One third of deaths following coronary artery bypass surgery are preventable

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June 11, 2008 By Vijayalakshmi Kunadian MBBS MD MRCP [1]

Circulation: A new study from Ontario demonstrates that one third of deaths (32%) following coronary artery bypass surgery are preventable and are related to operating room and intensive care unit problems.

With improvements in technology and operating techniques, the risk-adjusted mortality following coronary bypass surgery is low (~2%). However, it is not clear how many deaths following coronary artery bypass surgery are due to preventable causes. Guru and colleagues from Ontario performed a retrospective study of 347 in-hospital deaths following coronary artery bypass surgery (CABG) that were randomly selected from 9 hospitals in Canada between 1998 and 2003. This study was conducted to evaluate the relationship between all-cause, risk-adjusted, in-hospital mortality following CABG and proportion of preventable in-hospital deaths at an institutional level.

Hospital charts were reviewed by trained nurse-abstractors for baseline and clinical characteristics data using a standardized database. The nurse-abstracted chart summaries were reviewed by 2 experienced cardiac surgeons who were blinded to the identity of the patient, surgeon who operated on the patients and the hospital where the procedure was carried out. In case of disagreement between the two surgeons, a third surgeon evaluated the nurse summaries. The evidence of preventability of deaths was scored on a 7-point Likert scale. An increasing score on the Likert scale indicated an increasing strength of preventability.

At the end of the review process, 32% of deaths (111/347) were judged preventable. A large proportion of preventable deaths were related to problems with the operating room (86%) [Operative judgment, detection of graft patency, completeness of revascularization, communication, separation from bypass, completion of anastomosis, assessment of appropriateness of graft for particular target, initiation and maintenance of bypass, assessment of hemodynamic stability for off-pump surgery, assessment of aorta, selection and preparation of bypass graft and inspection of hemostasis], intensive care unit problems (61%) [Diagnosis of life threatening event, response of nurse and/or physician, patient monitoring, decision for timing of re-operation, medication dosage and administration and communication] and a minority of deaths occurring on the ward (15%) [Diagnosis of life threatening event, response of a nurse and/or physician, patient monitoring, communication and obtaining help from another member of healthcare team]. There was no significant correlation between all-cause, risk adjusted mortality rates and the proportion of preventable deaths across the nine hospitals (r=-0.42, p=0.26). Furthermore, the reviewers identified factors that can be implemented to avoid preventable deaths including communication, credentialing, education measures, quality assurance programs, enhanced resources and retraining (p<0.05).

The investigators also demonstrated that the preventable deaths occurred more among patients with lower predicted operative risk. Older age [OR 0.97 (95% CI 0.95-1.00)], left main stem disease [OR 0.67 (95% CI 0.41-1.11)], 3-vessel coronary disease [0.73 (95% CI 0.42-1.27)], emergent status [OR 0.38 (95% CI 0.13-1.04)], and diabetes mellitus [OR 0.38 (95% CI 0.22-0.65)] were identified on a multivariate model to be protective against preventable death. Female gender was the only factor that increased the risk of a preventable death [OR 1.47 (95% CI 0.90-2.39)].

The authors conclude that assessment of quality of care using all-cause, risk adjusted mortality statistics and institutional outcome report cards alone are not accurate screening tools for identifying problems at the individual and institution level. Instead they recommend independent, standardized, expert audits to identify specific quality problems that may exist within a hospital and across other hospitals. This could help rectify problems which could lead to improved outcomes among patients undergoing coronary artery bypass surgery.