Perioperative cardiac arrest and the impact of surgical timing: a nationwide cohort study

BACKGROUND: Perioperative cardiac arrest (PO-CA) is a rare but critical event. The impact of surgical timing, i.e. whether procedures are conducted during office hours or out-of-hours, on its occurrence remains unknown. We aimed to outline the incidence and mortality of PO-CA in Sweden, and assess whether surgical timing influences the risk of PO-CA in non-cardiothoracic, non-obstetric emergency surgery. METHODS: We conducted a retrospective cohort study of adult patients (≥18 years) in the Swedish Perioperative Register between 2019 and 2023. We examined the incidence and mortality of PO-CA, defined as cardiac arrest in the operating theatre or post-anaesthesia care unit (PACU). In a subset of non-cardiothoracic, non-obstetric emergency surgery, we estimated the odds of PO-CA in procedures commenced out of hours compared with during office hours, adjusting for sex, age, comorbidities, ASA class, and case urgency, using mixed-effects logistic regression. RESULTS: Among 1,568,877 procedures, PO-CA occurred in 395 cases (314 in the operating theatre, 81 in the PACU), corresponding to a crude incidence of 2.5/10,000 procedures, with a subsequent 30-day mortality of 42.5 %. In non-cardiothoracic, non-obstetric emergency surgery, the crude odds ratio for PO-CA out of hours vs. office hours was 1.31 (95 % CI 1.00-1.70), while the adjusted odds ratio was 1.13 (95 % CI 0.86-1.48). CONCLUSIONS: In this nationwide study, PO-CA was rare, with over half of affected patients surviving beyond 30 days. Although crude incidence appeared higher out of hours in non-cardiothoracic, non-obstetric emergency surgery, this pattern likely reflects greater patient complexity rather than out-of-hours circumstances per se.