What should be done to obtain an accurate potassium (K+) level during a blood draw?

To obtain an accurate potassium (K+) level during a blood draw, it is essential to obtain a serum sample. Serum is the liquid portion of blood that remains after coagulation has occurred, and it provides a reliable measurement of the potassium concentration in the blood. This is typically achieved by allowing the blood to clot before centrifugation, which separates the serum from the cellular components of the blood.

Using a serum sample is crucial because it minimizes the risk of potassium being released from the cells after the blood is drawn. If blood is drawn using anticoagulants or collected in tubes that do not allow for clotting, such as those containing EDTA, it can lead to inaccurate results. This is due to potential hemolysis or the interference of other substances that can affect potassium measurements.

Obtaining a venous blood gas would not be appropriate for solely measuring potassium levels, as this test is geared towards assessing blood pH and carbon dioxide and oxygen levels rather than specific electrolyte concentrations. Choosing a green top tube, which typically contains heparin, may also provide potassium readings, but using a serum sample is generally the preferred and more standard approach for accurate potassium measurement.