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Biomedical subjects

A D Krystal

Publications and source records attributed to A D Krystal.

32 records · Page 2Linked to original sources
PubMed1995

Seizure threshold in electroconvulsive therapy (ECT) II. The anticonvulsant effect of ECT.

To measure the anticonvulsant effects of a course of electroconvulsive therapy (ECT), we used a flexible stimulus dosage titration procedure to estimate seizure threshold at the first and sixth ECT treatments in 62 patients with depression who were undergoing a course of brief pulse, constant current ECT given at moderately suprathreshold stimulus intensity. Seizure threshold increased by approximately 47% on average, but only 35 (56%) of the 62 patients showed a rise in seizure threshold. The rise in seizure threshold was associated with increasing age, but not with gender, stimulus electrode placement, or initial seizure threshold. Dynamic impedance decreased by approximately 5% from the first to the sixth ECT treatment, but there was no correlation between the change in dynamic impedance and the rise in seizure threshold. No relation was found between the rise in seizure threshold and either therapeutic response status or speed of response to the ECT treatment course. These findings confirm the anticonvulsant effect of ECT but suggest that such effects are not tightly coupled to the therapeutic efficacy of moderately suprathreshold ECT.

Adult↗
PubMed1995

Seizure threshold in electroconvulsive therapy: I. Initial seizure threshold.

We measured initial seizure threshold by means of a structured stimulus dosage titration procedure in a clinical sample of 111 depressed patients undergoing brief-pulse, constant-current electroconvulsive therapy (ECT). Initial seizure threshold was approximately 60 millicoumbs (mc) (10 Joules) on average, but varied widely (6-fold) across patients. Initial seizure threshold was predicted by four variables: electrode placement (higher with bilateral), gender (higher in men), age (higher with increasing age), and dynamic impedance (inverse relationship). Use of neuroleptic medication was associated with a lower seizure threshold. EEG seizure duration was inversely related to initial seizure threshold, but no other relations with seizure duration were found. These findings may have important clinical implications for stimulus dosing strategies in ECT.

Adult↗
PubMed1995

The ictal EEG as a marker of adequate stimulus intensity with unilateral ECT.

Relative stimulus intensity above seizure threshold has been shown to affect therapeutic outcome with unilateral ECT. The authors sought to explore whether a multivariate ictal EEG model would permit ongoing clinical assessment of this parameter. Twenty-five depressed subjects were randomized to either barely (T) or moderately (2.5T) suprathreshold ECT treatments. Seizures in 2.5T subjects had significantly greater ictal spectral amplitude and coherence, greater postictal suppression, and shorter latency until ictal slow-wave onset. A multivariate logistic regression ictal EEG model distinguished between stimulus intensity groups with 90% accuracy. Preliminary evidence suggests a relationship between several ictal EEG indices and therapeutic outcome. A multivariate ictal EEG algorithm holds promise as a tool for clinical determination of adequate stimulus intensity with unilateral ECT.

Adult↗
PubMed1995

Ambulatory cassette polysomnography: findings from a large cohort of drug-free insomnia patients.

Technology for conducting ambulatory polysomnography (APSG) has been available for more than a decade, but relatively few studies have used this technology to study the sleep of subjects in their usual home sleeping environments. Herein we suggest the usefulness of this technology for the study of normal sleepers and insomniacs, and we report our APSG findings with a large cohort (n = 117) of drug-free insomnia outpatients. All patients completed a sleep-history questionnaire, a clinical interview with a sleep-disorders clinician, and one night of APSG in their homes. Most sleep parameters derived were consistent with previously reported laboratory PSG findings for insomniacs, except that values of rapid-eye-movement sleep latencies were generally shorter than typically found in laboratory studies. Moreover, results showed that APSG served to differentiate major age groups and diagnostic subtypes within our larger sample, and patient tolerance for APSG was within acceptable limits. We conclude that APSG is a useful technique for evaluating insomnia complaints.

Adult↗
PubMed1995

ECT seizure duration: reliability of manual and computer-automated determinations.

Reliable monitoring of electroencephalographic (EEG) and electromyographic electroconvulsive therapy (ECT) seizure duration has become important as these assessments have become a routine part of the clinical practice of ECT. In this regard, accurate automated seizure duration determinations would be particularly valuable. As a result, the present study was performed to assess the reliability of available computer-automated determinations of seizure duration (Thymatron Model DGx ECT machine; Somatics, Inc.) and to explore the factors upon which such reliability as well as the determinations of experienced raters depend. We found that the experienced human raters had very high interrater reliability, significantly higher than either did with the automated Thymatron DGx ratings. In general, the reliability of all ratings declined in the context of artifact, poor postictal suppression, or an EEG seizure end point that was reached gradually. Reliability was also greater for continuation ECT as compared with the index course. The reliability of Thymatron DGx versus experienced human ratings was particularly sensitive to these factors, ranging from 0.68 when several of these factors were simultaneously present to 0.999 when all these factors were absent.

