Prq. N-PsychopharmacoL & BioL Psychtat 1994. Vol. 18. pp. 497-502

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EEG SEIZURE DURATION MONITORING OF ECT

MICHAEL LAMBERT and FREDERICK PETTY

Department of Veterans Affairs Medical Center and Department of Psychiatry, University of Texas

Southwestern Medical Center at Dallas, Dallas, TX, U.S.A.

(Final form, June 1993)

Lambert, Michael and Frederick Petty: EEG Seizure Duration Monitoring of ECT. Prog. Neuro-Psychopharmacol. & Biol. Psychiat. 1994, 18(3) 497502.

The use of electroencephalographical monitoring in convulsive therapy has gained widespread acceptance in the United States where devices with this capability are readily available. In other countries, clinical monitoring alone is more common. Discrepancies between electroencephalographic and clinical observation (such as the “cuff method” described below) have been known to exist. Duration guidelines have evolved based on concerns about decreased effectiveness of very short seizures and neurotoxicity of overly long seizures. While these guidelines need further research to verify the assumptions they are based on, they have been recommended for use in clinical decision making. Currently available guidelines do not indicate how to manage disparate results when two measurement methods are used simultaneously. The authors examine the controversy and report the frequency of discrepancies across several guidelines.

Kev Words: electroconvulsive therapy, electroencephalogram

Abbreviations: electroconvulsive therapy (ECT), electroencephalogram (EEG)

Introduction

Electroconvulsive therapy (ECT) is an effective treatment of severe depression and mania.

One important recent technical development has been the addition of

electroencephalographic (EEG) monitoring to ECT devices made in the United States. Prior

to the addition of this capability most clinicians monitored seizure duration by observing the

497

498 M. Lambert and F. Petty

motor movements in a limb that had been isolated from the paralyzing agent by inflating a

blood pressure cuff above the systolic blood pressure (Addersly and Hamilton, 1953). In

current practice, many American clinicians utilize both monitoring methods concurrently.

Clinicians in Great Britain more often rely on clinical assessment alone due to the limited

availability of ECT devices with EEG monitoring capability (Scott et al., 1989).

Generally accepted guidelines for seizure duration are evolving. The most recent

American Psychiatric Association (APA) report recommends that seizures be at least 20 to 30

seconds in duration, but no longer than 180 seconds (American Psychiatric Association,

1990). Since that report, Abrams has re~mmend a more conservative upper limit of 120

seconds (Abrams, 1990). Based on concerns that a very short seizure may be ineffective, it

has been recommended that the patient be restimulated if the duration is less than about 25

seconds (Fink, 1989). If the seizure is prolonged, it is recommended that it be

pharmacologically terminated because of concerns about possible neurologic sequelae

(Abrams, 1990). While the exact duration re~mmendations are largely empirical and many of

the assumptions on which they are based need further research, they do serve to emphasize

the importance of seizure duration monitoring. With different interventions recommended

based on the duration estimate, discrepancies between methods of estimating seizure

duration could have an impact on clinical decision making and possibly outcome and side

effects.

The earliest report comparing EEG and cuff duration found a remarkable 90% agreement

between the two techniques (Fink and Johnson, 1982). Generally, subsequent studies have

shown the cuff measurement averages about 70% of the EEG seizure duration (Liston et al.,

1988) but large variations between the two methods make simple e~rapolation of any single

cuff estimate impossible. In Ries’ (1985) study the period of EEG activity after the cessation

of motor movements varied from 4.4 seconds to 116.2 seconds. Couture et al. (1988) also

found a wide range of variation, stating “variable differences in the two duration estimates

caution against the use of formulae that predict from one technique to the other.” For longer

seizures the discrepancy may be more marked. The cuff method has been shown less

sensitive in detecting prolonged seizures (Greenberg, 1985). McCreadie et al. (1989) only

found serious discrepancies between the EEG duration and clinical observation in patients

treated with unilateral ECT.

In the present study, the authors examined the frequency of discrepancies across currently

recognized thresholds for simultaneously measured EEG and cuff techniques. The data was

examined to see if electrode placement had an effect on the frequency of discrepancies.

Monitoring ECT 499

Four hundred consecutive ECT seizures that had been ~minister~ with a MECTA SR-1

(MECTA Corporation, Portland, Oregon, USA, 1986) under the supervision of experienced

clinicians were retrospectively reviewed. The treatments had been administered to 30

patients (28 males, 2 females) with an average age of 48.5 years. All of the patients were

medication-free during the treatments. The diagnoses included major depressive disorder

(15), bipolar disorder, depressed (9), s~izoaff~ive disorder, depressed (5), and chronic

undifferentiated schizophrenia (I). Treatments were modified in a standard manner with

succinylcholine, methohexital, glycopyrrolate, and 100% oxygen (Fink, 1979). Two hundred

and twenty-six of the treatments were unilateral (dElia position, nondominant hemisphere)

and 174 were bilateral.

Duration estimates for simultaneously measured motor cuff method and single lead EEG

were available. A cross-threshold discrepancy was defined as disagreement between the two

methods across a duration guideline. This data was reviewed for cross-threshold

discrepancies at a lower threshold of 25 seconds, and at upper thresholds of 120 seconds

(Abrams, 1990) and 180 seconds (American Psychiatric Association, 1990).

Results

At the lower threshold of 25 seconds, 21.8% of the treatments had cross-threshold

discrepancies between the two methods. Seizure length measured by EEG averaged 33

seconds longer than the cuff method for the treatments in which this occurred. In every

instance the EEG duration was equal to or exceeded the cuff duration.

Using an upper threshold of 120 seconds, the methods were discrepant in 4% of the

treatments. The cuff method did not measure any seizure as over 120 seconds. For

treatments discordant across this threshold, the EEG duration averaged 101 seconds longer

than the motor method.

