Inhaled prostacyclin (PGI2) versus inhaled nitric oxide in adult respiratory distress syndrome

A Narrative Review on the Administration of Inhaled Prostaglandins in Critically Ill Adult Patients With Acute Respiratory Distress Syndrome

OBJECTIVE

To describe the effect of inhaled prostaglandins on both oxygenation and mortality in critically ill patients with acute respiratory distress syndrome (ARDS), with a focus on safety and efficacy in coronavirus disease 2019 (COVID-19)-associated ARDS and non-COVID-19 ARDS.

DATA SOURCES

A literature search of MEDLINE was performed using the following search terms: inhaled prostaglandins, inhaled epoprostenol, inhaled nitric oxide, ARDS, critically ill. All abstracts were reviewed.

STUDY SELECTION AND DATA EXTRACTION

Relevant English-language reports and studies conducted in humans between 1980 and June 2023 were considered.

DATA SYNTHESIS

Data regarding inhaled prostaglandins and their effect on oxygenation are limited but show a benefit in patients who respond to therapy, and data pertaining to their effect on mortality is scarce. Concerns exist regarding the formulation of inhaled epoprostenol (iEPO) utilized in addition to modes of medication delivery; however, the limited data surrounding their use have shown a reasonable safety profile. Other avenues and beneficial effects may exist with inhaled prostaglandins, such as use in COVID-19-associated ARDS or non-COVID-19 ARDS patients undergoing noninvasive mechanical ventilation or during patient transport.

RELEVANCE TO PATIENT CARE AND CLINICAL PRACTICE

The use of inhaled prostaglandins can be considered in critically ill patients with COVID-19-associated ARDS or non-COVID-19 ARDS who are experiencing difficulties with oxygenation refractory to nonpharmacologic strategies.

CONCLUSIONS

The use of iEPO and other inhaled prostaglandins requires further investigation to fully elucidate their effects on clinical outcomes, but it appears these medications may have a potential benefit in COVID-19-associated ARDS and non-COVID-19 ARDS patients with refractory hypoxemia but with little effect on mortality.

Adjunctive Therapies in Acute Respiratory Distress Syndrome

Despite significant advances in understanding acute respiratory distress syndrome (ARDS), mortality rates remain high. The appropriate use of adjunctive therapies can improve outcomes, particularly for patients with moderate to severe hypoxia. In this review, the authors discuss the evidence basis behind prone positioning, recruitment maneuvers, neuromuscular blocking agents, corticosteroids, pulmonary vasodilators, and extracorporeal membrane oxygenation and considerations for their use in individual patients and specific clinical scenarios. Because the heterogeneity of ARDS poses challenges in finding universally effective treatments, an individualized approach and continued research efforts are crucial for optimizing the utilization of adjunctive therapies and improving patient outcomes.

The Use of an Inspiration-Synchronized Vibrating Mesh Nebulizer for Prolonged Inhalative Iloprost Administration in Mechanically Ventilated Patients-An In Vitro Model

Mechanically ventilated patients suffering from acute respiratory distress syndrome (ARDS) frequently receive aerosolized iloprost. Because of prostacyclin's short half-life, prolonged inhalative administration might improve its clinical efficacy. But, this is technically challenging. A solution might be the use of inspiration-synchronized vibrating mesh nebulizers (VMNsyn), which achieve high drug deposition rates while showing prolonged nebulization times. However, there are no data comparing prolonged to bolus iloprost nebulization using a continuous vibrating mesh nebulizer (VMNcont) and investigating the effects of different ventilation modes on inspiration-synchronized nebulization. Therefore, in an in vitro model of mechanically ventilated adults, a VMNsyn and a VMNcont were compared in volume-controlled (VC-CMV) and pressure-controlled continuous mandatory ventilation (PC-CMV) regarding iloprost deposition rate and nebulization time. During VC-CMV, the deposition rate of the VMNsyn was comparable to the rate obtained with the VMNcont, but 10.9% lower during PC-CMV. The aerosol output of the VMNsyn during both ventilation modes was significantly lower compared to the VMNcont, leading to a 7.5 times longer nebulization time during VC-CMV and only to a 4.2 times longer nebulization time during PC-CMV. Inspiration-synchronized nebulization during VC-CMV mode therefore seems to be the most suitable for prolonged inhalative iloprost administration in mechanically ventilated patients.

Right ventricle-specific therapies in acute respiratory distress syndrome: a scoping review

OBJECTIVE

To summarize knowledge and identify gaps in evidence regarding treatment of right ventricular dysfunction (RVD) in acute respiratory distress syndrome (ARDS).

DATA SOURCES

We conducted a comprehensive search of MEDLINE, Embase, CINAHL, Web of Science, and the Cochrane Central Register of Controlled Trials.

STUDY SELECTION

Studies were included if they reported effects of treatments on right ventricular function, whether or not the intent was to modify right ventricular function.

DATA EXTRACTION

Data extraction was performed independently and in duplicate by two authors. Data items included the study design, patient population, type of intervention, comparison group, and RV-specific outcomes.

DATA SYNTHESIS

Of 1,430 studies screened, 51 studies reporting on 1,526 patients were included. By frequency, the included studies examined the following interventions: ventilator settings (29.4%), inhaled medications (33.3%), extracorporeal life support (13.7%), intravenous or oral medications (13.7%), and prone positioning (9.8%). The majority of the studies were non-randomized experimental studies (53%), with the next most common being case reports (16%). Only 5.9% of studies were RCTs. In total, 27% of studies were conducted with the goal of modifying RV function.

CONCLUSIONS

Given the prevalence of RVD in ARDS and its association with mortality, the dearth of research on this topic is concerning. This review highlights the need for prospective trials aimed at treating RV dysfunction in ARDS.

Use of Aerosolized Prostacyclins in Critically Ill Patients and Association With Clinical Outcomes

Aerosolized prostacyclins are frequently used in patients with severe acute respiratory distress syndrome and refractory hypoxia. Previous studies have shown improvement in oxygenation with use of pulmonary vasodilators such as iloprost and epoprostenol; however, there is no head-to-head comparison between these agents.

OBJECTIVES

To compare the effects of inhaled epoprostenol and inhaled iloprost in critically ill patients with refractory hypoxia.

DESIGN SETTING AND PARTICIPANTS

We performed a retrospective cohort analysis of patients admitted to the ICUs at the University of Oklahoma Health Sciences Center between 2015 and 2018. Adult patients who received aerosolized epoprostenol or iloprost for more than 4 hours were included in the analysis.

