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Dexmedetomidine infusions improve cardiovascular and renal function in anaesthetised, experimentally endotoxaemic
Sera Lee1, Rachel C Hector1, Lynn Pezzanite1
1Department of Clinical Sciences, College of Veterinary Medicine and Biomedical Sciences, Colorado State University, Fort Collins, Colorado, USA.
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 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.
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.
