Enhancing Anesthesia Safety: Study reveals Effective Techniques to Prevent Etomidate-Induced Myoclonus

Etomidate is favored for inducing general anesthesia in hemodynamically unstable patients due to its rapid action and minimal cardiovascular impact. However, its use is associated with etomidate-induced myoclonus (EIM), which can result in complications like increased intraocular pressure and myocardial oxygen consumption. Recent study aimed to evaluate the effectiveness of three different etomidate administration techniques—control, priming, slow injection, and a combination of priming with slow injection—in preventing EIM.

Methods

A total of 296 patients scheduled for elective surgeries and classified as ASA physical status I or II were enrolled in this randomized controlled trial. Patients were assigned to four groups: Group C (control), Group P (priming), Group S (slow injection), and Group T (priming with slow injection). Myoclonus incidence, time of onset, and severity were analyzed, alongside pain during injection and hemodynamic parameters. Statistical significance was set at p<0.05.

Results

Results indicated that the incidence of myoclonus was highest in Group C at 73%, followed by Group P at 52.7%, Group S at 48.6%, and Group T at 37.8%, with a significant difference among the groups (P=0.001). The combination of priming with slow injection (Group T) was most effective, showing a significantly lower incidence of grade 3 myoclonus compared to the control group (6.76% vs. 52.7%, P=0.0001).

Hemodynamic Parameters

Hemodynamic parameters showed significant differences in heart rate within the first two minutes after induction, with other parameters like mean arterial pressure and oxygen saturation yielding no substantial differences. Reports of postoperative nausea and vomiting and oral secretions were comparable across groups. The findings align with previous studies, highlighting that both priming and slow administration techniques reduce EIM effects, but their combination proved superior. The mechanisms may involve synchronized inhibition of excitatory and inhibitory circuits in the central nervous system, leading to decreased subcortical disinhibition.

Conclusion

Despite the promising results, operators could not be blinded due to different injection techniques, and the study acknowledged limitations such as the potential masking effect of neuromuscular blockade on myoclonic movements. Overall, the combination of priming and slow injection appears to be the best strategy for preventing EIM during etomidate administration in general anesthesia, suggesting a shift in clinical practice for improving patient outcomes.

Key Points

- Etomidate is an intravenous anesthetic induction agent known for its stability in hemodynamically unstable patients; however, it often causes myoclonus, which can result in complications such as increased intraocular pressure and myocardial oxygen consumption. Preventing etomidate-induced myoclonus (EIM) is therefore essential.

- A clinical study involving 296 patients aged 18 to 60 years, classified as ASA physical status I and II, aimed to compare the effectiveness of four administration techniques: control (C), priming (P), slow administration (S), and a combination of priming and slow administration (T). Patients with contraindications such as adrenal disease and steroid use were excluded.

- Results demonstrated significant differences in EIM incidence among the groups, with Group C showing the highest rate (73.0%), followed by Group P (52.7%), Group S (48.6%), and Group T (37.8%) (P = 0.001). Severe cases of EIM (grade 3) were substantially fewer in Group T (6.76%) compared to Group C (52.7%), indicating the superior efficacy of the combined techniques.

- Secondary outcomes indicated the highest pain intensity upon injection in Group C due to the rapid administration speed; however, the lipid-emulsion formulation of etomidate used in this study resulted in overall decreased pain incidences. Hemodynamic stability, assessed through heart rate and mean arterial pressure, remained consistent across all groups, affirming etomidate's safety regarding cardiac function.

- The findings illustrate a synergistic effect of using both priming and slow administration techniques to effectively lower the incidence of EIM compared to each method used separately. Gradually transitioning from a rapid injection to slow administration after a priming dose yielded additional benefits in minimizing muscle twitching.

- Limitations of the study include the absence of operator blinding and the inability to assess intraoperative neuromuscular blockade effects; moreover, postoperative measurements such as creatine phosphokinase levels could have provided further insights into potential muscle injury associated with myoclonus. The study recommends the favored approach of combining priming and slow administration to enhance patient safety and comfort during etomidate induction.

Reference –

Ridhi Rao et al. (2025). To Compare The Efficacy Of Three Techniques In Reducing Etomidate-Induced Myoclonus - A Randomised Controlled Trial. *Indian Journal Of Anaesthesia*, 69, 282 - 288. https://doi.org/10.4103/ija.ija_948_24.