Using the APA Task Force upper limit of 180 seconds, only three seizures (0.75%) were

discrepant, by an average of 163 seconds (Table 1).

500 M. Lambert and F. Petty

The EEG estimate was equal to or longer than the motor estimate in all 400 treatments.

The incidence of discrepant results was similar between unilateral and bilateral electrode

placements, (X2 = 1.9, n.s.).

Table 1

Discrepanices Between Two ECT Measurement Techniques

Discrepancy Threshold Unilateral Bilateral Combined (N=226) (N=174) (N=400)

25 Seconds 55 (24.3%) 32 (18.4%) 87 (21.8%) 120 Seconds 8 (3.5%) 8 (4.6%) 16 (4.0%) 180 Seconds 0 3 (1.7%) 3 (.75%)

Total Treatments = 400

For all discrepanices the EEG duration exceeded the cuff duration.

Discussion

Given that a significant percentage of “adequate” seizures by EEG are simultaneously read

as “inadequate” by the cuff method, these results would argue against relying on the cuff

method as the sole determination method. If restimulation of seizures shorter than 25

seconds had been performed on this sample using the cuff method alone, one fifth of the

patients could have received restimulation while the electrical seizure was continuing. When

data from both sources are available, most clinicians utilize the longer of the two

determinations when deciding whether to restimulate or terminate a seizure. For this sample,

that would have been the EEG for all 400 treatments. The ill effects, if any, of unnecessary

restimulation or undetected prolonged seizures cannot be determined except by a prospective

study design.

While this study does not answer the question of which data source is most valid, the

common clinical dilemma is the patient with a short or nonexistent motor seizure. In this

sample the EEG alone could have served as a guide whether or not to restimulate. In the

smaller percentage of patients with prolonged ictal activity, the EEG again appears to be the

more sensitive technique. While the measurement of motoric seizure activity clearly has

limitations in sensitivity and in detecting the true extent of prolonged seizures, in our

experience the single lead EEG has been an excellent tool for measuring seizure response.

In this study, there were no patients who manifested a motoric seizure without a

Monltorhg ECT 501

corresponding EEG activity. The reverse was not true. For these reasons, the routine use of

EEG monitoring is recommended.

The result of this report support those who question the cuff methods role in seizure

duration monitoring (Chesen, 1983; Greenberg, 1985, Couture et al., 1988). The risk of leak

across the cuff of succinylcholine, metabolic exhaustion of the limb muscle in longer seizures,

and non-motoric electrical seizures decrease its utility for accurately measuring seizure

length.

Conclusion

The cuff method may retain a useful and unique role in confirming the bilateral

generalization of unilaterally induced ECT seizures. However, routine EEG monitoring should

become the standard.

Acknowledaments

Supported by the Department of Veterans Affairs and a Department of Veterans Affairs

Research Development Award to Frederick Petty, Ph.D., M.D. Also supported by an NIMH

Research Grant (MH37899) NIAAA (AA07234) and by MHCRC Grant (MH41115) to the

Department of Psychiatry, University of Texas Southwestern Medical Center at Dallas. The

authors thank Dinah Turner-Knight for excellent secretarial support in preparing the

manuscript.

References

ABRAMS R [I9901 Termination of ECT-induced prolonged seizures. Convulsive Therapy &54-58.

ADDERSLY DJ and HAMILTON M [I9531 Use of succinylcholine in E.C.T. with particular reference to its effect on blood pressure. Br Med J 1: 195-I 97.

AMERICAN PSYCHIATRIC ASSOCIATION (19901 The Practice of ECT: Recommendations for Treatment, Training, and Privileging. Washington, DC, American Psychiatric Press, pp. 11.8.2-I 1.8.4.

502 M. Lambert and F. Petty

CHESEN ES [I9831 EEG monitoring of ECT preferred to cuff method. Am J Psychiat 140 (letter): 1648-l 649.

COUTURE LJ, LUCAS LF, LIPPMANN SB, SHALTOUT T, PALOHEIMO, MPJ and EDWARDS, HL. [1988] Monitoring seizure duration during electroconvulsive therapy. Convulsive Therapy &206-214.

FINK M and JOHNSON L [1982] Monitoring the duration of electroconvulsive therapy seizures. Arch Gen Psychiatry %:1189-l 191.

FINK M [I 9891 An adequate treatment? Convulsive Therapy 3:31 l-31 3.

FINK M [I9791 Convulsive Therapy: Theory and Practice. New York, Raven Press pp. 105 227.

GREENBERG LB [I 9851 Detection of prolonged seizures during electroconvulsive therapy: A comparison of electroencephalogram and cuff monitoring. Convulsive Therapy _1:32-37.

LISTON EH, GUZE BH, BAXTER LR, RICHEIMER SH and GOLD ME [1988] Motor versus EEG seizure duration in ECT. Biol Psychiatry 394-96.

MCCREADIE RG, PHILLIPS K, ROBINSON ADT, GILHOOLY G and CROMBIE W [1989] Is electroencephalographic monitoring of electroconvulsive therapy clinically useful? Br J Psychiatry -:229-231.

RIES RK 119851 Poor interrater reliability of MECTA EEG seizure duration measurement during ECT. Biol Psychaitry 2094-98.

SCOTT AIA, SHERING A and DYKES S [1989] Would monitoring by electroencephalogram improve the practice of electroconvulsive therapy? Br J Psychiatry =:853-857.

Inquiries and reprint requests should be addressed to:

Michael Lambert, M.D. Psychiatry Service (116A) Veterans Affairs Medical Center 4500 So. Lancaster Road Dallas, TX 75216 (214) 376-5451, Ext. 5474