Enhanced postoperative surveillance versus standard of care to reduce mortality among adult surgical patients in Africa (ASOS-2): a cluster-randomised controlled trial

The ASOS-2 Investigators

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Background Risk of mortality following surgery in patients across Africa is twice as high as the global average. Most of these deaths occur on hospital wards after the surgery itself. We aimed to assess whether enhanced postoperative surveillance of adult surgical patients at high risk of postoperative morbidity or mortality in Africa could reduce 30-day in-hospital mortality.

Methods We did a two-arm, open-label, cluster-randomised trial of hospitals (clusters) across Africa. Hospitals were eligible if they provided surgery with an overnight postoperative admission. Hospitals were randomly assigned through minimisation in recruitment blocks (1:1) to provide patients with either a package of enhanced postoperative surveillance interventions (admitting the patient to higher care ward, increasing the frequency of post-operative nursing observations, assigning the patient to a bed in view of the nursing station, allowing family members to stay in the ward, and placing a postoperative surveillance guide at the bedside) for those at high risk (ie, with African Surgical Outcomes Study Surgical Risk Calculator scores >= 10) and usual care for those at low risk (intervention group), or for all patients to receive usual postoperative care (control group). Health-care providers and participants were not masked, but data assessors were. The primary outcome was 30-day in-hospital mortality of patients at low and high risk, measured at the participant level. All analyses were done as allocated (by cluster) in all patients with available data.

Findings Between May 3, 2019, and July 27, 2020, 594 eligible hospitals indicated a desire to participate across 33 African countries; 332 (56%) were able to recruit participants and were included in analyses. We allocated 160 hospitals (13 275 patients) to provide enhanced postoperative surveillance and 172 hospitals (15 617 patients) to provide standard care. The mean age of participants was 37.1 years (SD 15.5) and 20 039 (69.4%) of 28 892 patients were women. 30-day in-hospital mortality occurred in 169 (1.3%) of 12 970 patients with mortality data in the intervention group and in 193 (1.3%) of 15 242 patients with mortality data in the control group (relative risk 0.96, 95% CI 0.69-1.33; p=0.79). 45 (0.2%) of 22 031 patients at low risk and 309 (5.6%) of 5500 patients at high risk died. No harms associated with either intervention were reported.

Interpretation This intervention package did not decrease 30-day in-hospital mortality among surgical patients in Africa at high risk of postoperative morbidity or mortality. Further research is needed to develop interventions that prevent death from surgical complications in resource-limited hospitals across Africa. Copyright (C) 2021 The Author(s). Published by Elsevier Ltd.

Original languageEnglish
Pages (from-to)e1391-e1401
Number of pages11
JournalThe Lancet Global Health
Issue number10
Early online date14 Sept 2021
Publication statusPublished - Oct 2021

Bibliographical note

Funding Information:
R M Pearse reports grants from Edwards Lifesciences and Intersurgical; and personal fees from Edwards Lifesciences and GlaxoSmithKline, outside of the submitted work. R M Pearse also reports being a member of the editorial boards of the British Journal of Anaesthesia and the British Journal of Surgery. A B A Prempah was the recipient of the World Federation of Societies of Anaesthesiologists–International Anesthesia Research Society Clinical Research Fellow in Global Surgery and Anaesthesia in Africa. All other authors declare no competing interests.

Funding Information:
The ASOS-2 pilot and trial were partially supported by a grant (OPP#1161108) from the Bill & Melinda Gates Foundation, as a subaward from Praekelt. Researchers for the process evaluation were supported by a grant from the World Federation of Societies of Anaesthesiologists.

Publisher Copyright:
© 2021 The Author(s). Published by Elsevier Ltd. This is an Open Access article under the CC BY 4.0 license

Data Availability Statement

Data will be disclosed only upon request and approval of the proposed use of the data by the steering committee (B M Biccard, H-L Kluyts, M Lesosky, L Myer, L du Toit, P Forget, T Stephens, and R M Pearse). Data are available to the journal for evaluation of reported analyses. Data requests from other non-ASOS-2 investigators will not be considered until 2 years after the close out of the trial. Data will be de-identified for participant, hospital, and country, and will be available with a signed data access agreement.


  • Adult
  • Africa/epidemiology
  • Female
  • Hospitalization
  • Hospitals
  • Humans
  • Postoperative Period
  • Standard of Care


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