Priming with Non-Depolarizing Muscle Relaxants is Not Recommended by Current Guidelines
No major contemporary guidelines recommend routine priming (defasciculation) with non-depolarizing muscle relaxants before succinylcholine for rapid sequence induction in otherwise healthy adults. This practice has been largely abandoned in modern anesthesia protocols.
Guideline Evidence
The most recent and authoritative guidelines explicitly address this issue:
French Guidelines (2019-2020)
The French Society of Anaesthesia and Intensive Care guidelines on muscle relaxants 1 do not recommend priming for routine rapid sequence induction. These guidelines focus on:
- Direct administration of rapid-onset muscle relaxants (succinylcholine or rocuronium 0.9-1.2 mg/kg)
- No mention of defasciculation doses or priming techniques for standard RSI in healthy patients
European Society Guidelines (2023)
The European Society of Anaesthesiology and Intensive Care (ESAIC) guidelines 2 recommend:
- Fast-acting muscle relaxants for RSII: succinylcholine 1 mg/kg or rocuronium 0.9-1.2 mg/kg (Grade 1B)
- No recommendation for priming or defasciculation in their comprehensive 2023 guideline
Society of Critical Care Medicine (2023)
The SCCM guidelines for RSI in critically ill adults 3 suggest:
- Either rocuronium or succinylcholine for RSI when no contraindications exist (Conditional recommendation, Low quality evidence)
- No mention of priming techniques in their evidence-based recommendations
Pediatric Guidelines (2019)
The French pediatric airway management guidelines 4 explicitly state:
- Use rapid-onset muscle relaxants during classic RSI (Grade 1+)
- Succinylcholine as first choice, rocuronium as alternative (Grade 2+)
- No recommendation for priming or defasciculation doses
Historical Context
The 2008 AAP guidelines 5 mention that "a defasciculation dose of a non-depolarizing agent (e.g., 0.01 mg/kg of vecuronium) may be considered" for patients with increased ICP, but this is presented as an optional consideration, not a standard recommendation. This represents older thinking that has not been carried forward in contemporary guidelines.
Clinical Rationale
Modern guidelines have moved away from priming because:
- Lack of efficacy evidence: No demonstrated benefit for preventing fasciculations in reducing aspiration risk or improving outcomes
- Potential complications: Priming can cause muscle weakness, making mask ventilation difficult if intubation fails
- Time delays: Adds unnecessary steps to an emergency procedure where speed is critical
- Alternative options: Rocuronium at high doses (0.9-1.2 mg/kg) provides excellent intubating conditions without fasciculations
Common Pitfall
Do not confuse historical practice with current evidence-based recommendations. While priming was taught and practiced in the 1990s-2000s, contemporary guidelines from 2019-2023 consistently omit this technique, indicating it is no longer considered standard of care for routine RSI in healthy adults.
The only scenario where a small dose of non-depolarizing agent might still be considered is in patients with significantly elevated ICP, but even this is not strongly recommended in current guidelines and should be weighed against the risk of compromising airway management.