Supplementation of crystalloid solutions with potassium (K+) is common, but the accuracy of this practice has not been examined in veterinary medicine. In this observational study, K concentration ([K+]) was measured in 210 bags of crystalloid solutions supplemented with potassium chloride (KCl) administered to small animal patients. Samples were drawn from the injection ports during active administration. The intended [K+] ranged from 10 to 40 mmol/L. The measured [K+] ranged from 9 to >300 mmol/L, with a mean difference between intended and measured [K+] of 9 mmol/L. There were 3 samples >300 mmol/L; the intended [K+] in these samples was 20 to 25 mmol/L. In 2 of these samples, KCl was added to partial bags, which suggests possible calculation or labeling errors.
The study also examined [K+] under controlled conditions. KCl supplementation with a target [K+] of 20 mmol/L was performed based on bag weight and baseline measured [K+]. KCl was injected with the injection port uppermost, and the bag was inverted 4 times to ensure adequate mixing. The mean difference between targeted and measured [K+] was only 0.7 mmol/L. The effect of inadequate mixing was assessed through KCl administration (rapidly or slowly) with the bags already hanging for infusion to mimic common clinical practice. Repeated [K+] measurements showed that, especially with slow injections, a high percentage of K+ traveled through the IV line within the first hour. Miscalculation and inadequate mixing could have serious clinical implications, especially in patients given initial fluid boluses. The authors suggest adoption of standard supplementation and mixing procedures.