Pulmonary Transit of Echocontrast Agents during Mechanical Ventilation: A Clinical Transthoracic Echocardiographic Study

Abstract

In this study, we investigated whether the ultrasound contrast agents Levovist or Sono Vue injected intravenously during mechanical ventilation effectively pass through the pulmonary circulation. With echocardiography, we measured the time for the contrast to pass through the lungs; and the intensity of right and left ventricular cavity opacification at four time points: during spontaneous breathing (baseline), 5 minutes after the beginning of mechanical ventilation, and 5 minutes and 30 minutes after extubation. Forty patients undergoing elective peripheral neurosurgical procedures were prospectively and randomly enrolled: 20 patients received intravenous Levovist 1 g and 20 patients received intravenous Sono Vue 1 mL, at the four predefined time points. After intravenous injection, both Levovist and Sono Vue effectively passed through the lungs and opacified the right and left ventricular cavities, at the four time points. Pulmonary transit times were similar and constant for the two contrast agents tested: 6 +/- 2 seconds at baseline, 5 +/- 2 seconds during mechanical ventilation, 7 +/- 2 seconds at 5 minutes and 6 +/- 2 seconds at 30 minutes after extubation with Levovist; and 6 +/- 4 seconds at baseline, 6 +/- 3 seconds during mechanical ventilation, 6 +/- 2 seconds at 5 minutes and 7 +/- 3 seconds at 30 minutes after extubation with Sono Vue. In all patients, each of the four contrast injections achieved high-grade right and left ventricular chamber opacification. In conclusion, both the ultrasound contrast agents tested in this study, Levovist and Sono Vue, after intravenous injection pass through the pulmonary circulation during mechanical ventilation. Ultrasound contrast agents with these characteristics are suitable for intraoperative organ perfusion studies, with intravenous injection.