DETECTION OF HYPOVOLEMIA BY THE HYPOTENSION PREDICTION INDEX IS ASSOCIATED WITH GASTROINTESTINAL MICROCIRCULATION DYSFUNCTION IN A PORCINE MODEL OF HEMORRHAGE

Background: Postoperative gastrointestinal (GI) dysfunction is a common complication following critical illness. The splanchnic circulation is sensitive to changes in volume status and is unduly impacted by volume loss compared to other organ systems. A raised Hypotension Prediction Index (HPI) value has been associated with decreased GI microcirculation flow in hemorrhage models at 5% volume loss. The aim of this study was to assess whether HPI can detect a 5% volume deficit and whether this is associated with a decrease in GI microvascular flow. Methods: Ten anesthetized, mechanically ventilated Yorkshire/Landrace crossbred pigs were studied. Hemorrhage was performed removing 1% aliquots of blood until 10% of blood volume was removed. Once complete, the removed blood was reinfused in 2% aliquots. Hemodynamic and intestinal microcirculatory measurements were performed at each stage. A repeated-measurement one-way ANOVA was used to compared changes from baseline measurements during hemorrhage and the final hemorrhage stage during reinfusion. Results: There was a significant change in MAP from baseline values at 3% hemorrhage with a 6.0 mm Hg decrease (95% confidence interval [CI], 0.2-11.8; P < 0.05) from 93 (3) mm Hg to 87 (4) mm Hg. HPI showed a significant rise from baseline values from 17 (6) to 44 (22) with a mean difference (MD) of 26.4 (95% CI, 2.1-50.7; P < 0.005) at 5% hemorrhage. For classifying if a model was greater than 5% volume deplete, the area under the curve for the analyzed variables was the following: HPI, 0.97 (95% CI, 0.90-0.98; P < 0.0001); stroke volume variation, 0.80 (95% CI, 0.73-0.89; P < 0.0001); and MAP, 0.90 (95% CI, 0.85-0.95; P < 0.0001). There were significant decreases in microcirculation scores comparing baseline with 1% hemorrhage (MD, -1.89; 95% CI, -2.49 to -1.29; P < 0.0001), 1% hemorrhage with 2% hemorrhage (MD, -1.90; 95% CI, -2.67 to -1.15; P < 0.0001), up to 4% hemorrhage compared with 5% (MD, -1.34; 95% CI, -2.31 to -0.37; P < 0.0001). Conclusion: Intestinal microcirculation is disrupted with minimal volume loss and is reduced by almost 75% at a blood loss of 5% volume. The reduction in GI MFI is not captured in clinically significant changes in commonly measured parameters but is reflected in changes in the HPI at 5% volume loss.