In vivo near infrared (NIRS) sensor attachment using fibrin bioadhesive

Background: a€Tisseel' (Baxter Healthcare, Deerfield, IL) is a fibrin-based sealant that is commonly used during spine surgery to augment dural repairs. We wish to intra-operatively secure a near infrared spectroscopy (NIRS) sensor to the dura in order to monitor the tissue hemodynamics of the underlying spinal cord. To determine if a€Tisseel' sealant adversely attenuates NIR photon transmission. Methods: We investigated a€Tisseel' in both an in vitro and in vivo paradigm. For in vitro testing, we used a 1 mm pathlength cuvette containing either air or a€Tisseel' interposed between a NIR light source (760 and 850 nm) and a photodiode detector and compared transmittance. For in vivo testing, a continuous wave (760 and 850 nm) spatiallyresolved NIRS device was placed over the triceps muscle using either conventional skin apposition (overlying adhesive bandage) or bioadhesion with a€Tisseel'. Raw optical data and tissue saturation index (TSI%) collected at rest were compared. Results: In-vitro NIR light absorption by a€Tisseel' was very high, with transmittance reduced by 95% compared to air. In-vivo muscle TSI% values were 80% with conventional attachment and 20% using fibrin glue. Conclusion: The optical properties of a€Tisseel' significantly attenuate NIR light during in-vitro transmittance and critically compromise photon transmission in-vivo.