Diabetes and complications after cardiac surgery: comparison with a non-diabetic population

Diabetes is a well-recognized independent risk factor for mortality due to coronary artery disease. When diabetic patients need cardiac surgery, eithe r coronary-aortic by-pass (CABP) or valve operations (VO), the presence of diabetes represents an additional risk factor for these major surgical proc edures. Because of controversial data on mortality rates and post-operative complications in diabetic patients, probably due to not exactly comparable groups of patients, this retrospective study aimed to compare two homogene ous populations, which were different only for the presence or absence of d iabetes. We studied 700 patients undergoing cardiac surgery: 350 with and 3 50 without diabetes, mean age 62 +/- 9 years (67% males); 441 underwent CAB P and 259 VO. Apart from the diabetes, the two groups were strictly matched for age, body mass index, concomitant pathologies and smoking habits, exce pt for previous neurological injuries (more frequent in diabetic patients), and for a slightly lower ejection fraction in the diabetic group. Intra- a nd post-operative complications or events were evaluated carefully: death, number staying in postoperative intensive care unit (ICU), renal, hepatic a nd respiratory complications, necessity for reoperation and hemotransfusion s. Anesthesia and surgical procedures (including extra-corporeal circulatio n techniques) remained substantially unchanged over the period of recruitme nt of patients (1996-1998) and applied equally to both groups of patients. All diabetic patients were treated with insulin by using standard procedure s in order to optimize metabolic control. Diabetic patients in our study, d id not show higher rates of mortality in comparison with non-diabetic patie nts, but had more total neurological complications, more renal complication s, a higher re-opening rate, more prolonged ICU stay, and they needed more blood transfusions. Diabetes remains an independent risk factor for these e vents even in a multivariate logistic regression model analysis. In the sub group of diabetic patients who underwent CABP a higher rate of renal dysfun ction, re-opening, need for hemotransfusions and prolonged ICU stay were co nfirmed. In the subgroup of diabetic patients undergoing VO we found a high er rate of renal dysfunction, reopening, prolonged ICU stay and major lung complications. In conclusion, diabetes does not seem to increase the mortal ity rates of cardiac surgery, but diabetic patients undergoing CABP have, o n the basis of the relative risk evaluation, a 5-fold risk for renal compli cations, a 3.5-fold risk for neurological dysfunction, a double risk of bei ng hemotransfused, reoperated or being kept 3 or more days in the ICU in co mparison with non-diabetic patients. Moreover, diabetic patients undergoing VO have a 5-fold risk of being affected by major lung complications.