Pre-operative anaemia-does it influence post-operative outcomes after isolated coronary artery bypass grafting?

Introduction Preoperative anaemia is prevalent in a number of patients undergoing coronary artery bypass grafting. Studies provide conflicting results due to several reasons including variation in the threshold of haematocrit used to define anaemia. We aimed to assess the independent effect of preoperative anaemia on outcomes in patients undergoing off pump coronary artery bypass grafting (OPCAB). Methods In this retrospective study, patients with a hemoglobin level less than 11g/dl (haematocrit <33%) were considered to have moderate-to-severe anaemia as per the recommendations of the World Health Organization. Association between haematocrit <33% and mortality as well as adverse post-operative outcomes was assessed. Multivariable logistic regression (MLR) was carried out to assess the independent effect of haematocrit<33% on 30-day mortality and other outcomes. Results The study included 4957 consecutive patients undergoing isolated OPCAB surgery between 2015 and 2020. Out of 4957, 635 (12.8%) had haematocrit <33% and 4322 (81.2%) had haematocrit >= 33%. Patients with haematocrit < 33% had a 30-day mortality of 13 (2%) compared to 38 (0.9%) in patients without anaemia and had a greater requirement for blood transfusion (p<0.0001). It was also associated with an increased incidence of renal failure (p<0.0001), tracheostomy (p=.0.012) and risk of re-intubation (p=0.006). On multiple linear regression (MLR), haematocrit < 33% was not an independent predictor of 30-day mortality odds ratio (OR) 1.47, 95% confidence interval (CI) 0.745-2.917; p=0.26. It was however an important independent risk factor for blood transfusion (OR 1.80, 95% CI 1.29-2.50, p<0.001) and renal failure (OR 3.06, 95% CI 1.338-7.012, p=0.008). The receiver operating characteristic (ROC)-area under the curve (AUC) was 0.63 suggesting moderate discriminatory value of haematocrit < 33% for 30-day mortality. Conclusion Haematocrit < 33% is an important risk factor for adverse outcomes following isolated, primary, elective OPCAB.