MAIN OUTCOMES AND MEASURES

The primary endpoint measured was to compare the change in Pao₂/Fio₂ ratio between patients treated with iloprost compared with epoprostenol. Secondary outcomes measured were 90-day in-hospital mortality and improvement in vasopressor requirements.

RESULTS

A total of 126 patients were included in the study, 95 of whom received iloprost (75%) and 31 patients (25%) received epoprostenol. There were significant improvements in Pao₂/Fio₂ ratio in both the iloprost and epoprostenol group. Patients in the epoprostenol group appeared to have a higher 90-day mortality compared with the iloprost group. However, our study was not powered to detect a mortality difference and this finding likely represents a sicker population in the epoprostenol group and prescription bias. The use of iloprost was associated with higher vasopressor requirements in the first 12 hours of administration, an association was not observed in the epoprostenol group.

CONCLUSIONS AND RELEVANCE

In this retrospective cohort analysis, use of both pulmonary vasodilators was associated with similar improvement in gas exchange. The mortality difference observed likely represents difference in severity of illness. Further studies are needed to corroborate these findings.

Inhaled Nitric Oxide vs Epoprostenol During Acute Respiratory Failure: An Observational Target Trial Emulation

BACKGROUND

The inhaled vasodilators nitric oxide and epoprostenol may be initiated to improve oxygenation in mechanically ventilated patients with severe acute respiratory failure (ARF); however, practice patterns and head-to-head comparisons of effectiveness are unclear.

RESEARCH QUESTION

What are the practice patterns and comparative effectiveness for inhaled nitric oxide and epoprostenol in severe ARF?

STUDY DESIGN AND METHODS

Using a large US database (Premier Healthcare Database), we identified adult patients with ARF or ARDS who were mechanically ventilated and started on inhaled nitric oxide, epoprostenol, or both. Leveraging large hospital variation in the choice of initial inhaled vasodilator, we compared the effectiveness of inhaled nitric oxide with that of epoprostenol by limiting analysis to patients admitted to hospitals that exclusively used either inhaled nitric oxide or epoprostenol. The primary outcome of successful extubation was modeled using multivariate Fine-Grey competing risk (death or hospice discharge) time-to-event models.

RESULTS

Among 11,200 patients (303 hospitals), 6,366 patients (56.8%) received inhaled nitric oxide first, 4,720 patients (42.1%) received inhaled epoprostenol first, and 114 patients (1.0%) received both therapies on the same day. One hundred four hospitals (34.3%; 1,666 patients) exclusively used nitric oxide and 118 hospitals (38.9%; 1,812 patients) exclusively used epoprostenol. No differences were found in the likelihood of successful extubation between patients admitted to nitric oxide-only hospitals vs those admitted to epoprostenol-only hospitals (subdistribution hazard ratio, 0.97; 95% CI, 0.80-1.18). Also no differences were found in total hospital costs or death. Results were robust to multiple sensitivity analyses.

INTERPRETATION

Large variation exists in the use of initial inhaled vasodilator for respiratory failure across US hospitals. Comparative effectiveness analyses identified no differences in outcomes based on inhaled vasodilator type.

The Use of Inhaled Epoprostenol for Acute Respiratory Distress Syndrome Secondary due to COVID-19: A Case Series

Introduction

Inhaled epoprostenol (iEpo) is a pulmonary vasodilator used to treat refractory respiratory failure, including that caused by Coronavirus 2019 (COVID-19) pneumonia.

Aim of Study

To describe the experience at three teaching hospitals using iEpo for severe respiratory failure due to COVID-19 and evaluate its efficacy in improving oxygenation.

Methods

Fifteen patients were included who received iEpo, had confirmed COVID-19 and had an arterial blood gas measurement in the 12 hours before and 24 hours after iEpo initiation.

Results

Eleven patients received prone ventilation before iEpo (73.3%), and six (40%) were paralyzed. The partial pressure of arterial oxygen to fraction of inspired oxygen (P/F ratio) improved from 95.7 mmHg to 118.9 mmHg (p=0.279) following iEpo initiation. In the nine patients with severe ARDS, the mean P/F ratio improved from 66.1 mmHg to 95.7 mmHg (p=0.317). Ultimately, four patients (26.7%) were extubated after an average of 9.9 days post-initiation.

Conclusions

The findings demonstrated a trend towards improvement in oxygenation in critically ill COVID-19 patients. Although limited by the small sample size, the results of this case series portend further investigation into the role of iEpo for severe respiratory failure associated with COVID-19.

Randomized, Placebo-controlled Trial of Inhaled Treprostinil for Patients at Risk for Acute Respiratory Distress Syndrome

Rationale: Inhaled treprostinil may improve oxygenation and have additional antiinflammatory effects in early acute hypoxemic respiratory failure, potentially preventing or reducing the severity of acute respiratory distress syndrome (ARDS).Objectives: To determine whether administration of inhaled treprostinil to patients at risk for ARDS is feasible, safe, and efficacious.Methods: We performed a double-blind, placebo-controlled, single-center randomized pilot trial at a quaternary care academic medical center. Patients with acute hypoxemia due to pneumonia or signs of low-pressure pulmonary edema with a unilateral or bilateral infiltrate on chest imaging and a 4 L/min supplemental oxygen requirement not requiring positive pressure ventilation were evaluated. Randomized patients received study drug or placebo (2:1 ratio). Treatment was initiated at 6 breaths every 4 hours and titrated up to 12 breaths. Subjects were maintained on treatment for 7 days and then tapered off over a period of 4 days. Study drug was stopped if positive pressure ventilation was required (invasive or noninvasive).Results: Fourteen patients were enrolled over a period of 31 months. Baseline characteristics were not significantly different between treatment groups with respect to age, sex, race, Acute Physiologic Assessment and Chronic Health Evaluation score, lung injury prediction score, or baseline mean oxygen saturation as measured by pulse oximetry (Sp_O2):fraction of inspired oxygen (Fi_O2) ratio. Trends in daily baseline and 30-minute postdose Sp_O2:Fi_O2 ratio for all treatment points were not significantly different between placebo and treprostinil. Four patients required positive pressure ventilation in the treprostinil group versus one in the placebo group.Conclusions: Inhaled treprostinil administration is feasible in patients at risk for ARDS but was not associated with improvement in the Sp_O2:Fi_O2 ratio relative to placebo. Drug-associated adverse events were not severe nor unexpected based on the known adverse effect profile of inhaled treprostinil. The clinical benefit of this intervention is unclear at this time in the absence of larger studies.Clinical trial registered with Clinicaltrials.gov (NCT02370095).

