Extraction of cyclic AMP for the determination in the competitive protein binding assay

The changes in free calcium, total calcium, albumin, protein, pH, lactate, sodium, magnesium, and potassium values during and following venous stasis (3 min at an external pressure of 100 mmHg) with and without forearm exercise have been measured. The pattern of changes observed with time were dependent on the presence or absence of forearm exercise. Without exercise significant changes are only observed at l min following stasis and then the increases are only moderate (free calcium 2.0%, total calcium 2.4%, albumin 6.9%, and protein 5.9%). However, when the forearm is exercised, larger increases (free calcium 8.6%, total calcium 8.4%, albumin and protein 12.4%) were observed for all parameters following stasis. These increases took 1 to 3 min to return to baseline for most parameters. Only potassium and magnesium went below baseline during the recovery period. It is recommended that when a tourniquet is used to aid in obtaining venous blood samples for these analytes, exercise of the forearm be avoided. If forearm exercise is unavoidable, then the sample should be obtained 1 to 3 min after release of the tourniquet.