Factors contributing to intra-individual variation of serum constituents: 4. Effects of posture and tourniquet application on variation of serum constituents in healthy subjects.

We studied the effects on 18 serum constituents of posture and prolonged tourniquet application. The subjects were 11 healthy men, ages 20-25 years. The assays were performed on the AutoChemist Multi-Channel Analyzer (AutoChem Instrument AB, Liding#{244}, Sweden). To compensate for the within-hour variation in these constituents, we drew blood samples at 1100 h and 1130 h on several days. The 1100-h sample was taken after the subjects had been sitting erect for 60 mm. The 1130-h sample followed different posture regimens: Control day: sitting for 15 mm; experimental days: after (a) being supine for 30 mm, (b) standing for 30 mm, and (c) sitting erect for 30 mm. The 1 130-h/i 100-h ratios for the three experimental days were compared with those for the control day. Significant differences (P <.05) were foundfor serum potassium,calcium, total protein, albumin, aspartate aminotransferase, and acid phosphatase under condition a; for phosphate ion, total protein, total lipid, cholesterol, and alkaline phosphatase under condition b; and for aspartate aminotransferase under condition c. The effect of a 3-minute tourniquet application was similarly studied. The ratio of the “prolonged tourniquet application day” differed significantly from the control day with regard to serum potassium, total protein, iron, total lipid, cholesterol, aspartate aminotransferase, and bilirubin. Significance of posture and tourniquet time in blood-sampling and their effect on total intra-individual variation are discussed.