Selective pulmonary vasodilation by inhaled prostacyclin in a newborn with congenital heart disease and cardiopulmonary bypass

Perioperative pharmacological management of pulmonary hypertensive crisis during congenital heart surgery

Pulmonary hypertensive crisis is an important cause of morbidity and mortality in patients with pulmonary arterial hypertension secondary to congenital heart disease (PAH-CHD) who require cardiac surgery. At present, prevention and management of perioperative pulmonary hypertensive crisis is aimed at optimizing cardiopulmonary interactions by targeting prostacyclin, endothelin, and nitric oxide signaling pathways within the pulmonary circulation with various pharmacological agents. This review is aimed at familiarizing the practitioner with the current pharmacological treatment for dealing with perioperative pulmonary hypertensive crisis in PAH-CHD patients. Given the life-threatening complications associated with pulmonary hypertensive crisis, proper perioperative planning can help anticipate cardiopulmonary complications and optimize surgical outcomes in this patient population.

Pharmacotherapy for pulmonary hypertension

Pulmonary arterial hypertension is a serious disease with significant morbidity and mortality. Although it can occur idiopathically, it is more commonly associated with other cardiac or lung diseases. While most of the available therapies have been tested in adult populations and most therapies in children remain off-label, new reports and randomized trials are emerging that inform the treatment of pediatric populations. This review discusses currently available therapies for pediatric pulmonary hypertension, their biological rationales, and evidence for their clinical effectiveness.

Review of inhaled iloprost for the control of pulmonary artery hypertension in children

In the pediatric population, pulmonary hypertension may present as an acute event in the setting of lung or cardiac pathology or as a chronic disease, mainly as idiopathic pulmonary hypertension or associated with congenital heart disease. Recently, new pharmacologic approaches have demonstrated significant efficacy in the management of adults with pulmonary arterial hypertension; these include intravenous epoprostenol, prostacyclin analogs, endothelin receptor antagonists and phosphodiesterase type 5 inhibitors. The same treatment strategies are currently used in children. There are only few reports of the use of inhaled iloprost in pediatrics, only one of which reported the use of chronic inhaled iloprost in a significant number of children. This report showed that 1) the acute pulmonary vasodilator response to inhaled iloprost is equivalent to that of inhaled nitric oxide; 2) acute inhalation of iloprost can induce bronchoconstriction 3) the addition of inhaled iloprost can reduce the need for intravenous prostanoid therapy in some patients; 4) most children tolerated the combination of inhaled iloprost and endothelin receptor antagonist or phosphodiesterase inhibitors; 5) Several patients had clinical deterioration during chronic inhaled iloprost therapy and required rescue therapy with intravenous prostanoids. In this review we will discuss the role of inhaled iloprost in acute and chronic pulmonary hypertension in children.

Treatment of refractory pulmonary arterial hypertension with inhaled epoprostenol in an infant with congenital heart disease

Epoprostenol is a potent arterial vasodilator, and its administration by inhalation localizes its effects to the pulmonary circulation. In this case report, we describe a 3-month-old male patient with significant refractory pulmonary hypertension after pulmonary artery banding and placement of a Blalock-Taussig shunt. This patient continued to have significant hypoxic episodes despite maximal therapy with sedation, alkalinization, sildenafil, and inhaled nitric oxide. After the addition of inhaled epoprostenol, improvements in both clinical response and echocardiography-based hemodynamics were observed. The case supports a synergistic role among the agents in the treatment of pulmonary arterial hypertension from congenital heart disease.

Nebulized therapies for childhood pulmonary hypertension: an in vitro model

OBJECTIVES

Sildenafil, tezosentan, and prostacyclin reduce pulmonary vascular pressures in pulmonary hypertension, but have potential to vasodilate the systemic circulation. Nebulized vasodilators allow targeted drug delivery, high local drug concentrations, less systemic hypotension, and better matching of the lung's ventilation and perfusion. We aimed to estimate pulmonary deposition of these drugs from commonly employed nebulizers using in vitro techniques and to create a mathematical model to predict inspired mass of aerosol.

DESIGN

Lung deposition was estimated by characterization of drug output and particle size distribution (PSD) of nebulizers using helium-neon laser diffraction techniques. A mathematical model for each device was created to estimate pulmonary deposition using patients' breathing patterns and was verified with a mechanical-breathing model.

