Temperature Management During Circulatory Arrest in Cardiac Surgery

Surgery for complex aortic pathologies, such as acute dissections and aneurysms involving the aortic arch, remains one of the most technically and strategically challenging intervention in aortic surgery, requiring thorough understanding not only of cardiovascular physiology but also of neurophysiology (cerebral and spinal cord), and is still associated with significant mortality and morbidity. The introduction of deep hypothermia in the mid 1970s, allowing defined periods of circulatory arrest, has made possible the advent of modern aortic surgery requiring prolonged ischemic tolerance of central nervous system. In the late 1980s, when deep hypothermic circulatory arrest was the standard operative strategy for aortic surgery, selective cerebral perfusion, as an adjunct to deep hypothermia, made possible excellent neuroprotection and improved overall outcome. This encouraged the use of selective cerebral perfusion in combination with steadily increasing body core temperatures, a trend culminating in progressive promotion of moderate to mild hypothermia and even normothermia. The motivation for progressive temperature elevation was the limitation of adverse effects of deep hypothermia, in particular, reduction of systemic inflammatory response (and organ dysfunctions) and diminution of the risk of severe postoperative bleeding. However, adverse outcomes due to inappropriate temperature management (core temperatures too high for the required duration of circulatory arrest) are probably underreported. Indeed, complications historically associated with hypothermia are possibly overestimated.