The object of this question is to alert you to the fact that there is continued metabolism of cells at room temperature. Blood metabolism continues in the syringe; the PO2 and the pH decreases and the PCO2 increases. The magnitude of change is determined by time, temperature and white count.

An interesting phenomenon occurs in leukemics. If the cells are permitted to continue to metabolize, they will consume oxygen and the partial pressure of oxygen will be spuriously low. This is called leukocyte larceny.

In addition, when the hemoglobin is saturated at a PO2 above 150 mm Hg, a small change in oxygen content represents a large drop in PO2 because of the oxygen-hemoglobin dissociation curve.

Icing the specimen stops the metabolism of cells and reliable results could be obtained up to 24 hours.

REF: Kemp GL. Questions and answers: Arterial blood samples should be stored in ice for gas analysis. JAMA 1973; 223:696-697.