Reprinted from the German Journal of Psychiatry · http://www.gjpsy.uni-goettingen.de · ISSN 1433-1055

ECT Dosing by the Benchmark Method
Conrad M. Swartz
Department of Psychiatry
Southern Illinois University School of Medicine
Corresponding author: Conrad Swartz, Ph.D., M.D., Professor and Chief, Division of Psychiatric Research,Box 19642, Southern Illinois University School of Medicine, Springfield, Illinois 62794-9642

Abstract
Background: The methods used to select ECT stimulus dose have no basis in physiology and are incomplete.
They are not related to the quality of the ECT seizure, such as its intensity or its generalization through thebrain. These methods are not substantially individualized and do not guide the dose along the course. A rational system is described that does not have these shortcomings. Method: On the basis of the axioms thathigher dose produces greater effect, and meaningful physiological measurements reflect efficacy, the principle toguide ECT dosing is that diminished physiological intensity indicates decreased treatment quality. Results:
The corresponding strategy for dosing begins with a strong stimulus at the first ECT treatment. The measured
resulting physiological effects should be intense, and these serve as benchmarks. At later treatments the electrical stimulus dose is gradually adjusted to approximate the lowest dose that produces physiological effects thatare near these benchmarks. Smaller physiological effects suggest increase in stimulus dose. Conclusions: Thismethod uses physiological measurements in a manner analogous to blood drug levels in pharmacotherapy. A
strong first-ECT stimulus typically has a dose 3.5 to 4 times age with bilateral or 5 times age with unilateralelectrodes at 0.5ms pulsewidth and 30-70 Hz; wider pulsewidths necessitate higher dosage. Recent studies suggest that peak seizure heart rate and several computer-processed EEG aspects are suitable physiological measurements to use in this method. The use of peak heart rate requires no special EEG equipment or EEG training (German J Psychiatry 2002; 5: 1-4)
Keywords: ECT, electroconvulsive therapy, dose, charge, EEG, heart rate
Received: 20.11.2001
Published: 16.01.2002

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physiological, therapeutic, and adverse effects. In otherwords, for suitably selected physiological measurements,
physiology corresponds to the amount of therapeutic benefit. Generally, clinically effective ECT produces strong
physiological effects, while weak physiological effects indicate weak treatment.

The "Benchmark Method" is a rational method for ECT
dosing. It accounts for the wide individual variations
among patients, and it is based on the principle that higher
electrical doses generally produce larger changes, including

Accordingly, a goal for the ECT stimulus is to produce
physiological effects of about the same size as accompany aneffective ECT, for that same patient. These physiologicaleffects are a representative, or proxy, for efficacy. In contrast, there is no relationship between the weakest possible
ECT (i.e., seizure threshold) and effective ECT, and noreason for one. Similarly, there is no relationship between
seizure threshold and a logical ECT dose, but only theabsence of a relationship; a recent review describes therelevant details (Swartz 2001).

Introductionn selecting the dose to use in electroconvulsive therapy(ECT) treatment, the goal is effectiveness and avoidanceof overdose side- effects. The usual motivation to administer ECT is need for its efficacy. Although side-effects are
only temporary and a secondary consideration, patient andstaff morale are high when noticeable side-effects are rare. A
rational method to set the stimulus dose should help tominimize side-effects.

SWARTZ
The Benchmark Method guides the ECT dose with physiological measurements, using ordinary equipment. In thismethod larger physiological effects are analogous to higher
drug doses in pharmacotherapy, with more rapid response.
With the Benchmark Method, values of suitable physiological effects that accompany an effective ECT represent its
efficacy, and are goals for every ECT. The method begins by
establishing personal benchmarks for physiological measurements, with each patient. The method is more complete
when it includes several physiological effects that are at least
partially independent of each other. Still, a single sensitive"target measurement" may suffice. In specific, the peak heart
rate during the ECT seizure (peak HR) has shown clear
sensitivity; patients who showed higher peak HR relative totheir personal benchmark required fewer ECTs (Swartz
2000). The peak HR will be referred to as the target measurement to illustrate the method, but other physiologicaleffects (e.g., EEG measurements) might sometimes be usefulwith it or instead. The Benchmark Method has four steps.

