Chapter 106. Anticonvulsants: Seizure Prophylaxis and Chronic Treatment

• Prophylactic anticonvulsant therapy prior to neurosurgery is controversial
• Patients should continue their preoperative anticonvulsants as long as they have therapeutic drug levels
• Phenytoin 100 mg Q8 hours or levetiracetam 500 mg are the most common regimens
• Levetiracetam is now being used more often due to broad-spectrum seizure coverage and lower side effects, and serum therapeutic levels do not need to be checked

Anesthetic Choice

• Inhalational anesthetics are primarily antiepileptic
• Nitrous oxide tends to inhibit seizure spikes
• Benzodiazepines and propofol are antiepileptic
• Ketamine, etomidate, and methohexital can be proconvulsant with low dosages and should be avoided
• High doses of fentanyl and alfentanil can trigger epileptiform spike activity on EEG
• Large doses of meperidine, atracurium, or cisatracurium should be avoided due to epileptogenic metabolites normeperidine and laudanosine
• Regional anesthesia is encouraged as long as optimal surgical environment is maintained

If seizure occurs

• Treat with small dose of thiopental 2 mg/kg, midazolam 2–5 mg, or propofol 1–2 mg/kg
• Consider phenytoin 500–1000 mg IV slow loading dose (or the equivalent as fosphenytoin: less likely to cause hypotension) for prevention of recurrent seizures
• If seizures refractory to above, administer general anesthetic doses of inhalational or IV anesthetics

• Drug levels of older antiepileptics such as phenytoin need to be monitored
• If patient cannot take po postoperatively, convert to IV and adjust dose