Warning over clenched fists during phlebotomy | nursing times


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Patients should not be made to tightly clench their fists during phlebotomy procedures because it can cause misleadingly high blood potassium readings, according to a study. Researchers


calculated mean monthly serum potassium concentrations for all GP requested analyses between January 2002 and December 2005. The percentage of results in a higher threshold above 5.8 mmol/L


were calculated and plotted against mean monthly temperature. They were also plotted before and after a change in phlebotomy practice, where patients were no longer asked to clench their


fists if giving blood was difficult. Results showed that incidents of high blood potassium fell significantly after the change in practice in 2003, after variations caused by ambient


temperature were factored in. Authors wrote: ‘Suboptimal phlebotomy practice, particularly requesting patients to fist clench to ease venesection can lead to quantitatively serious


overestimation of serum potassium and the percentage of patients with reported hyperkalaemia falls when such practice is corrected.’ Annals of Clinical Biochemistry (2008) 00:1-4