Accuracy of Hemolyzed Potassium Levels in the Emergency Department
Abstract
Introduction: In the emergency department (ED), pseudohyperkalemia from hemolysis mayindirectly harm patients by exposing them to increased length of stay, cost, and repeat blooddraws. The need to repeat hemolyzed potassium specimens in low-risk patients has not beenwell studied. Our objective was to determine the rate of true hyperkalemia among low-risk, adultED patients with hemolyzed potassium specimens.
Methods: We conducted this prospective observational study at two large (129,000 annualvisits) academic EDs in the mid-Atlantic. Data were collected from June 2017–November2017 as baseline data for planned departmental quality improvement and again from June2018–November 2018. Inclusion criteria were an initial basic metabolic panel in the ED with ahemolyzed potassium level > 5.1 milliequivalents per liter that was repeated within 12 hours, age≥18, and bicarbonate (HCO3) > 20. Exclusion criteria were age > 65, glomerular filtration rate(GFR) < 60, creatine phosphokinase > 500, hematologic malignancy, taking potassium-sparing orangiotensin-acting agents, or treatment with potassium-lowering agents (albuterol, insulin, HCO3,sodium polystyrene sulfonate, or potassium-excreting diuretic) prior to the repeat lab draw.
Results: Of 399 encounters with a hemolyzed, elevated potassium level in patients with GFR≥ 60 and age > 18 that were repeated, we excluded 333 patients for age > 64, lab repeat > 12hours, invalid identifiers, potassium-elevating or lowering medicines or hematologic malignancies.This left 66 encounters for review. There were no instances of hyperkalemia on the repeated,non-hemolyzed potassium levels, correlating to a true positive rate of 0% (95% confidenceinterval 0-6%). Median patient age was 46 (interquartile range [IQR] 34 - 56) years. Medianhemolyzed potassium level was 5.8 (IQR 5.6 - 6.15) millimoles per liter (mmol/L), and medianrepeated potassium level was 3.9 (IQR 3.6 - 4.3) mmol/L. Median time between lab draws was145 (IQR 87 - 262) minutes.
Conclusion: Of 66 patients who met our criteria, all had repeat non-hemolyzed potassiumswithin normal limits. The median of 145 minutes between lab draws suggests an opportunity todecrease the length of stay for these patients. Our results suggest that in adult patients < 65 withnormal renal function, no hematologic malignancy, and not on a potassium-elevating medication,there is little to no risk of true hyperkalemia. Further studies should be done with a larger patientpopulation and multicenter trials.