Hypothermic Circulatory Arrest and Other Methods of Cerebral Protection During Operations on the Thoracic Aorta

Abstract

Current surgical techniques in operations on the thoracic aorta frequently require exclusion of the cerebral circulation for varying periods. During these periods, hypothermic circulatory arrest (HCA), selective cerebral perfusion (SCP), and retrograde cerebral perfusion (RCP) can be used for cerebral protection. Hypothermia is the principle component of these methods of protection. The main protective effect of hypothermia is based on reduction of cerebral energy expenditures and largely depends on adequate suppression of cerebral function. It is most effective at deep hypothermic levels (13 degrees C to 15 degrees C). Measures that preserve autoregulation of cerebral blood flow help increase the margin of safety with all methods of protection. There is solid experimental and clinical data indicating the safe limits and outcome following HCA. Current applications of SCP and RCP are fairly recent developments and do not have comparable supporting data. SCP can be used without deep hypothermia and allows prolonged periods of cerebral protection, but is complex in application. RCP is simpler, but always requires deep hypothermia. Present clinical data do not allow separation of its protective effect from that of HCA alone. Recent modifications in the application of HCA include monitoring of cerebral O2 extraction, and selective use of supplemental SCP to limit arrest times to less than 50 minutes, or RCP to prevent embolic strokes, as indicated. These changes appear to have reduced the overall mortality, the severity of embolic strokes, and stroke-related mortality.

Longer Duration of Cardiopulmonary Bypass Is Associated With Greater Numbers of Cerebral Microemboli

“…57 Retrograde cerebral perfusion, which was first used to treat air embolism during CPB, 58 may be useful to wash out particulate emboli. 59 We have data from a single case that supports that concept. We studied a subject who had retrograde cerebral perfusion (data not shown), and we found far fewer microemboli than would be predicted.…”

Operação de Bentall e De Bono para correção das doenças da raiz aórtica: análise de resultados a longo prazo

“…It is still used, but only for patients with coronary ostia with some level of difficulty of mobilization -for example, in situations in which there are large aneurysms and for patients who have undergone reoperations [13].…”

Cerbral Protection Strategies for

“…Furthermore, deep hypothermia has been shown to be a strong risk factor for bleeding requiring re-exploration following arch reconstruction (16). Furthermore, despite the cerebral metabolic suppressive effects of profound hypothermia, a linear relationship has been demonstrated between the incidence of TND and the duration of DHCA alone (53). In an attempt to avoid the morbidity associated with DHCA, reduce cardiopulmonary bypass times and improve neurologic outcomes there has been a strong initiative from many different high volume aortic centers to begin performing arch replacements under moderate hypothermia circulatory arrest with ACP.…”