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Equine veterinary journal2025; doi: 10.1111/evj.14534

Volume kinetics of lactated Ringer’s solution in adult horses.

Abstract: Fluid therapy in horses is primarily empirical. Evidence-based quantification of the disposition of intravenous (IV) crystalloids used in clinical practice could enhance the effectiveness of fluid therapy. Objective: To determine the pharmacokinetics (i.e., volume kinetics: VK) and associated haemodynamic effects of IV lactated Ringer's solution (LRS) in adult euvolemic horses. Methods: Unmasked multiple subjects, single baseline design. Methods: Thirteen healthy, euvolemic adult female horses were administered an IV bolus of LRS and monitored over 4 h. Haemoglobin, albumin and haematocrit concentrations were used to generate VK parameter estimates through a non-linear mixed effects model and stepwise covariate testing. Cardiorespiratory effects, hormonal parameters and urine output were monitored. Results: Administration of an IV bolus of LRS increased heart rate and systolic arterial pressure. Kinetic analysis was based on plasma albumin, as fluctuations in haemoglobin concentration suggested splenic recruitment of erythrocytes. Fluid disposition was best described by a two-volume fluid space model. Covariate analysis showed that a high systolic arterial pressure is associated with a decrease in urine output, and that haemoglobin recruitment was associated with the transfer of fluid from the central compartment, which was estimated to be 26.2 L, to a peripheral space. Kinetic constants showed rapid fluid distribution to the peripheral compartment and slow return to the central compartment, impeding fluid elimination from the body. Distribution of LRS from the central compartment was rapid but elimination from the body was slow. Conclusions: Limited sample size and sample collection duration may have influenced model selection and covariate identification. Conclusions: Volume kinetics provides a method for quantitatively describing the volume expanding effects of administered fluids. Fluid infusion is associated with an increase in heart rate and arterial blood pressure. Volume kinetic analysis offers a context-dependent method for developing and refining more effective fluid infusion protocols. Unassigned: Die Infusionstherapie bei Pferden erfolgt in erster Linie auf empirischer Basis. Eine evidenzbasierte Quantifizierung der Dosierung der in der klinischen Praxis verwendeten intravenösen (IV) kristalloiden Flüssigkeiten könnte die Wirksamkeit der Infusionstherapie verbessern. Unassigned: Ziel der Studie war es, die Pharmakokinetik (d.h. die Volumenkinetik: VK) und die damit verbundenen hämodynamischen Auswirkungen der intravenösen Verabreichung von laktierter Ringerlösung (LRS) bei adulten euvolemischen Pferden zu bestimmen. Methods: Unverblendete Studie, mehrere Probanden und einzelner Ausganswert. Methods: Dreizehn gesunde, euvolemische, adulte weibliche Pferde wurden nach der Verabreichung von einem IV‐Bolus von LRS für vier Stunden überwacht. Hämoglobin‐, Albumin und Hämatokrit‐Konzentrationen wurden zur Erstellung von VK‐Parameter‐Schätzungen mittels eines Modells mit nichtlinear gemischten Effekten und schrittweiser Kovariatenprüfung verwendet. Kardiorespiratorische Effekte, hormonelle Parameter und die Urinausscheidung wurden überwacht. Unassigned: Die Verabreichung eines IV‐Bolus von LRS erhöhte die Herzfrequenz und den systolischen arteriellen Blutdruck. Die kinetische Analyse basierte auf Plasmaalbumin, da Schwankungen der Hämoglobinkonzentration auf eine Rekrutierung von Erythrozyten aus der Milz hindeuteten. Die Flüssigkeitsdisposition wurde am besten durch ein zweivolumiges Flüssigkeitsraummodell beschrieben. Die Kovarianzanalyse zeigte, dass ein hoher systolischer arterieller Druck mit einer Abnahme der Urinausscheidung verbunden ist und dass die Hämoglobin‐Rekrutierung mit dem Transfer von Flüssigkeit aus dem zentralen Kompartiment, das auf 26,2 l geschätzt wurde, in einem peripherin Raum verbunden war. Die kinetischen Konstanten zeigten eine schnelle Flüssigkeitsverteilung in das periphere Kompartiment und eine langsame Rückkehr in das zentrale Kompartiment, was die Flüssigkeitsausscheidung aus dem Körper behinderte. Die Verteilung von LRS aus dem zentralen Kompartiment war schnell, aber die Ausscheidung aus dem Körper war langsam. WESENTLICHE EINSCHRÄNKUNGEN: Der begrenzte Umfang an Probanden und die Dauer der Datenerhebung könnten die Modellauswahl und die Identifizierung der Kovarianten beeinflusst haben. Unassigned: Die Volumenkinetik bietet eine Methode zur quantitativen Beschreibung der volumenvergröβernden Wirkung verabreichter Flüssigkeiten. Flüssigkeitinfusionen sind mit einem Anstieg der Herzfrequenz und des arteriellen Blutdrucks verbunden. Die volumenkinetische Analyse bietet eine kontextabhängige Methode zur Entwicklung und Verfeinerung effektiver Flüssigkeitinfusionsprotokolle.
© 2025 The Author(s). Equine Veterinary Journal published by John Wiley & Sons Ltd on behalf of EVJ Ltd.
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Publication Date: 2025-05-13 PubMed ID: 40357908DOI: 10.1111/evj.14534Google Scholar: Lookup
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Summary