RESULTS

Total output and PSD were similar for the Hudson Updraft II and Whisperjet nebulizers, consisting of half the nebulizer's charge, with (1/4) of particles < or = 5 microm, in the respirable fraction (RF). Drug output increased with inspiratory flow for the Pari LC Star. Differences were noted in device performance, depending on the drug tested. Estimated pulmonary deposition (mean, 95% CI) was 8.1 (7.2, 9.0)% of the initial drug charge for the Hudson Updraft II, 6.4 (5.8, 7.0)% for the Whisperjet, and 33.0 (28.3, 37.9)% for the Pari LC Star. A mechanical model was consistent with our mathematical model.

CONCLUSIONS

All drugs could be nebulized, but expected pulmonary deposition varied depending on the nebulizer and drug.

Efficacy of nitroglycerin inhalation in reducing pulmonary arterial hypertension in children with congenital heart disease

BACKGROUND

There has been a renewed interest in nitric oxide donor drugs, such as nitroglycerin, delivered by the inhalational route for treatment of pulmonary arterial hypertension (PAH). We investigated the acute effects of inhaled nitroglycerin on pulmonary and systemic haemodynamics in children with PAH associated with congenital heart disease.

METHODS

Nineteen children with acyanotic congenital heart disease and a left to right shunt with severe PAH, undergoing routine diagnostic cardiac catheterization were included in this study. Systolic, diastolic and mean systemic as well as pulmonary artery pressures, right atrial pressure and pulmonary capillary wedge pressure (PCWP) were recorded and systemic vascular resistance index (SVRI) and pulmonary vascular resistance index (PVRI) were calculated at room air, following 100% oxygen as well as after nitroglycerin inhalation in all patients.

RESULTS

Systolic, diastolic and mean pulmonary artery pressure and PVRI decreased significantly, whereas heart rate, systolic, diastolic and mean systemic arterial pressure, PCWP and SVRI did not change significantly following 100% oxygen or inhalation of nitroglycerin.

CONCLUSION

Inhaled nitroglycerin significantly decreases systolic, diastolic and mean pulmonary artery pressure as well as PVRI without affecting systemic haemodynamics, and thus can be used as a therapeutic modality for acute reduction of PAH in children with congenital heart disease.

Incidence and significance of abnormal hepatic venous Doppler flow velocities before cardiac surgery

OBJECTIVE

The purpose of this study was to determine the incidence and significance of abnormal hepatic Doppler venous flow velocities as signs of an abnormal right ventricular filling pattern before cardiac surgery.

DESIGN

Retrospective and prospective validation study.

SETTING

Tertiary care hospital.

PARTICIPANTS

Cardiac surgical patients (121 patients).

INTERVENTIONS

Not applicable.

MEASUREMENTS

Demographic, hemodynamic, and echocardiographic variables; vasoactive support; and difficult separation from bypass were compared between patients with or without abnormal hepatic venous Doppler flow. Logistic regression analysis was performed to identify predictors of difficult separation from bypass. Abnormal hepatic venous flow was observed in 23 (29%) and 17 patients (41%) in the retrospective and prospective study. Abnormal hepatic venous flow before surgery was associated with more vasoactive support in both the retrospective (p = 0.0362) and prospective study (p = 0.0163). In the prospective study, abnormal hepatic venous flow was associated with a higher Parsonnet score (p = 0.0005), more atrial fibrillation (p < 0.0001), pacemaker requirement (p = 0.0124), mitral valve replacement (p = 0.0325), reoperation (p = 0.0050), lower mean arterial pressure to pulmonary artery pressure ratio (p = 0.0127), higher wall motion score index (p = 0.0491), and higher incidence of abnormal right ventricular systolic function (p = 0.0139). Abnormal hepatic venous flow was not found to be an independent predictor of difficult separation from bypass.

CONCLUSIONS

Abnormal hepatic venous flow velocities before cardiac surgery are frequent and are associated with increased need for vasoactive support after cardiopulmonary bypass. However, it is not an independent predictor of difficult separation from bypass and worse outcome.

Pulmonary edema and cardiac dysfunction following subarachnoid hemorrhage

BACKGROUND

Pulmonary edema (PE) can occur in the early or late period following subarachnoid hemorrhage (SAH). The incidence of each type of PE is unknown and the association with ventricular dysfunction, both systolic and diastolic, has not been described.

