Hypothermia and rewarming after cardiac surgery

Ensuring adequate oxygen delivery to the tissues with respect to oxygen demand is an important operative challenge during cardiac surgery. The state of the art in myocardial preservation in the 1990s has evolved to include pretreatment of the myocardium; intraoperative use of systemic hypothermia with cardiopulmonary bypass (CPB), topical cooling of the myocardium, cold cardioplegia, and myocardial reperfusion; and postoperative oxygen transport support. These techniques optimize myocardial preservation while providing adequate cardiac surgery operative times by decreasing the myocardial ischemic period, decreasing cellular metabolic requirements, and preserving energy stores. Awareness of the physiologic consequences of hypothermia in the postoperative cardiac patient improves nursing assessment of the hypothermic patient. Appropriate temperature monitoring and reporting support timely medical and nursing interventions for hypothermia, such as internal and external rewarming techniques or drug administration to facilitate the rewarming process and suppress or treat shivering. This article addresses the physiologic condition of hypothermia, the elective hypothermia techniques used during cardiac surgery, and the medical or nursing rewarming and management techniques for the postoperative cardiac surgery patient.