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Equine veterinary journal2026; doi: 10.1002/evj.70173

Dexmedetomidine infusions improve cardiovascular and renal function in anaesthetised, experimentally endotoxaemic horses.

Abstract: Dexmedetomidine infusions are beneficial in anaesthetised endotoxaemic horses when administered concurrent to endotoxin, but post-conditioning effects are unknown. Objective: To evaluate whether a dexmedetomidine infusion is beneficial in horses administered Escherichia coli O55:B5 lipopolysaccharides (LPS) endotoxin prior to anaesthesia. Methods: Randomised controlled in vivo experiment. Methods: Ten systemically healthy horses were instrumented for acquisition of cardiac index (CI) using thermodilution. Horses received IV LPS (0.1 μg/kg bwt) immediately prior to anesthesia. Horses received IV xylazine (control, LPS; n = 5) or dexmedetomidine (treatment, LPS-Dex; n = 5), followed by IV ketamine and midazolam and sevoflurane in oxygen. In LPS-Dex, dexmedetomidine (1.75 μg/kg bwt/h IV) was administered and target end-tidal sevoflurane concentration was reduced (1.8% vs. 3% LPS). Cardiopulmonary function, acid-base, cytokine, and creatinine values were assessed every 30 min for 180 min. Data were compared between groups using mixed model analysis (p < 0.05). Results: Mean ± standard deviation CI was significantly higher in LPS-Dex at 30 and 60 min (57.9 ± 15.6 mL/min/kg bwt versus 43.1 ± 9.4, 30 min, p = 0.03; 60.2 ± 11.8 mL/min/kg bwt versus 38.9 ± 11.2, 60 min, p = 0.003). Creatinine was elevated and significantly higher in LPS from 90 min onward but remained normal in LPS-Dex throughout (201 ± 38 μmol/L versus 124 ± 26, 180 min, p = 0.003). Significantly improved base excess values were seen in LPS-Dex at 150 and 180 min (2.9 ± 2 mmol/L versus 0.6 ± 1, 150 min, p = 0.03; 3.4 ± 1.96 mmol/L versus 0.6 ± 1.41, 180 min, p = 0.01). Cytokine concentrations were similar between groups. Conclusions: The experimental protocol is not representative of all surgical colics. Conclusions: Dexmedetomidine infusion and concurrent reduction in inhalant anaesthetic could benefit anaesthetic management of horses even when endotoxaemia is already present.
© 2026 The Author(s). Equine Veterinary Journal published by John Wiley & Sons Ltd on behalf of EVJ Ltd.
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Publication Date: 2026-05-04 PubMed ID: 42076924DOI: 10.1002/evj.70173Google Scholar: Lookup
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Summary

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Overview

  • This study investigated whether dexmedetomidine, a sedative drug, provides cardiovascular and renal benefits when given to horses that have been exposed to endotoxin before anesthesia.
  • The results showed that dexmedetomidine infusion improved heart function and kidney health during anesthesia in endotoxaemic horses compared to a control group.

Background and Aim

  • Endotoxaemia, caused by bacterial toxins like lipopolysaccharides (LPS), can severely affect horses undergoing anesthesia, compromising cardiovascular and renal functions.
  • Previous studies showed benefits of dexmedetomidine given concurrently with endotoxin, but it was unclear if the drug is beneficial when endotoxin exposure occurs prior to anesthesia (post-conditioning effects).
  • The main goal was to evaluate cardiovascular and renal effects of dexmedetomidine infusion started after endotoxin administration but before anesthesia in healthy horses.