Physiological mechanism and spatial distribution of increased alveolar dead-space in early ARDS: An experimental study

BACKGROUND

We aimed to investigate the physiological mechanism and spatial distribution of increased physiological dead-space, an early marker of ARDS mortality, in the initial stages of ARDS. We hypothesized that: increased dead-space results from the spatial redistribution of pulmonary perfusion, not ventilation; such redistribution is not related to thromboembolism (ie, areas with perfusion = 0 and infinite ventilation-perfusion ratio, V ˙ / Q ˙ ), but rather to moderate shifts of perfusion increasing V ˙ / Q ˙ in non-dependent regions.

METHODS

Five healthy anesthetized sheep received protective ventilation for 20 hours, while endotoxin was continuously infused. Maps of voxel-level lung ventilation, perfusion, V ˙ / Q ˙ , CO₂ partial pressures, and alveolar dead-space fraction were estimated from positron emission tomography at baseline and 20 hours.

RESULTS

Alveolar dead-space fraction increased during the 20 hours (+0.05, P = .031), mainly in non-dependent regions (+0.03, P = .031). This was mediated by perfusion redistribution away from non-dependent regions (-5.9%, P = .031), while the spatial distribution of ventilation did not change, resulting in increased V ˙ / Q ˙ in non-dependent regions. The increased alveolar dead-space derived mostly from areas with intermediate V ˙ / Q ˙ (0.5≤ V ˙ / Q ˙ ≤10), not areas of nearly "complete" dead-space ( V ˙ / Q ˙ >10).

CONCLUSIONS

In this early ARDS model, increases in alveolar dead-space occur within 20 hours due to the regional redistribution of perfusion and not ventilation. This moderate redistribution suggests changes in the interplay between active and passive perfusion redistribution mechanisms (including hypoxic vasoconstriction and gravitational effects), not the appearance of thromboembolism. Hence, the association between mortality and increased dead-space possibly arises from the former, reflecting gas-exchange inefficiency due to perfusion heterogeneity. Such heterogeneity results from the injury and exhaustion of compensatory mechanisms for perfusion redistribution.

Endothelial Damage in Acute Respiratory Distress Syndrome

The pulmonary endothelium is a metabolically active continuous monolayer of squamous endothelial cells that internally lines blood vessels and mediates key processes involved in lung homoeostasis. Many of these processes are disrupted in acute respiratory distress syndrome (ARDS), which is marked among others by diffuse endothelial injury, intense activation of the coagulation system and increased capillary permeability. Most commonly occurring in the setting of sepsis, ARDS is a devastating illness, associated with increased morbidity and mortality and no effective pharmacological treatment. Endothelial cell damage has an important role in the pathogenesis of ARDS and several biomarkers of endothelial damage have been tested in determining prognosis. By further understanding the endothelial pathobiology, development of endothelial-specific therapeutics might arise. In this review, we will discuss the underlying pathology of endothelial dysfunction leading to ARDS and emerging therapies. Furthermore, we will present a brief overview demonstrating that endotheliopathy is an important feature of hospitalised patients with coronavirus disease-19 (COVID-19).

Inhaled epoprostenol utilization pattern after implementation of an administration policy

Epoprostenol, a pulmonary vasodilator, is used to reduce pulmonary artery pressure. Its inhaled administration results in ventilation and perfusion matching with oxygenation improvement. Epoprostenol is used as treatment for various conditions, particularly acute respiratory distress syndrome (ARDS) and pulmonary arterial hypertension. In 2018, Baylor University Medical Center implemented a policy for inhaled epoprostenol utilization aimed at standardizing clinical practice. This study analyzed epoprostenol utilization patterns in patients with ARDS after implementation of this administration policy. Drug responders and nonresponders were compared for clinical outcomes and physiologic changes before and after use, and policy compliance was evaluated. Of 79 eligible patients, 30 fulfilled inclusion criteria: 14 (47%) had ARDS and 16 (53%) had non-ARDS. In all patients with ARDS, epoprostenol was a second rescue agent after neuromuscular blockade, prone positioning, corticosteroids, and extracorporeal membrane oxygenation. Epoprostenol was associated with statistically significant improvement of oxygenation before and after utilization in patients with ARDS (ratio of arterial oxygen partial pressure to fractional inspired oxygen 70 vs 140, respectively; P = 0.04). Overall, 10 (71%) ARDS patients were epoprostenol responders; 9 (56%) were deemed responders among subjects with non-ARDS. Comparison of outcomes between responders and nonresponders showed no statistically significant variations. Policy compliance was obtained in 24 (80%) patients.

A Simple Effective Pharmacological Treatment of Hypoxemia During One-Lung Ventilation

Hypoxemia during one-lung ventilation is a challenge in the clinical practice. Moving from the results of the study conducted by Choi et al., we discuss the possibility to modulate hypoxemia by administering iloprost via inhalation, in the light of the physiological mechanisms.

The Effects of Iloprost on Oxygenation During One-Lung Ventilation for Lung Surgery: A Randomized Controlled Trial

Hypoxemia can occur during one-lung ventilation (OLV) in thoracic surgery, leading to perioperative complications. Inhaled iloprost is a selective pulmonary vasodilator with efficacy in patients with pulmonary hypertension. The purpose of this study was to evaluate the effects of off-label inhaled iloprost on oxygenation during OLV in patients undergoing lung surgery. Seventy-two patients who were scheduled for elective video-assisted thoracoscopic lobectomy were assigned to receive an inhaled nebulizer of distilled water (control group), 10 μg iloprost (IL10 group), or 20 μg iloprost (IL20 group). Arterial and venous blood gas and hemodynamic analyses were obtained. Changes in partial pressure of oxygen in arterial blood (PaO₂), after the initiation of OLV and the resumption two-lung ventilation (TLV), were similar in all three groups. However, PaO₂ in the IL10 group was comparable to that in the control group, whereas PaO₂ in the IL20 group was significantly higher than that in the control group at 10, 20, and 30 min after administration of iloprost (275.1 ± 50.8 vs. 179.3 ± 38.9, p < 0.0001; 233.9 ± 39.7 vs. 155.1 ± 26.5, p < 0.0001; and 224.6 ± 36.4 vs. 144.0 ± 22.9, p < 0.0001, respectively). The shunt fraction in the IL20 group was significantly higher than that in the control group after administration of iloprost (26.8 ± 3.1 vs. 32.2 ± 3.4, p < 0.0001; 24.6 ± 2.2 vs. 29.9 ± 3.4, p < 0.0001; and 25.3 ± 2.0 vs. 30.8 ± 3.1, p < 0.0001, respectively). Administration of inhaled iloprost during OLV improves oxygenation and decreases intrapulmonary shunt.

