Monitoring superficial water content for systemic burn resuscitation with spatial frequency domain imaging

Adequate resuscitation is critical for burn wound patients where the affected total body surface area (TBSA) exceeds 20%, as fluid loss leads to organ failure, shock, and patient mortality. Protocols have been developed to combat fluid loss, however excess fluids can also lead to compartment syndromes. Here, we used spatial frequency domain imaging (SFDI), a non-contact wide field imaging technique to measure in-vivo water changes in a 40 % TBSA porcine burn model. In this pilot study one pig received intravenous fluids according to the Parkland formula on top of enteral fluid resuscitation, while a second pig received no fluids during the experiment. Unburned regions of skin were imaged with SFDI from 3 to 22 hours post-burn. This imaging technique uses structured illumination, projected at multiple spatial frequencies and wavelengths, to measure tissue reflectance, which is used to obtain the reduced scattering and absorption coefficients. Water fraction is based upon absorption in the near-infrared spectrum at 971 nm, where water has a high extinction coefficient. SFDI measurements of superficial tissue hydration showed increased water fraction for the pig that received fluid resuscitation (+17%), and a decrease for the pig that received no fluids (-5%). Analysis showed decreased scattering measured in the pig that received fluids (+13%), suggesting increased interstitial water pressure. These preliminary results are consistent with systemic hydration, as estimated based on CT-measured subcutaneous fat thickness. SFDI may, therefore offer the possibility of non-invasively monitoring fluid resuscitation of large TBSA patients.