In vitro evaluation of the air separation ability of four cardiovascular manufacturer extracorporeal circuit designs

Abstract

Neurologic impairment is a common complication of adult cardiac surgery. Cerebral gaseous microemboli (GME) detected during cardiopulmonary bypass has been associated with cognitive impairment after adult cardiac surgery. Several previous studies have shown that components comprising the extracorporeal circuit (ECC) can affect the ability of the ECC to eliminate air. The differences in the air separation ability of four manufacturer's commonly used ECCs were studied. The air-separating ability of Cobe Cardiovascular, Gish Biomedical, Medtronic, and Terumo Cardiovascular Systems Corp. ECCs were studied in vitro under clinically relevant conditions. Bolus and continuous venous air were introduced and output GME patterns by size, time, and count were measured (using an embolus detection device) and statistically analyzed. Graphic representations depicting elapsed time, GME size, and bubble count helped to visually rank the air-handling performance of the ECCs. There are significant air-handling differences between the ECCs tested. Overall, the blinded results reveal that ECC A and ECC C removed significantly (p < 0.001) more suspended GME than ECC B and ECC D. In the 50-mL venous room-air bolus and the 100 mL/min pulsed air challenges, ECC B and ECC D allowed significantly more GME to pass (p < 0.001) compared with ECC A and ECC C. For example, in a 2-hour pump run ECC C would deliver 480 potential high-intensity transient signals (HITS) compared with the 9600 from the ECC B during venous room air entrainment at 100 mL/min. There are substantial and significant air-handling differences between the ECCs from the four different manufacturers. The results from this work allow for objective characterization of ECCs air-separating ability. This additional information provides an opportunity for clinicians to potentially minimize the risks of arterial air embolization and its associated deleterious neurologic effects, while allowing clinicians to make better-informed consumer decisions.

FIGURE 1.

In vitro GME test circuit.

FIGURE 2.

50 mL room-air bolus device.

FIGURE 3.

Main effects of GME percent removal versus GME sizes.

FIGURE 4.

The GME counts at all sizes and elapsed times up to 2 minutes post-venous 50 mL room-air bolus at 4 L/min pump flow, 28% glycerin flow, and 34°C perfusate temperature.

FIGURE 5.

Main effects of GME counts at all GME sizes versus elapsed time.

FIGURE 6.

The GME counts at all sizes and elapsed times up to 2 minutes post-venous room-air 100 mL/min pulse air stream at 4 L/min pump flow, 28% glycerin flow, and 34°C perfusate temperature.

FIGURE 7.

Main effects of GME counts at all sizes versus elapsed time.