A review of myocardial normothermia: its theoretical basis and the potential clinical benefits in cardiac surgery

Myocardial protection during cardiac surgery aims to preserve myocardial fu nction while providing a bloodless and motionless operating field to make s urgery easier. Myocardial protection is achieved by decreasing the oxygen n eeds using hypothermia and producing electromechanical cardiac arrest using potassium infusion which allows surgery to be performed on a non-beating h eart. The deleterious effects of hypothermia include dysfunction of enzymat ic systems, development of acidosis, a decrease in tissue oxygen delivery, an increase in blood viscosity and a decrease in erythrocyte deformability. Ninety percent of the decrease in oxygen consumption is obtained by induci ng electromechanical arrest and inducing hypothermia has little additional benefit. Maintenance of systemic and myocardial normothermia reduces proble ms and provides a more physiological approach for cardiopulmonary bypass (C PB). The current results obtained using normothermic protection are very en couraging, and it Is an easier inexpensive option. This review summarizes t he current knowledge on the benefits of normothermia, based upon experiment al and clinical studies. (C) 2000 The International Society for Cardiovascu lar Surgery. Published by Elsevier Science Ltd. All rights reserved.