Boyd O, Mackay C J, Lamb G, Bland J M, Grounds R M, Bennett E D
General Intensive Care Unit, St George's Hospital, London, UK.
Lancet. 1993 Jan 16;341(8838):142-6. doi: 10.1016/0140-6736(93)90005-2.
The measurement of gastric intramucosal pH (pHi) has been advocated to assist in decision-making for critically ill patients. To assess whether the information obtained from the measurement of pHi can be obtained from other measurements of metabolic acidosis, we studied 20 consecutive patients admitted to the intensive care unit. A mean of eight (range two to fourteen) data sets per patient were obtained, comprising measurement of arterial pH, pO2, pCO2, and oxygen saturation, tonometer balloon fluid pCO2, arterial pressures, and cardiac output. Bicarbonate concentration, base deficit or excess in blood and extracellular fluid, and pHi were calculated from these measurements. Relations between the variables and pHi were assessed by within-subject correlation comparisons. There were significant correlations (r > 0.6, p < 0.001) between markers of metabolic acidosis (base deficit in blood and extracellular fluid and bicarbonate concentration) and pHi. A blood base deficit of -4.65 or less and an extracellular-fluid base deficit of -6.13 or less could estimate pHi below 7.32 (lower limit of normal range) with sensitivity of at least 77% and specificity of at least 96%. There was no patient in whom either pHi or blood base deficit consistently reflected acidosis when the other variable did not. We conclude that the information that is obtained by gastric tonometry for pHi can be obtained more simply from measurements of metabolic acidosis; these variables can be calculated from routinely available blood-gas measurements.
有人主张测量胃黏膜内pH值（pHi）以辅助危重病患者的决策制定。为了评估从pHi测量中获得的信息是否可以从代谢性酸中毒的其他测量中获得，我们对20例连续入住重症监护病房的患者进行了研究。每位患者平均获得8个（范围为2至14个）数据集，包括动脉pH值、pO2、pCO2、血氧饱和度、眼压计球囊液pCO2、动脉压和心输出量的测量。根据这些测量结果计算碳酸氢盐浓度、血液和细胞外液中的碱缺失或过剩以及pHi。通过受试者内相关性比较评估变量与pHi之间的关系。代谢性酸中毒指标（血液和细胞外液中的碱缺失以及碳酸氢盐浓度）与pHi之间存在显著相关性（r>0.6，p<0.001）。血液碱缺失≤ -4.65以及细胞外液碱缺失≤ -6.13时，可以估计pHi低于7.32（正常范围下限），敏感性至少为77%，特异性至少为96%。当另一个变量未反映酸中毒时，没有患者的pHi或血液碱缺失始终反映酸中毒。我们得出结论，通过胃张力测定法获得的pHi信息可以更简单地从代谢性酸中毒测量中获得；这些变量可以从常规可用的血气测量中计算得出。
