Muscle Relaxant for ECT
Succinylcholine at a dose of 0.9 mg/kg IV is the standard muscle relaxant used in electroconvulsive therapy to minimize violent muscle contractions. 1
Primary Recommendation
The American Academy of Child and Adolescent Psychiatry establishes succinylcholine as the standard muscle relaxant for ECT, with acceptable alternatives including atracurium and mivacurium. 1 This recommendation is based on succinylcholine's rapid onset, short duration of action, and predictable muscle relaxation profile during induced seizures.
Dosing Strategy
The standard dose of succinylcholine is 0.9 mg/kg IV, though research demonstrates the minimum effective dose ranges from 0.77-1.27 mg/kg to produce acceptable muscle blockade in 50-90% of patients. 1, 2
The dose should be selected based on each patient's preprocedural condition, with higher doses (approaching 1.27 mg/kg) needed for more robust patients or when greater muscle control is required. 2
A twitch suppression of >90% is necessary for adequate control of motor contractions during ECT. 2
Alternative Muscle Relaxants
Rocuronium as an Alternative
Rocuronium (0.36-0.6 mg/kg) combined with neostigmine reversal is a safe alternative when succinylcholine is contraindicated or undesirable. 2
When using rocuronium, the minimum effective dose ranges from 0.36-0.46 mg/kg for 50% of patients and 0.5-0.6 mg/kg for 90% of patients. 2
Rocuronium with sugammadex reversal (8 mg/kg) produces equally rapid recovery compared to spontaneous recovery from succinylcholine, making it a viable option. 3
The American Society of Anesthesiologists recommends rocuronium can be safely used in patients with seizure disorders when combined with sugammadex for reversal, as it does not lower the seizure threshold. 4
Mivacurium Limitations
Low-dose mivacurium (0.08 mg/kg) is unsuitable for ECT as it provides inadequate seizure modification compared to succinylcholine. 5
Research shows mivacurium was unsatisfactory in 50% of cases (8 out of 16 patients), leading to early study termination due to poor seizure control. 5
However, mivacurium may be considered in special circumstances such as patients with neuroleptic malignant syndrome where succinylcholine should be avoided due to malignant hyperthermia concerns. 6
Clinical Considerations and Monitoring
Neuromuscular monitoring is essential when using any muscle relaxant to ensure adequate blockade and complete recovery before patient discharge. 4, 2
Recovery time from succinylcholine averages 9.7 ± 3.5 minutes, while rocuronium with neostigmine reversal takes approximately 19.5 ± 5.7 minutes. 2
For rocuronium reversal, sugammadex dosing depends on depth of blockade: 2.0 mg/kg for moderate, 4.0 mg/kg for deep, or 8.0 mg/kg for very deep blockade. 4
Important Caveats
Avoid succinylcholine in patients with neuroleptic malignant syndrome due to potential cross-reactivity with malignant hyperthermia triggers; use mivacurium or rocuronium instead. 6
In obese patients, non-depolarizing muscle relaxants (rocuronium, atracurium, mivacurium) should be dosed based on lean body weight rather than actual body weight. 4
The efficacy of sugammadex for rocuronium reversal may be decreased in elderly patients and those with severe renal failure, requiring dose adjustments and careful monitoring. 4