The fourth report of the Perioperative Mortality Review Committee (POMRC) covering the period from 2008-2012 includes several new areas: coronary artery bypass grafts (CABG), percutaneous transluminal coronary angioplasty (PCTA), bariatric surgery and severe postoperative infections.
It also includes for the first time patients with American Society of Anaesthesiologists (ASA) scores over four or five – a rating system used to assess a patient’s overall physical health before undertaking surgery. ASA scores of four or five represent those most at risk of dying without a procedure.
Consistent with previous reports, the Committee identified a higher mortality rate for those with comorbidities and poor overall health (those with a higher ASA score), the elderly and those who underwent an acute or emergency operation.
The mortality rate for patients who underwent a bariatric surgery was low – 0.7 percent of all admissions. It is possible this is a reflection of New Zealand’s overall mortality rate, and further research is needed to determine whether this is the case. The committee also found this rate suggests the selection of patients who undergo such an operation in New Zealand is appropriate, despite such people often having significant illness or other ailments.
After adjusting for clinical and demographic factors, morbidity rates among those who underwent a coronary artery bypass graft were higher for older people, Māori, acute admissions and those with a higher ASA score.
For those who underwent a percutaneous transluminal coronary angioplasty procedure, the mortality rate was 1.66 percent of total admissions – 369 deaths from 22,211 admissions. Having adjusted for other factors the rate was higher among older people, those with a higher ASA score and Pacific peoples.
The mortality rates for patients with an ASA score of four or five were higher over the five-year period, with 2,099 deaths representing 13.7 percent of admissions.
While having the fewest admissions of the three main age groups, the 80+ range had the highest rate of mortality for those with an ASA score of four or five, with 6.56 deaths per 100. This compares to 5.29 for 65-79 and 2.89 for 45-64.
There were 305 deaths in the period compared to 1,406 admissions as a result of infections, equating to 21.7 percent. This is lower than the most relevant international comparison, the United States, which has a mortality rate of 38.5 percent. Those who underwent acute procedures were most at-risk, with 80 percent of the deaths occurring among acute patients.
The Committee has made several recommendations based on the report’s findings.
- Further work should be undertaken to reduce the risk of thromboembolic disease. Consideration should be given to continuing prophylaxis after discharge from hospital including engaging patients in the ways they can reduce their risk.
- The POMRC continues to participate in the development and evaluation of World Health Organization metrics for monitoring and strengthening global surgery and anaesthesia.
- All providers (public and private) should contribute data on health care to the National Minimum Dataset.
- The ASA status should be recorded for all patients for all procedures (including all procedures that do not involve an anaesthetist).
- Given the high mortality associated with severe postoperative sepsis, further investigation into prophylaxis, early detection, diagnosis and management should be undertaken.
- A targeted evaluation of the mortality rate of Māori patients undergoing CABG should be undertaken.
- Local multidisciplinary mortality review committees should be developed. Review should not be limited to patients viewed as low risk, as investigation of higher risk patients (older, high ASA status, acute) who died may help prevent future deaths by identifying common factors and determining preventable strategies or more appropriate treatment pathways.
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