ECT Protocol: Stimulus Parameters, Charge, and Dosing Strategy

The Core Formula

Charge (mC) = Current amplitude (A) × Pulse width (ms) × 2 × Pulse-pair frequency (Hz) × Train duration (s)

Stimulus Parameters at a Glance

Pulse Width: 0.5 ms vs 1.0 ms vs Ultrabrief (0.25-0.3 ms)?

• Ultrabrief pulse (0.25-0.3 ms) at 6x seizure threshold = equivalent efficacy to brief pulse bilateral ECT, with dramatically less cognitive impairment
• Patients treated with ultrabrief RUL ECT showed no deterioration in any cognitive measure vs. pre-ECT baseline
• This is now the preferred modern approach for RUL ECT

• Use brief pulse (0.5-1.0 ms) - ultrabrief + bilateral has NOT been shown to be consistently effective
• Keep dose moderate-suprathreshold to limit cognitive side effects
• Do not exceed 1 ms pulse width in modern ECT practice

Starting Charge: 0.8 mC/s vs 1.2 mC/s (Machine-Based Fixed Dosing)

Strategy 1 - Empirical Titration (Most Precise)

• First stimulus set deliberately low (so seizure occurs in only a minority)
• Restimulate every 30-60 seconds using progressively greater charge until a seizure is produced
• Use that estimated seizure threshold to calculate the treatment dose:
  • Right unilateral: dose at 5-6× seizure threshold (some recommend up to 8-12×)
  • Bilateral: dose at 1.5-2.5× seizure threshold (moderately suprathreshold)
• Seizure threshold varies 50-fold across patients - titration accounts for this
• Seizure threshold rises 20-100% over the treatment course; retitration may be needed

Strategy 2 - Formula-Based Dosing

• Uses factors like age, sex, electrode placement, pulse width to estimate starting dose
• Simple formula: age alone (e.g., starting at age% of max charge)
• More detailed formulas account for gender, electrode placement, medications
• Even best formulas only explain ~40% of seizure threshold variance
• Acceptable when titration is not practical

Strategy 3 - Fixed High-Dose Method

• Set at a high fixed percentage of maximum output regardless of patient
• Less precise; risks either over- or under-dosing
• Acceptable for bilateral ECT where dose-response is less steep

Practical Starting Points (by machine program)

Dosing by Electrode Placement: Summary

What to Monitor During the Stimulus

• EEG (2-channel, frontal-mastoid montage) - adequate ictal activity
• Motor seizure via the "cuff method" (BP cuff inflated >250 mmHg on ipsilateral limb)
• Target seizure duration: ≥25 seconds (motor or EEG). Shorter seizures often indicate inadequate dose
• Adequate seizure quality on EEG includes ictal amplitude, regularity, and postictal suppression

Key Practical Rules

1. Never exceed 1 ms pulse width in modern ECT
2. Ultrabrief + bilateral = not recommended (may be ineffective)
3. Bilateral ECT = do NOT use ultrabrief pulse; stay with 0.5-1.0 ms
4. RUL ECT is preferred when ultrabrief protocol is used - best side-effect profile
5. Declare non-response only after ≥10 treatments at optimal placement and dose
6. If response plateaus mid-course, check for anticonvulsant medications (propofol, barbiturate anesthesia) - reduce or switch anesthetic agent
7. US devices are limited to 504-576 mC maximum output

Your Device: MEDICA UBE-409/6 (Medicaid)

What the Display is Currently Showing

How the Charge is Calculated on This Machine

Charge (mC) = Current (A) × PW (ms) × 2 × Hz × Duration (s)

0.9 × 0.5 × 2 × 140 × 1.2 = 151.2 mC ✓ (matches the display exactly)

Should You Start at 1.2 s or 0.8 s? (And What Does That Mean in mC?)

What to Actually Do: Step-by-Step Protocol

If Using Empirical Titration (Recommended, Most Precise)

1. Start at the LOWEST setting - reduce duration down to ~0.2-0.4 s on your device (charge ~25-50 mC)
2. Give stimulus - if no seizure, wait 30-60 seconds, step duration up
3. Keep increasing by one step each time until a generalized seizure ≥25 seconds is obtained
4. The charge at which seizure is first elicited = seizure threshold (ST)

• Right Unilateral (RUL) ECT: set dose to 5-6× ST
• Bilateral (BFT) ECT: set dose to 1.5-2.5× ST (moderate suprathreshold)

Your Current Settings (1.2 s, 140 Hz, 0.5 ms = 151 mC) in Context

• 151 mC is approximately 30% of maximum machine output
• This is a reasonable starting bilateral dose for a middle-aged adult if not titrating
• For RUL ECT, this is likely too low unless the patient's ST is very low (~25-30 mC)
• For age-based formula dosing: age × 2 = approximate starting mC (e.g., 50-year-old → ~100 mC start)

Pulse Width: Keep at 0.5 ms or Change?

