The effect of prolonged tourniquet application on serum bicarbonate.

Background: Many clinicians believe that prolonged tourniquet application lowers the serum bicarbonate concentration in samples drawn from that limb, but this effect has never been examined prospectively.

Objective: To test the effect of prolonged tourniquet application before phlebotomy on serum bicarbonate concentration in healthy adults.

Methods: We drew blood samples from 27 healthy adult volunteers without a tourniquet and again 1, 3, and 5 minutes after applying a blood pressure cuff and inflating it to the mean arterial pressure.

Results: The mean bicarbonate concentration was 27.3 +/- 2.26 mmol/L (standard deviation) at baseline, 27.7 +/- 2.39 mmol/L at 1 minute, 27.7 +/- 2.05 mmol/L at 3 minutes, and 27.7 +/- 1.96 mmol/L at 5 minutes. The mean change in bicarbonate concentration from baseline was -0.04 +/- 1.02 mmol/L at 1 minute, 0.44 +/- 1.05 mmol/L at 3 minutes, and 0.44 +/- 1.31 mmol/L at 5 minutes. The mean lactate concentration was 1.1 +/- 0.28 mmol/L at baseline, 1.3 +/- 0.65 mmol/L at 1 minute, 1.2 +/- 0.52 mmol/L at 3 minutes, and 1.2 +/- 0.36 mmol/L at 5 minutes. The mean change in lactate concentration from baseline was 0.15 +/- 0.67 mmol/L at 1 minute, 0.11 +/- 0.11 mmol/L at 3 minutes, and 0.12 +/- 0.37 mmol/L at 5 minutes.

Conclusions: Prolonged tourniquet application before phlebotomy does not lower the serum bicarbonate concentration in healthy adults.