Adult↗
PubMed1994

The present use of electroconvulsive therapy.

Physicians attempting to treat certain severe mental disorders have recently shown renewed interest in electroconvulsive therapy (ECT). A number of technical innovations have made ECT safer, as well as more effective. These innovations include oxygenation, muscular relaxation, unilateral nondominant electrode placement, use of brief-pulse stimuli, titrated stimulus dosing, electroencephalographic (EEG) monitoring, determination of seizure adequacy, and pharmacologic enhancement of treatment response.

Electroconvulsive Therapy↗
PubMed1994

ECT seizure therapeutic adequacy.

From the beginnings of convulsive therapy, the need for some way to assess the therapeutic adequacy of individual treatments has been apparent. Recent work suggests that seizure therapeutic adequacy and adverse effects are dependent on the extent to which the stimulus exceeds the seizure threshold (relative stimulus intensity). Applying this information in clinical practice is problematic because of the variable rise in the seizure threshold that takes place over the treatment course. Attributes of the ictal electroencephalogram (EEG) show promise for alleviating this problem by serving as a marker of relative stimulus intensity. Obstacles that need to be overcome in order to implement ictal EEG indices as a relative stimulus intensity marker in clinical practice are discussed and include artifacts, how to determine a threshold for deciding adequacy, variation in technique between sites, and inter-individual EEG variation; some strategies for overcoming these hurdles are described. It is anticipated that an ictal EEG algorithm that addresses these issues is likely to be of substantial clinical benefit in the practice of electroconvulsive therapy.

Biomarkers↗
PubMed1993

The effects of ECT stimulus dose and electrode placement on the ictal electroencephalogram: an intraindividual crossover study.

Recent evidence suggests that electroconvulsive therapy (ECT) efficacy depends upon both electrode placement and the degree to which stimulus dosage exceeds seizure threshold (T), and not simply on surpassing a minimum seizure duration as has been assumed. In light of these findings and studies reporting ictal electroencephalogram (EEG) differences between bilateral and unilateral ECT, we performed this 19-subject intraindividual crossover study of the effects of dose and electrode placement on the ictal EEG. We found ictal EEG evidence of greater seizure intensity with bilateral than unilateral ECT and with higher dosage (2.25 T) compared with barely suprathreshold stimuli. Seizure duration was not longer with bilateral than unilateral ECT and actually decreased with increased dose. A number of ictal EEG variables separated the unilateral 2.25 T and unilateral T conditions, which reportedly differ in efficacy, and therefore, these EEG measures show promise as markers of treatment adequacy.

Adult↗
PubMed1992

Ambulatory polysomnography: technical aspects and normative values.

Ambulatory polysomnographic (APSG) assessment of sleep disorders is now possible, but the technique of APSG is sufficiently different from in-laboratory PSG that normative data from in-laboratory PSG may not apply to APSG. This paper reviews the technical aspects of APSG and presents normative APSG data from 20 older healthy males. Subjects underwent medical and psychiatric screening before completing APSG in their homes. Total sleep time and the rapid-eye-movement sleep latency (RL) were both shorter than those reported by others using traditional in-laboratory techniques. The shorter total sleep may be related to behaviors at home that impinge upon sleep. The shorter RL may be related to differences in calculation methods. Periodic limb movements were common in our subjects but did not contribute to sleep disturbance. We conclude that APSG is sufficiently different from traditional PSG as to warrant collection of a large normative data base.

Ambulatory Care↗
PubMed1991

The monitoring and management of electrically induced seizures.

Because induced seizures have such a fundamental influence on both beneficial and adverse effects associated with ECT, it is crucial that they be monitored as effectively as possible. In practice this process involves a combination of both motor and EEG monitoring. The technology for such monitoring, although not overly sophisticated, is also not trivial, and a certain amount of training is required before a practitioner can meaningfully interpret this type of information. Efforts to standardize monitoring practices, at least within a particular ECT program, are also indicated. Our knowledge of what constitutes an adequate seizure is limited, with duration still the primary focus. Future studies of ictal electrophysiology may well provide better answers in this regard. One area where already accomplished work has proved productive involves the delineation of many of the factors which influence seizure threshold and duration. On the basis of these data, practitioners now can exert considerably greater control over such measures, and thereby make more optimal use of this treatment modality.

Electroconvulsive Therapy↗