Ocular surface microcirculation is better preserved with pulsatile versus continuous flow during cardiopulmonary bypass-An experimental pilot.

Abstract

Non-pulsatile cardiopulmonary bypass (CPB) may induce microvascular dysregulation. In piglets, we compared ocular surface microcirculation during pulsatile versus continuous flow (CF) bypass. Ocular surface microcirculation in small tissue volumes (~0.1 mm3 ) at limbus (high metabolic rate) and bulbar conjunctiva (low metabolic rate) was examined in a porcine model using computer assisted video microscopy and diffuse reflectance spectroscopy, before and after 3 and 6h of pulsatile (n=5 piglets) or CF (n=3 piglets) CPB. Functional capillary density, capillary flow velocity and microvascular oxygen saturation were quantified. At limbus, velocities improved with pulsatility (p < 0.01) and deteriorated with CF (p < 0.01). In bulbar conjunctiva, velocities were severely reduced with CF (p < 0.01), accompanied by an increase in capillary density (p < 0.01). Microvascular oxygen saturation decreased in both groups. Ocular surface capillary densities and flow patterns are better preserved with pulsatile versus CF during 6h of CPB in sleeping piglets.