Non-invasive Dual-Channel Broadband Diffuse Optical Spectroscopy of Massive Hemorrhage and Resuscitative Endovascular Balloon Occlusion of the Aorta (REBOA) in Swine.

Objective: To quantitatively measure tissue composition and hemodynamics during resuscitative endovascular balloon occlusion of the aorta (REBOA) in two tissue compartments using non-invasive two-channel broadband diffuse optical spectroscopy (DOS).
Methods: Tissue concentrations of oxy- and deoxyhemoglobin (HbO2 and HbR), water, and lipid were measured in a porcine model (n = 10) of massive hemorrhage (65% total blood volume over 1 h) and 30-min REBOA superior and inferior to the aortic balloon.
Results: After hemorrhage, hemoglobin oxygen saturation (StO2 = HbO2/[HbO2 + HbR]) at both sites decreased significantly (-29.9% and -42.3%, respectively). The DOS measurements correlated with mean arterial pressure (MAP) (R2 = 0.79, R2 = 0.88), stroke volume (SV) (R2 = 0.68, R2 = 0.88), and heart rate (HR) (R2 = 0.72, R2 = 0.88). During REBOA, inferior StO2 continued to decline while superior StO2 peaked 12 min after REBOA before decreasing again. Inferior DOS parameters did not associate with MAP, SV, or HR during REBOA. Conclusions: Dual-channel regional tissue DOS measurements can be used to non-invasively track the formation of hemodynamically distinct tissue compartments during hemorrhage and REBOA. Conventional systemic measures MAP, HR, and SV are uncorrelated with tissue status in inferior (downstream) sites. Multi-compartment DOS may provide a more complete picture of the efficacy of REBOA and similar resuscitation procedures.