Non-Invasive Hemodynamic Monitoring using near Infrared Frequency Domain Photon Migration in Rabbit Hemorrhagic Shock Model

Abstract

Background Currently, there are no reliable, accurate, non-invasive methods of assessing hemodynamic parameters, tissue hemoglobin, and 0, content for physiologic monitoring. Recent advances in the field of optical diagnostics have lead to new imaging modalities capable of evaluating regional in-vivo tissue composition using its optical properties. The advantage of Frequency Domain Photon Migration (FDPM) over previously studied bulk NIR spectroscopy is that it allows for quantitative measurements of both light absorption and scattering in tissues. Devices based on FDPM principles have the potential to accurately and non-invasively monitor hemodynamics and other parameters in patients with shock and physiologic disturbances. Purpose This study investigated FDPM methods for monitoring shock and the response to treatment with volume expansion and pressors in a hemorrhagic rabbit model. The sensitivity of this monitoring method for discriminating changes in hemodynamic parameters compared to traditional invasive monitoring devises, as well as the ability to accurately measure hemoglobin and tissue 0, was assessed. Methods New Zealand White (NZW) rabbits (n=25) were used in this study. Aprototype FDPM device developed in our laboratory was used. Aprobe was placed on the inner thigh of the rabbits. The rabbits underwent concurrent traditional invasive monitoring including cardiac output (CO), pulmonary arterial pressure (PA), systemic blood pressure via arterial line, hemoglobin, and arterial and venous blood gases. Hemorrhage was performed via a syringe either in stages or in a single step. After measurements were obtained the animals were resuscitated with vasopressors, or with crystalloid solution. Results The FPDM measurements of tissue hemoglobin (Hb), Oxyhemoglobin (HbO,), water content and tissue 0, saturation were obtained. The tissue Hb (r=0.7) and oxygen content (r=0.6) closely correlated with the measurements made with invasive methods. The FDPM measurements also correlated with CO. Conclusion: Broad-bandwidth FDPM may be a reliable, accurate and non-invasive means of monitoring patients with hemorrhagic shock and their response to treatment. FDPM may potentially be adapted for use in early shock recognition for triage or in settings where aggressive invasive monitoring is problematic.