Abstract
This prospective, randomized, blinded, interventional cross-over study investigated the distribution, elimination, plasma volume expansion, half-life, comparative potency, and ideal fluid prescription of three commonly prescribed intravenous (IV) fluids in 10 healthy conscious cats using volume kinetic analysis that is novel to veterinary medicine. Each cat received 20 mL/kg of balanced isotonic crystalloid (PLA), 3.3 mL/kg of 5% hypertonic saline (HS), and 5 mL/kg of 6% tetrastarch 130/0.4 (HES) over 15 min on separate occasions. Hemoglobin concentration, red blood cell count, hematocrit, heart rate, and blood pressure were measured at baseline, 5, 10, 15, 20, 30, 40, 50, 60, and every 15 min until 180 min. Urine output was estimated every 30 min using point-of-care bladder ultrasonography. Plasma dilution derived from serial hemoglobin concentration and red blood cell count served as input variables for group and individual fluid volume kinetic analyses using a non-linear mixed effects model. In general, the distribution of all IV fluids was rapid, while elimination was slow. The half-lives of PLA, HS, and HES were 49, 319, and 104 min, respectively. The prescribed fluid doses for PLA, HS, and HES resulted in similar peak plasma volume expansion of 27–30%. The potency of HS was 6 times higher than PLA and 1.7 times greater than HES, while HES was 3.5 times more potent than PLA. Simulation of ideal fluid prescriptions to achieve and maintain 15 or 30% plasma volume expansion revealed the importance of a substantial reduction in infusion rates following initial IV fluid bolus. In conclusion, volume kinetic analysis is a feasible research tool that can provide data on IV fluid kinetics and body water physiology in cats. The rapid distribution but slow elimination of IV fluids in healthy conscious cats is consistent with anecdotal reports of fluid overload susceptibility in cats and warrants further investigation.
Highlights
The clinical practice of intravenous (IV) fluid therapy in human and veterinary medicine is changing based on new findings [1,2,3] as well as ongoing debate [4] regarding ideal fluid choice, dose, rate, efficacy, and safety of fluid therapy [4,5,6]
Throughout the study periods, all cats were normotensive with a median systolic arterial pressure (SAP) of 116 mmHg (IQR 108–124)
Our study demonstrated that volume kinetic (VK) modeling and analysis is a feasible research tool that has the potential to provide valuable data on IV fluid distribution, elimination, halflife, plasma volume expansion, fluid efficacy, and body water physiology in cats
Summary
The clinical practice of intravenous (IV) fluid therapy in human and veterinary medicine is changing based on new findings [1,2,3] as well as ongoing debate [4] regarding ideal fluid choice, dose, rate, efficacy, and safety of fluid therapy [4,5,6]. Limited veterinary scientific literature on IV fluid therapy [7] has given rise to empirical fluid therapy recommendations that are based on broad assumptions, historical physiological principles, clinician’s anecdotal experiences, or extrapolation from human clinical trials and canine experimental models. The diverse elimination half-lives (t1/2) of balanced isotonic crystalloid and colloid solutions, administered under a wide variety of physiological conditions, have provided further scientific evidence of the importance of context-sensitive fluid therapy [14]
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