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

Abstract

BACKGROUND: Dexmedetomidine infusions are beneficial in anaesthetised endotoxaemic horses when administered concurrent to endotoxin, but post-conditioning effects are unknown. OBJECTIVES: To evaluate whether a dexmedetomidine infusion is beneficial in horses administered Escherichia coli O55:B5 lipopolysaccharides (LPS) endotoxin prior to anaesthesia. STUDY DESIGN: 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&#x2009;&#x3bc;g/kg bwt) immediately prior to anesthesia. Horses received IV xylazine (control, LPS; n&#x2009;=&#x2009;5) or dexmedetomidine (treatment, LPS-Dex; n&#x2009;=&#x2009;5), followed by IV ketamine and midazolam and sevoflurane in oxygen. In LPS-Dex, dexmedetomidine (1.75&#x2009;&#x3bc;g/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&#x2009;min for 180&#x2009;min. Data were compared between groups using mixed model analysis (p&#x2009;<&#x2009;0.05). RESULTS: Mean&#x2009;&#xb1;&#x2009;standard deviation CI was significantly higher in LPS-Dex at 30 and 60&#x2009;min (57.9&#x2009;&#xb1;&#x2009;15.6&#x2009;mL/min/kg bwt versus 43.1&#x2009;&#xb1;&#x2009;9.4, 30&#x2009;min, p&#x2009;=&#x2009;0.03; 60.2&#x2009;&#xb1;&#x2009;11.8&#x2009;mL/min/kg bwt versus 38.9&#x2009;&#xb1;&#x2009;11.2, 60&#x2009;min, p&#x2009;=&#x2009;0.003). Creatinine was elevated and significantly higher in LPS from 90&#x2009;min onward but remained normal in LPS-Dex throughout (201&#x2009;&#xb1;&#x2009;38&#x2009;&#x3bc;mol/L versus 124&#x2009;&#xb1;&#x2009;26, 180&#x2009;min, p&#x2009;=&#x2009;0.003). Significantly improved base excess values were seen in LPS-Dex at 150 and 180&#x2009;min (2.9&#x2009;&#xb1;&#x2009;2&#x2009;mmol/L versus 0.6&#x2009;&#xb1;&#x2009;1, 150&#x2009;min, p&#x2009;=&#x2009;0.03; 3.4&#x2009;&#xb1;&#x2009;1.96&#x2009;mmol/L versus 0.6&#x2009;&#xb1;&#x2009;1.41, 180&#x2009;min, p&#x2009;=&#x2009;0.01). Cytokine concentrations were similar between groups. MAIN LIMITATIONS: 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.