Complications in Cardiac Surgery

Abstract

OF DISSERTATION COMPLICATIONS IN CARDIAC SURGERY Quality of care and outcomes from cardiac surgery have always been of primary importance to providers and the entire health care team when caring for cardiac surgical patients. Providers in cardiac surgery have had a long history of tracking procedural morbidity and mortality rates in programs nationally and internationally. Morbidity and mortality rates vary widely among hospitals. In most studies in which procedural outcomes from cardiac surgery are evaluated, the focus has been on operative morbidity and mortality and the probability of death after a cardiac surgical procedure. Less attention has been paid to predictors of perioperative complications, and sample sizes have been relatively small in the studies done. The focus of this dissertation was identification of perioperative predictors of perioperative complications associated with cardiac surgery to identify patients who could be at risk for morbidity or mortality related to the cardiac surgical procedure. We used a large hospital registry and had large sample sizes for our studies. By identifying those patients at risk for perioperative complications, modifiable risk factors can be addressed in order to prevent untoward outcomes. The purpose of this dissertation was to identify demographic, clinical and surgical predictors of selected common perioperative complications that can lead to morbidity and mortality in the cardiac surgical patient and the contribution of these complications to length of stay in the Intensive Care Unit (ICU) and overall length of stay in the hospital after an open chest cardiac surgical procedure with cardiopulmonary bypass. By identifying predictors of perioperative complications, we can identify patients preoperatively who may be at higher risk and intervene before a complication occurs. There are three manuscripts included in this dissertation. The aim of the first study (N = 2399) reported in manuscript one was to determine demographic, clinical and surgical predictors of perioperative packed red blood cell transfusion in coronary artery bypass graft surgery patients undergoing cardiopulmonary bypass, and to test gender-specific models. The following predictors of transfusion were included: 1) age; 2) gender; 3) previous coronary artery bypass graft surgery; 4) body surface area; 5) number of grafts; 6) hematocrit prior to surgery; 7) hypertension; 8) diabetes mellitus; 9) history of heart failure; 10) dyslipidemia; 11) cardiopulmonary bypass time; and 12) elective versus emergent surgery. In the overall sample the following predictors were identified: 1) age; 2) body surface area; 3) cardiopulmonary bypass time; 4) prior coronary artery bypass graft surgery; 5) preoperative hematocrit; and 6) elective versus emergent surgery. Older age, lower body surface area, longer cardiopulmonary bypass time, history of prior coronary artery bypass graft surgery, lower preoperative hematocrit and emergent surgery were independently predictive of transfusion. In the male only model (n = 1721) the following were predictors of transfusion: 1) preoperative hematocrit; 2) body surface area; 3) cardiopulmonary bypass time; and 4) elective versus emergent surgery. In the female only model (n = 678) the following were predictors of transfusion: 1) preoperative hematocrit; 2) cardiopulmonary bypass time; and 3) body surface area. The aim of the second study was to determine the association of number of major perioperative complications of open-chest cardiac surgery and cardiopulmonary bypass (N = 2350) with ICU and hospital length of stay. The number of complications was predictive of a prolonged length of ICU stay and overall hospital length of stay. Major complications were considered to be neurological complications, specifically stroke, renal insufficiency and failure, respiratory failure, myocardial infarction, heart failure and bleeding which led to reoperation. We showed that one complication did increase the length of stay in the ICU but when there were two or more complications the length of stay increased significantly, revealing that it is imperative to optimize the patient as much as possible before surgery to avoid potential complications. The purpose of the third study was to (1) determine predictors (i.e. gender, age, surgical procedure, body mass index, last creatinine level, chronic lung disease, diabetes control, history of stroke in the past, history of myocardial infarction, class of heart failure, hypertension, cerebrovascular disease prior to surgery, previous cardiac procedure, postsurgical complications, re-operative bleeding, and number of major complications) of ischemic and hemorrhagic stroke in patients who had undergone cardiothoracic surgery and (2) determine if neurological complications prolonged patient length of stay. We found three significant predictors of post-surgery stroke: body mass index (Wald(1) = 6.21, p = 0.01), having chronic lung disease (Wald(1) = 5.37, p = 0.02), and having diabetes control at the time of surgery (Wald(1) = 4.82, p = 0.03). More specifically, the results indicated that (1) having a higher body mass index decreased the odds of patients experiencing postsurgery stroke with a one unit increase in body mass index decreasing the odds of experiencing post-surgery stroke by 91%, (2) having chronic lung disease increased the odds of patients experiencing post-surgery stroke by 196%, and (3) diabetes control at the time of surgery decreased the odds of patients experiencing post-surgery stroke by 31%. This dissertation has filled an important gap in the evidence base for complications related to cardiac surgery in patients by identifying complications that could lead to a prolonged length of stay as well as predictors of stroke and the use of blood transfusion. The results of these studies can lead to the prevention of these complications and therefore the reduction in perioperative morbidity and mortality. The findings from this dissertation provide further evidence of the value of identifying patients at higher risk of complication undergoing cardiac surgery.