METHODS

Retrospective chart review of 178 consecutive patients with SAH surgically treated over a three-year period. Patients with pulmonary edema diagnosed by a radiologist were included. Early onset SAH was defined as occurring within 12 hours. Cardiac function at the time of the PE was analyzed using hemodynamic and echocardiographic criteria of systolic and diastolic dysfunction. Pulmonary edema was observed in 42 patients (28.8%) and was more often delayed (89.4%). Evidence of cardiac involvement during PE varied between 40 to 100%.

RESULTS AND CONCLUSIONS

Pulmonary edema occurs in 28.8% of patients after SAH, and is most commonly delayed. Cardiac dysfunction, both systolic and diastolic, is commonly observed during SAH and could contribute to the genesis of PE after SAH.

Aerosolized iloprost as a bridge to lung transplantation in a patient with cystic fibrosis and pulmonary hypertension

We describe a patient with cystic fibrosis, end-stage lung disease, and secondary pulmonary hypertension in whom aerosolized iloprost was effective in lowering pulmonary artery pressure and improving functional status, thus proving successful as a bridge to lung transplantation. Inhaled iloprost may be an efficient and selective approach to treat pulmonary hypertension related to end-stage obstructive pulmonary disease.

Aerosolized PGE1: a selective pulmonary vasodilator in neonatal hypoxemic respiratory failure results of a Phase I/II open label clinical trial

Twenty term/near term neonates with hypoxemic respiratory failure and oxygenation index >/=20 were enrolled in a Phase I/II feasibility, safety and dose escalation study of inhaled PGE(1) (IPGE(1)). Incremental doses of IPGE(1), delivered by a jet nebulizer over a 2-h period, followed by weaning over 1 h, were given to 13 patients before receiving inhaled nitric oxide (INO) (Group I), and to seven patients, who failed to respond to INO (Group II). Response was defined as an increase in P(a)O(2) of either >/= 25 (full) or 10-25 (partial) torr. Exit criteria included an acute deterioration in oxygenation status, a persistent oxygenation index above 35 in Group I, or the availability of extracorporeal membrane oxygenation (ECMO) in Group II. The mean (SD) increase in P(a)O(2) at the end of IPGE(1) administration was 63 (62.3) in Group I (p = 0.024), and 40 (62.1) in Group II (p > 0.05). In Group I, 8 of 13 neonates had a full response, but 4 deteriorated following discontinuation of IPGE(1). Of these four, two responded to INO and two were placed on ECMO. Five patients deteriorated before or during IPGE(1,) and none of them responded to INO. In Group II, three of seven patients had a full response to IPGE(1). One patient with a partial response and all patients exiting before or during IPGE(1) administration were placed on ECMO. The results of our study indicate that IPGE(1) may be a safe, selective pulmonary vasodilator in neonatal hypoxemic respiratory failure.

[Aerosolized and intravenous prostacyclin during one-lung ventilation. Hemodynamic and pulmonary effects]

BACKGROUND

One-lung ventilation is frequently used in thoracic surgery. However, hypoxic pulmonary vasoconstriction of the atelectatic lung may produce pulmonary hypertension. The objective of the present study was to compare the acute effects of intravenous versus aerosolized prostacyclin (PGI(2)) on pulmonary and systemic circulation.

METHODS

PGI(2) was administered in 11 anesthetized and unilaterally ventilated pigs by infusion (5, 10, and 20 ng/kg body weight/min) and by inhalation (4, 8, and 16 ng/kg body weight/min) in a cross-over design.

RESULTS

Infusion of PGI(2) reduced both pulmonary (PVR) and systemic vascular resistance (SVR). Due to a concomitant increase in cardiac index (CI) mean arterial (MAP) and pulmonary artery pressures (MPAP) did not change significantly. In contrast, aerosolized PGI(2) produced a significant decrease in PVR (-21.4 to -32.8%) and MPAP (-12.0 to -17.8%) without affecting SVR, MAP, and CI. Arterial oxygenation tension (p(a)O(2)) was not affected.

CONCLUSION

During one-lung ventilation only aerosolized prostacyclin produced a selective pulmonary vasodilation.

