**2.3. CABG in patients with renal dysfunction**

Even though conflicting studies exist, a large study has shown that although there is in‐ creased risk of mortality in patients with ESRD undergoing CABG when compared to pa‐ tients without significant renal disease, it still portends a better outcome in terms of mortality when compared to percutaneous revascularization in this patient population [15].

myocardial injury and cardiac arrest. Use of blood transfusions and acute kidney injury

Impact of Renal Dysfunction and Peripheral Arterial Disease on Post-Operative Outcomes ...

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The mode of dialysis is equally important in influencing CABG outcomes, namely perito‐ neal (PD) and hemo-dialysis (HD). Peritoneal dialysis has been associated with worse out‐ comes when compared with hemodialysis [21,22]. Following CABG, diaphragmatic splinting, atelectasis and hypoxemia can occur after early post-operative initiation of PD. In a retrospective analysis of 105 patients, among whom 40 were on PD, and 65 on HD and all patients had been on dialysis for at least 2 months prior to CABG, it was demonstrated that the incidence of post- operative dialysate leak and peritonitis was 10% and 12.5% respective‐ ly in patients on PD. On the other hand, incidence of arterio-venous access thrombosis was 4.6% in patients on HD. Besides older age, PD was an independent risk factor of high opera‐ tive mortality (adjusted OR for in hospital mortality in PD patients was 22.58). Actual causes of mortality included sepsis, cardiac arrest, pneumonia and gastrointestinal bleed. Chief in‐ fective organisms in septic patients were Staphylococcus aureus (coagulase negative), Pseu‐ domonas aeruginosa, and Enterococcus faecalis [21]. Risk of peritonitis is higher if gastroepiploic artery is harvested for CABG as it requires diaphragmatic incision [22].

Diabetes and hypertension are the most common causes of CKD and they are also the major risk factors for coronary artery disease, therefore, the incidence of CAD is higher in these patients.

Diabetes is present in almost one third of CKD patients undergoing CABG and is considered

Szabo et al showed in a study of 2779 CABG patients that in 19.4% of patients with diabetes, the cross-clamp and cardiopulmonary bypass times as well as the need for inotropic sup‐ port, transfusion of blood products and progression of renal failure were all higher in pa‐ tients with CKD. Additionally, the incidence of post-operative stroke was greater in diabetic patients (4.3% vs. 1.7%). Five year survival rate was 84.4% in diabetic group while it was 91.3% in the non- diabetic group [25]. Another study showed that diabetes was an inde‐ pendent major predictor of morbidity and mortality in CABG patients. In 12,198 patients, it was observed that the diabetic group had higher rates of post-operative mortality (3.9% vs. 1.6%) and stroke (2.9% vs. 1.4%). The five and ten year survival rates were 78% and 50% among patients with diabetes as compared to 88 and 71% in the non-diabetic group [26]. Morris et al demonstrated in a study of 5654 patients undergoing CABG that the five year survival rate for diabetic patients was 80% as compared to 91% for non- diabetics [27]. Out‐ comes of CABG are improved in diabetic patients who undergo grafting of internal mam‐ mary arteries, with two being better than one. In a retrospective analysis of 4382 patients undergoing CABG, it was shown at 10 year follow-up that bilateral internal mammary ar‐

were strongly associated with in-hospital death in CKD patients.

**2.6. Impact of comorbidities in patients with CKD undergoing CABG**

a strong predictor of mortality in this patient group [23,24].

*2.6.1. Diabetes*

**2.5. Impact of mode of dialysis on outcomes after CABG**

### **2.4. Hard endpoints after CABG**

It has been shown that the lower the GFR, the worse the mortality after CABG. In a study of 2067 patients, it was found that estimated GFR was a powerful and independent predictor of mortality in multivariate analysis. Estimated average GFR in patients who died was 57.9+/-17.6 mL/min per 1.73 m2 mg/dl, as compared to 64.7 +/- 13.8 mL/min per 1.73 m2 in those who survived at an average follow-up for 2.3 years [16].

In a database review of 483,914 CABG patients over a three year period, it was shown that the post-operative mortality rates for stage 2, stage 3, and stage 4 CKD patients were 1.8%, 4.3% and 9.3 % respectively. Also, there was a higher incidence of stroke, need for re-opera‐ tion, sternal infection, prolonged mechanical ventilation greater than 48 hours and a hospital stay of longer than two weeks [17]. In a prospective study of 15,500 CABG patients over a five year period, it was shown that dialysis dependent patients with CABG had higher risk of in-hospital mortality as compared to non- dialysis dependent CABG patients (12.2% as compared to 3.1%) and also significantly higher risk of mediastinitis (3.6 vs. 1.2%) [18].

One of the largest initial studies on CABG outcomes in ESRD patients 13 years ago was a retrospective study on 82 patients in which patients had a mean follow-up of 3 years. 18.5 % of the patients had left ventricular ejection fraction (LVEF) <0.45 and the aortic cross clamp time was fairly good at 50 ± 3 minutes [10]. Mean number of grafts was 2.3. Sixty-two per‐ cent of patients received left internal mammary grafts. In this study, 30-day mortality rate was 14.6%, and the mean survival rate at one, three and five years was 71%, 56% and 39% respectively. Thirty day mortality was 14.6% due to a variety of causes including myocardial infarction, cardiac arrest or cardiac tamponade. This study showed that although there was high peri and post- operative as well as long term mortality in ESRD patients undergoing CABG, there was a significant improvement in functional status as a result of CABG. The use of internal mammary artery grafts was related with less in-hospital mortality as well. Perioperative atrial fibrillation occurred in 12.1 % of patients within the first thirty days. With patients having preoperative Newyork Heart Association (NYHA) class III or class IV symptoms, LVEF less than 45% and age greater than 60 years, there was higher long term mortality. The incidence of post- operative bleeding and sternal infection was 3.6% which was higher when compared to patients not on dialysis.

Patients with CKD have a poor baroreceptor reflex. Therefore, they do not adjust very well in conditions like post-operative hypotension. Therefore, poor cardiac output can be more symptomatic in this group of patients [19].

In a study of 2438 CKD patients undergoing CABG over a three year period, operative mor‐ tality was 4.8% in individuals with stage 3 CKD and 7.1% in individuals with stage 4–5 CKD while it was 2.2% in those without significant CKD [20]. CKD was associated with increased post-operative blood transfusion requirement, acute kidney injury superimposed on CKD, myocardial injury and cardiac arrest. Use of blood transfusions and acute kidney injury were strongly associated with in-hospital death in CKD patients.
