How the electrical stimulus dose is adjusted session-to-session across a full multi-week ECT course — not the single-session threshold search (see the companion Seizure Threshold Titration simulator for that first-treatment method).
Before a course of electroconvulsive therapy proceeds beyond the first treatment, the clinical team must decide how the stimulus dose for every remaining session will be anchored. Two starting approaches dominate practice — empirical titration to seizure threshold at treatment 1, or an age/formula-based dose estimate — but the number that matters for the rest of the course is the working multiple chosen once a threshold (measured or estimated) is known. That multiple, not the raw millicoulomb value, is what gets titrated session to session.
Empirical titration (covered in depth in the companion Seizure Threshold Titration simulator) determines the patient’s actual seizure threshold at treatment 1 by administering incrementally larger stimuli until a generalized seizure is elicited. Age/formula-based dosing instead estimates a starting percentage of device output from age and electrode placement (e.g., roughly half-age percent for bilateral placement), without a dedicated threshold-finding session.
Whatever the starting method, the clinically decisive step for the rest of the course is choosing the working multiple of threshold: right unilateral (RUL) placement is far less efficient per unit of charge above threshold, so it is conventionally dosed at 5–6× threshold ("high-dose unilateral") to achieve comparable antidepressant efficacy to bilateral placement. Bilateral placements (bitemporal or bifrontal) are dosed much closer to threshold, typically 1.5×, because their anatomic current path already engages both hemispheres efficiently.
This single starting decision — placement and multiple — becomes the anchor value that every later session’s dose adjustment is expressed relative to.
It is easy to conflate two related but distinct titration problems in ECT: (1) within-session empirical titration, used once (or occasionally re-used) to locate a patient’s seizure threshold by stepping the dose up until a seizure occurs, and (2) across-course titration, used at every subsequent session to decide whether the already-established working dose should go up, stay the same, or come down. The first problem is solved in a single sitting with a step-titration protocol. The second problem unfolds over weeks and is driven by a longitudinal seizure and symptom log, not a single-session search.
A course typically comprises 6–12 sessions delivered two to three times weekly. The dose set from the treatment-1 threshold (or formula estimate) is only a starting point — it is expected to require retitration as seizure threshold itself rises over the course, sometimes by 25–200%.
Every ECT session generates a data point: how long the seizure lasted by motor (cuff) observation, how long it lasted on EEG, and whether its morphology (spike-and-wave amplitude, regularity, and postictal suppression) looked like a robust generalized seizure. This running log is reviewed before each subsequent stimulus is set — it is the raw material the whole across-course titration strategy is built on.
Two duration measures are captured routinely: the motor (cuff) seizure duration, observed in a limb isolated from the muscle relaxant by a blood-pressure cuff, and the EEG seizure duration, read directly off the ictal tracing. EEG duration is usually somewhat longer than motor duration because peripheral muscular seizure activity can end before central electrical seizure activity fully resolves.
Beyond raw duration, the ictal EEG is reviewed qualitatively: robust polyspike and high-amplitude slow-wave activity, symmetric bihemispheric involvement, a clear termination, and a postictal suppression period (a flat or attenuated EEG segment immediately after the seizure ends) are all reassuring markers of an adequate, well-generalized seizure — durations alone can be misleading if morphology is poor.
No single session’s seizure is titrated in isolation. Clinicians look at the trend across the last several sessions: is duration trending down (habituation, insufficient dose, or concurrent anticonvulsant medication effect), staying consistently adequate, or occasionally spiking into the prolonged range? Isolated borderline sessions are usually not enough to trigger a dose change; a pattern across two or more consecutive sessions is weighted more heavily before the working dose is revised.
This tracking discipline is what separates course-long titration from the single-session empirical method used at treatment 1: instead of stepping the dose up within one sitting to find a threshold, the team reviews a multi-session log and adjusts the already-established working dose forward, one treatment at a time.
Three distinct clinical situations prompt raising the stimulus dose for the next session: the seizure was too short to be considered therapeutically adequate, no generalized seizure was elicited at all (a missed seizure), or seizures have remained adequate by duration and morphology but the patient is simply not improving clinically after a reasonable number of treatments at the current dose.
