Background: Venous blood sampling is usually performed using a tourniquet to help locate and define peripheral veins to achieve successful and safe venipuncture. Despite widespread usage of tourniquets for venipuncture by medical and laboratory staff, very few are aware of the effects of tourniquet application on laboratory parameters. In addition, definitive guidelines regarding when and how to use a tourniquet for blood sampling are lacking. The aim of the present study was to define the optimal sampling time after tourniquet removal to avoid adverse impact on laboratory analytes.
Methods: Blood oxygen and carbon dioxide partial pressure, pH, oxyhemoglobin saturation (satO(2)), hematological parameters, serum electrolyte concentrations, erythrocyte, deformability and aggregation, leukocyte activation and nitrite/nitrate concentrations obtained 180 s after tourniquet release were compared with baseline values for 10 healthy subjects.
Results: Blood gases, hematological parameters and serum electrolyte levels were not affected by the application and removal of a tourniquet. However, there were significant decreases in erythrocyte deformability at 90, 120, 180 s, and increases in erythrocyte aggregation at 5 and 30 s following removal of the tourniquet. A significant increase in granulocyte respiratory burst at 60 s was observed, confirming leukocyte activation due to application of the tourniquet. There were no significant alterations of blood nitrite/nitrate levels.
Conclusions: Our blood sampling technique which mimicked the application and release of a tourniquet indicated unaltered values for routine blood gases, hematological testing and serum electrolyte levels. Conversely, hemorheological measurements can be affected. Therefore, it is strongly recommended that tourniquet application should be avoided during blood sampling or, if this is not possible, the procedure should be well standardized and details of the sampling method should be reported.