Abstract

The temperature-corrected values of blood gas analysis were compared to uncorrected values in 40 cases of open heart surgery under moderate hypothermic cardiopulmonary bypass. The results were as follows. 1. The corrected value of pH was significantly higher than uncorrected value, and it's relationship was ΔpH=-0.015 ΔTemp+0.005 (r=0.81, P<0.01). 2. The corrected value of PCO₂ was lower than uncorrected value, and it's relationship was ΔPCO₂=1.11 ΔTemp+1.81 (r=0.50, P<0.01). 3. The corrected value of PO₂ was lower than uncorrected value, and it's relationship was ΔPO₂=5.21 ΔTemp-1.45 (r=0.32, P<0.01). But there was no clinical significance. 4. The corrected values of HCO₃-, base excess, CO₂ content and oxygen saturation were similar with uncorrected values. In summary, the values of pH and PCO₂ were significantly changed by temperature-correction. Because of the neutral point of water (pH=pOH) rise as temperature falls and it change in parallel with the changes in blood pH, a corrected pH of 7.4, PaCO₂ of 40 mmHg during deep hypothermia would reflect a profound respiratory acidosis. Therefore, the use of the uncorrected value at 37℃ is more preferable and valid means of assessing acid-base management regardless of actual patient temperature.