Succinylcholine and postoperative pulmonary complications: a retrospective cohort study using registry data from two hospital networks

Background: Neuromuscular blocking agents (NMBAs) with a non-depolarising mechanism of action carry the risk of postoperative residual paralysis and are associated with postoperative pulmonary complications (POPC). Owing to the shorter duration of action, the depolarising NMBA succinylcholine may be associated with less postoperative residual paralysis, and hence fewer POPC. We tested the association of succinylcholine administration during anaesthesia and POPC. Methods: In a retrospective cohort study of registry data from two large US academic medical centres, 244 850 adult noncardiac surgical patients undergoing general anaesthesia were included. The primary outcome was POPC, defined as post-extubation haemoglobin oxygen de-saturation to <90%, or re-intubation requiring intensive care unit admission within 7 days after surgery. The association between succinylcholine and POPC and its dose-dependency were tested in a hierarchical fashion using a multivariable logistic regression model. Results: A total of 13 206 patients (5.4%) experienced POPC. Use of succinylcholine was associated with increased risk of POPC (adjusted odds ratio [OR_Adj]=1.11; 95% confidence interval [CI], 1.06–1.16; P<0.001; adjusted risk=5.18%; 95% CI, 5.06–5.30 without and 5.69%; 95% CI, 5.53–5.85 with succinylcholine), with a dose-dependent relationship (OR_Adj=1.08; 95% CI, 1.05–1.11 per mg kg⁻¹; P<0.001). In patients receiving non-depolarising NMBAs, succinylcholine further increased the risk of POPC (ORAdj=1.08; 95% CI, 1.03–1.14; P=0.001). The association between succinylcholine and POPC was modified (P=0.03 for interaction) by the duration of surgery with higher odds of POPC in patients undergoing surgeries of <2 vs ≥2 h (OR_Adj=1.24; 95% CI, 1.15–1.33 and 1.05; 95% CI, 1.00–1.10, respectively). Conclusions: In contrast to our prediction, succinylcholine administration was associated with an increased risk of POPC. This association was dose-dependent and magnified in surgeries of shorter duration.