Models of deposition, pharmacokinetics, and intersubject variability in respiratory drug delivery

INTRODUCTION

Aerosol drug delivery to the lungs via inhalation is widely used in the treatment of respiratory diseases. The deposition pattern of inhaled particles within the airways of the respiratory tract is key in determining the initial delivered dose. Thereafter, dose-dependent processes including drug release or dissolution, clearance, and absorption influence local and systemic exposure to inhaled drugs over time.

AREAS COVERED

Empirical correlations, numerical simulation, and in vitro airway geometries that permit improved prediction of extrathoracic and lung deposition fractions in a variety of age groups and breathing conditions are described. Efforts to link deposition models with pharmacokinetic models predicting lung and systemic exposure to inhaled drugs over time are then reviewed. Finally, new methods to predict intersubject variability in extrathoracic deposition, capturing variability in both size and shape of the upper airways, are highlighted.

EXPERT OPINION

Recent work has been done to expand in vitro deposition experiments to a wide range of age groups and breathing conditions, to link regional lung deposition models with pharmacokinetic models, and to improve prediction of intersubject variability. These efforts are improving predictive understanding of respiratory drug delivery, and will aid the development of new inhaled drugs and delivery devices.

Salvage therapies for refractory hypoxemia in ARDS

Acute Respiratory Distress Syndrome (ARDS) is a condition of varied etiology characterized by the acute onset (within 1 week of the inciting event) of hypoxemia, reduced lung compliance, diffuse lung inflammation and bilateral opacities on chest imaging attributable to noncardiogenic (increased permeability) pulmonary edema. Although multi-organ failure is the most common cause of death in ARDS, an estimated 10-15% of the deaths in ARDS are caused due to refractory hypoxemia, i.e.- hypoxemia despite lung protective conventional ventilator modes. In these cases, clinicians may resort to other measures with less robust evidence -referred to as "salvage therapies". These include proning, 48 h of paralysis early in the course of ARDS, various recruitment maneuvers, unconventional ventilator modes, inhaled pulmonary vasodilators, and Extracorporeal membrane oxygenation (ECMO). All the salvage therapies described have been associated with improved oxygenation, but with the exception of proning and 48 h of paralysis early in the course of ARDS, none of them have a proven mortality benefit. Based on the current evidence, no salvage therapy has been shown to be superior to the others and each of them is associated with its own risks and benefits. Hence, the order of application of these therapies varies in different institutions and should be applied following a risk-benefit analysis specific to the patient and local experience. This review explores the rationale, evidence, advantages and risks behind each of these strategies.

Perioperative Management of the Adult Patient on Venovenous Extracorporeal Membrane Oxygenation Requiring Noncardiac Surgery

The use of venovenous extracorporeal membrane oxygenation is increasing worldwide. These patients often require noncardiac surgery. In the perioperative period, preoperative assessment, patient transport, choice of anesthetic type, drug dosing, patient monitoring, and intraoperative and postoperative management of common patient problems will be impacted. Furthermore, common monitoring techniques will have unique limitations. Importantly, patients on venovenous extracorporeal membrane oxygenation remain subject to hypoxemia, hypercarbia, and acidemia in the perioperative setting despite extracorporeal support. Treatments of these conditions often require both manipulation of extracorporeal membrane oxygenation settings and physiologic interventions. Perioperative management of anticoagulation, as well as thresholds to transfuse blood products, remain highly controversial and must take into account the specific procedure, extracorporeal membrane oxygenation circuit function, and patient comorbidities. We will review the physiologic management of the patient requiring surgery while on venovenous extracorporeal membrane oxygenation.

Aerosolized prostacyclins for acute respiratory distress syndrome (ARDS)

BACKGROUND

Acute respiratory distress syndrome (ARDS) is a critical condition that is associated with high mortality and morbidity. Aerosolized prostacyclin has been used to improve oxygenation despite the limited evidence available so far.This review was originally published in 2010 and updated in 2017.

OBJECTIVES

To assess the benefits and harms of aerosolized prostacyclin in adults and children with ARDS.

SEARCH METHODS

In this update, we searched CENTRAL (2017, Issue 4); MEDLINE (OvidSP), Embase (OvidSP), ISI BIOSIS Previews, ISI Web of Science, LILACS, CINAHL (EBSCOhost), and three trials registers. We handsearched the reference lists of the latest reviews, randomized and non-randomized trials, and editorials, and cross-checked them with our search of MEDLINE. We contacted the main authors of included studies to request any missed, unreported or ongoing studies. The search was run from inception to 5 May 2017.

SELECTION CRITERIA

We included all randomized controlled trials (RCTs), irrespective of publication status, date of publication, blinding status, outcomes published or language. We contacted trial investigators and study authors to retrieve relevant and missing data.

DATA COLLECTION AND ANALYSIS

Three authors independently abstracted data and resolved any disagreements by discussion. Our primary outcome measure was all-cause mortality. We planned to perform subgroup and sensitivity analyses to assess the effect of aerosolized prostacyclin in adults and children, and on various clinical and physiological outcomes. We assessed the risk of bias through assessment of methodological trial components and the risk of random error through trial sequential analysis.

MAIN RESULTS

We included two RCTs with 81 participants.One RCT involved 14 critically ill children with ARDS (very low quality of evidence), and one RCT involved 67 critically ill adults (very low quality evidence).Only one RCT (paediatric trial) provided data on mortality and found no difference between intervention and control. However, this trial was eligible for meta-analysis due to a cross-over design.We assessed the benefits and harms of aerosolized prostacyclin. One RCT found no difference in improvement of partial pressure of oxygen in arterial blood/fraction of inspired oxygen (PaO₂/FiO₂) ratio (mean difference (MD) -25.35, 95% confidence interval (CI) -60.48 to 9.78; P = 0.16; 67 participants, very low quality evidence).There were no adverse events such as bleeding or organ dysfunction in any of the included trials. Due to the limited number of RCTs, we were unable to perform the prespecified subgroup and sensitivity analyses or trial sequential analysis.

AUTHORS' CONCLUSIONS

We are unable to tell from our results whether the intervention has an important effect on mortality because the results were too imprecise to rule out a small or no effect. Therefore, no current evidence supports or refutes the routine use of aerosolized prostacyclin for people with ARDS. There is an urgent need for more RCTs.

Comparison of inhaled milrinone, nitric oxide and prostacyclin in acute respiratory distress syndrome

AIM

To evaluate the safety and efficacy of inhaled milrinone in acute respiratory distress syndrome (ARDS).

