Anaemia is a predictor of mortality in patients undergoing aortic valve surgery

Abstract

We read the article ‘Preoperative anaemia is a risk factor for mortality and morbidity following aortic valve surgery (AVS)’ by Elmistekawy et al. [1] with interest. They aimed to investigate the incidence of preoperative anaemia in patients undergoing nonemergency AVS and its association with postoperative outcomes. They concluded that preoperative anaemia is a common finding in patients undergoing AVS and is an important and potentially modifiable risk factor for postoperative morbidity and mortality. We believe that these findings will pave the way for further studies about the relationships between preoperative anaemia and AVS. Thanks to the authors for their contribution. It is actually believed that patients undergoing heart surgery have a lower margin of safety for tolerance of low haemoglobin (Hg) levels. A significant association between anaemia with adverse outcomes (death, stroke and renal impairment) in patients undergoing cardiac and non-cardiac surgery has been demonstrated in previous studies [2]. Blood transfusion is dangerous with regard to in-hospital mortality, morbidity and long-term survival. Blood transfusion is frequently used as a volume expander while simultaneously increasing the haematocrit. Transfusions have been independently associated with increased mortality after cardiac surgery. Transfusion is also dose-dependent risk factor for early mortality after revascularization. Blood transfusions have been linked to postoperative renal dysfunction, pneumonia, wound infections, severe sepsis and hospital mortality [3]. Based on this point of view, because anaemia and need for blood transfusions lead to very significant adverse effects after cardiopulmonary bypass surgery, it is necessary to research the effective methods of anaemia correction to reduce the need for blood transfusions. Nowadays, although anaemia is a predictor of postoperative complications and is a risk factor for mortality in patients after cardiac surgery treatment, red distribution width (RDW) is known as an independent early marker of Hg evolution and independently identified risk of new onset anaemia, providing predictive information for haematological abnormalities beyond Hg concentrations and other known risk factors. RDW has recently been identified as an independent predictor of all-cause long-term mortality in patients with coronary artery disease [4]. So, if the authors had mentioned RDW, the results of the study might be different. Reduced glomerular filtration rate (GFR) may also be associated with adverse outcomes in patients with cardiovascular disease. In previous study, preoperative GFR was predictive of all-cause mortality, cardiovascular mortality and combined cardiovascular mortality and morbidity. GFR may be useful to identify those patients undergoing cardiovascular surgery with subclinical chronic kidney disease [5]. For this reason, it would be better, if the authors mentioned any of these possible conditions. Finally, it would be better if the authors might define how much time they specified on measuring Hg levels, because it can be associated with haemodilutional anaemia [6]. Following cardiac surgery, some factors including longer hospital stays, increased risk of infection, higher rate of pulmonary complications, prolonged ventilation, stroke, renal failure, atrial fibrillation, myocardial infarction, pneumonia, prolonged ventilation and operation time are associated with increased morbidity and mortality rates in patients undergoing AVS [3]. So, the further studies should evaluated these factors in patients with AVS.