Open heart surgery has been performed at our center for less than a decade, with an annual increase in number and diversity of performed procedures. This is the first report describing the 30-day operative complications following isolated coronary surgery and their predictors. Pneumonia, renal impairment, and sternal wound infection within 30 days after surgery were the studied outcomes. Patients who died with any of these end points were also included. Of all patients, 3.6% developed pneumonia, 5.9% developed renal failure, and 8.5% developed sternal wound infection. These findings were fairly similar to earlier studies [9
Prolonged inotropic support in the ICU and per-operative transfusion of one or more packed red blood cells units (PRBC), were predictors of the three end points. Both of these factors are reflections of low cardiac output syndrome with resultant tissue hypoperfusion. Besides, blood transfusion significantly increases the risk of respiratory failure and ICU stay [13
]. Measures directed to reduce blood loss during surgery may help reduce the need for blood transfusion: reduction of CPB prime volume, meticulous surgical haemostasis, and utilization of autologous blood transfusion.
Concern for high operative complications among old age group was raised in different previous reports [14
]. In our multivariate analysis, patients > 65 years were found to be at an increased risk of developing renal failure, but not pneumonia or surgical wound infection. Stoica SC et al [15
] reported a significantly increased risk of developing post-operative renal failure in the elderly. This group of patients may be susceptible to many forms of acute renal failure because an aging kidney loses function and the ability to withstand acute insults and may have reduced ability to cope with critical circulation [16
In the major morbidity risk models developed, the impact of female gender was not consistent across different complications. For example; the impact of female gender appears to be slightly protective for the major morbidity endpoints of renal failure requiring dialysis [17
]. However, female gender appears to predispose to higher adverse event rates for the outcomes of prolonged ventilation, and deep sternal wound infection [5
]. Female gender in our study was an independent predictor of developing post-operative pneumonia. However, the incidence of post-operative renal impairment and sternal wound infection was not affected by gender difference.
Many studies have suggested the importance of chronic comorbidities (COPD, pre-operative myocardial infarction, hypertension, diabetes mellitus, peripheral vascular disease, and renal impairment) in predicting the outcome of cardiac operations. Conflicting results have been reported in different studies regarding the impact of these different comorbid conditions and their reflection on the operative complications [5
]. This may be related to the lack of sufficiently large numbers that may minimize the potential effects of chance or may be due to the different prevalence of comorbidities among different populations. In our series, history of smoking and some of the studied pre-operative comorbidities were not significant predictors of post-operative complications. The smaller sample size of some of the above mentioned comorbidities have contributed to the non-predictive strength of these risk factors.
Diabetes has long been described as an independent risk factor for the development of coronary artery disease, and the proportion of diabetic patients undergoing CABG is steadily increasing [8
]. As with other reports [18-22
], diabetic patients were found to have significantly higher incidences of post-operative complications. Diabetics had higher risk of developing post-operative pneumonia and sternal wound infection, but not acute renal failure. Chukwuemeka et al [21
] found no correlation between diabetes mellitus and the development of post-operative renal failure. Previous studies have reported an association between diabetes and sternal wound infections [21
Patients with COPD and those who spent > 12 hours on mechanical ventilation were at a significantly increased risk of developing post-operative pneumonia. Also, prolonged mechanical ventilation was an independent predictor of post-operative renal failure, confirming previous reports [23-25
]. This group of patients has an impaired physiologic reserve and function of their lungs, in addition to the burden of being at an increased risk of sepsis, due to the prolonged ventilation and ICU stay. Filsoufi et al [25
] reported a three-times-increased rate of respiratory failure in patients with a history of COPD and a significantly increased risk of renal failure requiring dialysis. Although this is a single center study, the association with the duration of ventilation should be interpreted carefully, because the duration of ventilation is often affected by other factors unrelated to the patient. Not adjusting for these unmeasured variables is an important source of bias in epidemiologic studies.
In the present study, our data showed that peripheral vascular disease was an independent predictor of post-CABG renal failure. Stallwood et al [18
] reported the role of peripheral arteriopathy on post-CABG renal failure. This may be the result of renal parenchymal disease or renal artery stenosis [26
]. On the other hand Chu et al [27
] concluded that patients with peripheral vascular disease had similar incidence of post-CABG renal failure when compared to patients without peripheral vascular disease.
A higher than normal serum creatinine level was associated with an increased risk of both, post-operative renal failure and sternal wound infection by univariate analysis, and it was an in dependent predictor of post-operative renal failure requiring dialysis by multivariate analysis. This is consistent with previous peer reviews [18
Ahmadi et al [28
] reported an increased risk of post-operative renal failure in patients taken for CABG surgery on emergency basis. Our emergency cases were at a significantly increased risk to develop post-operative pneumonia and renal failure but not sternal wound infection. The majority of these patients had a preoperative cardiac status instability that may compromise renal perfusion and enhance the effect of renal ischemic events that occur during CPB.
In conclusion, age, female gender, a history of diabetes mellitus, COPD, peripheral vascular disease, renal impairment, emergency surgery, per-operative blood transfusion, mechanical ventilation > 12 hours and prolonged inotropic support are associated with the 30-day complications after on-pump isolated CABG surgery.