Therapeutic options for severe pulmonary hypertension

The management of acute pulmonary arterial hypertension

Acute pulmonary arterial hypertension (PAH), which may complicate the course of many complex disorders, is always underdiagnosed and its treatment frequently begins only after serious complications have developed. Acute PAH is distinctive because they differ in their clinical presentation, diagnostic findings, and response to treatment from chronic PAH. The acute PAH may take either the form of acute onset of chronic PAH or acute PAH or surgery-related PAH. Significant pathophysiologic differences existed between acute and chronic PAH. Therapy of acute PAH should generally be aimed at acutely relieving right ventricular (RV) pressure overload and preventing RV dysfunction. There are three classes of drugs targeting the correction of abnormalities in endothelial dysfunction, which have been approved recently for the treatment of PAH: (1) prostanoids; (2) endothelin receptor antagonists; and (3) phosphodiesterase-5 inhibitors. The efficacy and safety of these compounds have been confirmed in uncontrolled studies in patients with PAH. Intravenous epoprostenol is suggested to serve as the first-line treatment for the most severe patients. In the other situations, the first-line therapy may include bosentan, sildenafil, or a prostacyclin analogue. Recent advances in the management of PAH have markedly improved prognosis.

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 microg/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.

Pulmonary hypertension complicating twin pregnancy: continuous spinal anaesthesia for caesarean section

A case of secondary pulmonary hypertension complicating twin pregnancy and necessitating caesarean section is presented. A planned team approach involving senior consultants in obstetrics, cardiology, neonatology and cardiac and obstetric anaesthesia resulted in successful perioperative management. Continuous spinal anaesthesia was the chosen technique to give adequate operating conditions with least haemodynamic disturbance. This is the first report of continuous spinal anaesthesia in such a condition.

Combination therapy with inhaled nitric oxide and intravenous dobutamine during pulmonary hypertension in the rabbit

Combination therapy with an intravenous inovasodilator and inhaled nitric oxide (NO) may be appropriate in patients with pulmonary hypertension and associated right ventricular failure. We examined whether dobutamine and inhaled NO would have additive pulmonary vasodilator effects in experimental pulmonary hypertension. Pulmonary hypertension was produced in anesthetized, mechanically ventilated rabbits by infusion of U46619, a thromboxane analogue. Dobutamine was administered in increasing doses (2.5-20 microg/kg/min) with and without inhaled NO (40 ppm). Dobutamine produced dose-dependent decreases in pulmonary vascular resistance (PVR) and mean arterial pressure (MAP) and increases in cardiac output (CO). Inhaled NO alone decreased pulmonary artery pressure (PAP) and PVR with no effect on MAP or CO. The effects of dobutamine and inhaled NO were additive, so that at each dose of dobutamine, inhaled NO decreased PAP and PVR with no effect on systemic hemodynamics. This study suggests that the combination of dobutamine and inhaled NO should produce additive pulmonary vasodilation in patients with pulmonary hypertension and associated right ventricular dysfunction.

Additive effects of inhaled nitric oxide and intravenous milrinone in experimental pulmonary hypertension

OBJECTIVE

To determine whether inhaled nitric oxide (IN0) and intravenous milrinone have additive pulmonary vasodilator effects in a rat model of pulmonary hypertension.

DESIGN

Prospective, experimental study.

SETTING

Animal laboratory of a university medical center.

SUBJECTS

Male New Zealand White rabbits.

INTERVENTIONS

Anesthetized rabbits were mechanically ventilated and instrumented for measurement of systemic mean arterial pressure (MAP), pulmonary artery pressure (PAP), left atrial pressure, and cardiac output (CO). After baseline measurements, the nitric oxide synthase inhibitor N(G)-nitro-L-arginine methyl ester (30 mg/kg iv) was administered. Pulmonary hypertension was produced by the continuous infusion of U46619, a thromboxane A2 mimetic. INO (40 ppm) was added to the inspired gas, and hemodynamic measurements were obtained before and after INO. Milrinone was administered sequentially as a 30-mg/kg bolus followed by a 3-microg/kg/min infusion, a 100-mg/kg bolus followed by a 10-microg/kg/min infusion, and a 300-mg/kg bolus followed by a 30-microg/kg/min infusion (M3). Hemodynamic measurements were obtained with and without INO at each dose of milrinone.

