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Effects of night surgery on postoperative mortality and morbidity: a multicentre cohort study
  1. Friederike C Althoff1,
  2. Luca J Wachtendorf1,
  3. Paul Rostin1,2,
  4. Peter Santer1,
  5. Maximilian S Schaefer1,
  6. Xinling Xu1,
  7. Stephanie D Grabitz1,
  8. Hovig Chitilian2,
  9. Timothy T Houle2,
  10. Gabriel A Brat3,
  11. Oluwaseun Akeju2,
  12. Matthias Eikermann1
  1. 1Anesthesia, Critical Care and Pain Medicine, Beth Israel Deaconess Medical Center, Boston, Massachusetts, USA
  2. 2Anesthesia, Critical Care and Pain Medicine, Massachusetts General Hospital, Boston, Massachusetts, USA
  3. 3Surgery, Beth Israel Deaconess Medical Center, Boston, Massachusetts, USA
  1. Correspondence to Professor Matthias Eikermann, Anesthesia, Critical Care and Pain Medicine, Beth Israel Deaconess Medical Center, Boston, MA 02215, USA; meikerma{at}


Background Surgery at night (incision time 17:00 to 07:00 hours) may lead to increased postoperative mortality and morbidity. Mechanisms explaining this association remain unclear.

Methods We conducted a multicentre retrospective cohort study of adult patients undergoing non-cardiac surgery with general anaesthesia at two major, competing tertiary care hospital networks. In primary analysis, we imputed missing data and determined whether exposure to night surgery affects 30-day mortality using a mixed-effects model with individual anaesthesia and surgical providers as random effects. Secondary outcomes were 30-day morbidity and the mediating effect of blood transfusion rates and provider handovers on the effect of night surgery on outcomes. We further tested for effect modification by surgical setting.

Results Among 350 235 participants in the primary imputed cohort, the mortality rate was 0.9% (n=2804/322 327) after day and 3.4% (n=940/27 908) after night surgery. Night surgery was associated with an increased risk of mortality (ORadj 1.26, 95% CI 1.15 to 1.38, p<0.001). In secondary analyses, night surgery was associated with increased morbidity (ORadj 1.41, 95% CI 1.33 to 1.48, p<0.001). The proportion of patients receiving intraoperative blood transfusion and anaesthesia handovers were higher during night-time, mediating 9.4% (95% CI 4.7% to 14.2%, p<0.001) of the effect of night surgery on 30-day mortality and 8.4% (95% CI 6.7% to 10.1%, p<0.001) of its effect on morbidity. The primary association was modified by the surgical setting (p-for-interaction<0.001), towards a greater effect in patients undergoing ambulatory/same-day surgery (ORadj 1.81, 95% CI 1.39 to 2.35) compared with inpatients (ORadj 1.17, 95% CI 1.02 to 1.34).

Conclusions Night surgery was associated with an increased risk of postoperative mortality and morbidity. The effect was independent of case acuity and was mediated by potentially preventable factors: higher blood transfusion rates and more frequent provider handovers.

  • anaesthesia
  • adverse events
  • epidemiology and detection
  • surgery
  • standards of care

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  • FCA, LJW and PR contributed equally.

  • Contributors Study concept and design: FCA, PR, PS, SDG, MSS, XX, HC, OA, GAB, TTH, ME. Acquisition, analysis or interpretation of data: All authors. Drafting of the manuscript: FCA, PR, LJW, ME. Critical revision of the manuscript for important intellectual content: All authors. Statistical analysis: XX, TTH, FCA, PR, LJW, PS, GAB, MSS, ME. Obtained funding: ME. Administrative, technical or material support: All authors. Study supervision: XX, TTH, GAB, ME. All authors had full access to the data in the study and can take responsibility for the integrity of the data and the accuracy of analyses.

  • Funding The authors have not declared a specific grant for this research from any funding agency in the public, commercial or not-for-profit sectors.

  • Competing interests ME has received unrestricted funds from philanthropic donors Jeffrey and Judith Buzen during the study period and has received grants for investigator-initiated trials not related to this manuscript from Merck & Co and serves as a consultant on the advisory board of Merck & Co. ME holds equity of Calabash Bioscience Inc. and is an Associate Editor of the British Journal of Anaesthesia.

  • Patient consent for publication Not required.

  • Provenance and peer review Not commissioned; externally peer reviewed.

  • Data availability statement Data are available on reasonable request. Due to the sensitive nature of the data collected for this study, requests to access the dataset from qualified researchers trained in human subjects research and confidentiality may be sent to Matthias Eikermann at

  • Supplemental material This content has been supplied by the author(s). It has not been vetted by BMJ Publishing Group Limited (BMJ) and may not have been peer-reviewed. Any opinions or recommendations discussed are solely those of the author(s) and are not endorsed by BMJ. BMJ disclaims all liability and responsibility arising from any reliance placed on the content. Where the content includes any translated material, BMJ does not warrant the accuracy and reliability of the translations (including but not limited to local regulations, clinical guidelines, terminology, drug names and drug dosages), and is not responsible for any error and/or omissions arising from translation and adaptation or otherwise.

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