THE CLINICAL VALUE OF URINE pH DETERMINED BY LITMUS PAPER IN MONITORING ACIDOSIS DURING INTRA-CARDIAC SURGERY

The pH of 60 urine specimens was determined both by litmus paper and pH meter. The results demonstrated that there was no significant difference between the values obtained by both methods （t=0.898, p＞0.05）, although they were markedly and positively related to each other （r=0.937, p＜0.01）. Analyses of the urine pH of 159 specimens and the corresponding data of blood gas analyses showed: （1） urine pH was positively related to blood pH （r=0.224, p＜0.01） and BE （r=0.181, p＜0.05）; but it was negatively related to PaCO2 （r=0.518, p≈0.05）; （b） the difference among the mean values of the urine pH obtained at 3 different blood pH levels also disclosed that the urine pH 7.23 and 7.41 can be used as an index indicating the upper limit of acidosis and the lower limit of alkalosis respectively during bypass; （c） with PaCO2 at an almost constant level during bypass, the urine pH should be kept within the limit of 7.23 to 7.41 if the blood pH is expected to be maintained within normal range. The authors concluded that the urine pH determined by litmus paper can be used as a guide for alkaline solution supplement during extracorporeal circulation.