In several species, there is a strong correlation between indicators of red cell mass (RCM) and thromboelastometry results. The horse has a reliable, temporary, polycythemia in response to phenylephrine infusion. Our objective was to evaluate the effects of an in-vivo increase in circulating RCM on thromboelastometry results in an equine model of transient polycythemia. Six healthy research horses had whole blood thromboelastometry with contact activator and tissue factor initiation after recalcification of citrated samples. Additional samples were frozen for thrombin-antithrombin (TAT). Complete blood count biochemical analysis, fibrinogen, activated partial thromboplastin time (aPTT), and prothrombin time (PT) were performed. Additional samples were taken at 5 min and 2 h after phenylephrine infusion. Thromboelastometry was performed separately on four horses not receiving phenylephrine with the samples divided and spiked with phenylephrine ex vivo. Red cell count (P<0.001) and hematocrit (P<0.001) were significantly higher at 5 min after phenylephrine compared with baseline and 2 h. There was no change in platelet count, fibrinogen, PT, aPTT, or TAT at any time point. Both ex-tem and in-tem parameters were hypocoagulable at 5 min after phenylephrine compared to baseline and 2 h. There was no effect of phenylephrine in the ex-vivo spiking studies on any of the thromboelastometry parameters. Whole blood thromboelastometry results were hypocoagulable in this equine model of in-vivo transient polycythemia only during the polycythemic phase. All other coagulation parameters were unchanged. In the absence of other indicators of hypocoagulability, this may point to an artifact of thromboelastometry. Alternatively, the data may reflect true in-vivo hypocoagulability in patients with increased circulating RCM.

Reduced HRV was strongly associated with ischemic gastrointestinal disease and nonsurvival. HRV analysis is a noninvasive technique that may provide diagnostic and prognostic information pertinent to the management of postoperative horses with severe gastrointestinal disease.

Background: Cardiac output (CO) is not routinely measured in critically ill adult horses because of invasiveness of currently validated methods. Noninvasive CO monitoring would complement clinical assessment of hemodynamic status in adult horses.Hypothesis: Volumetric methods for measuring CO will have better agreement with lithium dilution than Dopplerbased methods.Animals: Eight healthy adult horses. Methods: Prospective study. CO was manipulated with continuous rate infusions of dobutamine and romifidine to achieve high and low CO states, respectively. At each level, CO was measured by lithium dilution and various echocardiographic methods. Images stored as video loops were reviewed by an individual blinded to the lithium dilution results.Results: Lithium dilution determinations of CO ranged between 16.6 and 63.0 L/min. There was a significant effect of method of CO measurement (P < .001), but no significant effect of CO level (P = .089) or interaction between level and method (P = .607) on the absolute value of the bias. The absolute values of the bias of the right ventricular outflow tract (RVOT) Doppler, Simpson, 4-chamber area-length, and bullet methods [5.5, 6.1, 6.5, 8.8 L/min, respectively] were significantly lower than that of the left ventricular outflow tract (LVOT) Doppler or cubic methods [14.8, 24.3 L/min, respectively].Conclusions and Clinical Importance: The 4-chamber area-length, Simpson, bullet, and RVOT Doppler provided better agreement with lithium dilution than the other methods evaluated. These methods warrant further investigation for use in critically ill adult horses.

BackgroundThe prevalence of multiple organ dysfunction syndrome (MODS) in horses with acute surgical gastrointestinal (GI) disease is unknown. Currently, there are no validated criteria to confirm MODS in adult horses.ObjectivesTo develop criteria for a MODS score for horses with acute surgical colic (MODS SGI) and evaluate the association with 6‐month survival. To compare the MODS SGI score with a MODS score extrapolated from criteria used in people (MODS EQ).AnimalsAdult horses that required exploratory laparotomy (n = 62) for colic. Healthy adult horses undergoing elective surgical procedures (n = 12) established the reference range of some variables.MethodsProspectively, a MODS SGI score was developed based on organ‐specific criteria established from a literature review, data collection, and clinical judgment. Data for scoring each horse were collected on Days 1 and 2 postoperatively. Horses were scored retrospectively using both scoring criteria. The prognostic performance of the MODS SGI score and its overall performance compared with the MODS EQ score were assessed with receiver operating characteristic (ROC) curve analysis.ResultsThe MODS SGI score had excellent performance for predicting 6‐month survival with an area under the ROC curve (AUC) of 0.95 (95% CI: 0.87–0.99). The AUC for the MODS SGI score was significantly higher than the MODS EQ (AUC: 0.76; 0.63–0.86).Conclusions and Clinical ImportanceThe MODS SGI score predicts 6‐month survival from discharge in horses with acute surgical colic. The MODS SGI score performed better than a score extrapolated from human scoring systems.

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