MEASUREMENTS AND MAIN RESULTS

During U46619-induced pulmonary hypertension, INO decreased PAP and pulmonary vascular resistance (PVR) but did not affect MAP, systemic vascular resistance (SVR), or CO. Milrinone dose dependently decreased PAP, PVR, MAP, and SVR and increased CO. At each dose of milrinone, INO further decreased PVR but not SVR. M3 decreased PVR 49%, and the addition of INO decreased PVR an additional 19% so that PAP and PVR decreased to baseline values.

CONCLUSIONS

Milrinone and INO both decrease pulmonary hypertension individually, and the combination produces additive effects. Combination therapy may produce potent and selective pulmonary vasodilation during the treatment of pulmonary hypertension.

Combined therapy with inhaled nitric oxide and intravenous vasodilators during acute and chronic experimental pulmonary hypertension

Both inhaled nitric oxide (NO) and IV vasodilators decrease pulmonary hypertension, but the effects of combination therapy are unknown. We studied the response to inhaled NO (100 ppm) alone, IV vasodilator alone, and combined therapy during acute (U46619-induced) and chronic (monocrotaline-induced) pulmonary hypertension in the pentobarbital-anesthetized rat. Vasodilator doses were 1.0, 3.2, 10, and 32 microg x kg(-1) x min(-1) sodium nitroprusside (SNP); 50, 100, 150, 200, and 300 microg x kg(-1) x min(-1) adenosine; or 25, 50, 150, 200, and 300 ng x kg(-1) x min(-1) prostacyclin. In the absence of IV vasodilator therapy, inhaled NO decreased mean pulmonary artery pressure without decreasing mean systemic arterial pressure. In both acute and chronic pulmonary hypertension, the addition of inhaled NO to the largest dose of adenosine or prostacyclin, but not of SNP, decreased pulmonary artery pressure. Because inhaled NO and SNP activate guanylyl cyclase and adenosine and prostacyclin activate adenylyl cyclase, the results suggest that adding inhaled NO to a vasodilator not dependent on guanylyl cyclase may produce additional selective pulmonary vasodilation.

IMPLICATIONS

In therapy of pulmonary hypertension, inhaled nitric oxide should produce additional selective pulmonary vasodilation when combined with a vasodilator whose mechanism of action is not dependent on cyclic guanosine 3',5'-monophosphate.

[Pulmonary thromboendarterectomy with video-angioscopy and circulatory arrest: an alternative to cardiopulmonary transplantation and post-embolism pulmonary artery hypertension]

The best predictor of poor or suboptimum outcome from pulmonary thromboendarterectomy (PTE) is insufficient relief of obstruction, especially in the lower lobes. The aim of this study is to emphasize that the use of video-assisted angioscopy may increase the quality of PTE and thus improve outcome. PTE included a median sternotomy, intrapericardial dissection limited to the superior vena cava, institution of cardiopulmonary bypass, deep hypothermia and sequential circulatory arrest periods. PTE was always bilateral and performed through two separate arteriotomies of both main intrapericardial pulmonary arteries. A rigid 5 mm angioscope connected to a video camera was introduced through the arteriotomy into the lumen to increase the visibility and perform the video-assisted endarterectomies of all obstructed segmental branches, including normally inaccessible anterior segmental branches. Between January 1996 and December 1997, 48 patients with severe postembolic pulmonary hypertension had PTE. Patients were in New York Heart Association (NYHA) class II (n = 2), III (n = 28) or IV (n = 18) with the following hemodynamics: mean pulmonary arterial pressure (PAP) 53 +/- 13 mmHg, cardiac index 2.16 +/- 0.5 L/min/m2, pulmonary vascular resistances (PVR): 1,152 +/- 414 dyne.s-1.cm-5. Six patients died from alveolar hemorrhage (n = 1), high residual pulmonary pressure and rethrombosis (n = 4) and hypoxic cardiac arrest (n = 1). The functional outcome in surviving patients was as follows: (NYHA) class I (n = 24), II (n = 16) or III (n = 2) with improved hemodynamics: mean pulmonary arterial pressure: 30 +/- 9 mmHg, cardiac index: 2.78 +/- 0.5 L/min/m2, pulmonary vascular resistances (PVR): 484 +/- 159 dynes.s-1.cm-5. Video-assisted angioscopy allows much improved quality and degree of pulmonary endarterectomy. This expands the indications to include patients with previously inaccessible distal disease and candidates for heart-lung transplantation.