Temperature correction of blood gas values.

The popularity of routine temperature correcting of pH, PCO2 and PO2 values is based on the observation that large differences in the blood gas values are present when the patient's temperature is profoundly hypo- or hyperthermic. This observation leads some clinicians to the unsubstantiated conclusion that uncorrected 37 degrees C values are "wrong." The danger in this superficial thought process is that one might reach the unfounded conclusion that temperature-corrected values are "right." The simple truth is: With significant changes in patient temperature, we do not fully understand the complexity of the effects on metabolism, vascular function, and respiration. Both corrected and uncorrected blood gas values, therefore, are of uncertain usefulness in patients with significant deviations in body temperature. There is no logical or scientific basis for the assumption that temperature-corrected values are better than the values obtained at 37 degrees C. In fact, the available technical and biological data lead to the conclusion that, in almost all circumstances, there is no clinical advantage to using values other than those at 37 degrees C. In addition, the routine process of temperature correction of blood gases involves several practical disadvantages. First, interpretation of the corrected values demands deviation from the familiar and well-documented guidelines for interpreting 37 degrees C values. Second, temperature correction assumes the laboratory has received the patient's true temperature at the time of sampling. My experience is that the patient's true temperature often is not reported or is reported erroneously. Third, temperature-corrected values can be confused with uncorrected values and vice versa. Available data support the practice that only uncorrected (37 degrees C) blood gas values should be used and reported routinely. Temperature-corrected values should be calculated only when specifically requested and the onus for clinical use of temperature-corrected values lies with the clinician who requests them.