Association of Operative Timing with Clinical Outcomes and Safety in Thoracic Organ Transplantation: A Meta-Analytic Synthesis of Evidence.

BACKGROUND: Thoracic organ transplantation is often performed at night because of donor availability and the need to minimize cold ischemia time. Whether operative timing is independently associated with short- and long-term outcomes after heart and lung transplantation remains uncertain. METHODS: We conducted a PRISMA-guided systematic review and meta-analysis with PROSPERO registration. PubMed, Scopus, the Cochrane Library, and Web of Science were searched through November 2025 for studies comparing daytime versus nighttime heart or lung transplantation. Primary outcomes included short-term mortality (in-hospital, 30-day, and 90-day) and mid-to-long-term survival (1, 3, and 5 years). Secondary outcomes included major postoperative complications and resource utilization. Pooled risk ratios or mean differences were estimated, with prespecified subgroup and sensitivity analyses. RESULTS: Eight studies were included. Definitions of daytime and nighttime varied considerably across cohorts. Daytime transplantation was associated with a lower incidence of in-hospital mortality (RR, 0.89; 95% CI, 0.82 to 0.97; P = 0.029). However, no statistically significant differences were observed in 30-day, 90-day, or 1-, 3-, and 5-year mortality. Secondary outcomes, including ECMO support, pacemaker implantation, major complications, ICU length of stay, and overall hospital length of stay (LOS), were largely comparable between groups. A subgroup analysis suggested shorter hospital LOS after daytime heart transplantation, although this finding was not observed for lung transplantation or overall hospital LOS. Sensitivity analyses showed that the observed association with in-hospital mortality was influenced by the largest contributing cohort. CONCLUSIONS: Daytime transplantation was associated with a lower incidence of in-hospital mortality, but this association was not observed across subsequent mortality time points. Safety outcomes and resource utilization were otherwise comparable, and the available evidence did not demonstrate consistently worse outcomes following nighttime transplantation within structured thoracic transplant systems.