Effect of a Stabilized Microbubble Contrast Agent on CW Ultrasound Induced Red Blood Cell Lysis In Vitro

Human red blood cells (RBCs) in vitro at various fractional hematocrits (HCTs) were exposed for 60–120 seconds in a dialysis tubing vessel to 1 MHz continuous wave ultrasound (0–5 W/cm² SPTA intensity); exposure vessels were either rotated at 200 rpm or stationary. Some RBC suspensions also contained Albunex® (ALX; a commercially-produced microbubble clinical ultrasound contrast agent) at final concentrations ranging from 0–41 μL/mL RBC suspension. Isonation was either by one transducer or by two opposing, continuously-gated, balanced transducers. For the vessel rotation / no rotation experiments, ultrasound-induced cell lysis was always increased with the ALX regimen relative to that of the no-ALX regimen at HCTs up to about 10%; at higher HCTs (including whole blood), ultrasound-induced hemol-ysis essectially ceased to occur. The data are consistent with reports of the ineffectiveness of continuous wave ultrasound at 3–5 W/cm² to lyse cells in vitro at physiological cell densities with or without echocontrast medium supplemantation.