METHODS

Open-label prospective cross-over pilot study where fifteen adult patients with hypoxemic failure meeting standard ARDS criteria and monitored with a pulmonary artery catheter were recruited in an academic 24-bed medico-surgical intensive care unit. Random sequential administration of iNO (20 ppm) or nebulized epoprostenol (10 μg/mL) was done in all patients. Thereafter, inhaled milrinone (1 mg/mL) alone followed by inhaled milrinone in association with inhaled nitric oxide (iNO) was administered. A jet nebulization device synchronized with the mechanical ventilation was use to administrate the epoprostenol and the milrinone. Hemodynamic measurements and partial pressure of arterial oxygen (PaO₂) were recorded before and after each inhaled therapy administration.

RESULTS

The majority of ARDS were of pulmonary cause (n = 13) and pneumonia (n = 7) was the leading underlying initial disease. Other pulmonary causes of ARDS were: Post cardiopulmonary bypass (n = 2), smoke inhalation injury (n = 1), thoracic trauma and pulmonary contusions (n = 2) and aspiration (n = 1). Two patients had an extra pulmonary cause of ARDS: A polytrauma patient and an intra-abdominal abscess Inhaled nitric oxide, epoprostenol, inhaled milrinone and the combination of inhaled milrinone and iNO had no impact on systemic hemodynamics. No significant adverse events related to study medications were observed. The median increase of PaO₂ from baseline was 8.8 mmHg [interquartile range (IQR) = 16.3], 6.0 mmHg (IQR = 18.4), 6 mmHg (IQR = 15.8) and 9.2 mmHg (IQR = 20.2) respectively with iNO, epoprostenol, inhaled milrinone, and iNO added to milrinone. Only iNO and the combination of inhaled milrinone and iNO had a statistically significant effect on PaO₂.

CONCLUSION

When comparing the effects of inhaled NO, milrinone and epoprostenol, only NO significantly improved oxygenation. Inhaled milrinone appeared safe but failed to improve oxygenation in ARDS.

State of the Art: Bridging to lung transplantation using artificial organ support technologies

Lung transplantation increasingly is being performed in recipients of higher risk and acuity. A subset of these patients has severely abnormal gas exchange and/or right ventricular dysfunction, such that artificial organ support strategies are required to bridge patients to lung transplantation. We review the rationales and currently used and potential strategies for bridging to lung transplantation and characterize bridging outcomes. Based on physiologic reasoning and a study of the existing literature, we provide a working strategy for bridging to lung transplantation.

Nitric Oxide Signaling and Clinical Alternatives to Nitric Oxide

Nitric oxide has been implicated in numerous biological processes, particularly those involved with the cardiovascular system. Nitric oxide production is closely regulated and influenced by a number of factors in both health and disease. Nitric oxide is involved in maintaining the vascular system in its healthy, nondiseased state by producing vasorelaxation which enhances blood flow and prevents both leukocyte and platelet adhesion to the vascular wall. Dysfunctional endothelial cell nitric oxide production has been implicated in a number of disease states, including hypertension and atherosclerosis, and has been associated with adverse cardiac events. Various recent therapies may exert their beneficial effects in part by enhancing endothelial nitric oxide bloavallability. Nitric oxide has been used therapeutically in a number of cardiorespiratory disease states. An improved understanding of the pathologic processes underlying these diseases has resulted in several alternative agents being investigated and used clinically.

Catastrophic Antiphospholipid Syndrome

Catastrophic antiphospholipid syndrome is a rapidly progressive life-threatening disease that causes multiple organ thromboses and dysfunction in the presence of antiphospholipid antibodies. A high index of clinical suspicion and careful investigation are required to make an early diagnosis so that treatment with anticoagulation and corticosteroids can be initiated; plasma exchange and/or intravenous immunoglobulins can be added if the life-threatening condition persists. Despite aggressive treatment and intensive care unit management, patients with catastrophic antiphospholipid syndrome have a 48% mortality rate, primarily attributable to cardiopulmonary failure. This article reviews the current information on the etiopathogenesis, clinical manifestations, diagnosis, management, and prognosis of catastrophic antiphospholipid syndrome.

Clinical and Economic Impact of Formulary Conversion From Inhaled Flolan to Inhaled Veletri for Refractory Hypoxemia in Critically Ill Patients

BACKGROUND

Flolan (iFLO) and Veletri (iVEL) are 2 inhaled epoprostenol formulations. There is no published literature comparing these formulations in critically ill patients with refractory hypoxemia.

OBJECTIVE

To compare efficacy, safety, and cost outcomes in patients who received either iFLO or iVEL for hypoxic respiratory failure.

METHODS

This was a retrospective, single-center analysis of adult, mechanically ventilated patients receiving iFLO or iVEL for improvement in oxygenation. The primary end point was the change in the PaO2/FiO2 ratio after 1 hour of pulmonary vasodilator therapy. Secondary end points assessed were intensive care unit (ICU) length of stay (LOS), hospital LOS, duration of study therapy, duration of mechanical ventilation, mortality, incidence of adverse events, and cost.

RESULTS

A total of 104 patients were included (iFLO = 52; iVEL = 52). More iFLO patients had acute respiratory distress syndrome compared with the iVEL group (61.5 vs 34.6%; P = 0.01). There was no difference in the change in the PaO2/FiO2 ratio after 1 hour of therapy (33.04 ± 36.9 vs 31.47 ± 19.92; P = 0.54) in the iFLO and iVEL groups, respectively. Patients who received iVEL had a shorter duration of mechanical ventilation (P < 0.001) and ICU LOS (P < 0.001) but not hospital LOS (P = 0.86) and duration of therapy (P = 0.36). No adverse events were attributed to pulmonary vasodilator therapy, and there was no difference in cost.

CONCLUSIONS

We found no difference between iFLO and iVEL when comparing the change in the PaO2/FiO2 ratio, safety, and cost in hypoxic, critically ill patients. There were differences in secondary outcomes, likely a result of differences in underlying indication for inhaled epoprostenol.