• Bilateral ECT (standard; do NOT use ultrabrief for bilateral)
• Right Unilateral ECT (acceptable; ultrabrief 0.25-0.3 ms is better if your machine supports it)

Frequency (Hz): Your Machine Shows 140 Hz

Quick Reference Card for Your MEDICA UBE-409/6

Why 5 Patients Had No Seizure - Systematic Troubleshooting

🔴 Most Likely Culprit: Your Frequency is 140 Hz - This May Be Suppressing Seizures

"Frequencies in the range of 25-60 Hz are optimal for seizure induction. Frequencies above 100 Hz are still effective but less suitable for production of long-lasting after-discharges. High-frequency stimulation has been shown to suppress ongoing ictal activity." (ECT Stimulus Parameters: Rethinking Dosage, PMC2933093)

Full Checklist of Causes (Most to Least Likely)

1. TECHNICAL / MACHINE ISSUES

2. ANESTHESIA - Very Common Cause

3. PATIENT MEDICATIONS

• Benzodiazepines (lorazepam, diazepam, clonazepam) - very common and often overlooked
• Anticonvulsants (sodium valproate, carbamazepine, lamotrigine, levetiracetam)
• Lithium (can paradoxically raise threshold)
• Beta-blockers (in high doses)
• Theophylline (risk of status if seizure does occur)

4. PATIENT PHYSIOLOGICAL FACTORS

5. STIMULUS PARAMETERS - What to Change on Your Machine

0.9 × 0.5 × 2 × 140 × 1.6 = ~202 mC

• Increase duration to max (your device likely goes to ~8 s)
• Switch electrode placement to bilateral if using unilateral
• Ensure valid IMP reading before firing

• Hyperventilate the patient for 60-90 seconds before stimulation (most effective simple measure)
• Switch anesthetic agent from propofol to thiopentone/ketamine
• Consider caffeine sodium benzoate IV (500-2000 mg) 20-30 min before ECT - evidence-based seizure threshold lowering agent

Action Priority List for Your Next Session

1. Reduce Hz from 140 → 60 Hz (most important single change)
2. Confirm IMP reads a number (200-3000 Ω) before pressing TREAT - if "---", do not fire
3. Check and improve skin prep - clean with abrasive, apply gel properly
4. Review anesthetic agent - avoid propofol; switch to thiopentone/ketamine if possible
5. Hold benzodiazepines 12-24 h before treatment
6. Hyperventilate the patient for 60-90 seconds before stimulus delivery
7. If all above done and still no seizure, check the machine with biomedical engineering - the UBE-409/6 may have a fault in current delivery

Before You Fire the Stimulus

1. Check IMP first - after applying electrodes and gel, the display should show a number between 200-3000 Ω. If it still shows "---", do not fire. Re-prep the skin and recheck contact before proceeding.
2. Start lower and titrate up - with 70 Hz, your charge at various durations will be:

1. Hyperventilate each patient with 100% O2 for 60-90 seconds just before firing - lowers seizure threshold cheaply and effectively.
2. Document the anesthetic agent being used - note it down so we can review if patients still don't seize.

What a Successful Seizure Looks Like

• Motor: tonic stiffening followed by rhythmic clonic jerking, best seen in the cuffed limb
• Duration: aim for ≥25 seconds motor, ≥25-30 seconds on EEG
• Less than 15 seconds = likely subtherapeutic, increase dose next session

If Still No Seizure at 70 Hz Tomorrow

• Confirm the anesthetic agent (switch from propofol if in use)
• Hold any benzodiazepines the night before
• Get biomedical engineering to test the machine's actual current output

Your Starting Settings: 70 Hz / 1.0 ms PW / 0.8 s

0.9 A × 1.0 ms × 2 × 70 Hz × 0.8 s = 100.8 mC

One Note on Pulse Width 1.0 ms

• 1.0 ms is the maximum recommended in modern ECT - do not go higher
• At 1.0 ms, cognitive side effects are slightly more than at 0.5 ms
• Once you establish a reliable protocol and patients are seizing consistently, you could consider stepping back to 0.5 ms to reduce cognitive burden

Titration Steps if 0.8 s Doesn't Produce a Seizure

Start with 1.0 ms tomorrow, not 0.5 ms

The Simple Rule

• Use 1.0 ms now - to reliably establish seizures in patients who previously failed
• Once patients are seizing consistently over several sessions, you can drop to 0.5 ms if you want to reduce cognitive side effects

Kaplan & Sadock's Comprehensive Textbook of Psychiatry

Chapter / Section 33.20a - "Electroconvulsive Therapy" Author: Joan Prudic, M.D.