The Benchmark Method Step-bystep
1. At the first ECT a stimulus dose is selected to produce anintense seizure. For bilateral electrode placements such as
bitemporal, bifrontal, or LART (Swartz, 1994) a dose (inmC) of 3.5 to 4 times age (%Energy or expected joules = 7080% of age) usually suffices for this. This is because a doseof 2.5 times age virtually always induces seizure (Petrides
and Fink, 1996), and small dose additions rapidly increase
seizure intensity with bilateral ECTs. For unilateral placement the mC dose would be about 5 times age (%Energy =age). The first ECT is usually especially vigorous (Krystal etal., 1996), which makes useful benchmarks easier to obtainat ECT#1. The goal is not mere seizure occurrence, but
vigor. This plan is opposite to giving a stimulus near seizure
threshold to produce a weak seizure, per the "stimulus titration" method (Sackeim et al., 2000).
2. Measure baseline HR and peak HR during the seizure.
Common digital ECG monitors and pulse oximeters display HR continuously, which facilitates this measurement.
Some ECT instruments report peak HR. The peak HR at
the first ECT becomes the initial benchmark. A peak HRthat exceeds it at a later ECT supersedes it. In a recent
study of 24 patients the benchmark HR over the course of
ECT ranged from 121 to 190 bpm, with a median of 151
bpm (Swartz 2000). If peak HR is only 10 bpm above baseline, or less, there is a problem. Either the seizure is weak
and unsuitable to produce benchmarks, or HR accelerationis blocked, pharmacologically or physiologically. Several
medications diminish HR acceleration, e.g., the anesthetic
propofol, beta-blockers, calcium channel blockers. If peak
HR cannot rise much above baseline other physiologicalmeasurements should be used instead.

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3. When using a type of bilateral ECT consider a lower
dose at the second treatment. Dose reduction is a stronger
consideration when potential adverse effects are more important than urgency; for such cases the mC dose withbilateral ECT might be decreased to about 2.5 times age(i.e., %Energy = half age). Dose reduction with unilateral
ECT is a potential consideration for patients at high riskfor problematic adverse effects, e.g., those with cerebrovascular disease.
4. At the second and following ECTs measure peak HR. If
it is within 6 bpm of the benchmark the efficacy is probably
maximal. When efficacy is maximal the dose is not too low,
and a small dose decrease (25-50 mC) can be considered. If
peak HR is 6 to 12 bmp below benchmark the efficacy isprobably moderate; consider a small dose increase, e.g., by
25 mC. If peak HR is at least 12 bpm below benchmark,efficacy is probably low; consider a moderate dose increase,e.g., by 75 mC. If there are no signs of seizure consider alarge dose increase, e.g., by 100-125 mC.
This fourth step is repeated with each ECT. It helps regulate dosage along the ECT course, that is, when to increaseor decrease and by how much. About half of patients-particularly elderly men--show increasing seizure thresholdalong the course (Coffey et al., 1995); their dosage needs
reconsideration repeatedly. The use of EEG measurements(instead of peak HR) is not completely understood, specifically the amount of change large enough to indicate a dose
increase. Still, prima facie considerations suggest that a
result within 5% of the benchmark is generally good, whilea result more than 25% below the benchmark seems deficient. Conversely, if a useful dose increase does not elevatea specific physiological effect, measurement of that effectmight have little value for that patient.
The steps are summarized in Table 1.
Table 1. Summary of Benchmark Method Steps-At ECT #1 use a high-dose stimulus to produce aclearly effective treatment-

Take the resulting physiological measurement as thebenchmark, e.g., peak seizure HR-

At later ECT sessions try to decrease the electricaldose, while maintaining the physiological effect near
the benchmark, e.g., peak HR within 6 bpm ofbenchmark-If the physiological effect falls substantially below thebenchmark, increase the electrical dose. If thebenchmark is surpassed it is superseded by thehigher result

Interpretation of Observations
Any sign of seizure weakness at the first ECT suggests that
this ECT is not suitable to produce good benchmarks.

