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Night-time operations could double risk of death

2.17 times higher mortality risk from night surgery

Adrian O'Dowd

Tuesday, 30 August 2016

People who are operated on at night appear to be twice as likely to die as those operated on during regular daytime hours, suggests new research.*

The five-year study was presented at this year’s World Congress of Anaesthesiologists (WCA) being held in Hong Kong from 28 August to 2 September.

Previous studies have looked at postoperative mortality risk factors, which include patient age; the American Society of Anaesthesiologists (ASA) overall risk score and emergency status.

However, research studies analysing the time of surgery and postoperative mortality have had ambiguous results.

Therefore, Dr Michael Tessler, associate professor of anesthesiology and Dr Ning Nan Wang, chief resident at the Department of Anesthesia at McGill University Health Centre, Montreal, Canada, and colleagues set out to investigate the relationship between postoperative mortality and the time of the day of surgery.

They carried out a retrospective review of 30 day postoperative in hospital mortality at the Jewish General Hospital in Montreal, Canada, which is also a teaching hospital.

The study evaluated all surgical procedures for the past five years, starting from April 2010 to March 2015 and a database was constructed collecting variables about surgical interventions.

All elective and emergent surgical cases were included except ophthalmic and local anaesthesia cases.

The working day was divided into three time blocks - daytime 07:30-15:29, evening 15:30-23:29 and night time 23:30-07:29. The start time of the anaesthetic recorded by staff was used to determine in which time block the operation began.

During the five-year time period, there were 41,716 elective and emergency surgeries performed on 33,942 patients in 40,044 hospitalisations.

Of these, 10,480 were emergency procedures and there were 3,445; 4,951; and 2,084 emergency procedures with anaesthesia starting between day, evening and night, respectively.

 There were 226, 97 and 29 deaths of all cases during day, evening and night surgery (79, 95, 29 mortalities for emergency surgery in the same time periods) respectively.

The researchers found that after adjusting for age and ASA scores, the patients operated in the night were 2.17 times more likely to die than those operating on during regular daytime working hours.

Patients operated on in the late day were 1.43 times more likely to die than those operated on during regular daytime working hours.

The researchers said: “This study demonstrates that late day and night emergency surgery are associated with higher mortality when factoring in ASA score and patient age.

“Postoperative 30-day in-hospital mortality rate should include start time of anaesthesia, along with other known variables, as a risk factor.”

Possible causes for what they had observed includes doctors’ fatigue during surgery, overnight hospital staffing issues, delays in treatment (for example how many operating rooms were available), or the patient being too sick to be postponed prior to treatment.

The authors added: “Analysis of each of these possibilities is important to understand the reasons for this increased mortality and to direct any remedial action in an effort to reduce postoperative mortality.”


* Wang NN, et al. Retrospective analysis of time of day of surgery and its 30-day in hospital postoperative mortality rate at a single Canadian institution.

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