Current Concepts in Fluid Therapy in Horses.

Naomi E Crabtree,Kira L Epstein

doi:10.3389/fvets.2021.648774

Naomi E Crabtree, Kira L Epstein

Open Access

https://doi.org/10.3389/fvets.2021.648774

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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.

Highlights

Fluid therapy is a key component in treatment and supportive care of horses with a variety of conditions, especially those with critical illness
An older study evaluating 72 h of water restriction resulted in an average of 10.7% dehydration, while 24 h of restriction has resulted in a 3–6.3% decrease in body weight in other studies [14, 21, 22]. Horses in those studies did not experience signs of shock, other studies performed to evaluate the cardiovascular effects of dehydration reported two thirds of horses who were dehydrated to the point of 6.5–7% developed severe neurologic signs, signs of colic, and significant hyperlactatemia consistent with shock [23, 24]. These findings suggest that severe dehydration would develop more slowly than duration of disease in many cases presenting with critical illness, and that percent dehydration traditionally considered as moderate can result in severe clinical signs in some horses
A separate part of this study evaluated how far orally fluid migrated in horses and found it rarely reached the level of the pelvic flexure [53]

Summary

Introduction

Fluid therapy is a key component in treatment and supportive care of horses with a variety of conditions, especially those with critical illness. It remains challenging to make evidence-based treatment recommendations. This is due to the limited number and design of studies related to fluid therapy that have been performed in horses [1]. The majority of those that have been published are either experimental (healthy or healthy with induced pathology) or retrospective and, provide only low-level evidence. As a result of the minimal species-specific information available, recommendations for fluid therapy often rely heavily on the lowest levels of evidence - expert opinion, theory, physiology, and extrapolation from other animal species and human medicine

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