ECT DOSING
Common signs of weakness include little if any tonic motor
activity, such as only clonic activity (Cronholm and Ottosson, 1960), motor duration under 18 sec (Swartz and Larson 1989), indistinct postictal EEG suppression (Nobler etal. 1993), and peak HR under 120 bpm (Swartz, 2000).
Another sign of weakness is absence of high-amplitude lowfrequency waves with superimposed high frequencies(Swartz, 1995), except when EEG electrodes are locatedsymmetrically, e.g., above the two eyes. Unfortunately, thiscommonly-used symmetrical EEG placement causes cancellation of low-frequency waves. If at least one sign of seizure
weakness occurs at the first ECT, consider increasing thedose by 75 mC and looking for new benchmarks.
To be useful, the physiologic target measurement shouldmeet two particular expectations. It should be sensitive tostimulus dose, e.g., larger with higher doses. It should also
be sensitive to efficacy, e.g., larger with greater efficacy. Of
course, sensitivity to dose and efficacy represents sensitivity
to seizure intensity. In turn, seizure intensity refers to seizure spread through the brain as well as amplitude. Accordingly, distinctions in ECT seizure intensity are easier todetect at greater distances from the stimulus electrodes.
This means that physiological effects at greater distancesfrom the stimulus electrodes are generally more sensitive tostimulus dose and treatment efficacy. Conversely, measurements of brain regions near the stimulus electrodes are
relatively insensitive, so that only large differences are detectable. The same conclusion follows the slightly different
perspective that important gradations in seizure intensity
are most noticeable in brain areas where intensity is weakest.
Indeed, none of a wide range of EEG phenomena recorded
from electrodes located about 5 cm from the stimulus electrodes showed sensitivity to doubling of stimulus dose,
while peak HR was sensitive (Swartz 2000). That is, 5 cm
between stimulus and EEG electrodes is too close. In contrast, the site for peak HR effect is relatively far from thestimulus electrodes. This site is the right medulla, the brain
area that mediates cardioacceleration. Logically, then, EEG
electrodes are best located more than 5 cm from the nearest
stimulus electrode; sensitive configurations await determination.
Besides peak HR, physiological effects that have shown
some sensitivity to stimulus dose or electrode placement(and by implication stimulus dose) include prolactin andcortisol release. Several EEG measurements including seizure amplitude and postictal suppression have shown somesensitivity to dose or efficacy, although this sensitivity was at
the lowest significance (p<.05) and it reached saturation at
low efficacy (Nobler et al. 1993). Such saturation is analogous to a serum drug assay that reaches its maximum limit
well below minimum therapeutic level; only the most severe
deficiencies can be detected, and therapeutic adequacy
cannot be assessed.
Some patients might show little physiological effect but
respond anyway; this can happen if the physiological effectis blocked. In this case other physiological effects should be
used instead. Other patients might show intense physiological effects but deny benefit from treatment; this canresult from concurrent conditions that resist ECT, e.g.,
post-traumatic stress disorder. Still other patients mightshow a peculiarly high physiological result not approachedlater; this should be dismissed as a peculiarity. For example,
a 75 year old depressed woman showed a peak HR of 184
at ECT #1, which is extraordinarily high for age. The peak
HR was 170 at ECT #2, a more realistic benchmark value;
peak HRs ranged from 163 to 166 at ECTs #2 through #5.

Previous Methods
Close matching to individual patient physiology is an unusual virtue of the Benchmark Method. Other methods do
not consider individual variations with regard to other
patients of the same seizure threshold or age.
Just as basic is that previous methods identify only an initial
dose; this is a double omission. First, the initial dose is only
an estimate. It can be too weak or unnecessarily strong forthe individual patient; an assessment is needed and consideration given to adjustment. Second, ECT itself is anticonvulsant and stimulus dose increases can be needed along
the course, and frequently with some patients. One method
took similarity to the weakest (threshold) seizure to suggest
stimulus increase (Krystal et al. 2000). This is analogous todosing lithium through serum lithium level similarity to thelowest detectable level (e.g., 0.1 meq/L)--the relationship isweak and unreliable.
The fixed dose method was used in comparison between
unilateral and bilateral ECT at a high dose of 378 mC(Abrams et al., 1991). A fixed dose of 403 mC was more
effective in unilateral ECT than the threshold multiple
method at 2.25 multiple (McCall et al., 2000). The fixed
dose method is most applicable to unilateral ECT because
the side-effects of moderate overdosage are usually mild.
Still, about one third of ECT responders remit with lowdose unilateral ECT, while others relapse quickly after highdose unilateral ECT and should have responded better to abilateral placement (Sackeim et al., 2000).
In setting the dose proportional to age, the rationale is thatthe dose needed to induce an effective seizure rises withage. This rationale is probably true but has not been specifically verified; it is related to the rise in seizure thresholdwith age only by analogy. In the "full-age method" for unilateral ECT %Energy (or expected joules) is set to patientage; this equals setting mC to age times five. The "half-age
method" uses a dose half this, and is most applicable to thevarious types of bilateral ECT (Petrides and Fink, 1996).
The rationales for the seizure threshold multiple method
are that dosage must exceed threshold and higher dosage
produces larger effects. Unfortunately, the relationship3

