Report finds small increased risk of death from weekend surgery

9 Jun 2016 | Perioperative Mortality Review Committee

The latest report from the Perioperative Mortality Review Committee (POMRC) has found that there is a slightly greater likelihood that people will die following surgery, if that surgery is carried out in the weekend.

The POMRC reviews deaths related to surgery and anaesthesia that occur within 30 days of an operation. It advises the Health Quality & Safety Commission on how to reduce these deaths and makes recommendations to make surgery safer for patients.

POMRC Chair Dr Leona Wilson says that while overseas figures on weekend surgical death rates have been available for some time, this is the first time such figures have been published using New Zealand data.

'As is the case internationally, the New Zealand figures show a small increased risk of death following weekend operations compared with those carried out on a weekday.

'In New Zealand, the death rate was 1.71 deaths per 100 operations on a Saturday and 1.48 deaths per 100 operations for Sunday. On Monday to Friday, rates were between 0.48 and 0.52 deaths per 100 operations. The difference in weekend compared with weekday death rates is greater for patients undergoing elective surgery than for those undergoing emergency surgery.'

She says understanding the underlying reasons for this ‘weekend effect’ is challenging.

'There are two main suggested causes. The first is that patients having operations in the weekend may differ from weekday patients because they could be sicker when they arrive at hospital.

'The second suggested cause is that the quality of weekend care may differ from weekday care. Staff levels can vary, with fewer senior consultants, and fewer diagnostic services available. It may also be that hospitals are more equipped to provide emergency care on weekends and may lack the appropriate mix of expertise to manage postoperative care.'

Dr Wilson says how great a role each aspect plays in the weekend effect and the role of other, unidentified, factors is unclear.

'This is why the Committee is recommending hospitals investigate all weekend surgery deaths to find out whether the timing of the operation had an impact on the outcome.

'This could mean district health boards re-investigating previous deaths with a ‘weekend lens’ or, from now, beginning to apply this lens to all weekend elective surgical deaths.

'We are also calling for further research into the difference in mortality between patients having procedures in the weekend compared with weekdays, particularly those having elective surgery.'

She says it is important to remember surgery in New Zealand is very safe.

'The main risk factors for dying after surgery remain being older, sicker and admitted to hospital because of an emergency.'

Other findings from the report include:

  • Between 2009 and 2013, there were 6755 deaths following a general anaesthetic. Most of these deaths occurred among acute admissions and at public hospitals. New Zealand’s same or next day death rate following a procedure with one or more general anaesthetics is similar to rates seen internationally.
  • Cardiovascular causes were the most common reasons for death following a general anaesthetic.
  • The death rate following a general anaesthetic were significantly higher for those aged over 65 years, those with poorer health and those admitted to hospital because of an emergency.
  • Deaths following a general anaesthetic were significantly higher for Māori than for Europeans, after socio-demographic and clinical factors were adjusted for.

Mortality rates relating to the procedures below can be found in the report’s executive summary:

  • Cholecystectomy
  • General anaesthesia (same or next day mortality)
  • Hip arthroplasty
  • Knee arthroplasty
  • Colorectal resection
  • Coronary artery bypass graft (CABG)
  • Percutaneous transluminal coronary angioplasty (PTCA).

Report recommendations include:

1. Improvements to care
    a. Not operating on patients who are assessed as being very unwell (but providing other treatment)
    b. The risk of dying from surgery should be discussed with all patients contemplating an operation with a significant risk. 
    c. Death following elective surgery performed on the weekend should be investigated in depth by that health care institution, assessing all potentially contributing factors.

2. Better documentation
    a. All patients should have their ASA status (how well or unwell they are) recorded in their clinical anaesthetic record.

3. Further research and research funding
    a. The difference in mortality between patients having procedures in the weekend compared with weekdays, in particular those admitted electively, should be investigated. 
    b. The reasons for increased perioperative mortality of Māori should be further investigated.

4. Recommendations from the Māori Caucus to the POMRC for better data analysis
    a. The impact that the Māori population age structure has on analyses of perioperative mortality should be investigated. 
    b. The Charlson Comorbidity Index should be considered to strengthen future analyses and better understand how severity of illness impacts Māori perioperative mortality.

Last updated 09/08/2017