Aoki M, Nomura F, Stromski M E, Tsuji M K, Fackler J C, Hickey P R, Holtzman D H, Jonas R A
Department of Cardiovascular Surgery, Children's Hospital, Boston, Massachusetts.
Ann Thorac Surg. 1993 May;55(5):1093-103. doi: 10.1016/0003-4975(93)90014-9.
The pH management that provides optimal organ protection during hypothermic circulatory arrest is uncertain. Recent retrospective clinical data suggest that the pH-stat strategy (maintenance of pH at 7.40 corrected to core temperature) may improve brain protection during hypothermic cardiopulmonary bypass with a period of circulatory arrest in infants. The impact of alpha-stat (group A) and pH-stat (group P) strategies on recovery of cerebral high-energy phosphates and intracellular pH measured by magnetic resonance spectroscopy (A, n = 7; P, n = 5), organ blood flow measured by microspheres, cerebral metabolic rate measured by oxygen and glucose extraction (A, n = 7; P, n = 6), and cerebral edema was studied in 25 4-week-old piglets undergoing core cooling and 1 hour of circulatory arrest at 15 degrees C. Group P had greater cerebral blood flow during core cooling (54.3% +/- 4.7% versus 34.2% +/- 1.5% of normothermic baseline, respectively; p = 0.001). The intracellular pH during core cooling showed an alkaline shift in both groups but became more alkaline in group A than in group P at the end of cooling (7.08 to 7.63 versus 7.09 to 7.41, respectively; p = 0.013). Recovery of cerebral adenosine triphosphate (p = 0.046) and intracellular pH (p = 0.014) in the initial 30 minutes of reperfusion was faster in group P. The cerebral intracellular pH became more acidotic during early reperfusion in group A, whereas it showed continuous recovery in group P. Brain water content postoperatively was less in group P (0.8075) than in group A (0.8124) (p = 0.05). These results suggest that compared with alpha-stat, the pH-stat strategy provides better early brain recovery after deep hypothermic cardiopulmonary bypass with circulatory arrest in the immature animal. Possible mechanisms include improved brain cooling by increased blood flow to subcortical areas, improved oxygen delivery, and reduction of reperfusion injury, as well as an alkaline shift in intracellular pH with hypothermia in spite of a stable blood pH.
在低温循环停搏期间能提供最佳器官保护的pH管理尚不确定。近期回顾性临床数据表明，pH稳态策略（将pH维持在根据核心温度校正后的7.40）可能会改善婴儿在低温体外循环并伴有一段时间循环停搏期间的脑保护。在25只4周龄仔猪中研究了α稳态（A组）和pH稳态（P组）策略对通过磁共振波谱测量的脑高能磷酸盐和细胞内pH恢复的影响（A组，n = 7；P组，n = 5）、通过微球测量器官血流量、通过氧和葡萄糖摄取测量脑代谢率（A组，n = 7；P组，n = 6）以及脑水肿情况，这些仔猪接受核心降温并在15℃下循环停搏1小时。P组在核心降温期间脑血流量更大（分别为正常体温基线的54.3%±4.7%和34.2%±1.5%；p = 0.001）。核心降温期间两组的细胞内pH均出现碱化偏移，但在降温结束时A组比P组更碱化（分别为7.08至7.63和7.09至7.41；p = 0.013）。P组在再灌注最初30分钟内脑三磷酸腺苷（p = 0.046）和细胞内pH（p = 0.014）的恢复更快。A组在早期再灌注期间脑内细胞内pH变得更酸，而P组则持续恢复。术后P组脑含水量（0.8075）低于A组（0.8124）（p = 0.05）。这些结果表明，与α稳态相比，pH稳态策略在未成熟动物进行深低温体外循环并伴有循环停搏后能提供更好的早期脑恢复。可能的机制包括通过增加皮质下区域血流量改善脑冷却、改善氧输送、减少再灌注损伤，以及尽管血液pH稳定但低温时细胞内pH出现碱化偏移。