SWARTZ
between dosage-over-threshold and clinical effect is notknown for individuals, but it must be known to apply theseizure threshold to treatment (Swartz 2001). Physiologicalmeasurements should be able to provide details about thisrelationship, but there is no reason for the resulting
method to be better than the Benchmark Method, and so
there is no rationale to measure seizure threshold.

Clinical Case Example
To illustrate, here is how the Benchmark Method was usedwith a 58 year old depressed man who received ECT with
LART electrode placement. At ECT #1 a 202 mC dose gave
a seizure with peak HR (PHR) of 128; this is the benchmark. At ECT #2 a 302 mC dose produced seizure
PHR=118; this PHR suggests increase in the dose for two
separate reasons. First it is 8% under benchmark. Second it
is generally low. At ECTs #3 and #4 a 328 mC dose produced PHRs of 123 and 109; the latter suggests dose increase. At ECT #5 a 353 mC dose gave PHR=115, suggesting increase. At ECTs #6 and #7 a 454 mC dose produced
seizure PHRs of 126 and 120; the latter led to dose increase. At ECTs #8 and #9, with 504 mC dose, PHRs were
134 and 135, and the course concluded with remission.

Limitations
Peak HR cannot be used with the Benchmark Method inpatients whose cardiac disease or medication blocks essentially all HR elevation with ECT. Nevertheless, only partial
attenuation of HR elevation does not necessarily prevent its
use in ECT monitoring. HR elevation can be diminished by
the anesthetic agent propofol and by beta-blockers andcalcium-channel blockers. Propofol and some beta-blockers
weaken the ECT seizure, a drawback to their routine use.
Labetalol or esmolol administration to prevent post-ECT
hypertension is an occasional consideration for elderly
patients. Diseases that can interfere with HR elevation at
ECT include dysfunctions of the cardiac conduction system, e.g., bundle branch blocks and nodal blocks. Suchdysfunctions tend to follow cardiovascular disease, acuteMI, stroke, electrolyte disturbances, and elevated intracranial pressure. Nevertheless, little is known about the natureof effects by drugs and diseases on peak HR. These HR
effects are not necessarily stronger than effects by CNS
drugs and conditions on the EEG, which include the suppression of alertness into unconsciousness by anesthesia.
The Benchmark Method and its use with peak HR arebased on a study in which higher average peak HR relative
to benchmark HR was associated with fewer ECTs in thecourse (Swartz, 2000). Because the data from this study
guided the formulation of this method, independent testing

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would require new data. A new data collection might compare the clinical outcome for patients whose stimulus dose
produces a mean peak HR within 6 bpm of benchmark
against another group whose dose produces a mean peak
HR of 12-18 bpm below benchmark. Such a comparison
would require controlling for influences by age, stimulus
electrode placement, and subtype of major depression.
Another study might compare the clinical outcome with useof benchmarks based on different physiological measurements, such as peak HR and EEG postictal suppression.
Still another study might compare a group treated by the
Benchmark Method against a group treated by a different
method, but it is not plain what a good alternative shouldbe.
Disclosure
Dr. Swartz has equity interests in Somatics, LLC, a manufacturer of ECT instruments.

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ECT DOSING
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The German Journal of Psychiatry · ISSN 1433-1055 · http:/www. gjpsy.uni-goettingen.de
Dept. of Psychiatry, The University of Göttingen, von-Siebold-Str. 5, D-37075 Germany; tel. ++49-551-396607; fax:++49-551-392004; e-mail: gjpsy@gwdg.de5