Effects of IMAGENT on pulmonary hemodynamics and gas exchange in dogs

Microbubble Size and Dose Effects on Pharmacokinetics

Optimization of contrast-enhanced imaging and focused ultrasound therapy requires a comprehensive understanding of in vivo microbubble (MB) pharmacokinetics. Prior studies have focused pharmacokinetic analysis on indirect techniques, such as ultrasound imaging of the blood pool and gas chromatography of exhaled gases. The goal of this work was to measure the MB concentration directly in blood and correlate the pharmacokinetic parameters with the MB size and dose. MB volume dose (MVD) was chosen to combine the size distribution and number into a single-dose parameter. Different MB sizes (2, 3, and 5 μm diameter) at 5-40 μL/kg MVD were intravenously injected. Blood samples were withdrawn at different times (1-10 min) and analyzed by image processing. We found that for an MVD threshold < 40 μL/kg for 2 and 3 μm and <10 μL/kg for 5 μm, MB clearance followed first-order kinetics. When matching MVD, MBs of different sizes had comparable half-lives, indicating that gas dissolution and elimination by the lungs are the primary mechanisms for elimination. Above the MVD threshold, MB clearance followed biexponential kinetics, suggesting a second elimination mechanism mediated by organ retention, possibly in the lung, liver, and spleen. In conclusion, we present the first direct MB pharmacokinetic study, demonstrate the utility of MVD as a unified dose metric, and provide insights into the mechanisms of MB clearance from circulation.

Safety of echocardiographic contrast in hospitalized patients with pulmonary hypertension: a multi-center study

AIMS

Echocardiographic contrast (EC) improves the diagnostic accuracy of suboptimal echocardiograms. In October 2007, the Food and Drug Administration (FDA) placed a black box warning on the label of the perflutren-based agents Definity and Optison, contraindicating their use in patients with pulmonary hypertension (PHT) and unstable cardiopulmonary status, after serious cardiopulmonary reactions occurred in temporal relation to EC administration. In 2008 and 2011, the FDA revised the black box warning allowing their use in this same population. However, limited data exist regarding the safety profile of these agents in patients with PHT.

METHODS AND RESULTS

Consecutive hospitalized patients with PHT who were referred for echocardiographic evaluation, but required the use of EC, were included. All our patients received the EC agent Definity. We evaluated these patients for serious adverse events (respiratory decompensation, hypotension, syncope, convulsions, arrhythmias, anaphylactic reactions, or death) occurring within 24 h of EC administration. The study group included 1513 patients (age 69 ± 14 years, 55% males, BMI 33 ± 9 kg/m(2)), of which 911 (60%) had mild PHT, 515 (34%) had moderate PHT, and 87 (6%) had severe PHT. The mean pulmonary artery systolic pressures (PASP) in the groups with mild, moderate, and severe PHT were 41 ± 4 (range 35-49) mmHg, 55 ± 5 (range 50-69) mmHg, and 78 ± 9 (range 70-122) mmHg, respectively. The incidence of adverse events in all subgroups was rare (0.002%) and they were not attributed to EC because of temporal and clinical considerations.

CONCLUSION

The use of the EC agent Definity is safe in hospitalized patients with PHT.