Accuracy of Potassium Supplementation of Fluids Administered Intravenously

BACKGROUND: Potassium (K(+)) supplementation of isotonic crystalloid fluids in daily fluid therapy is commonly performed, yet its accuracy in veterinary medicine is undetermined. OBJECTIVE: To investigate the accuracy of K(+) supplementation in isotonic crystalloid fluids. ANIMALS: None. METHODS: Observational study. 210 bags of fluid supplemented with KCl being administered to hospitalized dogs and cats intravenously (IV) were sampled over a 3‐month period. Measured K(+) concentration ([K(+)]) was compared to the intended [K(+)] of the bag. In a second experiment, 60 stock fluid bags were supplemented to achieve a concentration of 20 mmol/L K(+), mixed well and [K(+)] was measured. In another 12 bags of 0.9% NaCl, K(+) was added without mixing the bag, and [K(+)] of the delivered fluid was measured at regular time points during constant rate infusion. RESULTS: The measured [K(+)] was significantly higher than intended [K(+)] (mean difference 9.0 mmol/L, range 6.5 to >280 mmol/L, P < .0001). In 28% of clinical samples measured [K(+)] was ≥5 mmol/L different than intended [K(+)]. With adequate mixing, K(+) supplementation of fluids can be accurate with the mean difference between measured and intended [K(+)] of 0.7 (95% CI −0.32 to 1.7) mmol/L. When not mixed, K(+) supplementation of 20 mmol/L can lead to very high [K(+)] of delivered fluid (up to 1410 mmol/L). CONCLUSIONS AND CLINICAL IMPORTANCE: Inadequate mixing following K(+) supplementation of fluid bags can lead to potentially life threatening IV infused [K(+)]. Standard protocols for K(+) supplementation should be established to ensure adequate mixing.