Outcomes of after‐hours surgeries performed under general anaesthesia: a South Korean nationwide cohort study

Summary Introduction The day of the week or time of day that surgery is performed may influence postoperative mortality or complications. We aimed to examine whether surgery under general anaesthesia performed after‐hours was associated with increased rates of mortality and morbidity, compared with surgery performed in‐hours. Methods This population‐based cohort study obtained data for patients who underwent surgery under general anaesthesia from the National Health Insurance Service of South Korea. Propensity score‐matched groups of patients who underwent surgery either in‐hours (weekdays between 9.00 and 18.00) or after‐hours (weekdays between 18.00 and 09.00 or on a weekend/holiday) were compared for 90‐day and 1‐year mortality, and the incidence postoperative complications. Results A total of 1,416,844 patients were considered (63,567 in the after‐hours group and 1,353,277 in the in‐hours group) and after a 1:5 propensity score matching, 281,717 were included (57,497 in the after‐hours group and 224,220 in the in‐hours group). Patients in the after‐hours group showed 3.58‐fold (OR 3.58, 95%CI 3.47–3.69, p < 0.001) and 2.51‐fold (hazard ratio 2.51, 95%CI 2.46–2.57, p < 0.001) higher 90‐day and 1‐year all‐cause mortality rates, respectively, compared with those in the in‐hours group. Patients in the after‐hours group had a 2.14‐fold (OR 2.14, 95%CI 2.10–2.19, p < 0.001) greater incidence of postoperative complications compared with those in the in‐hours group. Discussion After‐hours surgery was associated with a higher risk of death within 90 days, an increase in all‐cause mortality after 1‐year and a higher incidence of postoperative complications.