Gaseous micro-emboli activity during cardiopulmonary bypass in adults: pulsatile flow versus nonpulsatile flow

Cardiopulmonary bypass (CPB) has a risk of cerebral injury, with an important role of gaseous micro-emboli (GME) coming from the CPB circuit. Pulsatile perfusion is supposed to perform specific conditions for supplementary GME activity. We aimed to determine whether pulsatile CPB augments production and delivery of GME and evaluate the role of different events in GME activity during either type of perfusion. Twenty-four patients who underwent on-pump coronary artery bypass grafting surgery at the University of Verona were divided equally into two groups-pulsatile perfusion (PP) group and nonpulsatile perfusion (NP) group. The circuit included a JostraHL-20 roller pump set in pulsatile or nonpulsatile mode, an open Sorin Synthesis membrane oxygenator with integrated screen-type arterial filter, and phosphorylcholine-coated tubes. Hemodynamic flow evaluation was performed in terms of energy equivalent pressure and surplus hemodynamic energy (SHE). GME were counted by means of a GAMPT BCC200 bubble counter (GAMPT, Zappendorf, Germany) with two probes placed at postpump and postarterial filter positions. Results were evaluated in terms of GME number, GME volume, number of over-ranged GME from both probes, and series of filtering indexes. In PP mode, the pump produced and delivered along the circuit significantly higher amounts of SHE than in NP mode. At the venous postpump site, GME number was significantly higher during PP but no difference was found in terms of GME volume or number of over-ranged bubbles. No significant difference in GME number, GME volume, or number of over-ranges was found at the postarterial filter site. Filtering indexes were similar between the two groups. Neither type of perfusion was shown to contribute to excessive GME production during the most important perfusionist manipulation. Pulsatility leads to GME increment by splitting and size diminishing of the existing bubbles but not by additional gas production. PP augmented GME number at the venous postpump site, while mean volume remained comparable with NP. Sorin Synthesis oxygenator showed high efficacy in GME removal during either type of perfusion. Supplementary GME production and delivery during typical perfusionist manipulations did not depend on perfusion type.