The role of inhaled prostacyclin in treating acute respiratory distress syndrome

Acute respiratory distress syndrome (ARDS) is a syndrome of acute lung injury that is characterized by noncardiogenic pulmonary edema and severe hypoxemia second to a pathogenic impairment of gas exchange. Despite significant advances in the area, mortality remains high among ARDS patients. High mortality and a limited spectrum of therapeutic options have left clinicians searching for alternatives, spiking interest in selective pulmonary vasodilators (SPVs). Despite the lack of robust evidence, SPVs are commonly employed for their therapeutic role in improving oxygenation in patients who have developed refractory hypoxemia in ARDS. While inhaled epoprostenol (iEPO) also impacts arterial oxygenation by decreasing ventilation-perfusion (V/Q) mismatching and pulmonary shunt flow, this effect is not different from inhaled nitric oxide (iNO). The most effective and safest dose for yielding a clinically significant increase in PaO2 and reduction in pulmonary artery pressure (PAP) appears to be 20-30 ng/kg/min in adults and 30 ng/kg/min in pediatric patients. iEPO appears to have a ceiling effect above these doses in which no additional benefit may be derived. iNO and iEPO have shown similar efficacy profiles; however, they differ with respect to cost and ease of therapeutic administration. The most beneficial effects of iEPO have been seen in adult patients with secondary ARDS as compared with primary ARDS, most likely due to the difference in etiology of the two disease states, and in patients suffering from baseline right ventricular heart failure. Although iEPO has demonstrated improvements in hemodynamic parameters and oxygenation in ARDS patients, due to the limited number of randomized clinical trials and the lack of studies investigating mortality, the use of iEPO cannot be recommended as standard of care in ARDS. iEPO should be reserved for those refractory to traditional therapies.

Noninferiority of Inhaled Epoprostenol to Inhaled Nitric Oxide for the Treatment of ARDS

Background: Inhaled nitric oxide and inhaled epoprostenol have been evaluated for the management of hypoxemia in acute respiratory distress syndrome, with clinical trials demonstrating comparable improvements in oxygenation. However, these trials have several limitations, making it difficult to draw definitive conclusions regarding clinical outcomes. Objective: The aim of this study was to evaluate the noninferiority and safety of inhaled epoprostenol compared with inhaled nitric oxide in mechanically ventilated acute respiratory distress syndrome (ARDS) patients with a primary outcome of ventilator-free days from day 1 to day 28. Methods: This was a retrospective, noninterventional, propensity-matched, noninferiority cohort study. Propensity score for receipt of inhaled nitric oxide was developed and patients were matched accordingly using a prespecified algorithm. Secondary objectives included evaluating day 28 intensive care unit–free days, changes in PaO2/FiO2 ratio after inhalation therapy initiation, and hospital mortality. Safety endpoints assessed included hypotension, methemoglobinemia, renal dysfunction, rebound hypoxemia, significant bleeding, and thrombocytopenia. Results: Ninety-four patients were included, with 47 patients in each group. Patients were well-matched with similar baseline characteristics, except patients in inhaled nitric oxide group had lower PaO2/FiO2 ratio. Management of ARDS was similar between groups. Mean difference in ventilator-free days between inhaled epoprostenol and inhaled nitric oxide was 2.16 days (95% confidence interval = −0.61 to 4.9), with lower limit of 95% confidence interval greater than the prespecified margin, hence satisfying noninferiority. There were no differences in any secondary or safety outcomes. Conclusions: Inhaled epoprostenol was noninferior to inhaled nitric oxide with regard to ventilator-free days from day 1 to day 28 in ARDS patients.

Management of Right Heart Failure in the Intensive Care Unit

Right heart failure is a clinical syndrome of various causes that commonly involves failure of the right ventricle (RV). The hemodynamic hallmark of the syndrome is increasing central venous pressure and worsening cardiac output with a rising RV end-diastolic pressure. When dealing with RV failure, clinicians must assess and optimize the intravascular volume state, support RV contractility, and address any pathologic elevations of afterload so that systemic perfusion is preserved. Despite these measures, there may still be a need to offer rescue interventions to the failing RV in carefully selected patients.

The use of inhaled prostaglandins in patients with ARDS: a systematic review and meta-analysis

OBJECTIVE

This study aimed to determine whether inhaled prostaglandins are associated with improvement in pulmonary physiology or mortality in patients with ARDS and assess adverse effects.

METHODS

The following data sources were used: PubMed, EMBASE, CINAHL, Cochrane Central Register of Controlled Trials, Cochrane Database of Systematic Reviews, reference lists, conference proceedings, and ClinicalTrials.gov. Studies selected included randomized controlled trials and nonrandomized studies. For data extraction, two reviewers independently screened titles and abstracts for eligibility. With regard to data synthesis, 25 studies (two RCTs) published over 21 years (1993-2014) were included. The PROSPERO registration number was CRD42014013180.

RESULTS

One randomized controlled trial showed no difference in the change in mean Pao2 to Fio2 ratio when comparing inhaled alprostadil to placebo: 141.2 (95% CI, 120.8-161.5) to 161.5 (95% CI, 134.6-188.3) vs 163.4 (95% CI, 140.8-186.0) to 186.8 (95% CI, 162.9-210.7), P = .21. Meta-analysis of the remaining studies demonstrated that inhaled prostaglandins were associated with improvement in Pao2 to Fio2 ratio (16 studies; 39.0% higher; 95% CI, 26.7%-51.3%), and Pao2 (eight studies; 21.4% higher; 95% CI, 12.2%-30.6%), and a decrease in pulmonary artery pressure (-4.8 mm Hg; 95% CI, -6.8 mm Hg to -2.8 mm Hg). Risk of bias and heterogeneity were high. Meta-regression found no association with publication year (P = .862), baseline oxygenation (P = .106), and ARDS etiology (P = .816) with the treatment effect. Hypotension occurred in 17.4% of patients in observational studies.

CONCLUSIONS

In ARDS, inhaled prostaglandins improve oxygenation and decrease pulmonary artery pressures and may be associated with harm. Data are limited both in terms of methodologic quality and demonstration of clinical benefit. The use of inhaled prostaglandins in ARDS needs further study.

Acute right ventricular dysfunction: real-time management with echocardiography

In critically ill patients, the right ventricle is susceptible to dysfunction due to increased afterload, decreased contractility, or alterations in preload. With the increased use of point-of-care ultrasonography and a decline in the use of pulmonary artery catheters, echocardiography can be the ideal tool for evaluation and to guide hemodynamic and respiratory therapy. We review the epidemiology of right ventricular failure in critically ill patients; echocardiographic parameters for evaluating the right ventricle; and the impact of mechanical ventilation, fluid therapy, and vasoactive infusions on the right ventricle. Finally, we summarize the principles of management in the context of right ventricular dysfunction and provide recommendations for echocardiography-guided management.

Emerging drugs for acute lung injury

INTRODUCTION

Acute respiratory distress syndromes (ARDS) are devastating disorders of overwhelming pulmonary inflammation and hypoxemia, resulting in high morbidity and mortality.

AREAS COVERED

The main pharmacological treatment strategies have focused on the attempted inhibition of excessive inflammation or the manipulation of the resulting physiological derangement causing respiratory failure. Additionally, such interventions may allow reduced occurence mechanical ventilation injury. Despite promising preclinical and small clinical studies, almost all therapies have been shown to be unsuccessful in large-scale randomized controlled trials. The evidence for pharmacological treatment for ARDS is reviewed. Potential future treatments are also presented.