Intraoperative administration of nitric oxide

Despite its therapeutic efficacy in various clinical scenarios in the intensive care unit setting, there are limited reports regarding the intraoperative applications of nitric oxide (NO). The authors present 2 pediatric patients to whom inhaled NO was administered intraoperatively. In one patient, NO was used to treat hypoxemia that developed after the institution of one-lung ventilation during thoracoscopic resection of a bronchiectatic section of lung. In the second patient, NO was used to alleviate pulmonary hypertension and cardiovascular dysfunction with pulmonary artery cross-clamping for placement of a modified Blalock-Taussig shunt. The potential intraoperative applications and techniques for the intraoperative delivery of NO are presented.

Comparison of acute hemodynamic effects of aerosolized and intravenous iloprost in secondary pulmonary hypertension in children with congenital heart disease

Both aerosolized and intravenous infusion of iloprost caused a significant decrease in mean pulmonary artery pressure and pulmonary vascular resistance. Although intravenous infusion caused a large decrease in mean systemic arterial pressure, this was only slightly affected by aerosolized iloprost. Aerosolized iloprost caused a significant decrease in the pulmonary-to-systemic vascular resistance ratio; however, intravenous infusion did not cause a prominent decrease in this ratio.

[Perioperative implications of heart transplant]

Over the past 30 years, heart transplantation has evolved into a definitive therapy for patients with end-stage cardiomyopathy. However, perioperative management of patients undergoing heart transplantation remains a challenge for anesthesiologists. The presence of biventricular failure, arrhythmias and associated multisystem organ dysfunction may contribute to significant intraoperative hemodynamic instability prior to the initiation of cardiopulmonary bypass (CPB). Even after an uneventful transplantation, weaning from CPB may be difficult. Acute right ventricular failure can develop in the recipient secondary to pre-existing pulmonary hypertension. Treatment options frequently focus on therapeutic interventions directed towards decreasing pulmonary vascular resistance and improving right ventricular contractility. Intraoperative use of transesophageal echocardiography (TEE) enables the anesthesiologist to diagnose acute right ventricular failure early on and guide therapy. Concurrent pathology including kinking of the pulmonary artery anastomosis or valvular insufficiency in the transplanted heart can also be recognized and addressed. The number of patients undergoing cardiac transplantation is continually increasing. In addition, the use of more effective immunosuppressive agents has curtailed transplant rejection and permitted longer survival. Consequently, heart transplant recipients are more frequently presenting for non-cardiac surgical procedures. Thus, an understanding of physiological and pharmacological implications associated with heart transplantation is crucial for managing these patients in the perioperative period.

Pulmonary arterial hypertension in congenital heart disease

Pulmonary arterial hypertension (PAH) is a recognized complication of congenital systemic to pulmonary arterial cardiac shunts. The prognosis of PAH in this situation is better than primary or other secondary forms of PAH. Our knowledge of the pathophysiology of PAH complicating congenital heart disease has evolved over the past decade. Despite differences in etiology and pathobiology, therapies that have proven successful for primary PAH may benefit this group of patients.

Searching the ideal inhaled vasodilator: from nitric oxide to prostacyclin

Today, the technique to directly administer vasodilators via the airway to treat pulmonary hypertension and to improve pulmonary gas exchange is widely accepted among clinicians. The flood of scientific work focussing on this new therapeutic concept had been initiated by a fundamental new observation by Pepke-Zaba [1]and Frostell in 1991 [2]: Both scientists reported, that inhalation of exogenous nitric oxide (NO) gas selectively dilates pulmonary vessels without a concomittant systemic vasodilation. No more than another decade ago NO was identified as an important endogenous vasodilator [3]while having merely been regarded an environmental pollutant before that time. Although inhaled NO proved to be efficacious, alternatives were sought-after due to NO's potential side-effects. In search for the ideal inhaled vasodilator another group of endogenous mediators -- the prostanoids -- came into the focus of interest. The evidence for safety and efficacy of inhaled prostanoids is -- among a lot of other valuable work -- based on a series of experimental and clinical investigations that have been performed or designed at the Institute for Surgical Research under the guidance and mentorship of Prof. Dr. med. Dr. h.c. mult. K. Messmer [4-19]. In the following, the current and newly emerging clinical applications of inhaled prostanoids and the experimental data which they are based on, will be reviewed.

