Seizures with etomidate anesthesia.

Anecdotal reports are almost invariably the initial form for the presentation of new and previously unexpected events. Clinical and experimental studies characteristically follow them should enough questions be raised by these reports. The author must agree with Dr. Keats that more cases of seizures have been reported associated with fentanyl than with isoflurane. The only inference that can be drawn from this, however, is that if there is really an incidence of seizures with either drug, it is extremely rare. The approach of using a seizure-anecdote-score as an attempt to quantify these anecdotal reports is an innovative one but cannot possibly serve to confirm the occurrence of seizures with one drug while denying the other. Rather, it can only show the perhaps very unusual nature of the incidence with each. Interestingly enough, since the beginning of anecdotal reports of seizure activity associated with fentanyl, clinical investigative studies have been carried out. To date, EEG substantiation of seizure activity associated with fentanyl anesthesia (at least in high dose fentanyl anesthesia) remains absent (1). In examining other anecdotal reports of seizure activity also associated with fentanyl, a substantial difference exists between circumstances in this reported case, and those previously reported (2-5). Dr. Keats indicates that isoflurane is eliminated rapidly, whereas fentanyl takes more time. This is the case. However, the primary determinant of the duration of action of fentanyl in low doses (as in this case) is that of redistribution from the vessel-rich brain. In this instance there was a time interval of greater than one-half hour from the administration of the 10O-pg bolus of fentanyl until the slowly progressive onset of seizure activity. In a patient without otherwise complicating medical conditions, the fentanyl level in the brain should be exceedingly low. I t should also be noted that of all the drugs listed as given in the case that may potentially complicate the situation, i.e., fentanyl, d-tubocurarine, thiopental, succinylcholine, nitrous oxide, and isoflurane, only fentanyl (and now isoflurane) have been implicated as potentially causing seizure-like activity. The utilization of intraoperative encephalographic monitoring is, and may always be, the exception rather than the rule in all but a select number of cases. This fact, coupled with the clear rarity of seizure activity with either of the above-mentioned drugs, makes the likelihood of observing it on an EEG very low. In fact, when specifically looked for under the appropriate circumstances, they did not occur (1). Finally, it should be noted that if one cannot believe anecdotal reports of seizures without the assistance of a relatively recent invention such as an electroencephalogram, epilepsy would be a very young disease indeed. LETTERS TO THE EDITOR