Doppler ultrasound estimation of microbubbles in the arterial line during extracorporeal circulation

A pulsed Doppler ultrasound system was used to analyse microbubble intensity and size in the arterial line during extracorporeal circulation (ECC). Thirty male patients, younger than 70 (range 28-69) years, underwent isolated coronary artery bypass grafting with either a bubble oxygenator (Shiley S-100) without (group 1, n = 10) or with (group 2, n = 10) a depth adsorption arterial line filter (Swank High Flow 6000); or with a membrane oxygenator (Shiley M-2000) without a filter (group 3, n = 10). Mean ECC and aortic crossclamp times were similar in the three groups. Measurements were performed during the initial five minutes of cooling, after 30-40 minutes of ECC and after 10 minutes of rewarming. Microbubble intensity and size did not differ significantly in the three groups at the different intervals. Significantly more and larger bubbles were detected in group 1 (15-150μm) compared to group 2 (< 35μm) (p< 0.001). In group 3 only a minimal number of small bubbles (< 65μm) were observed. An arterial line filter significantly reduced the number and size of microbubbles detected in the arterial line during ECC. A membrane oxygenator was associated with a further reduction of microbubble intensity.