Etomidate for RSI: Seizure Considerations

Introduction

Rapid sequence intubation (RSI) is a process whereby an induction agent and a neuromuscular blocking agent are given in rapid succession to facilitate endotracheal intubation. Etomidate remains the most commonly used induction agent; however, it is not without its own pharmacologic considerations such as the decrease in seizure threshold.

Key Considerations for RSI Agent Selection

The clinical scenario, including cardiorespiratory and neurologic status
Patient factors: allergies, comorbidities, and seizure history
Clinician experience/training and institutional factors
Pharmacologic characteristics of the sedative — including seizure threshold effects

Pharmacology of Etomidate

Parameter	Details
Dose	IV: 0.3 mg/kg
Administration	IV push
Formulation*	20 mg/10 mL · 40 mg/20 mL *Various formulations may appear; check your institution formulary
PK/PD	Onset: ~20 seconds Duration: 4–10 min Metabolism: Hydrolysis of ethyl ester side chain Renal excretion: 75%
Adverse Effects	Injection site pain Nausea/Vomiting Myoclonus
Drug Interactions	No major reactions
Compatibility	Incompatible: Vitamin C, vecuronium
Comments	Hypothetical concerns about adrenal insufficiency with a single dose. Hemodynamically neutral.

Clinical Pearl

Etomidate is hemodynamically neutral, making it the most commonly used RSI induction agent. However, clinicians must weigh the risk of myoclonus and potential seizure threshold lowering in patients with known seizure disorders.

Hemodynamic Comparison of RSI Agents

Drug	Hemodynamic Effects	Comments
Etomidate	↔ BP ↔ CO ↔ HR ↓ Cortisol ↔ ICP	Prolonged inhibition of steroid synthesis in critically ill; withdrawn from a number of countries
Ketamine	↑ BP ↑ HR ↑ CO ↔ Cortisol ↑↓ ICP	↔ or ↑ CPP and ↔ ICP with standard anesthetic management
Propofol	↓ BP ↔ HR ↓ CO ↔ Cortisol ↓ ICP	Hemodynamic compromise marked in elderly, ASA 3+ or hypovolemic patients with standard induction dose

Overview of Key Evidence

6 Studies

Author / Year	Design (n)	Intervention	Key Findings
Perier et al., 2018²	Retrospective n=97	Etomidate vs sodium thiopental for RSI in convulsive status epilepticus	Seizure recurrence: 56% etomidate vs 44% thiopental
Gabor, 2006¹⁰	Retrospective n=30	Propofol 1 mg/kg vs etomidate 0.2 mg/kg for electroconvulsive therapy	Longer seizure durations with etomidate (EEG & EMG)
Zuckerbraun et al., 2006³	Retrospective n=101	Etomidate for RSI in general population	No relationship between seizures & prior history (p=0.25)
Guldner, 2003⁵	Retrospective n=105	Etomidate for RSI in general population	No myoclonus, status epilepticus, or new-onset seizures 3 pts vomited within 10 min
Reddy, 1993⁶	Prospective RCT n=68	Etomidate, thiopental, methohexital, or propofol for anesthesia induction	Myoclonus: etomidate 86% No generalized epileptiform activity on EEG vs thiopental 16.6%, methohexital 12.5%, propofol 5.5%
Ebrahim, 1986⁷	Case Reports n=12	Etomidate for anesthesia induction in patients with intractable seizures	9/12 pts: increased epileptiform activity 6/9 had marked increase; EEG via subdural electrodes

Clinical Conclusions

Bottom Line

Etomidate elicits myoclonus in a significant number of patients, but whether myoclonus is associated with EEG-confirmed epileptiform activity remains uncertain. Risk versus benefit assessment is required for patients with seizure history.

Etomidate has been shown to elicit myoclonus in a significant number of patients. However, whether myoclonus is associated with EEG-confirmed epileptiform activities remains uncertain.

Depending on the origin and type of seizure, it may be challenging for EEG to differentiate between non-seizure and seizure activity during myoclonic events.

Due to the low level of evidence, patients with a history of seizures should have a risk versus benefit assessment to determine the best induction agent.

Full Reference List

10 refs

Micromedex [Electronic version]. Greenwood Village, CO: Truven Health Analytics. Retrieved September 6, 2021.
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Zuckerbraun NS. Acad Emerg Med. 2006 Jun;13(6):602–9. PMID: 16636355.
Grant IS, et al. Epileptiform seizures during prolonged etomidate sedation. Lancet 1983;322(8348):511–2.
Guldner G, et al. Acad Emerg Med 2003;10:134–139.
Reddy RV, et al. Anesth Analg 1993;77:1008–11.
Ebrahim ZY, et al. Anesth Analg 1986;65:1004–6.
Krieger W, et al. Seizures with etomidate anesthesia [letter]. Anesthesiol Analg. 1985;64:1226–7.
Ghoneim MM. Anesth Analg 1977;56:479–85.
Gabor G. Neuropsychopharmacol Hung 2007;9(3):125–30.