In situ impedance spectroscopy of the intestinal mucosa in an ischemia-reperfusion model

The disruption of the intestinal mucosa plays a key role in the evolution of shock and is the "motor of multiple organ failure". In this study, a novel technique is proposed and evaluated for assessing tissue damage to prevent MOF. Complex impedance spectroscopy measurements in a frequency range of 10²-10⁶ Hz were performed on ischemic intestinal tissues of pigs using a minimally invasive gastrointestinal catheter. The experimental protocol relied on an intestinal ischemia model produced by total occlusion of the superior mesenteric artery (SMA) in thirteen anesthetized pigs (15-25 kg) assigned to four different ischemia-reperfusion groups. Complex impedance spectra were recorded with simultaneous measurements of tonometric pHi in the ileum and SMA blood flow for 4 hours. Impedance spectra were reproducible each time within each group, and those of tissue under prolonged ischemia were significantly differentiable (p<0.05) from those of normally perfused tissue. Spectral changes over time were characterized and compared to measurements of ischemia (pHi) and perfusion (SMA blood flow). It is concluded that impedance spectroscopy does indeed measure changes in tissue injury, and could be a very useful tool to monitor end-organ status and guide therapy of patients in shock.