Comparison of gastric reactance with commonly used perfusion markers in a swine hypovolemic shock model.

Abstract

Abstract Background: The gut has been hypothesized to be a protagonist tissue in multiple organ dysfunction syndrome (MODS) for the past three decades. Gastric reactance (XL) is a potential perfusion marker derived from gastric impedance spectroscopy (GIS), which is an emerging tool through which living tissue can be continuously measured to determine its pathophysiological evolution. This study aimed to compare the performance of XL (positive predictive values (PPV), negative predictive values (NPV), and area-under-the-curve (AUC)) against commonly-used perfusion markers before and during hypovolemic shock in swine subjects. Methods: Prospective, controlled animal trial with two groups, control group (CG) N=5 and shock (MAP ≤ 48 mmHg) group (SG) N= 16. Comparison time points were defined as T-2 (two hours before shock), T-1 (one hour before shock), T0 (shock), T1 (one hour after shock), T2 (two hours after shock). Shock severity was assessed through blood gases, systemic and hemodynamic variables, and via histological examination for assessing inflammation-oedema, and detachment in the gastric mucosa. Macroscopic assessment of the gastric mucosa was defined in five levels (0 - normal mucosa, 1 -stippling or epithelial haemorrhage, 2 - pale mucosa, 3 - violet mucosa, and 4 - marmoreal mucosa). Receiver Operating Curves (ROC) of perfusion markers and XL were calculated to identify optimal cut-off values and their individual ability to predict hypovolemic shock. Results: Comparison among CG and SG shows statistically significant differences in XL measurements at T-1, T0, T1 and T2, while lactate showed statistically significant differences until T1 and T2. Statistically significant differences were detected in mucosa class p<0.001 and in inflammation-oedema in the gastric body and fundus (p=0.021 and p=0.043). The performance of the minimum XL value per event and subject (XL_Min) was better (0.81 ≤ AUC ≤ 0.96, 0.93 ≤ PPV ≤ 1.00, 0.45 ≤ NPV ≤ 0.83) than maximum lactate value (Lac_Max) per event and subject (0.29 ≤ AUC ≤ 0.82, 0.82 ≤ PPV ≤ 0.91, 0.24 ≤ NPV ≤ 0.82). The optimal cut-off values of XL_Min show a progressive increase at each timepoint, while Lac_Max increases only at T2. Conclusions: XL proved to be an indirect and consistent marker of inadequate gastric mucosal perfusion, which shows significant and detectable changes before commonly-used markers of global perfusion under the hypovolemic shock conditions outlined in this work.