Inhaled nitric oxide versus aerosolized iloprost in secondary pulmonary hypertension in children with congenital heart disease: vasodilator capacity and cellular mechanisms

BACKGROUND

Inhaled nitric oxide (iNO) has been used to assess the vasodilator capacity of the pulmonary vascular bed in children with congenital heart disease and elevated pulmonary vascular resistance. Inhaled iloprost is a pulmonary vasodilator for the long-term treatment of pulmonary hypertension (PHT). Because these 2 vasodilators act through different pathways (release of cGMP or cAMP, respectively), we compared the pulmonary vasodilator capacity of each.

METHODS AND RESULTS

A total of 15 children with congenital heart disease and PHT who had elevated pulmonary vascular resistance (preoperative, n=10; immediately postoperative, n=5) were first given 20 ppm of iNO for 10 minutes; then, after baseline values were reached again, they were given aerosolized iloprost at 25 ng. kg(-1). min(-1) for another 10 minutes. Finally, iNO and iloprost were given simultaneously for 10 minutes. With iNO, the pulmonary vascular resistance and systemic vascular resistance ratio decreased from 0.48+/-0.38 to 0.27+/-0.16 (P:<0.001). Similarly, iloprost decreased the ratio from 0.49+/-0.38 to 0.26+/-0.11 (P:<0.05). The combination had no additional effect on the resistance ratio. Plasma cGMP increased from 17.6+/-11.9 to 34.7+/-21.4 nmol/L during iNO (P:<0.01), and plasma cAMP increased from 55.7+/-22.9 to 65.1+/-21.2 nmol/L during iloprost inhalation (P:<0.05).

CONCLUSIONS

In children with PHT and congenital heart disease, both iNO and aerosolized iloprost are equally effective in selectively lowering pulmonary vascular resistance through an increase in cGMP or cAMP, respectively. However, the combination of both vasodilators failed to prove more potent than either substance alone. Aerosolized iloprost might be an alternative to iNO for early testing of vascular reactivity and for the postoperative treatment of acute PHT.

Recognition and management of pulmonary hypertension

Pulmonary hypertension (mean pulmonary arterial pressure > 20mm Hg at rest or > 30mm Hg during exercise) occurs (i) as primary pulmonary hypertension (no known underlying cause), (ii) as persistent pulmonary hypertension of the newborn or (iii) secondary to a variety of lung and cardiovascular diseases. In the last 10 to 15 years there have been significant advances in the medical management of this debilitating and life-threatening disorder. The main drugs in current use are anticoagulants (warfarin, heparin) and vasodilators, especially oral calcium antagonists, intravenous prostacyclin (prostaglandin I2; epoprostenol) and inhaled nitric oxide. Calcium antagonists, (e.g. nifedipine, diltiazem) are used chiefly in primary pulmonary hypertension. They are effective in patients who give a pulmonary vasodilator response to an acute challenge with a short acting vasodilator (e.g. prostacyclin, nitric oxide or adenosine), and are used in doses greater than are usual in the treatment of other cardiovascular disorders. Prostacyclin, given by continuous intravenous infusion, is effective in patients even if they do not respond to an acute vasodilator challenge. The long term benefit in these patients is thought to reflect the antiproliferative effects of the drug and/or its ability to inhibit platelet aggregation. It is used either as long term therapy or as a bridge to transplantation. Inhaled nitric oxide, which is used mainly in persistent pulmonary hypertension of the newborn, has the particular benefit of being pulmonary selective, due to its route of administration and rapid inactivation. Anticoagulants have a specific role in the treatment of pulmonary thromboembolic pulmonary hypertension and are also used routinely in patients with primary pulmonary hypertension. Nondrug treatments for pulmonary hypertension include (i) supplemental oxygen (> or = 15 h/day), which is the primary therapy in patients with pulmonary hypertension secondary to chronic obstructive pulmonary disease and (ii) heart-lung or lung transplantation, which nowadays is regarded as a last resort. Different types of pulmonary hypertension require different treatment strategies. Future advances in the treatment of pulmonary hypertension may come from the use of drug combinations, the development of new drugs, such as endothelin antagonists, nitric oxide donors and potassium channel openers, or the application of gene therapy.

Efficacy of inhaled prostanoids in experimental pulmonary hypertension

OBJECTIVES

To evaluate the effects of inhaled prostacyclin (PGI2) and inhaled as well as intravenous prostaglandin E1 (PGE1) on thromboxane A2 mimetic-induced pulmonary vasoconstriction. Active pulmonary vasoconstriction was to be distinguished from passive resistance to blood flow.

DESIGN

Prospective, randomized, crossover study.

