Abstracts

Intracarotid injections of methohexital and amobarbital have been used for Wada testing to assess language and memory lateralization in the presurgical evaluation of patients with epilepsy. Sporadic case reports indicate that methohexital, in contrast to other barbiturates, may decrease seizure threshold in epilepsy patients and even provoke seizures in individuals without underlying seizure disorder [1, 2, 3, 4].
A retrospective chart review of 677 consecutive Wada tests carried out at the Cleveland Clinic Foundation between 1996 and 2003 was performed. Patients underwent left (n=68), right (n=69), or bilateral (n=540) internal carotid artery catheterization. Methohexital (n=131; 3-5 mg) or amobarbital (n=538; 75-175 mg) was injected. Angiography was performed and all patients were monitored with simultaneous EEG recording according to the 10-20 system. Data are given as mean +- SD and were tested for significance using Pearson[rsquo]s Chi square test or t-test.
Ten out of 677 (341 males, 336 females; mean age 32 +- 14 years) patients had a seizure during the Wada procedure. Two seizures occurred prior to barbiturate injection. Eight patients had a seizure following barbiturate injection (5 males). These patients were significantly younger (21 +-9 y) than the mean test population (t-test, p=0.023). Four seizures occurred after Methohexital injection (4/131=3.1 %), two of them were secondarily generalized. After injection of amobarbital, four out of 538 patients (0.7 %) had a seizure; one of them was secondarily generalized. The seizure incidence after injection of methohexital was significantly increased as compared to amobarbital (Chi square = 4.582, p [lt] 0.05).
These results suggest that seizures after barbiturate injection are more frequent than seizures prior to injection despite the fact that the duration of EEG monitoring prior to injection is approximately as long as after injection. Additionally, seizures occur more often after methohexital than after amobarbital injection. Furthermore younger patients are at greater risk for seizures following barbiturate injection. On the one hand, methohexital has a shorter half-life than amobarbital facilitating dose titration. On the other hand, the use of methohexital during wada testing bears a higher risk of seizures as compared to amobarbital.
[1] Barra D, Dru M, Truffa-Bachi J: Generalized seizure induced by methohexital. [italic]Ann Fr Anesth Reanim[/italic] 1987, 6(2): 120-1
[2] Metriyakool, K: Seizures induced by methohexital. [italic]Anesthesiology[/italic] 1981, 55(6): 718
[3] Modica PA, Tempelhoff R, White PF: Pro- and anticonvulsant effects of anesthetics (Part II[italic]). Anesth Analg[/italic] 1990, 70(4): 433-44
[4]Rockoff MA, Goudsouzian NG: Seizures induced by methohexital. [italic]Anesthesiology[/italic] 1981, 54(4): 333-5
[Supported by: Author TL was supported by Innovative Medizinische Forschung, WWU Münster (FoeKz. LO 610101).]