EXPERT OPINION

We suggest for future clinical trials addressing prevention and early intervention to attenuate lung injury and progression to respiratory failure.

A review of inhaled nitric oxide and aerosolized epoprostenol in acute lung injury or acute respiratory distress syndrome

Acute respiratory distress syndrome (ARDS) and acute lung injury (ALI) are conditions associated with an estimated mortality of 40–50%. The use of inhaled vasodilators can help to improve oxygenation without hemodynamic effects. This article reviews relevant studies addressing the safety and efficacy of inhaled nitric oxide (iNO) and aerosolized epoprostenol (aEPO) in the treatment of life-threatening hypoxemia associated with ARDS and ALI. In addition, the article also provides a practicable guide to the clinical application of these therapies. Nine prospective randomized controlled trials were included for iNO reporting on changes in oxygenation or clinical outcomes. Seven reports of aEPO were examined for changes in oxygenation. Based on currently available data, the use of either iNO or aEPO is safe to use in patients with ALI or ARDS to transiently improve oxygenation. No differences have been observed in survival, ventilator-free days, or attenuation in disease severity. Further studies with consistent end points using standard delivery devices and standard modes of mechanical ventilation are needed to determine the overall benefit with iNO or aEPO.

Gas exchange and ventilation-perfusion relationships in the lung

This review provides an overview of the relationship between ventilation/perfusion ratios and gas exchange in the lung, emphasising basic concepts and relating them to clinical scenarios. For each gas exchanging unit, the alveolar and effluent blood partial pressures of oxygen and carbon dioxide (PO2 and PCO2) are determined by the ratio of alveolar ventilation to blood flow (V'A/Q') for each unit. Shunt and low V'A/Q' regions are two examples of V'A/Q' mismatch and are the most frequent causes of hypoxaemia. Diffusion limitation, hypoventilation and low inspired PO2 cause hypoxaemia, even in the absence of V'A/Q' mismatch. In contrast to other causes, hypoxaemia due to shunt responds poorly to supplemental oxygen. Gas exchanging units with little or no blood flow (high V'A/Q' regions) result in alveolar dead space and increased wasted ventilation, i.e. less efficient carbon dioxide removal. Because of the respiratory drive to maintain a normal arterial PCO2, the most frequent result of wasted ventilation is increased minute ventilation and work of breathing, not hypercapnia. Calculations of alveolar-arterial oxygen tension difference, venous admixture and wasted ventilation provide quantitative estimates of the effect of V'A/Q' mismatch on gas exchange. The types of V'A/Q' mismatch causing impaired gas exchange vary characteristically with different lung diseases.

Iloprost for idiopathic pulmonary arterial hypertension

Idiopathic pulmonary arterial hypertension is a rare but serious and life-threatening disease that leads to right heart failure and death within 2.8 years without specific treatment. This review focuses on the stable prostacyclin analog iloprost, its biologic action and pharmacology and, finally, on its clinical development, efficacy and safety in patients with idiopathic pulmonary arterial hypertension, which led to its approval for this indication. Furthermore, this review assesses the role of iloprost compared with other newly developed drugs, such as the endothelin receptor antagonist bosentan and the phosphodiesterase-5 inhibitor sildenafil, as well as other modes of application of prostacyclin and its analogs for the treatment of idiopathic pulmonary arterial hypertension. Based on the different modes of action of these substances, a combination of these treatments could be most promising for the future.

Gas exchange in the respiratory distress syndromes

This article describes the gas exchange abnormalities occurring in the acute respiratory distress syndrome seen in adults and children and in the respiratory distress syndrome that occurs in neonates. Evidence is presented indicating that the major gas exchange abnormality accounting for the hypoxemia in both conditions is shunt, and that approximately 50% of patients also have lungs regions in which low ventilation-to-perfusion ratios contribute to the venous admixture. The various mechanisms by which hypercarbia may develop and by which positive end-expiratory pressure improves gas exchange are reviewed, as are the effects of vascular tone and airway narrowing. The mechanisms by which surfactant abnormalities occur in the two conditions are described, as are the histological findings that have been associated with shunt and low ventilation-to-perfusion.

Iloprost improves gas exchange in patients with pulmonary hypertension and ARDS

OBJECTIVE

We hypothesized that nebulized iloprost would improve ventilation-perfusion matching in patients with pulmonary hypertension and ARDS as reflected by an improved Pao2/Fio2 ratio and Pao2 without adversely affecting lung mechanics or systemic hemodynamics.

METHODS

Patients with ARDS and pulmonary hypertension were enrolled. With constant ventilator settings, hemodynamics, airway pressures, and gas exchange measured at baseline were compared with values 30 min after administration of 10 μg nebulized iloprost, and again 30 min after a second, larger, 20 μg dose of iloprost, and then a final measurement 2 h after the second dose. The primary outcome variable was Pao2; secondary outcomes were Pao2/Fio2 ratio, mean arterial BP, and lung-compliance ventilatory equivalents for oxygen and CO2.

RESULTS

After informed consent was obtained, 20 patients (nine men, 11 women; median age, 59 years [interquartile range, 44-66 years]) with ARDS were enrolled. Baseline PaO2 improved from a mean (±SD) of 82 (13) mm Hg to 100 (25) mm Hg after both the first and second doses of iloprost, and the baseline mean (±SD) PaO2/FIO2 ratio of 177 (60) improved to 213 (67) and 212 (70) (all P<.01). PaCO2, peak and plateau airway pressures, systemic BP, and heart rate were not significantly changed after iloprost.

CONCLUSIONS

The improvement in gas exchange without any detrimental effects on pulmonary mechanics or systemic hemodynamics suggests nebulized iloprost may be a useful therapeutic agent to improve oxygenation in patients with ARDS.

TRIAL REGISTRY

ClinicalTrials.gov; No.: NCT01274481; URL: www.clinicaltrials.gov.

Cardiopulmonary interactions in acute lung injury

PURPOSE OF REVIEW

Through shared anatomy, pressures, and endothelial connections, the respiratory and cardiovascular systems affect each other in complex but clinically important ways.

RECENT FINDINGS

Lung injury has clinically important circulatory effects, especially with regards to right ventricular function. Mechanical ventilation and PEEP produce a host of circulatory consequences, some beneficial, some life-threatening. At the same time, circulatory impairments and treatments can magnify the impact of lung failure.

SUMMARY

Cardiopulmonary interactions underpin current views of fluid management and mechanical ventilation. Understanding cardiopulmonary interactions and their physiological basis has direct clinical relevance.

