How Risky Is Having Surgery at Night?

Anya Romanowski, MS, RD


September 28, 2016


Are nighttime surgeries really riskier than those performed during the day? A recent commentary by Peter Russell that appeared on WebMD Health News, "Night Time Surgery 'Doubles Death Risk,'" raised copious questions and comments from medical professionals.

We decided to take a closer look at the results of the 30-day hospital survival-rate study of patients at a hospital in Montreal, Canada, to shed some more light on the findings and to respond to some of these questions. [Editor's note: Some readers' comments have been edited for clarity or length.]

Elective vs Emergent Surgeries

As Russell reported, in the study, "41,716 emergency and routine operations [were] carried out on 33,942 patients." Many commenters assumed that the strikingly increased mortality findings were due to the fact that most of the nighttime surgeries included in the analysis were emergent.

As a registered nurse (RN) commented:

"It goes without saying that the percentage of operations that are emergent is higher at night than during the day, so of course the mortality rate is higher!"

A general surgeon concurred:

"This should not be surprising, as nighttime surgeries are emergent and performed on sicker patients, possibly having comorbidities making them a much higher risk. What is troubling to me is the increased mortality, not the time period (3:30 pm-11:30 pm). Some of these patients are emergent and understandable."

In looking closer at the study, however, it turns out that only 10,480 of the 41,716 surgeries were emergency procedures (approximately one quarter of the surgeries). Of these emergent surgeries, 3445 were performed in the day (7:30 AM – 3:30 PM, with 226 deaths reported), 4951 occurred in the evening (3:30 PM – 11:30 PM, with 97 deaths reported), and 2084 were conducted at night (11:30 PM – 7:30 AM, with 29 deaths reported).

The conclusion was that in patients with American Society of Anesthesiologists (ASA) scores of 5—"Moribund patients who are not expected to survive without the operation"—late day/early evening (3:30 PM – 11:30 PM) rather than late emergency surgery was associated with higher mortality. In healthier patients, nighttime surgery was associated with higher mortality.

Possible Complications Requiring Repeat Surgeries

Another general surgeon pointed out that the study didn't address the reasons for performing later-day procedures, while others felt that the shortage of staff and patients delaying their visits to the emergency room may play a key role in the mortality data:

"The unavailability of rapid access to physicians, diagnostic testing (due to ancillary staff having to be called in from home), and the fact that many patients wait too long to finally come to the ER for help, makes their condition more acutely emergent than had they come in earlier in the day."

Others felt that the blame on fatigue and staffing shortages is unwarranted:

"One might conclude from this article that fatigue and lack of staffing are the predominant cause of demise. I'd say probably a contributing factor, but not the primary factor."

"It is not like these people are being scheduled for night time surgery. It is probably because they need the surgery right away and cannot wait till the morning. So they are at higher risk for death, because they are so acutely ill that they need to get into the operating room quickly. To place the blame solely on fatigue and staffing, though I am sure there is some of that, is evidence someone is not thinking this through. Perhaps unanticipated delays due to the length of the surgeries, preceding the ones in question, might play a part, but patient acuity should also be added in."


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