Tissue perfusion evaluation with near-infrared spectroscopy during treatment with activated protein C

Introduction

In sepsis the link between the systemic inflammatory response and the development of multiorgan failure is represented by microcirculatory and mitochondrial distress syndrome, which causes an important cellular deoxygenation not corrigible exclusively with a restoration of a normal hemodynamic state and a satisfactory systemic transport of oxygen. We determine the changes caused by a stagnant ischemia in the tissue oxygenation with near-infrared spectroscopy (NIRS) in patients with severe sepsis, during therapy with activated protein C (APC), evaluating whether APC influences tissue saturation (index of O₂ER) and whether alterations of the hemodynamic state are connected with these changes.

Methods

A prospective observational study. We evaluated 10 septic patients (treated with APC) from December 2005 to September 2007. We carried out evaluation with NIRS of the tissue oxygen saturation (StO₂) with the InSpectra spectrometer (Hutchinson Technology Inc., MN, USA), putting a probe of 15 mm into the brachioradialis muscle of the patients. The measurements were made in five steps: pre-APC, at 24 hours, at 48 hours, at 72 hours, at 96 hours and 24 hours after the end of the infusion (post-APC). Each measurement (of the basic StO₂ and of the slope during and after the ischemia) is registered and transformed from the InSpectra Analysis software. The parameters are studied with the Wilcoxon nonparametric test for repeated measurement (P < 0.05).

Results

The increase of the basic StO₂ during and after the treatment and its decrease during the arterial occlusion are statistically relevant (P < 0.05). The increase of the StO₂ slope after arterial occlusion is statistically relevant starting from the second day of infusion of APC (P < 0.03).

Conclusion

There is an improvement of all the NIRS parameters after the infusion of APC; that is, an increase of O₂ER. We have to verify whether that increase is connected either with a reduced shunt effect in the microcirculation or with the end of metabolic downregulation that involves the mitochondrial system. NIRS has been used in this study for the first time during treatment with APC. Spectroscopy and videomicroscopy focus our attention on perfusion and tissue oxygenation, which it is not possible to separate during the evaluation of severity, of therapeutic choice and of the treatment response of severe sepsis.