This research summary has been generated with artificial intelligence and may contain errors and omissions. Refer to the original study to confirm details provided. Submit correction.

The study looks into the volume kinetics of intravenous lactated Ringer’s solution (a type of fluid therapy) administered to adult horses, and its effects on their haemodynamics – the blood flow within their systems. The findings will help enhance the effectiveness of fluid therapy in horses.

Methodology

  • The study used a sample of thirteen healthy, euvolemic (normal levels of bodily fluids) adult female horses. They were each given an intravenous bolus of lactated Ringer’s solution (LRS).
  • Various factors such as the horses’ heart rates, hormonal parameters, urine output and hemoglobin, albumin, and hematocrit concentrations were monitored for a period of four hours post-administration.
  • A nonlinear mixed effects model and stepwise covariate testing were used to generate volume kinetic parameter estimates based on those observations.

Results

  • Administration of the LRS led to increased heart rate and systolic arterial pressure in the horses. There was also evidence of splenic recruitment of erythrocytes (red blood cells), reflected in the fluctuation of hemoglobin concentrations.
  • The way the fluid dispersed through the horse’s body was best described by a two-volume fluid space model. This means that the fluid rapidly distributed to a peripheral compartment before slowly returning to a central compartment—which impeded the fluid’s elimination from the body. This made the distribution of LRS from the central compartment quick, but its elimination slow.
  • A high systolic arterial pressure (the pressure exerted on the arteries when the heart contracts) was found to be associated with a decrease in urine output. It was also found that haemoglobin recruitment correlated with the transfer of fluid from the central to peripheral space.

Conclusions

  • Due to the small sample size and the limited sample collection duration, these factors may have influenced the selection of the model and the identification of covariates.
  • Volume kinetics provides a method for quantitatively describing the effects of administered fluids in terms of volume expansion. An increase in heart rate and arterial blood pressure is associated with the administration of fluids.
  • The volume kinetic analysis framework can thus be used to develop more tailored and effective fluid infusion protocols, which might vary depending on different situations or the characteristics of individual horses.

Cite This Article

APA
Muir WW, Yiew XT, Bateman SW, Hahn RG. (2025). Volume kinetics of lactated Ringer’s solution in adult horses. Equine Vet J. https://doi.org/10.1111/evj.14534

Publication

Equine veterinary journal
ISSN: 2042-3306
NlmUniqueID: 0173320
Country: United States
Language: English

Researcher Affiliations

Muir, William W
  • College of Veterinary Medicine at the Lincoln Memorial University, Harrogate, Tennessee, USA.
Yiew, Xiu Ting
  • Ontario Veterinary College at the University of Guelph, Guelph, Ontario, Canada.
Bateman, Shane W
  • Ontario Veterinary College at the University of Guelph, Guelph, Ontario, Canada.
Hahn, Robert G
  • Department of Anesthesiology and Intensive Care, Karolinska Institute at Danderyds Hospital, Stockholm, Sweden.

Grant Funding

  • 23-0314 / Fu00e9du00e9ration Equestre Internat

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