The effect of temporary venous occlusion on trace mineral concentrations in plasma.

The effects of short-term venous occlusion on plasma concentration of trace minerals--zinc, iron, and copper--were studied in normal volunteers. In one experiment, antecubital vein blood samples were drawn simultaneously from both arms of 14 subjects while their left arms remained free and their right arms had been occluded from 60 s at 40 mm Hg pressure. Statistical comparison of paired samples showed a significant increase in zinc (p less than 0.05) and iron (p less than 0.001), but not copper concentrations in plasma from the occluded extremity. The mean increase in concentration in the right (ligated) arms with respect to the left (unligated) arms was 3.7 and 24.6%, for zinc and iron, respectively. In a second experiment, simultaneous blood samples were drawn from five subjects with neither arm occluded. No significant difference between right and left was observed. Thus, application of tourniquets during the sampling of venous blood for trace mineral analysis introduces a nonrandom factor. Standardization of sampling techniques is essential to overall reliability of trace mineral determinations.