The Application of a Dried Balanced Heparin Syringe Can Attenuate the Dilution Effect in Rapid Point-of-care Potassium Testing for the Early Identification of Hyperkalemia in the Emergency Department

Abstract

Purpose: Current methods to evaluate the blood concentration of potassium (K) on point-of-care (POC) are influenced by the relative volumes of heparin and arterial blood. Blood potassium concentration may be underestimated with a high volume of heparin or low volume of blood. This dilution effect can produce false negative results that negatively affect decision-making of clinicians and throw critical patients into crisis. We hypothesized that the application of a dried balanced heparin syringe in rapid POC-K+ could attenuate the dilution effect and would more accurately and consistently measure the concentration of potassium compared with reference testing in emergency situations. Methods: This retrospective study was conducted between January, 1, 2008 and September, 30, 2013 at an urban hospital affiliated with our institution. To attenuate the dilution effect, dried balanced heparin syringes (HS) were also used between October, 1, 2011 and September, 30, 2013. Concentrations of potassium were compared between the dried balanced HS group and the liquid HS group. The reliability of each of these outcome measures was assessed using intra-class correlation coefficient analysis. Results: Application of dried balanced HS improved the degree of concordance for potassium using two different assays. The false negative rate was significantly improved from 9.1% (95% CI 7.3-11.0) to 5.7% (95% CI 3.5-8.0) in the dried balanced HS group compared with the liquid HS liquid group (p=0.037). Conclusion: This study suggests that the usage of dried balanced HS could attenuate the dilution effect in rapid POC-K+ and predict potassium levels more accurately for identification of patients at risk of hyperkalemia in emergency situations.