Hemolysis of albunex-supplemented, 40% hematocrit human erythrocytes in vitro by 1-MHz pulsed ultrasound: acoustic pressure and pulse length dependence.

The tested hypothesis was that ultrasound-induced hemolysis in blood supplemented with a microbubble contrast agent varies with ultrasound intensity and pulse duration. Human erythrocytes in autologous plasma containing 3.6% v:v Albunex microspheres were exposed to 1.07-MHz ultrasound pulses of 5 to 1000 mus at SPTP intensities of 0 to 1100 W/cm2. The dependence of hemolysis on the mechanical index (MI) value of the exposures was also examined. Ultrasound-induced hemolysis: (1) was evident at all pulse/intensity combinations; (2) increased generally with increasing pulse duration at constant intensity; and (3) increased with increasing MI at constant pulse duration. For pulses of 10 to 30 mus, ultrasound-induced hemolysis remained low (< or = 2%) at MI values < approximately 2 and increased sharply with further increase in MI; for 5-mus pulses, this abrupt increase in hemolysis was associated with a larger MI (approximately 3).