Letters to the Editor: Letter to the Editor
To the Editor
We read with interest the carefully performed study by Mirzakhani et al1 regarding dosing of muscle relaxants during electroconvulsive therapy (ECT). In our practice, we have reached similar conclusions about the optimal mean dose of succinylcholine for acceptable muscle relaxation during ECT. We previously published these data showing a mean succinylcholine dose of 0.9 mg/kg2; this is very similar to the reported 0.85-mg/kg dose of the Mirzakhani et al’s study. We would like to point out, however, that a small but not insignificant number of patients are outliers in regard to their succinylcholine requirements. Some patients will need dose increases, whereas others will need far less succinylcholine than predicted. This may be because of various reasons, including genetic variability in enzyme level, concomitant medications, or other, harder-to-elucidate mechanisms.
We reviewed 500 patients who received ECT at Mount Sinai Hospital in New York. Assuming that these data fit a standard normal distribution, we found that the mean dose of succinylcholine required was 0.96 mg/kg with a standard deviation of 0.26 mg/kg. The minimum required dose in our sample was 0.29 mg/kg, whereas the maximum dose was 2.10 mg/kg. Six patients (1.2%) required succinylcholine doses >2 standard deviations below the mean, or <0.43 mg/kg. Twenty-three patients (4.6%) required succinylcholine doses >2 standard deviations above the mean, or >1.48 mg/kg. In this sample, patients were more likely to need and to tolerate higher doses of succinylcholine rather than lower doses for adequate muscle relaxation.
In medicine, we strive to achieve predictability, replicability, and patient safety. Among the drugs we use in ECT, succinylcholine is the least predictable. Our data suggest that standard dosing will result in inadequate muscle relaxation for approximately 5% of patients. Inadequate muscle relaxation results in cosmetically unattractive treatments and a small risk of musculoskeletal injury. Most of the drugs used in ECT are highly predictable, including succinylcholine for most patients. However, providers must be aware that significant variability in response does exist and should adjust succinylcholine dose accordingly for efficacy and safety.
Erin H. Li, MDEthan O. Bryson, MDCharles H. Kellner, MDIcahn School of Medicine at Mount SinaiNew York, NY 10029Charles.firstname.lastname@example.org
1. Mirzakhani H, Guchelaar HJ, Welch CA,Minimum effective doses of succinylcholine and rocuronium during electroconvulsive therapy: a prospective, randomized, crossover trial. Anesth Analg. 2016;123:587596.
2. Bryson EO, Aloysi AS, Popeo DM, et al. Methohexital and succinylcholine dosing for electroconvulsive therapy (ECT): actual versus ideal. J ECT. 2012;28:e29e30.