Initiation of cardiopulmonary bypass triggers an extremely complex and multifactorial response involving activation of complement, platelets, neutrophils, monocytes, and macrophages, thus initiating the coagulation, fibrinolytic, and kallikrein cascades. The systemic inflammatory response to cardiopulmonary bypass is further amplified by subsequent stimulated release of various endotoxins and cytokines, including interleukins and tumor necrosis factor, which further promote endothelial cell permeability.
Preparation for separation from cardiopulmonary bypass must be based on a clear understanding of the patient's preoperative condition and events of the operative course. Weaning from cardiopulmonary bypass is initiated after review and adjustment of numerous physiologic and technical variables, including temperature, laboratory data, heart rate and rhythm, myocardial contractility, and mechanical ventilation.
The anesthetic management of patients undergoing coronary artery bypass graft surgery requires an understanding of myocardial oxygen supply and demand, patient monitoring, and the anesthetic techniques that provide myocardial protection and favor oxygen supply over demand.
Patients with coronary artery disease presenting for coronary artery bypass graft surgery require special considerations in their anesthetic management. First and foremost are techniques that minimize myocardial oxygen demand while maximizing myocardial oxygen delivery. These considerations include preoperative preparation, intraoperative monitoring, and the use of anesthetic agents with hemodynamic effects that favor oxygen supply over demand and allow for myocardial protection. Postoperative management that provides particular attention to pain management, temperature control, and hemodynamic monitoring to avoid tachycardia, hypotension, and hypertension also must be considered.
Modern practices that focus on early extubation and "fast-tracking" cardiac surgical patients through the postoperative period use smaller narcotic doses, with supplementation by short-acting hypnotic agents.
Patients at risk for increased mortality after coronary artery bypass graft surgery are identified by preoperative factors. The most significant risk factors that increase mortality are older than 80 years of age, emergent surgery, prior cardiac surgery, and renal failure.
The unifying concept in all valve surgery includes the principles of preserving myocardial function and the influence of preload, afterload, inotropy, rate, rhythm, and diastolic function on myocardial performance and mechanics.
Intraoperative transesophageal echocardiography is an essential diagnostic tool and monitor of cardiac performance for patients undergoing heart valve procedures.
Cardiac anesthesia for heart valve surgery is associated with a number of special considerations not found in other aspects of cardiothoracic anesthesiology. Among these considerations is familiarity with the type of repair technique or prosthetic valve used.
The process of repairing or replacing a portion of the thoracic aorta typically requires the temporary or permanent interruption of blood flow through the aorta or its major branch vessels, creating the potential for ischemia or infarction of almost any major organ system. Techniques to protect organs during temporary interruption of blood flow in the thoracic aorta include deep hypothermic circulatory arrest, selective antegrade cerebral perfusion, retrograde cerebral perfusion, and partial left heart bypass for distal aortic perfusion. Intraoperative neurophysiologic monitoring and lumbar cerebrospinal fluid drainage are recognized techniques commonly used for repairs involving the descending thoracic or thoracoabdominal aorta to decrease the risk of spinal cord ischemia and infarction.
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