ECT: Anes drug selection
Advanced, Special Problems or Issues in Anesthesiology
When considering drug selection for ECT, several things should be carefully considered.
1. Induction of GA that allows for quick emergence after the seizure
2. Use of medications that will not adversely affect the patients seizure (i.e. shorten duration)
3. Paralysis or some degree of muscle relaxation for patient safety during the seizure
4. Drugs to manage the hemodynamics that result from the parasympathetic and sympathetic responses that occur with ECT.
Based on these goals, induction and muscle relaxation is typically achieved by the use of methohexital and succinylcholine. Other drugs that may be considered for induction include propofol, etomidate, ketamine, and benzodiazepines. The benefit of methohexital is that it reduces the seizure threshold and does not reduce seizure duration. It also helps blunt the sympathetic surge that occurs. Etomidate may be a better choice as it may increase the duration of the seizure; however, it lacks the hemodynamic attenuation of methohexital. Propofol, ketamine, and benzodiazepines all decrease seizure duration making them less than ideal choices. Additionally, ketamine can lead to an increase in sympathetic tone and the quick recovery seen with propofol is not significantly longer than that of methohexital.
Succinylcholine is generally used for muscle relaxation as it provides a rapid onset and quick recovery without the need for neuromuscular blockade reversal. Some degree of muscle relaxation is required to prevent severe muscle contractions that may result in fractures or other patient harm due to the induced seizure. Non-depolarizing neuromuscular blockers may be administred for pre-treatment prior to succinylcholine administration or in patients with contraindications to succinylcholine.
Each patient’s degree of hemodynamic response to ECT varies; however, all will have an initial parasympathetic phase followed shortly by a sympathetic surge. The parasympathetic phase may be minimal or result in significant bradycardia with sinus pauses. The sympathetic response can also range from mild hypertension/tachycardia to severe hypertension/tachycardia. Shorting acting medications such as esmolol and labetalol are effective in dealing with a patient’s acute hemodynamic response and atropine may be necessary for the parasympathetic phase. As these patients undergo several ECT treatments, review of prior anesthetic records can provide excellent insight to a patient’s potential reaction and what previous interventions were used.