When motor and/or EEG duration falls persistently below the target range, or the ictal EEG shows poor generalization, weak amplitude, or an absent/brief postictal suppression period, the working dose is stepped up for the next treatment. A single borderline session is often observed rather than acted on immediately, but a repeated pattern of short or poor-quality seizures is a clear signal that the current multiple of threshold is no longer sufficient — commonly because the patient’s seizure threshold itself has risen over the course.
A missed seizure — stimulation with no generalized seizure activity at all — is managed acutely within the same session: after confirming device function and electrode contact, the team typically re-stimulates promptly at a meaningfully higher dose (often stepping well above the failed dose) to still deliver an adequate treatment that day. Regardless of the same-session outcome, the working dose carried forward into the next scheduled session is also increased, since a missed seizure signals the working multiple has fallen below the patient’s current threshold.
The trickiest trigger is non-response: seizures look adequate by every duration and EEG quality metric, yet the patient shows no meaningful symptom improvement after several sessions. Because seizure adequacy does not guarantee therapeutic adequacy for every individual, some protocols call for empirically raising the dose (or reassessing electrode placement) once a reasonable number of technically adequate but clinically unproductive sessions have accumulated, rather than continuing unchanged indefinitely.
All three increase triggers point the same direction — more electrical stimulus is needed to reliably produce (or to make more therapeutically effective) a generalized seizure — but they arise from different data: a duration/quality problem, an all-or-nothing failure to seize, or an efficacy problem despite technically fine seizures.
The counterpart set of triggers pushes the working dose down, or simply holds it steady: a seizure that runs too long, cognitive side effects that are becoming clinically significant, or — the best-case scenario — a patient who is already responding well at the current dose, where further increases would add cognitive burden without added benefit.
A seizure lasting beyond roughly 180 seconds by motor or EEG measurement is considered prolonged and is usually terminated pharmacologically (e.g., with additional benzodiazepine or propofol) if it has not self-terminated by a set time limit. A prolonged seizure at the next session is avoided by reducing the working dose, since it indicates the current multiple of threshold is now generating excessive electrical activity — again often because threshold itself continues to shift, or because concurrent medications or metabolic factors are lowering the seizure-terminating margin.
Post-ictal disorientation, anterograde or retrograde memory complaints, and prolonged reorientation time are monitored across the course, often with brief serial cognitive screening. When cognitive side effects become clinically significant, the dose (and sometimes electrode placement, e.g., shifting from bilateral toward unilateral) is reduced or held rather than advanced, even if seizures remain technically "adequate" — cognitive tolerability is titrated alongside seizure adequacy, not after it.
When a patient is showing a clear and steady symptomatic response at the current working dose, many protocols favor holding the dose rather than increasing it further, and some favor a modest taper as the course nears completion — since the therapeutic aim (adequate generalized seizures sufficient for response) is already being met, and any additional stimulus intensity mainly adds cognitive risk rather than additional benefit.
Decrease/hold decisions are as data-driven as increase decisions: a single prolonged seizure, a documented cognitive complaint, or a clearly improving symptom trajectory are each, independently, sufficient grounds to stop raising — or to start lowering — the working dose.
No single session’s dose decision is meaningful in isolation. Plotted across an entire course, the stimulus dose trajectory and the clinical response trajectory together tell the real story: dose typically drifts upward through the early-to-mid course as physiologic seizure threshold rises, then plateaus or tapers as symptoms improve and cognitive tolerability becomes the limiting consideration.
Overlaying the dose-per-session line with a symptom-severity-per-session line typically shows an inverse relationship over the course: as the working dose is retitrated upward through the early sessions to keep pace with rising seizure threshold, symptom severity begins a slower, steadier decline that usually lags the dose changes by a few sessions. By the second half of a typical course, symptom severity is falling consistently while dose changes become smaller and less frequent — often tapering — as the clinical target is reached.
It is important not to over-interpret a rising dose trajectory as evidence of worsening illness, or a falling one as evidence the treatment is "losing strength" — dose is being retitrated to keep seizures adequate against a moving physiologic target (threshold), not adjusted directly against mood or cognitive symptoms except through the increase/decrease trigger logic described in Stages 3 and 4. The clinical response trajectory is the outcome the whole titration process serves; the dose trajectory is simply the instrument being tuned along the way.
Across a typical 6–12 session course, the pattern that most consistently correlates with good outcomes is: adequate (not missed, not prolonged) seizures at every session, a dose trajectory that rises early and plateaus or tapers late, and a symptom trajectory that declines steadily from roughly the third or fourth session onward.