ECT requires both general anesthesia and paralysis. Pretreatment with glycopyrrolate may reduce the incidence of bradycardia and decrease oral secretions following the initial parasympathetic response. Induction is intravenous, followed by complete paralysis and placement of a bite block.
According to Miller, “Methohexital (0.75 to 1.0 mg/kg) is the most commonly used drug for ECT anesthesia and is considered the “gold standard”,” although there are data to suggest that outcomes are no different between methohexital and propofol, despite the decreased seizure duration with propofol.
Paralysis does not have to be complete (intubation is rarely performed) – often 0.5 mg/kg SCh is used.
Other important interactions: indirectly acting sympathomimetics can cause a hypertensive crisis in patients receiving MAOIs; lithium prolongs the action of NMBDs
ECT: Anesthetic Agents and Seizure Duration
- Increased Duration: Etomidate
- No Effect: Methohexital, ketamine, remifentanil, alfentanil
- Shortened Duration: Propofol, midazolam, lorazepam, thiopental, thiamylal, lidocaine
An adequate seizure in ECT is defined as one which lasts greater than 30 seconds.
Methohexital – gold standard for ECT, no change of seizure duration but better tolerated than etomidate secondary to ability to blunt hemodynamic response and better than propofol and thiopental because it does not decrease seizure duration.
Etomidate – it is also associated with myoclonus, a longer time to wake than methohexital and also does not block the hypertension and tachycardia often associated with ECT. Increases seizure duration.
Propofol and thiopental decrease seizure duration but blunt hemodynamic response.
Opioids are useful in the fact that they allow a lower dose of the anesthestic agent to be used, thus allowing faster wakeup and if using propofol or thiopental it will decrease the amount so the dose related decrease will help lengthen the seizure (i.e. you don’t have to give as much propofol so it won’t shorten the seizure as much).
Hyperventilation (hypocarbia) will lengthen seizure duration and thus effectiveness of ECT.
Zhengnian Ding, Paul F White Anesthesia for electroconvulsive therapy. Anesth. Analg.: 2002, 94(5);1351-64