SETTING

Experimental animal laboratory.

SUBJECTS

Eight anesthetized and paralyzed sheep.

INTERVENTIONS

The stable thromboxane A2 mimetic, U46619, was infused in increasing dosage to obtain a stable pulmonary hypertension of approximately 30 mm Hg. Subsequently, PGE1 aerosol (0.6, 6, 58, 259 ng/kg/min), intravenous PGE, (0.5 microg/kg/min), or PGI2 aerosol (27 ng/kg/min) were administered in randomized order.

MEASUREMENTS AND MAIN RESULTS

Active pulmonary vasoconstriction was assessed by determining the pulmonary pressure-flow relationship (PPFR). For measurement of pulmonary artery flow, an ultrasound flow probe was placed around the pulmonary artery after a sternotomy. Pulmonary arterial pressure was measured with a pulmonary artery flotation catheter. Flow was varied by partial occlusion of the inferior vena cava or incremental opening of an arterio-venous fistula between the large neck vessels. The primary end points were the slope of the resulting linear pressure-flow relationship, and pulmonary vascular resistance (PVR). Infusion of U46619 increased the slope of the PPFR (2.9+/-0.7 vs. 4.2+/-1.2 mm Hg/L/min [median+/-semi-interquartile range]; p < or = .05), and PVR (221+/-20 vs. 424+/-57 dyne x sec/cm5) (p < .05). Neither dose of PGE1 aerosol induced changes of the slope of PPFR or PVR. In contrast, intravenous administration of the same drug reduced the slope of the PPFR (4.0+/-1.0 vs. 3.1+/-0.4) (p < .05) but left PVR unchanged. Inhalation of PGI2 reduced both the slope of the PPFR, slightly but significantly, and PVR (424+/-98 vs. 323+/-26 dyne x sec/cm5) (p < .05).

CONCLUSIONS

This study is the first to show reduction of active pulmonary vasoconstriction by PGI2 aerosol. Neither inhalation nor intravenous administration of PGE1 reduced PVR but the latter reduced the slope of PPFR. We conclude that PGE1 has potential for pulmonary vasodilation, but that it is ineffective as an aerosol, even in high doses, in sheep. PVR may fail to reflect drug-induced pulmonary vasodilation.

Pulmonary hypertension and selective pulmonary vasodilators in acute lung injury

The pulmonary circulation and the mechanisms which generate pulmonary hypertension are reviewed. The role of these mechanisms in the common pulmonary hypertensive states are analysed, particularly those in acute lung injury. Management options are discussed, with particular emphasis on the use of selective pulmonary vasodilators.

Improvement of oxygenation induced by aerosolized prostacyclin in a preterm infant with persistent pulmonary hypertension of the newborn

OBJECTIVE

Case report on the effect of inhaled prostacyclin in a preterm infant (28 weeks gestational age) with respiratory distress syndrome complicated by marked hypoxemia due to persistent pulmonary hypertension of the newborn. Treatment with surfactant, hyperventilation, and elevation of systemic blood pressure had failed to improve oxygenation.

MEASURES

A solution containing 10 micrograms PGI2/ml was aerosolized by the SPAG-2 aerosol-generator and then introduced into the afferent loop of the ventilatory circuit.

RESULTS

Oxygenation improved dramatically and worsened when aerosolization was withdrawn. Intravenous prostacyclin had no additional effect on oxygenation. We observed no side effects on blood pressure and no bleeding complications. Inhalation was stopped after 40 hours and the baby was successfully weaned from the ventilator after 108 hours.

CONCLUSION

Inhaled PGI2 had a beneficial effect on the oxygenation of a preterm neonate with persistent pulmonary hypertension of the newborn.

Inhaled prostacyclin for treatment of pulmonary hypertension after cardiac surgery or heart transplantation: a pharmacodynamic study

OBJECTIVE

To study the effects of incremental concentrations of inhaled aerosolized prostacyclin (PGI2) on pulmonary and systemic hemodynamics after cardiac surgery or heart transplantation.

DESIGN

Pharmacodynamic dose-response study.

SETTING

Cardiothoracic intensive care unit (ICU) at a university hospital.

PARTICIPANTS

Nine patients with pulmonary hypertension after cardiac surgery or heart transplantation and an elevated pulmonary vascular resistance (PVR) (> 20 dynes.sec.cm-5) treated in the ICU with inotropic support were studied.

