A quality control procedure for central venous blood sampling based on potassium concentrations

Objectives To evaluate the extent of agreement between two blood collection methods for electrolytes, central venous blood sampling by the push-pull technique versus venipuncture, and to mitigate errors in blood sampling by a potassium-based quality control procedure. Methods A comparative within-subject study was carried out for adult patients in the intensive care unit. Intraclass correlation coefficients (ICCs) were used to estimate concordance, and Bland–Altman analysis and clinically acceptable limits were used to compare the equivalence of the two methods. An in-house checklist was designed to identify errors made by nurses throughout central venous blood sampling by the push-pull technique, the corrective training and quality control procedure were conducted, and the rate of errors, incidence of hemolysis and distribution of potassium concentrations were comparatively analyzed for the quality of central venous blood sampling before and after the quality control procedure. Results All the ICCs of 220 paired blood samples displayed excellent reliability, except for potassium. Most of the electrolyte variables were within the clinically acceptable limits, and the results showed that the potassium concentrations did not seem to sufficiently affect clinical decision-making. A total of 30 nurses accepted 90 observations before and after the quality control procedure, and the results showed that blood exposure and repeated disconnections of the line in the push-pull technique were always the main problems throughout the process of central venous blood sampling. In addition, after improvement, the number of patients with hypokalemia or hyperkalemia tended to decrease, but the difference was not statistically significant. For all of the blood samples, only three push-pull paired samples received hemolysis notice. Conclusions Central venous blood sampling by the push-pull technique could be an acceptable substitute for most electrolytes via venipuncture, but caution should be exercised for potassium-based quality control procedures.