Sub-therapeutic drug levels and electrolyte derangement are the two findings that move a case, and hypoglycemia is a reversible cause of seizures worth excluding before induction.

What the chart should tell you - Seizure type and frequency, date of the last seizure, aura, and known triggers, plus any prior EEG or MRI findings. Focal abnormalities on EEG or MRI mark the higher-recurrence patient.

Chronic AEDs and neuromuscular blockade - Chronic antiepileptic therapy produces resistance to nondepolarizing relaxants and you will need larger doses; follow TOF rather than dosing by weight. Acutely administered antiepileptics do the opposite and prolong the block. Lithium delays onset and prolongs both succinylcholine and nondepolarizers.

Induction agents move the seizure threshold - Propofol raises the threshold and shortens seizure duration, which makes it a reasonable default in the epileptic patient. Methohexital does not affect the threshold. Etomidate and ketamine both tend to lengthen seizures. Sevoflurane shortens seizure duration more than propofol, barbiturates, or ketamine, but attenuates the sympathetic response less.

Don't build the trigger - Sleep deprivation, prolonged fasting with hypoglycemia, missed doses, fever, and metabolic derangement all lower the threshold. First case of the day, early break in the fast, and the home drug regimen continued is the whole strategy.

If a seizure breaks through - A benzodiazepine is first-line, and underdosing is the classic error — give a full dose before adding another agent. Support airway, breathing, and circulation, and watch for the respiratory depression that follows. Anything continuing past five minutes is status epilepticus; see that entry for the ladder.

Paralysis hides the seizure - Once a relaxant is on board, motor signs disappear while cortical activity continues. If you suspect ongoing seizure in an intubated, paralyzed patient, get a stat EEG; when EEG isn't available, treat on the presumption that seizures are continuing.

Emergence and the postictal state - Confusion, fatigue, headache, and muscle pain follow a generalized seizure, so a slow-to-wake patient after a witnessed event is postictal until proven otherwise. Non-convulsive status can look like nothing more than persistent altered mental status, tonic eye deviation, or facial and extremity twitching — EEG is the only way to make that call.

Ketogenic diet patients - Drug-resistant epilepsy managed on ketogenic therapy means keeping the patient in ketosis. Avoid carbohydrate-containing IV fluids and premedication; oral midazolam and oral acetaminophen both carry carbohydrate, so use intranasal midazolam or dexmedetomidine instead. For cases over three hours, check pH, glucose, electrolytes, and bicarbonate hourly. Treat glucose under 40 mg/dL with 1 to 2 mg/kg dextrose and do not overcorrect; response to glucagon is blunted.

Patients already on anesthetic infusions for seizure control - If propofol, midazolam, or ketamine is running as antiseizure therapy titrated to EEG, carry the current dose through the case rather than decreasing it, and be cautious about increasing propofol further.

A seizure is a transient event caused by abnormal, excessive, synchronous neuronal activity — excitation of susceptible cortical neurons that recruits progressively larger groups of connected cells. Glutamate is the main excitatory transmitter and gamma-aminobutyric acid (GABA) the main inhibitory one; excess excitation or failed inhibition produces the paroxysmal depolarization shifts that start the discharge. Seizures are partial (one cortical area fires first) or generalized (diffuse cortical onset); partial-onset with rapid secondary generalization is the most common adult type. Epilepsy is recurrent unprovoked seizures.

Everyone sits somewhere on a seizure-threshold continuum, and medications, electrolyte derangement, sleep state, fever, infection, brain inflammation, and injury move a patient across it. That is why the perioperative period — missed drug doses, fasting, sleep disruption — is a setup for a breakthrough seizure.