Abstracts

RATIONALE: Various protocols exist for performing the intracarotid amobarbital test (ICAT). Most involve injection of a pre-determined amount of amobarbital. This sometimes produces inadequate hemi-anesthesia, and sometimes excessive sedation, requiring the injection be repeated (Blum et al J Epilepsy 1997 v10p42). A variable-dose protocol, with the amount of amobarbital individually titrated to the patient, is presented here.
METHODS: We retrospectively analyzed all ICAT performed from 1992 through 1999. Only the first injection, ipsilateral to the seizure focus, was examined in each case. Prior to April 1997 ICAT was done injecting 150 mg of amobarbital in each carotid (N=93). From then on, ICAT was performed injecting amobarbital at 50mg/second until the contralateral hand became paralyzed, plus one additional second (N=39). The amytal remaining in the catheter deadspace was then withdrawn. Doses used ranged from 40 to 300mg. We rated each injection as [ssquote]under-sedated[ssquote] if the patient did not remain hemiplegic for long enough to present at least 50% of the test items. We rated each injection as [ssquote]over-sedated[ssquote] if the patient was not awake enough to attend to stimuli and the injection was repeated.
RESULTS: The variable dose protocol resulted in fewer cases of over-sedation and fewer cases of under-sedation (chi-square 8.0, p=0.02). Fewer tests had to be repeated. No drawbacks were observed with this method.
CONCLUSIONS: The variable dose ICAT protocol increases the likelihood of obtaining useful data from the first amobarbital injection and reduces the risk of second injections.
Support: No funding provided