Current Concepts in Fluid Therapy in Horses

Abstract

Despite the frequent inclusion of fluid therapy in the treatment of many conditions in horses, there are limited studies available to provide evidenced-based, species-specific recommendations. Thus, equine fluid therapy is based on the application of physiology and extrapolation from evidence in other veterinary species and human medicine. The physiologic principles that underly the use of fluids in medicine are, at first glance, straightforward and simple to understand. However, in the past 20 years, multiple studies in human medicine have shown that creating recommendations based on theory in combination with experimental and/or small clinical studies does not consistently result in best practice. As a result, there are ongoing controversies in human medicine over fluid types, volumes, and routes of administration. For example, the use of 0.9% NaCl as the replacement fluid of choice is being questioned, and the theoretical benefits of colloids have not translated to clinical cases and negative effects are greater than predicted. In this review, the current body of equine research in fluid therapy will be reviewed, connections to the controversies in human medicine and other veterinary species will be explored and, where appropriate, recommendations for fluid therapy in the adult horse will be made based on the available evidence. This review is focused on the decisions surrounding developing a fluid plan involving crystalloids, synthetic colloids, and plasma.

Effects of 7.2% hypertonic saline solution on cardiovascular parameters and endogenous arginine vasopressin secretion in euvolemic isoflurane-anesthetized horses

“…These results indicate that increases in blood pressure in response to HS bolus administration in healthy horses are mediated by rapid intravascular volume expansion combined with AVP-mediated vasoconstriction. 26,27 Endogenous AVP release is stimulated after administration of HS as a result of hypernatremia and increased plasma osmolarity. [28][29][30] HS has four main effects on the cardiovascular system: rapid increase in circulating volume, initial vasoconstriction stimulated by osmoreceptors mediating a vagal reflex, transient vasodilation, and increased cardiac contractility.…”

“…41 The cardiovascular effects of endotoxic shock commonly discussed are hypotension and decreased SVR; however, direct myocardial depression can occur, which results in an increased risk of pulmonary and systemic edema formation following large-volume fluid resuscitation with crystalloid solutions. 16,27 HS aids in preservation of preload and limits vascular leakage resulting from leukocyte-endothelium reactions. 16, Hypotensive animals have increased concentrations of AVP with MAPs remaining low for as long as 12 hours during experimentally induced septic shock.…”

Advanced Strategies of Drug Delivery via Oral, Topical, and Parenteral Administration Routes: Where Do Equine Medications Stand?

“…The stable isotope breath test is another technique used to determine gastric emptying time [64]. It involves the measurement of the rate of increments in the expiration of 13 C: 12 C ratio, following the ingestion of a meal labeled with a stable non-radioactive isotope, 13 C [65]. The 13 C: 12 C ratio can then be used as an indirect measure of the gastric emptying rate for that particular meal.…”

“…It involves the measurement of the rate of increments in the expiration of 13 C: 12 C ratio, following the ingestion of a meal labeled with a stable non-radioactive isotope, 13 C [65]. The 13 C: 12 C ratio can then be used as an indirect measure of the gastric emptying rate for that particular meal. Sutton conducted several breath tests in the horse to assess the gastric emptying of various solid and liquid materials [47].…”

“…The test was conducted using 3 different methods: an induced LUBT, non-induced LUBT, and a dual-isotope test [76,77] (Table 2). An induced LUBT was performed by administering a priming dose of 12 C-LU to optimize equine lactose 13 C-ureide ( 13 C-LU) digestion [77]. A non-induced LUBT was conducted in the same fashion without the priming dose, and the dual-isotope test was always done following the same procedure but with an addition of 13 C-octanoic acid.…”