Methods

  • Study design: Randomized controlled in vivo experiment with 10 healthy horses.
  • Endotoxaemia induction: All horses received intravenous Escherichia coli O55:B5 LPS at 0.1 µg/kg immediately before anesthesia to mimic endotoxaemia.
  • Group allocation:
    • Control group (LPS; n=5): Received IV xylazine, ketamine, midazolam, and sevoflurane anesthesia.
    • Treatment group (LPS-Dex; n=5): Received IV dexmedetomidine infusion (1.75 µg/kg/h) after LPS, plus ketamine, midazolam, and a reduced sevoflurane dose.
  • Instrumentation: Thermodilution catheter was used to measure cardiac index (CI) to assess heart function.
  • Monitoring: Cardiopulmonary parameters, blood acid-base status, cytokine concentrations, and creatinine (kidney function marker) were measured every 30 minutes for 180 minutes under anesthesia.
  • Statistical analysis: Mixed model analysis was performed to compare groups, with significance set at p < 0.05.

Key Findings

  • Cardiac function:
    • The dexmedetomidine group had significantly higher cardiac index values at 30 and 60 minutes compared to control, indicating better heart output during anesthesia.
    • Example: At 30 minutes, CI was 57.9 ± 15.6 mL/min/kg in LPS-Dex vs. 43.1 ± 9.4 in LPS (p=0.03).
  • Renal function:
    • Control horses showed elevated creatinine from 90 minutes onward, indicating kidney impairment.
    • In contrast, creatinine remained within normal range in the dexmedetomidine group throughout the 180 minutes.
    • Example: At 180 minutes, creatinine was 201 ± 38 μmol/L in LPS vs. 124 ± 26 in LPS-Dex (p=0.003).
  • Acid-base balance:
    • Base excess values, reflecting metabolic status, were significantly better (more positive) in the dexmedetomidine group at 150 and 180 minutes, suggesting better acid-base homeostasis.
    • Example: At 180 minutes, base excess was 3.4 ± 1.96 mmol/L in LPS-Dex vs. 0.6 ± 1.41 in LPS (p=0.01).
  • Cytokine levels:
    • Inflammatory cytokine concentrations did not differ significantly between groups during the anesthesia period.

Conclusions and Implications

  • The study suggests that dexmedetomidine infusion started after endotoxin exposure and continued through anesthesia can improve heart function and protect kidney function in endotoxaemic horses.
  • Reduction of sevoflurane dose alongside dexmedetomidine may contribute to better cardiovascular stability.
  • The findings support using dexmedetomidine as part of anesthetic management in horses already affected by endotoxaemia, such as in cases of colic complicated by endotoxin release.
  • However, the experimental model may not fully represent the complexity of all clinical surgical colic cases, so clinical trials are needed to confirm applicability.
  • No significant effect on inflammatory cytokines was observed, indicating dexmedetomidine’s benefits are likely mediated through cardiovascular and renal mechanisms rather than immune modulation.

Cite This Article

APA
Lee S, Hector RC, Pezzanite L, Gilleland E, Rezende ML. (2026). Dexmedetomidine infusions improve cardiovascular and renal function in anaesthetised, experimentally endotoxaemic horses. Equine Vet J. https://doi.org/10.1002/evj.70173

Publication

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

Researcher Affiliations

Lee, Sera
  • Department of Clinical Sciences, College of Veterinary Medicine and Biomedical Sciences, Colorado State University, Fort Collins, Colorado, USA.
Hector, Rachel C
  • Department of Clinical Sciences, College of Veterinary Medicine and Biomedical Sciences, Colorado State University, Fort Collins, Colorado, USA.
Pezzanite, Lynn
  • Department of Clinical Sciences, College of Veterinary Medicine and Biomedical Sciences, Colorado State University, Fort Collins, Colorado, USA.
Gilleland, Eric
  • Department of Statistics, College of Natural Sciences, Colorado State University, Fort Collins, Colorado, USA.
Rezende, Marlis L
  • Department of Clinical Sciences, College of Veterinary Medicine and Biomedical Sciences, Colorado State University, Fort Collins, Colorado, USA.

Grant Funding

  • Colorado Racing Commission/Equine Foundation Funds via the Colorado State University College Research Council

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