Microcirculation Endotoxemia in horses
Description
Microcirculation is the essential link between macrocirculation and cellular metabolism. We hypothesized that acute endotoxemia affects microcirculatory variables in anaesthetized horses. This was a prospective, experimental trial. Six healthy adult horses were anesthetized with dexmedetomidine, ketamine, and midazolam and were mechanically ventilated under isoflurane anaesthesia. Endotoxemia was induced with 30 ng kg-1 E. coli lipopolysaccharide intravenously. A fluid bolus and noradrenaline (NA) infusion were administered to produce normotension. Microcirculation variables were obtained by a side-stream darkfield camera (de Backer density (DBD), perfused de Backer density (PDBD), proportion of perfused vessels (PPV), microvascular flow index (MFI), heterogeneity index (HI)), laser-doppler flowmetry (blood flow), and white light spectrometry (tissue oxygen saturation (tSO2)) in sublingual, jejunal, and genital area. Measurements were obtained at baseline, after endotoxin, at 60 and 120 minutes and during the normotensive phase. Data were analyzed by one-way ANOVA and Tukey-Kramer adjustment (p ≤ 0.05). The PPV decreased significantly over time by 30% (p < 0.001) at the jejunum. MFI decreased from baseline to ET60 and from baseline to ET120 in sublingual and genital mucosa (2.9 vs. 1.4, p = 0.0004 and 2.8 vs. 1.9, p < 0.01), respectively. The sublingual HI increased from baseline to ET60, ET120 and NA (0.1 vs. 0.9, p = 0.02; 0.1 vs. 0.6, p = 0.01; 0.1 vs. 0.3, p = 0.01), respectively. The genital HI increased from baseline to ET120 (0.2 vs 1.1 p ≤ 0.01) and NA (0.16 vs. 0.53, p < 0.05, respectively). Moderate agreement between observers for MFI assessment was present with total kappa = 0.4. The other assessed parameters were not statistically significantly different. Overall, short-term experimental endotoxemia did not alter tSO2, blood flow, DBD, PDBD or PPV, however, it did negatively alter MFI and HI. Fluids and NA were unable to restore MFI and HI to baseline values.