Decreasing oxygen consumption
Techniques which decrease oxygen consumption allow more effective use to be made of the oxygen reserves during periods of apnoea thereby conserving oxygenation. In particular, skeletal muscle fasciculations caused by suxamethonium have been shown to result in an increase in oxygen consumption of nearly 10% in animal models. Minimising or avoiding these fasciculations can prolong the time to critical desaturation. This can be achieved by the following techniques:
- Use of adjuvants to attenuate fasciculations: use of fentanyl & lignocaine during intubation has been shown to decrease both the intensity of fasciculations seen with suxamethonium use and cause a significant increase in the safe apnoea time. These drugs also cause a decrease in the mean arterial pressure and heart rate seen during intubation compared with use of suxamethonium alone, which could also potentially contribute to a decrease in whole body oxygen consumption.
- Use of rocuronium instead of suxamethonium: provides a small additional prolongation of the safe apnoea time compared with use of suxamethonium and adjuvant drugs by avoiding the occurrence of fasciculations entirely.
References:
Tang L, Li S, Huang S, Ma H, Wang Z. Desaturation following rapid sequence induction using succinylholine vs. rocuronium in overweight patients. Acta Anaesthesiol Scand 2011; 55: 203-208
Taha SK, El-Kathib MF, Baraka AS, Haidar YA, Abdallah FW, Zbeidy RA, Siddik-Sayyid SM. Effect of suxamethonium vs rocuronium on onset of oxygen desaturation during apnoea following rapid sequence induction. Anaesthesia 2010; 65: 358-361