Mechanical Support In Post Coronary Artery Bypass Surgery Patients

Abstract

Myocardial revascularization has been an established mainstay in the treatment of coronary artery disease, Coronary artery bypass grafting (CABG) is performed for patients with coronary artery disease (CAD) to improve quality of life and reduce cardiac-related mortality. Patients referred for cardiac surgery are increasingly, at high risk of perioperative mortality and morbidity because of advanced age, comorbidities, poor left ventricular (LV) function, and extensive coronary disease. Several therapeutic options are available to support failing heart during the perioperative period. Transition from physiological circulation to CPB results in contact between blood and number of non-biological surfaces that form the extracorporeal circuit. This, together with hypothermia, tissue trauma, organ ischemia and reperfusion and laminar flow, results in a very complex response involving the activation of complement, platelets, macrophages, neutrophils and monocytes, The resulting SIRS can exacerbate the ischemia /reperfusion injury associated with cardiac surgery. Cardiac surgery results in impairment of gas exchange for a variety of reasons. While most patients will display subclinical functional changes, the incidence of post-CPBacute respiratory disease syndrome (ARDS) is <2%. The mortality rate associated with post-CPB ARDS, however, is >50%. The principal causes of postoperative respiratory failure are: Atelectasis, Alterations in the production of surfactant, particularly during the period of lung collapse during CPB and as a result of SIRS; Transfusion-related acute lung injury (TRALI), transfusion related acute Summary 123 circulatory overload (TRACO), Altered chest wall mechanics resulting from sternotomy. Patients following CABG with postoperative ventricular dysfunction were encountered creating a need for a device capable of supporting the patient‘s circulation. The IABP is now a standard form of therapy for these patients with avariety of cardiovascular diseases. If patient cannot be weaned from cardiopulmonary bypass despite maximal pharmacologic support and use of an IABP, consideration should be given to placement of a circulatory assist device. These devices provide flow to support the systemic and/or pulmonary circulation while resting the heart, allowing it to undergo metabolic and functional recovery. Extracorporeal membrane oxygenation (ECMO) is a form of extracorporeal life support (ECLS) that serves as an alternative to ventricular assist devices. It represents a modified system of cardiopulmonary bypass (CPB), may assist or replace both the cardiac and the pulmonary function for up to a week or more. As the most common causes of perioperative respiratory failure are ARDS, atelectasis and TRALI. Patients with ARDS presented with hypoxemia and increased work-of-breathing, so that mechanical ventilation is indicated to reverse hypoxemia with the application of PEEP , delivery of a high Fi02 , and reduction of the work- of -breathing .