Kurth C D, O'Rourke M M, O'Hara I B, Uher B
Department of Anesthesiology and Critical Care Medicine, Children's Hospital of Philadelphia, Pa 19104, USA.
Circulation. 1997 Nov 4;96(9 Suppl):II-358-63.
For infant cardiac surgery, recent studies suggest improved neurological outcome after deep hypothermic circulatory arrest when pH-stat cardiopulmonary bypass is used compared with alpha-stat cardiopulmonary bypass. The pH-stat method is hypothesized to protect the brain through improved cooling and/or rewarming. We examined brain cooling and rewarming during pH-stat and alpha-stat cardiopulmonary bypass in 12 newborn pigs.
Microthermistors were inserted into the caudate and cortical gray and white matter, and a cranial window was created to map neocortical temperature gradients by using infrared imaging. Piglets were cooled with pH-stat or alpha-stat cardiopulmonary bypass until all brain regions were less than 20 degrees C; then they were subjected to 60 minutes of circulatory arrest, and afterward, rewarmed with cardiopulmonary bypass. During cardiopulmonary bypass cooling, cortical gray and white matter and caudate temperatures were up to 5 degrees C less in pH-stat than in alpha-stat (P<.05), although after 10 minutes of cooling, only cortical white matter temperature remained significantly less in pH-stat. Neocortical thermal gradients during cardiopulmonary bypass cooling were greater in pH-stat versus alpha-stat during the initial 8 minutes (4 degrees C to 5 degrees C versus 2 degrees C to 3 degrees C, P<.01) but were less by 18 to 20 minutes (0.9 degrees C versus 1.7 degrees C, P<.01). Cardiopulmonary bypass cooling time to less than 20 degrees C was shorter for pH-stat than for alpha-stat in cortical gray matter (14 versus 17 minutes, P<.05) and cortical white matter (17 versus 23 minutes, P<.001) but not in caudate (13 versus 16 minutes, P=NS). Cooling time to less than 1 degrees C neocortical thermal gradient was shorter in pH-stat than in alpha-stat (15 versus 23 minutes, P<.001). During rewarming, regional brain temperatures and neocortical thermal gradients were not different between groups.
pH-stat improves brain cooling efficiency during cardiopulmonary bypass because all regions cooled more rapidly, especially cortical white matter, and less time was required to achieve uniform cerebral deep hypothermia. pH-stat and alpha-stat cardiopulmonary bypass rewarm the brain similarly after deep hypothermic arrest.
对于婴儿心脏手术，最近的研究表明，与α-稳态体外循环相比，使用pH-稳态体外循环进行深低温循环停搏后神经功能结局有所改善。据推测，pH-稳态方法通过改善降温及/或复温来保护大脑。我们在12头新生猪中研究了pH-稳态和α-稳态体外循环期间的脑降温及复温情况。
将微型热敏电阻插入尾状核、皮质灰质和白质，并通过红外成像创建颅窗以绘制新皮质温度梯度。仔猪通过pH-稳态或α-稳态体外循环进行降温，直到所有脑区温度低于20℃；然后进行60分钟的循环停搏，之后通过体外循环进行复温。在体外循环降温期间，pH-稳态时皮质灰质、白质和尾状核温度比α-稳态时低达5℃（P<0.05），不过在降温10分钟后，仅皮质白质温度在pH-稳态时仍显著更低。在体外循环降温最初8分钟内，pH-稳态时新皮质热梯度大于α-稳态（4℃至5℃对2℃至3℃，P<0.01），但在18至20分钟时更小（0.9℃对1.7℃，P<0.01）。在皮质灰质（14对17分钟，P<0.05）和皮质白质（17对23分钟，P<0.001）中，pH-稳态时体外循环降温至低于20℃的时间比α-稳态时短，但在尾状核中并非如此（13对16分钟，P=无显著差异）。pH-稳态时降至新皮质热梯度低于1℃的降温时间比α-稳态时短（15对23分钟，P<0.001）。在复温期间，两组间脑区温度和新皮质热梯度无差异。
pH-稳态可提高体外循环期间的脑降温效率，因为所有区域降温更快，尤其是皮质白质，且实现均匀脑深低温所需时间更短。深低温停搏后，pH-稳态和α-稳态体外循环对脑的复温效果相似。
