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Research Christmas 2014: On the Wards, in the Surgery

Operating theatre time, where does it all go? A prospective observational study

BMJ 2014; 349 doi: (Published 15 December 2014) Cite this as: BMJ 2014;349:g7182
  1. Elizabeth Travis, orthopaedic house officer1,
  2. Sarah Woodhouse, doctoral researcher2,
  3. Ruth Tan, orthopaedic house officer1,
  4. Sandeep Patel, orthopaedic consultant1,
  5. Jason Donovan, orthopaedic consultant1,
  6. Kit Brogan, orthopaedic registrar1
  1. 1Waikato Hospital, Hamilton, New Zealand
  2. 2University of Sussex, UK
  1. Correspondence to: E Travis elizabeth.travis{at}
  • Accepted 7 November 2014


Objective To assess the accuracy of surgeons and anaesthetists in predicting the time it will take them to complete an operation or procedure and therefore explain some of the difficulties encountered in operating theatre scheduling.

Design Single centre, prospective observational study.

Setting Plastic, orthopaedic, and general surgical operating theatres at a level 1 trauma centre serving a population of about 370 000.

Participants 92 operating theatre staff including surgical consultants, surgical registrars, anaesthetic consultants, and anaesthetic registrars.

Intervention Participants were asked how long they thought their procedure would take. These data were compared with actual time data recorded at the end of the case.

Primary outcome measure Absolute difference between predicted and actual time.

Results General surgeons underestimated the time required for the procedure by 31 minutes (95% confidence interval 7.6 to 54.4), meaning that procedures took, on average, 28.7% longer than predicted. Plastic surgeons underestimated by 5 minutes (−12.4 to 22.4), with procedures taking an average of 4.5% longer than predicted. Orthopaedic surgeons overestimated by 1 minute (−16.4 to 14.0), with procedures taking an average of 1.1% less time than predicted. Anaesthetists underestimated by 35 minutes (21.7 to 48.7), meaning that, on average, procedures took 167.5% longer than they predicted. The four specialty mean time overestimations or underestimations are significantly different from each other (P=0.01). The observed time differences between anaesthetists and both orthopaedic and plastic surgeons are significantly different (P<0.05), but the time difference between anaesthetists and general surgeons is not significantly different.

Conclusion The inability of clinicians to predict the necessary time for a procedure is a significant cause of delay in the operating theatre. This study suggests that anaesthetists are the most inaccurate and highlights the potential differences between specialties in what is considered part of the “anaesthesia time.”


  • Contributors: ET is the primary author and guarantor; she contributed to the conception and design of the work, monitored data collection for the whole trial, and drafted and revised the paper. RT contributed to the design of the study, data collection, and drafting and revising the paper. SW provided statistical support and made substantial contributions to the data analysis and to drafting and revising the paper. SP, JD, and KB were the senior authors on the project and supervised the whole study. They contributed to the study design and interpretation of data analysis as well as revision of the paper. All authors approved the final version for publication and agree to be accountable for the work.

  • Funding: No funding was received for this study.

  • Competing interests: All authors have completed the ICMJE uniform disclosure form at (available on request from the corresponding author) and declare: no support from any organisation for the submitted work; no financial relationships with any organisations that might have an interest in the submitted work in the previous three years; no other relationships or activities that could appear to have influenced the submitted work.

  • Ethical approval: Approval was not required from an ethics committee as the study did not involve any alteration to normal practice within our organisation and was observational in nature. Permission for the conduction of the study was obtained from the head of department of each specialty.

  • Transparency: ET (the study’s guarantor) affirms that the manuscript is an honest, accurate, and transparent account of the study being reported; that no important aspects of the study have been omitted; and that any discrepancies are disclosed.

  • Data sharing: The technical appendix, statistical code, and dataset (with patient-level data anonymised) are available from the corresponding author (

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