Rocuronium Dosing for RSI in a 127 kg Patient
For rapid sequence intubation in a 127 kg patient, administer rocuronium 1.2 mg/kg based on lean body weight (approximately 70-80 mg total), NOT actual body weight, as non-depolarizing muscle relaxants distribute in lean mass and extracellular volumes rather than adipose tissue. 1
Dosing Algorithm for This Patient
Step 1: Calculate Lean Body Weight
- Use lean body weight (LBW) for rocuronium dosing in obese patients 1
- For a 127 kg patient, estimated LBW is approximately 60-70 kg (using Janmahasatian formula) 1
- This contrasts with suxamethonium, which should be dosed on actual body weight 1
Step 2: Select RSI Dose
- Standard RSI dose: 0.6-1.2 mg/kg of lean body weight 2
- For optimal RSI conditions in obese patients: use 1.2 mg/kg of LBW 3, 2
- This provides excellent intubating conditions in <2 minutes 2
- Total dose for this patient: approximately 72-84 mg (assuming LBW 60-70 kg)
Step 3: Timing Considerations
- Intubation conditions achieved in median 1 minute (range 0.4-6 minutes) 2
- Maximum blockade in <3 minutes 2
- Expected clinical duration: 31 minutes under opioid/N2O/O2 anesthesia 2
Critical Dosing Pitfall to Avoid
DO NOT dose rocuronium on actual body weight (127 kg) in obese patients 1
- Dosing on actual body weight causes dose-dependent prolongation of recovery time 1
- Increases variability in recovery 1
- May require reversal agents at end of procedure 1
- Non-depolarizing agents are water-soluble and distribute in lean mass, not adipose tissue 1
Reversal Planning for Obese Patients
Have sugammadex immediately available, dosed appropriately for obesity 3
Sugammadex Dosing Options:
- For moderate blockade (2 twitches on TOF): 2 mg/kg based on ideal body weight + 40% 4, 5
- For deep blockade (1-2 post-tetanic counts): 4 mg/kg based on ideal body weight or corrected body weight 5, 6, 7
- For immediate reversal: 8 mg/kg 1, 3
- Neuromuscular monitoring is essential to guide sugammadex dosing and detect recurarization 1, 3
Alternative: Suxamethonium for RSI
If no contraindications exist, suxamethonium remains the gold standard for RSI 1, 3
- Dose: 1.0 mg/kg based on ACTUAL body weight (127 mg for this patient) 1
- Provides excellent intubating conditions with maximum blockade 1
- Faster and more predictable than low-dose rocuronium 1
- Duration: 7-12 minutes 1
Key Clinical Considerations
Rocuronium-sugammadex is the recommended alternative when suxamethonium is contraindicated 1, 3
- Ensure adequate number of sugammadex vials immediately available before induction 1
- Monitor neuromuscular function throughout to adjust dosing 1, 2
- Be prepared for potential sugammadex failure requiring emergency airway access 1
- Inhalation anesthetics (enflurane, isoflurane) enhance rocuronium's neuromuscular blocking action 2