Ocular surface microcirculation is better preserved with pulsatile versus continuous flow during cardiopulmonary bypass – an experimental pilot
Abstract
Background
Non-pulsatile cardiopulmonary bypass may induce microvascular dysregulation. In piglets, we compared ocular surface microcirculation during pulsatile versus continuous flow bypass.
Methods
Ocular surface microcirculation in small tissue volumes (~0.1mm3) 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 6 hours of pulsatile (n=5 piglets) or continuous flow (n=3 piglets) cardiopulmonary bypass. Functional capillary density, capillary flow velocity and microvascular oxygen saturation were quantified.
Results
At limbus, velocities improved with pulsatility (p<0.01) and deteriorated with continuous flow (p<0.01). In bulbar conjunctiva, velocities were severely reduced with continuous flow (p<0.01), accompanied by an increase in capillary density (p<0.01). Microvascular oxygen saturation decreased in both groups.
Conclusion
Ocular surface capillary densities and flow patterns are better preserved with pulsatile versus continuous flow during 6 hours of cardiopulmonary bypass in sleeping piglets.