Comparison of the Usage of Intravenous Iloprost and Nitroglycerin for Pulmonary Hypertension during Valvular Heart Surgery
Background. Pulmonary hypertension secondary to valvular heart disease is a cause of acute right heart failure during valve replacement operations. This study compares the hemodynamic effects of intravenous use of iloprost and nitroglycerin in patients with pulmonary hypertension undergoing valvular replacement surgery. We sought to determine the acceptable doses of these medications for use in surgery to decrease mean pulmonary artery pressure to <30 mmHg without causing systemic side effects. The plasma nitric oxide levels that were obtained from pulmonary mixed venous blood have been compared to demonstrate the difference in the action mechanism of these drugs.
Methods. Eighteen patients undergoing mitral or aortic and mitral valvular replacement with pulmonary hypertension >25 mmHg were included in the study. The 2 groups received iloprost or nitroglycerin via a central pulmonary catheter, and the hemodynamic parameters were evaluated before incision (T1), 10 minutes after chest opening (T2), and 5 minutes and 20 minutes after cardiopulmonary bypass (T3 and T4). The plasma nitric oxide levels were obtained from the mixed venous blood at the T1 and T4 intervals.
Results. The data have been analyzed for each group and for repeated measurements of hemodynamic parameters at T1-T4 time points. The analysis of hemodynamic parameters before (T1 and T2) and after (T3 and T4) bypass showed similar responses depending on the use of either iloprost or nitroglycerin. The administration of iloprost after bypass (T3) at a dosage of 1.25 to 2.5 ng/kg per minute reduced mean pulmonary artery pressure (from 28.8 ± 7.89 to 20.63 ± 6.39 mmHg) and pulmonary vascular resistance (from 226.88 ± 101.93 to 118.00 ± 82.36 dyn sec cm -5) better than nitroglycerin at a dosage of 0.5 to 1 m g/kg per minute (from 23.20 ± 5.20 to 18.50 ± 5.10 mmHg and from 160.80 ± 39.76 to 137.40 ± 56.54 dyn sec cm -5, respectively). Iloprost causes significant increase in cardiac output (from 4.91 ± 0.91 to 5.49 ± 0.91 L/min) compared to nitroglycerin (from 5.23 ± 0.80 to 5.27 ± 0.74 L/min). The plasma nitric oxide levels of the iloprost group did not show an increase from T1 to T4, whereas the nitroglycerin group levels did (P <.05).
Conclusions. Intravenous use of both iloprost and nitroglycerin effectively reduces mean pulmonary artery pressure, although only the iloprost group was accompanied by an increase in cardiac output. During operation, where abrupt management of pulmonary hypertension is required, systemic use of iloprost or nitroglycerin at appropriate doses via a pulmonary artery catheter offers adequate relief of hypertension and is well tolerated without any significant adverse effects. The plasma nitric oxide levels did not rise with the use of iloprost.
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