Understanding healthcare-associated mortality: The case of elective colectomy surgery

Background: Understanding and improving patient safety is a public health priority. Up to 100,000 patients die annually due to complications of medical care; however, risk factors for healthcare-associated mortality are poorly understood. The purpose of this population-based study was to understand the risk factors and postoperative events associated with death after a common type of elective surgery, colectomy. Methods: Patients were studied who underwent colectomy surgery in the Michigan Surgical Quality Collaborative from 2005-2010. Data on surgical cases was prospectively collected for quality improvement by professional abstractors in 34 hospitals, including patient risk factors, surgery details, and 30-day postoperative outcomes. Because the goal was to understand cases with unexpected mortality, high-risk cases classified as emergencies, with pre-surgery sepsis, or in which the patient's condition was classified as life-threatening or moribund before surgery were excluded. Preoperative patient factors, surgery type, and postoperative events were evaluated for association with death, using univariate statistics and multiple logistic regression models. Results: The patient cohort is 5985 patients who underwent elective colectomy surgery in Michigan, of whom 93 died (1.55%). This low number reflects the selection criteria of cases at low risk for death. The mean age of all patients was 64 years, and most patients had surgery for neoplasms or diverticular disease. Preoperative patient factors independently associated with death included older age (p<0.0001), ascites (p<0.0001), disseminated cancer (p=0.0014), hypertension (p=0.0025), weight loss (p=0.011), dependent functional status at baseline (p=0.005), and indication for surgery (p=0.0011). Type of operation (eg minimally invasive) was not associated with risk of death after adjusting for patient factors. Postoperative events independently associated with death included myocardial infarction (p<0.0001), sepsis (p<0.0001), bleeding that required a blood transfusion (p<0.0001), and pneumonia (p<0.0001). In fact, 54% of all patients who died had one or more of these 4 events. Looking at all complications, 72 of 93 patients who died had one or more complication captured by the abstractors. Conclusions: There may be predictable patterns of patient factors and postoperative events that predict healthcare-associated mortality. In the case of colectomy surgery, there is a strong association between death and 4 postoperative complications: myocardial infarction, sepsis, bleeding requiring transfusion, and pneumonia. Identification of high-risk patients and focusing on prevention of specific complications may decrease mortality after elective surgery. Healthcare quality and safety initiatives such as the one from which these data were obtained may therefore have a public health impact through ongoing complication-prevention efforts.