Contrast-agent gas bodies enhance hemolysis induced by lithotripter shock waves and high-intensity focused ultrasound in whole blood.

Fresh canine whole blood was exposed in 1.3-mL disposable pipette bulbs with or without added Albunex contrast agent to lithotripter shock waves (rate: 2 Hz; mean pressure amplitude: 14.8 MPa) or 1.28-MHz high-intensity focused ultrasound up to a mean pressure amplitude of 17.8 MPa. Significant shock-wave-induced hemolysis up to about 10% was detected after 500 or more shock waves without added agent, after 200 with 1% added agent and after 100 with 10% added contrast agent. Hemolysis was increased somewhat with added contrast agent, but this enhancement was not statistically significant. For ultrasound exposure, significant hemolysis approaching 100% was detected for 100-ms continuous exposure at 17.8 MPa without added gas bodies. Addition of 1% contrast agent enhanced the hemolysis by reducing the apparent threshold to 10 MPa. Burst mode exposure with a 100-ms total on-time (20 microseconds, 100 microseconds and 1-ms bursts) also yielded hemolysis enhancement with added contrast agent, with results similar to the 100-ms continuous exposure. The added gas bodies appear to lower cavitation thresholds by serving as cavitation nuclei in the blood.