General anaesthesia abolishes spontaneous respiration. Use of general anaesthesia is frequently unavoidable during surgical procedures. The ability to maintain breathing by placing a tube in the windpipe of patients undergoing general anaesthesia is therefore crucial. A neuromuscular blocking agent (NMBA) is used for relaxation of muscles of the throat and is traditionally used to ease correct placement of the tube. However, use of an NMBA may cause unwanted side effects. On the other hand, large observational studies have indicated that avoiding NMBA may cause difficulties when the tube is placed during anaesthesia.
In the present systematic review, we assessed the effect of avoiding NMBA instead of using NMBA on difficulties associated with placing a tube in the windpipe of patients undergoing general anaesthesia. Further, we evaluated the consequences of using or avoiding NMBA on events of pain or injury in the upper part of the throat following placement of a tube in the windpipe.
We identified 34 randomized controlled trials that met our inclusion criteria. These trials included 3565 patients who were undergoing various surgical procedures in hospital departments. Most trials were conducted in high-income countries, and most patients were undergoing elective surgery. Trials included patients of both sexes; most were healthy and non-obese, and staff members did not expect difficulty when placing the tube in the windpipe.
This review supports that use of NMBA may ensure the best conditions for placing a tube in the windpipe during general anaesthesia. When an NMBA is avoided, risk for pain or injury in the throat is increased following placement of a tube in the windpipe.
Quality of the evidence
Conditions for which a tube is placed in the windpipe are defined in individual trials and may not reflect a situation that many clinicians would consider to be clinically serious. Regarding events of injury and sore throat, only sparse data are available from trials with low risk of bias, although among all included trials, avoiding NMBA increased the risk of pain or injury. We therefore consider our overall findings to reflect evidence of moderate quality.