Detection of hypovolaemia by the Hypotension Prediction Index is associated with gastrointestinal microcirculation dysfunction in a porcine model of haemorrhage.

Abstract

Background: Post operative gastrointestinal 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 gastrointestinal microcirculation flow in haemorrhage 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 anaesthetised, mechanically ventilated Yorkshire/Landrace cross breed pigs were studied. Haemorrhage was performed removing 1% aliquots of blood until 10% of blood volume was removed. Once complete the removed blood was reinfused in 2% aliquots. Haemodynamic and intestinal microcirculatory measurements were performed at each stage. A repeated measurement one-way ANOVA was used to compared changes from baseline measurements during haemorrhage, and the final haemorrhage stage during reinfusion.

Results: There was a significant change in MAP from baseline values at 3% haemorrhage with a 6.0 mmHg decrease (95% CI 0.2 to 11.8, p < 0.05) from 93(3) mmHg to 87(4) mmHg. HPI showed a significant rise from baseline values from 17(6) to 44(22) with a MD of 26.4 (95% CI 2.1 to 50.7, p < 0.005) at 5% haemorrhage. For classifying if a model was greater than 5% volume deplete the area under the curve for the analysed variables were HPI 0.97 (95% CI 0.90-0.98, p < 0.0001), SVV 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% haemorrhage (MD -1.89, 95% CI -2.49 to -1.29, P < 0.0001), 1% haemorrhage with 2% haemorrhage (MD -1.90, 95% CI -2.67 to -1.15, P < 0.0001), up to 4% haemorrhage 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 gastrointestinal MFI is not captured in clinically significant changes in commonly measured parameters, however, is reflected in changes in the hypotension prediction index at 5% volume loss.