Impact of Preoperative Anaemia on Outcome in Elective On-Pump Cardiac Surgery

Abstract

Introduction. Anaemia is a clinically important and increasingly frequent finding in cardiac surgery. Whether preoperative anaemia is an independent risk factor for adverse outcomes after elective cardiac surgery is still under discussion. We analysed prevalence of preoperative anaemia and its influence to outcome in patients undergoing elective on-pump cardiac surgery.

Aim of the Study. To analyse preoperative anaemia and its influence to outcome in patients undergoing elective cardiac surgery.

Material and Methods. Prospective study was done from October 2013 to January 2014 at the Cardiac Surgery Centre of Pauls Stradins Clinical University Hospital. Data were collected on 192 patients who underwent elective on-pump cardiac surgery. The prevalence of preoperative anaemia was defined as haemoglobin (Hb) for men < 130 g/l, for women < 120 g/l. Surgical bleeding was found for 17 patients during re-operation, those were excluded from future analysis. Consequently, 175 were divided into two groups: anaemic (n=69) and control group (n=106). Anaemia relationships with haemotransfusions, postoperative complications as acute heart failure, infections, atrial fibrillation, acute kidney injury (AKI) and length of mechanical ventilation and stay in hospital were obtained.

Results. The overall prevalence of preoperative anaemia was 39%. Preoperative Hb values were 111 ± 13 g/l, MCHC 329 ± 12 g/l, MCV 86 ± 8 fl in anaemic group and in a control group Hb 140 ± 11 g/l, MCHC 335 ± 8 g/l, MCV 89 ± 9 fl (p < 0,001; p < 0,001; p = 0,01). Anaemic patients in 80% received red blood cell (RBC) transfusions 586 ± 801 ml and 47% in control group, p < 0,0001. Fresh frozen plasma (FFP) and Cryoprecipitate (Cryo) transfused volumes did not differ statistically between groups (p = 0,15; p = 0,2). Sensitivity and specificity of preoperative anaemia to haemotransfusions: area under curve for RBC transfusions 0,71, for FFP 0,57, for Cryo 0,44. Hb levels before and 24 hours after surgery correlated with RBC transfusions (r = - 0,4, - 0,5; p < 0,001). Anaemia is an independent risk factor for postoperative infection (p=0.04; OR 4.2; 95% C.I. 1.2-16.7) and AKI (p=0,02; OR 2.3; 95% C.I. 1.1-4.6). RBC transfusion volume is adjusted to postoperative infections and AKI, respectively, p = 0.004 and p = 0.01. Anaemic patients had statistically longer mechanical lung ventilation (p = 0.02) and stay in hospital (p = 0.04).

Conclusions. Preoperative anaemia, mainly normocytic normochromic (72%) and microcytic hypochromic (13%), is observed in 39%. Anaemic patients received major RBC transfusions to compare with non-anaemic patients. Preoperative anaemia and volume of RBC transfused are associated with development of AKI and infections postoperatively. Preoperative anaemia prolongs mechanical lung ventilation and in-hospital stay.