Influence of Temperature on Arterial Blood Gases
Optimal values of arterial pH and PaCO2 have been established, in man, at 7.40 and 40 mmHg respectively. Hypothermia improves the solubility of carbon dioxide, which decreases PaCO2 and increases pH. It has therefore been agreed that the acid-base values, measured in vitro at 37 °C, required correction to the actual temperature of the patient before interpretation. The correction generally can be performed by the analyzer, if the patient’s temperature is entered. Consistently, it has been an usual practice, during peroperative hypothermia, to prevent hypocapnia and alkalemia by adding carbon dioxide to the inspired gas mixture. The underly- ing assumption of this traditional approach is that optimal values of PaCO2 and pH are unaffected by temperature.
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