Clinical application of electroencephalographic vigilance during electroconvulsive therapy

Author(s): Piana, R. C.

Journal/Book: Salud Ment. 1995; 18: Calz Mexico-Xochimilco #101, Mexico City 22 DF, Mexico. Inst Mex Psiquiatria. 28-33.

Abstract: Each electrically-induced seizure of electroconvulsive therapy (ECT) is accompanied by transient but dramatic changes in electroencephalographic (EEG) patterns, regional cerebral blood flow, glucose utilization, and oxygen consumption. Glucose uptake and oxygen consumption virtually double during the seizure to support the sudden, massive neuronal discharges affecting every part of the brain, and regional cerebral blood flow increases accordingly. It is thus not surprising that those who administer ECT, anesthesiologists and psychiatrists, have chosen to closely monitor two aspects of this general cerebral activation during ECT. Anesthesiologists now routinely use pulse oximetry to monitor blood oxygen levels during ECT, just as they do for most other procedures performed under general anesthesia, whereas psychiatrists have chosen to monitor the EEG. Since the pioneering studies of Ottosson, it has been generally acknowledged that the primary therapeutic component of ECT is the induced seizure, rather than any other aspect of the procedure. Although the electrical dosage itself plays an important role with regard to the generalization of the seizure throughout the brain, and may even directly contribute to therapeutic efficacy, all recognize that in the absence of a brain seizure there is no therapy. Moreover, all seizures are not equally potent. Abortive, parcial, and incomplete seizures have been shown to lack therapeutic efficacy, resulting in the recomendation that EEG seizures of less than about 25-30 seconds require restimulation at a higher dose. However, this does not imply any direct relation between seizure duration and therapeutic efficacy once this minimum duration has been achieved. In fact, none of the many studies attempting to correlate EEG seizure duration during ECT with therapeutic outcome have been successful: Once a generalized seizure of 25-30 seconds EEG duration has been obtained, there is simply no correlation between total seizure length and clinical efficacy. This fact has led investigators to study other physiologic aspects of the induced EEG seizure in a search for measures that actually inform the clinician of the clinical efficacy of the seizure he has just administered. In this paper, the authors considered several of these measures. EEG monitoring during ECT serves three main purposes: First, to ascertain that a cerebral seizure has occurred. Second, to determine that the seizure is sufficiently long and well-generalized throughout the brain to have a therapeutic effect and, finally to ensure that the seizure has ended and to document its length. Observation of the motor convulsion alone is inadequate for any of these purposes because there is often no close correspondence between the cerebral seizure and its peripheral manifestations. Even under ordinary conditions there is a systematic difference between EEG and motor seizure durations such that EEG seizure activity continues for many seconds after the motor convulsion stops. Occasionally the EEG seizure can continue for many minutes after all visible muscle activity has ceased. For over 50 years, the visual EEG has been the standard for recording and analyzing brain activity, which is why an EEG recorder is now incorporated in the most sophisticated ECT devices. However, EEG paper can unexpectedly run out during the middle of a seizure, leaving the doctor to guess exactly when the seizure ends. For this reason an auditory electroencephalograph was developed that converts the brain's EEG activity into a sound that fluctuates with the frequency and amplitude of the EEG, and thus corresponds precisely to the visual record. One general problem with EEG monitoring is that about 10-15 % of EEG records during ECT show an indeterminate endpoint. These problems have led to the recent application of computer-automated methods of EEG analysis for use during ECT. It compares the continuous moving mean integrated voltage of the EEG seizure activity with that of the inmediate prestimulus EEG. The heart rate response to ECT provides another interesting physiological correlation with EEG seizure duration, as well as, the analysis of the EEG seizure patterms, especially Postictal suppression phase, that probably reflects an active process of the brain in terminating the induced seizure, and seizure amplitude included in a computer derived method for automatically measuring total energy seizure. Correlational measures such as motor and EEG seizure duration, reflects the degree of spread or generalization of the seizure activity in the brain. Other equally important advances in technology, namely brief pulses stimulus and right unilateral treatment electrode application allow the psychiatrist to administer a highly effective form of treatment for the severest of the mentally ill patients, in a safe, sophisticated and humane manner that is virtually devoid of the undesirable side-effects that were so prominent in the past.

Note: Article R Abrams, Univ Hlth Sci Chicago Med Sch, Dept Psychiat & Behav Sci, 333 Green Bay Rd, N Chicago, IL 60064 USA

Keyword(s): POOR INTERRATER RELIABILITY; SEIZURE DURATION; ELECTRODE PLACEMENT; ECT; EFFICACY; EEG

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