Other ECT-related sections in the same book:

In Kaplan & Sadock's Synopsis of Psychiatry (shorter version):

Pulse Width by Electrode Placement - The Core Rule

Why Ultrabrief Works for Unilateral but NOT Bilateral

• RUL ECT - current is focused on the non-dominant (right) hemisphere. At 6× seizure threshold with ultrabrief pulse, you get good prefrontal current density with minimal spread. The narrow pulse (0.25-0.3 ms) is close to the neuron's chronaxie (the optimal depolarization time ~0.1-0.2 ms), so it stimulates efficiently with less excess current.
• Bilateral ECT - current must cross both hemispheres simultaneously. The ultrabrief pulse doesn't deliver enough total charge across that wider path to reliably generalize the seizure. At least one major RCT (Sackeim et al.) showed ultrabrief bilateral at 2.5× threshold was frankly ineffective - clinical response was no better than sham.

The Cognitive Side-Effect Gradient (Best to Worst)

Ultrabrief RUL  <  Brief RUL  <  Bifrontal Brief  <  Bitemporal Brief
(least cognitive)                                    (most cognitive)

• Ultrabrief RUL = first choice when minimizing cognitive side effects is priority
• Bilateral brief pulse = first choice when rapid response is needed (e.g., severe catatonia, acute suicidality, neuroleptic malignant syndrome)

Applied to Your Machine Tomorrow

• 0.5 ms or 1.0 ms pulse width = correct ✓
• 0.25-0.3 ms (ultrabrief) = do NOT use for bilateral ✗
• Your chosen setting of 70 Hz / 1.0 ms / 0.8 s is well-matched for bilateral ECT

Is Seizure Duration Important for ECT Efficacy?

Short Answer: Yes, but it is necessary - not sufficient

The Historical View (Now Partially Revised)

• Subconvulsive stimuli (no seizure) = poor response
• Shortening seizures with lidocaine = reduced efficacy

What Current Evidence Actually Says

"These tenets have been revised in light of observations from modern studies... the antidepressant effects of ECT are dependent on the anatomic specificity of the effects of current density rather than on seizure elicitation alone."

The Minimum Threshold: Why Duration Still Matters

What Matters More Than Duration: Seizure QUALITY

1. High amplitude ictal activity - sharp spike-and-wave pattern
2. Symmetrical generalization - both hemispheres engaged
3. Good post-ictal suppression - sudden flattening of EEG after seizure ends (this is actually a positive prognostic sign)
4. Adequate ictal amplitude - not just duration

Dose Intensity vs. Duration: Which Drives Efficacy?

• Stimulus intensity above seizure threshold drives both efficacy AND speed of response
• Increasing dose above threshold speeds up clinical response by 1-2 treatments
• This effect is independent of seizure duration per se
• For RUL ECT: dose-response relationship exists up to 8-12× seizure threshold

Practical Implications for Your Practice

Recent Evidence: Anesthetic Agent Directly Affects Seizure Duration

Etomidate produces significantly longer motor AND EEG seizure duration than propofol in ECT, with potentially better efficacy outcomes. The authors conclude etomidate should be considered the preferred induction agent in ECT.

Summary in One Table

Cardiovascular Changes in ECT - Useful Sign, Not an Efficacy Marker

He Was Partially Right - But for the Wrong Reason

What Happens Cardiovascularly During an ECT Seizure

• Brief parasympathetic surge (vagal)
• Bradycardia, sometimes asystole for a few seconds
• This is why atropine/glycopyrrolate is sometimes pre-given - to blunt this

• Sympathetic surge - catecholamine release
• Tachycardia (HR rises sharply - often 120-160 bpm)
• Hypertension (BP rises 20-40% above baseline)
• These are driven by the seizure activity itself

• HR and BP gradually return to baseline
• The return to normal (post-ictal cardiovascular settling) mirrors EEG post-ictal suppression

Why This IS Clinically Useful

Why It is NOT an Efficacy Marker

1. Even a poor-quality, brief, non-generalizing seizure can produce tachycardia - the autonomic response does not discriminate between a 15-second subtherapeutic seizure and a 45-second high-quality therapeutic one
2. Efficacy is determined by - stimulus dose relative to threshold, electrode placement, seizure quality on EEG, and current density in prefrontal regions - none of which are reflected in heart rate
3. Propofol reduces hemodynamic changes accompanying ECT - so a patient on propofol may have a blunted CV response even with an adequate seizure, making it an even less reliable marker in that context (Kaplan & Sadock, Ch. 33.20a)
4. Anticholinergic premedication (atropine, glycopyrrolate) further distorts the CV picture by blocking the vagal phase

The Correct Hierarchy of Monitoring

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