深低温停循环前血气管理方法的脑保护实验研究

Experimental cerebral protection study with blood gas management before deep hypothermic circulatory arrest

观察深低温停循环前降温期血气管理方法对术中脑血流及脑代谢的影响，探讨较佳的脑保护方法。方法：12头幼猪建立体外循环，常温（37℃）转流10分钟后，按下述血气管理方法转流20分钟降温至鼻咽温18℃：α－稳态方法（A组，n＝6），pH－稳态方法（P组，n＝6）。经过60分钟停循环，两组都用α－稳态方法复温至鼻咽温36℃。于常温转流10分钟、降温末、再灌注开始和复温末等4个时点测定脑血流量、脑耗氧量、鼻咽温、脑皮层温和深部温；在降温期连续测定脑皮层温、深部温及鼻咽温。结果：降温期P组脑深部和皮层部温差较A组小，降温末脑皮层温和深部温较A组显著降低；降温期各组脑血流量均显著减少，但降温末P组脑血流量较A组增加；降温末P组氧耗量较A组低。结论：深低温停循环降温期应用PH－血气管理方法比用α－血气管理方法可提供更好的脑保护。

Objective: In order to search for an optimal method on cerebral protection, the present study was madeto observe the effect of different blood gas management during cooling before deep hypothermic circulatory arrest oncerebral blood flow and cerebral metabolism. Metheds: Eighteen piglets were placed on cardiopulmonary bypass (37℃)for ten minutes. All animals were cooled for 20 minutes with different blood gas management as follows, until their nasopharyngeal tempratures (NBT) were at 18℃: alpha-stat strategy (group A, n=6), pH-stat strategy (group P, n=6). Animals underwent circulatory arrest for 60 minutes, were rewarmed with alpha-stat strategy till their NBT were36℃. Measurement of CarBF, CMO2, NBT, brain conical temperatures (BCT) and basilar brain temperatures (BBT)were made at the end of ten minutes' normothermic perfusion, at the end of cooling, and the beginning of reperfusionand after rewarming. NBT, BCT and BBT were also measured continuously during cooling. Results: The degree oftemperature gradient of BBT and BCT in group P was lower than that in group A during cooling. The BCT and BBT ingroup P at the end of cooling were significantly lower than that in group A. CBF was decreased in both groups duringcooling, but CBF of group P increased more than that of group A at the end of cooling. At given temperature (18℃ ),cerebral oxygen metabolism was suppressed mor e in group P. Conclusions: Better Cerebral protection is provided bypH-stat strategy during cooling before deep hypothermic circulatory arrest.