Less RSI desaturation with Roc

Some of my pre-hospital critical care colleagues in the UK exclusively use rocuronium in preference to suxamethonium for rapid sequence induction (RSI) of anaesthesia in critically ill patients. I couldn’t see a good reason to switch although now there’s some evidence that adds to the argument.

The muscle fasciculations caused by the depolarising effect of suxamethonium may increase oxygen consumption, which may shorten the apnoea time before desaturation. Non-depolarising neuromuscular blockers such as rocuronium should allow a longer apnoea time after RSI. In addition, drugs which reduce fasciculations (such as lidocaine and fentanyl) should delay the the onset of desaturation when given prior to suxamethonium.

A large dose of Roc

These hypotheses were tested in a blinded, randomised controlled trial in 60 ASA-1 or -2 patients, who were scheduled for elective surgery under general anaesthesia. All patients received 2mg/kg propofol. One group was randomised to receive suxamethonium 1.5 mg/kg, a second group received rocuronium 1mg/kg plus lidocaine 1.5mg/kg and fentanyl 2mcg/kg, and a third group was given suxamethonium 1.5 mg/kg plus lidocaine 1.5mg/kg and fentanyl 2mcg/kg. The facemask was removed 50 seconds after the neuromuscular blocker was given and patients were intubated; the tube was then left open to air until desaturation to 95% occurred, which was timed.

Desaturation occurred significantly sooner in the suxamethonium-only group, followed by the sux/lido/fentanyl group, followed by the roc/lido/fentanyl group.

Of course these results are not necessarily directly applicable to the critically ill patient, and in this study there was no direct comparison between induction agent + rocuronium only and induction agent + suxamethonium only. Nevertheless the argument that suxamethonium-induced muscle fasciculations contribute to an avoidable increase in oxygen consumption is persuasive.

Effect of suxamethonium vs rocuronium on onset of oxygen desaturation during apnoea following rapid sequence induction
Anaesthesia. 2010 Apr;65(4):358-61