Ultrasonically induced hemolysis at high cell and gas body concentrations in a thin-disc exposure chamber

Ultrasound image contrast may be enhanced by injecting gas bodies into the blood. This in vitro study was undertaken to assess the potential for induction of hemolysis due to ultrasonic activation of the contrast agent gas bodies. Canine whole blood with Albunex (R) (Mallinckrodt Medical, St. Louis, MO, USA) was exposed to near-field ultrasound beams in 1-mm-thick chambers held stationary (i.e., not rotated) in a 37 degrees C water bath. At 2.25 MHz, statistically significant hemolysis occurred in 0.5 hematocrit, 50% Albunex (R) suspensions for 0.28-MPa, 1-s continuous exposure and for 0.58-MPa, 100-mu s exposures with 10-mu s pulses and 1.0-ms pulse repetition period. Continuous exposure durations as short as 10 ms produced about 4.5% hemolysis, which only increased slightly to about 5.5% after 100 s. At a constant 1.6 MPa, hemolysis increased with increasing gas body concentration and with decreasing cell concentration. Hemolysis decreased with increasing frequency in a 50/50 mixture of whole blood and Albunex (R), with thresholds rising from 0.12 MPa continuous (1 s) and 0.37 MPa pulsed (10 mu s:1.0 ms for 100 s) at 1.06 MHz to 0.47 MPa continuous and 1.9 MPa pulsed at 5.3 MHz. (C) 1997 World Federation for Ultrasound in Medicine & Biology.