A sensor device includes a housing defining a cavity, an inlet to receive fluid pumped from an instrument device, an outlet to return the fluid to a fluid reservoir, and a fluid channel defined inside the cavity between the inlet and the outlet. A heat pump is mounted inside the cavity, and has a side surface thermally coupled to the fluid channel and an opposite side surface thermally coupled to a plate. The heat pump is configured to induce a temperature change. A sensor unit is aligned with an aperture in the plate and includes an optical component and a thermal component. The optical component configured to measure a vascular endothelial response from the induced temperature change.