Factors affecting the pulsatile hydraulic power output of the Stockert roller pump

A detailed assessment of the hydraulic power output of the Stockert roller pump was performed with the pump operating in its 'pulsatile' mode. Pressure and flow waveforms and the pulsatile power generated in a model of the human vascular bed were dependant upon the pump output, the pump control settings and the diameters of the arterial line, the pump insert and aortic cannula. The pulsatile power output was lower when a silicone rubber pump insert was used rather than a polyvinyl chloride insert. The incorporation of a Cobe CML flat-sheet membrane oxygenator into the arterial line reduced the pulsatile power to levels similar to those obtained with the pump operating in its 'continuous' mode. Incorporating a Sarns hollow fibre membrane oxygenator or a Pall extracorporeal blood filter had less effect and variations in perfusate viscosity or the length of the arterial line did not appear to have any effect. It seems probable that the experimental and clinical effects of 'pulsatile' flow during cardiopulmonary bypass with this pump will be highly dependant upon the operating conditions.

Does Roller Pump-Induced Pulsatile CPB Perfusion Affect Microvascular Fluid Shifts and Tissue Perfusion?

BACKGROUND

Pulsatile versus nonpulsatile cardiopulmonary bypass (CPB) perfusion remains debated. Beneficial effects on tissue perfusion, inflammation, and microvascular fluid exchange have been linked to pulsatile perfusion by some investigators and denied by others. This study evaluated fluid extravasation and tissue perfusion during nonpulsatile or pulsatile roller pump-induced CPB perfusion.

METHODS

Fourteen pigs underwent roller pump-induced pulsatile (n = 7) or nonpulsatile CPB perfusion (n = 7) for 90 minutes. Fluid input/losses, colloid osmotic pressures (plasma/interstitium), hematocrit, serum electrolytes, serum proteins, tissue perfusion, and total tissue water content were measured, and plasma volume and fluid extravasation were calculated.

RESULTS

Fluid additions/losses, plasma volume, and fluid extravasation changed similarly in both groups during CPB with no between-group differences. Neither was between-group differences observed for tissue perfusion and total tissue water content, with one exception. Total tissue water content of the right (3.92 ± 0.26 versus 4.32 ± 0.28 g/g dry weight) and left ventricle (4.02 ± 0.25 versus 4.33 ± 0.24 g/g dry weight) was lowered in the pulsatile group.

CONCLUSIONS

No important differences were found between pulsatile and nonpulsatile CPB perfusion for microvascular fluid balance and tissue perfusion.