INTERVENTIONS

Inhaled prostacyclin was administered at concentrations of 2.5, 5.0, and 10.0 micrograms/mL using conventional systems for nebulization.

MEASUREMENTS AND MAIN RESULTS

Pulmonary and systemic hemodynamics as well as right ventricular (RV) function variables (n = 3) were measured before, during, and 10 and 20 minutes after inhalation of PGI2. Inhaled PGI2 induced a dose-dependent decrease in PVR and the transpulmonary gradient (which decreased by -29% and -26%, respectively) at an inhaled concentration of 10 micrograms/mL. Inhaled PGI2 caused no changes in systemic vascular resistance. Central venous pressure decreased during PGI2 inhalation with no change in stroke volume, indicating an improvement in RV performance, which was particularly obvious in one patient with RV failure after heart transplantation. Twenty minutes after discontinuation of inhaled PGI2, hemodynamic variables returned to baseline.

CONCLUSIONS

Inhaled PGI2 induces a dose-dependent selective pulmonary vasodilation and may improve RV performance after cardiac surgery complicated by pulmonary hypertension and RV failure.

Eight hours' inhalation of prostacyclin (PGI2) in healthy lambs: effects on tracheal, bronchial, and alveolar morphology

OBJECTIVE

To study potential toxic effects of long-term (8 h) inhaled prostacyclin (PGI2) on respiratory tract tissues.

DESIGN

In a prospective, randomized order, either PGI2 (n =7) or normal saline (n = 7) was aerosolized during a time period of 8 h in healthy lambs.

SETTING

Institute for Surgical Research of the Ludwig-Maximilians University of Munich.

ANIMALS

14 health, anesthetized, ventilated lambs.

INTERVENTIONS

All animals were endotracheally intubated followed by tracheotomy. PGI2 solution or normal saline was administered with a jet nebulizer (delivery rate 4-10 ml/h; mass median diameter of aerosol particles 3.1 microns).

MEASUREMENTS AND RESULTS

Histomorphological changes after 8-h inhalation of PGI2 solution were compared to those after 8-h inhalation of normal saline. Tracheal and bronchoalveolar tissues were examined by light and electron microscopy in order to assess tissue damage induced by inhaled PGI2. Pathological changes were ranked by a blinded observer following a graduation system ranging from "absence of pathological changes" to "maximal pathological changes". Abnormalities were restricted to the trachea (focal flattening of the epithelium, loss of cilia, slight inflammatory cell infiltration) and alveolar tissue (focal alveolar septal thickening with slight inflammatory cell infiltration), but no statistically significant differences between the PGI2 and control groups were encountered.

CONCLUSION

Our findings indicate the absence of PGI2 aerosol-related respiratory tissue damage after 8-h inhalation of PGI2.

Inhalation of prostacyclin (PGI2) for 8 hours does not produce signs of acute pulmonary toxicity in healthy lambs

OBJECTIVE

To study the potential side effects and toxicity of inhaling prostacyclin (PGI2) aerosol for 8 h.

DESIGN

In a prospective, randomized study 14 healthy lambs received either PGI2 (n = 7) or 0.9% NaCl (n = 7) as an aerosol for 8 h.

SETTING

Institute for Surgical Research of the Ludwig-Maximilians-University of Munich.

INTERVENTIONS

All animals were studied under general anesthesia in a prone position. They were first intubated endotracheally and later tracheotomized. PGI2 solution (median dose 28 ng/kg per min) or 0.9% NaCl was administered with a jet nebulizer (delivery rate 4-10 ml/h; mass median diameter of aerosol particles 3.1 microns). Bronchoalveolar lavage was performed before and after the inhalation period to collect epithelial lining fluid of alveoli.

MEASUREMENTS AND RESULTS

Hemodynamic and respiratory parameters, systemic resorption (plasma levels of 6-keto-prostaglandin-F 1 alpha), in vitro bleeding time, collagen-induced platelet aggregation and global biochemical and cellular composition of the epithelial lining fluid were examined in order to assess the side effects and signs of acute pulmonary toxicity induced by inhaled PGI2. No statistically significant differences were found between the PGI2 and the control groups for any of the parameters examined.

CONCLUSION

Inhalation of PGI2 (28 ng/kg per min) over a period of 8 h in healthy lambs does not produce major side effects or acute pulmonary toxicity.