Inhaled epoprostenol vs inhaled nitric oxide for refractory hypoxemia in critically ill patients

PURPOSE

The purpose of this is to compare efficacy, safety, and cost outcomes in patients who have received either inhaled epoprostenol (iEPO) or inhaled nitric oxide (iNO) for hypoxic respiratory failure.

MATERIALS AND METHODS

This is a retrospective, single-center analysis of adult, mechanically ventilated patients receiving iNO or iEPO for improvement in oxygenation.

RESULTS

We evaluated 105 mechanically ventilated patients who received iEPO (52 patients) or iNO (53 patients) between January 2009 and October 2010. Most patients received therapy for acute respiratory distress syndrome (iNO 58.5% vs iEPO 61.5%; P=.84). There was no difference in the change in the partial pressure of arterial O2/fraction of inspired O2 ratio after 1 hour of therapy (20.58±91.54 vs 33.04±36.19 [P=.36]) in the iNO and iEPO groups, respectively. No difference was observed in duration of therapy (P=.63), mechanical ventilation (P=.07), intensive care unit (P=.67), and hospital lengths of stay (P=.26) comparing the iNO and iEPO groups. No adverse events were attributed to either therapy. Inhaled nitric oxide was 4.5 to 17 times more expensive than iEPO depending on contract pricing.

CONCLUSIONS

We found no difference in efficacy and safety outcomes when comparing iNO and iEPO in hypoxic, critically ill patients. Inhaled epoprostenol is associated with less drug expenditure than iNO.

Efficacy, Safety, and Medication Errors Associated with the Use of Inhaled Epoprostenol for Adults with Acute Respiratory Distress Syndrome: A Pilot Study

BACKGROUND:

Acute respiratory distress syndrome (ARDS) is a type of hypoxic respiratory failure that results from ventilation and perfusion mismatching. Inhaled epoprostenol induces relaxation of smooth muscle in pulmonary vasculature, leading to improved oxygenation.

OBJECTIVE:

To determine if the use of inhaled epoprostenol produced a 10% or greater increase in the ratio of arterial partial pressure of oxygen (PaO2) to fraction of inspired oxygen (FiO2) in ARDS patients and to review adverse events and medication errors.

METHODS:

An observational chart review was performed based on a report generated from the electronic medical record system. Patients who received at least 1 dose of inhaled epoprostenol from January 1, 2008, to December 31, 2010, at any hospital within the Florida Hospital Health System were considered for inclusion. Demographics, dose, duration of therapy, adverse effects, medication errors, and outcomes data were collected.

RESULTS:

Sixteen patients were included in the study. Oxygenation improved by 10% or more in 62.5% (10/16) of the patients, with an initial (within the first 4 hours) median increase of 44.5% in PaO2/FiO2. The mean (SD) starting dose was 30 (10) ng/kg/min. Medication errors were observed in 25% (4/16) of patients. Hypotension was the most frequently observed adverse event, with a rate of 18.8% (3/16).

CONCLUSIONS:

Based on study findings, inhaled epoprostenol may improve oxygenation in patients with ARDS, with findings suggesting a 62.5% response to therapy. The significance of these effects on improving survival remains unknown. The frequency of medication errors observed in this study poses a significant concern regarding the administration of epoprostenol. Further controlled prospective studies are needed to determine the role of inhaled epoprostenol in improving survival in patients with ARDS.

Clinical review: Acute respiratory distress syndrome - clinical ventilator management and adjunct therapy

Acute respiratory distress syndrome (ARDS) is a potentially devastating form of acute inflammatory lung injury with a high short-term mortality rate and significant long-term consequences among survivors. Supportive care, principally with mechanical ventilation, remains the cornerstone of therapy - although the goals of this support have changed in recent years - from maintaining normal physiological parameters to avoiding ventilator-induced lung injury while providing adequate gas exchange. In this article we discuss the current evidence base for ventilatory support and adjunctive therapies in patients with ARDS. Key components of such a strategy include avoiding lung overdistension by limiting tidal volumes and airway pressures, and the use of positive end-expiratory pressure with or without lung recruitment manoeuvres in patients with severe ARDS. Adjunctive therapies discussed include pharmacologic techniques (for example, vasodilators, diuretics, neuromuscular blockade) and nonpharmacologic techniques (for example, prone position, alternative modes of ventilation).

Acute effects of aerosolized iloprost in COPD related pulmonary hypertension - a randomized controlled crossover trial

Background

Inhaled iloprost potentially improves hemodynamics and gas exchange in patients with chronic obstructive pulmonary disease (COPD) and secondary pulmonary hypertension (PH).

Objectives

To evaluate acute effects of aerosolized iloprost in patients with COPD-associated PH.

Methods

A randomized, double blind, crossover study was conducted in 16 COPD patients with invasively confirmed PH in a single tertiary care center. Each patient received a single dose of 10 µg iloprost (low dose), 20 µg iloprost (high dose) and placebo during distinct study-visits. The primary end-point of the study was exercise capacity as assessed by the six minute walking distance.

Results

Both iloprost doses failed to improve six-minute walking distance (p = 0.36). Low dose iloprost (estimated difference of the means −1.0%, p = 0.035) as well as high dose iloprost (−2.2%, p<0.001) significantly impaired oxygenation at rest. Peak oxygen consumption and carbon dioxide production differed significantly over the three study days (p = 0.002 and p = 0.003, accordingly). As compared to placebo, low dose iloprost was associated with reduced peak oxygen consumption (−76 ml/min, p = 0.002), elevated partial pressure of carbon dioxide (0.27 kPa, p = 0.040) and impaired ventilation during exercise (−3.0l/min, p<0.001).

Conclusions

Improvement of the exercise capacity after iloprost inhalation in patients with COPD-associated mild to moderate PH is very unlikely.

Trial Registration

Controlled-Trials.com ISRCTN61661881

Respiratory manifestations of malaria

Respiratory distress develops in up to 25% of adults and 40% of children with severe falciparum malaria. Its diverse causes include respiratory compensation of metabolic acidosis, noncardiogenic pulmonary edema, concomitant pneumonia, and severe anemia. Patients with severe falciparum, vivax, and knowlesi malaria may develop acute lung injury (ALI) and ARDS, often several days after antimalarial drug treatment. ARDS rates, best characterized for severe Plasmodium falciparum, are 5% to 25% in adults and up to 29% in pregnant women; ARDS is rare in young children. ARDS pathophysiology centers on inflammatory-mediated increased capillary permeability or endothelial damage leading to diffuse alveolar damage that can continue after parasite clearance. The role of parasite sequestration in the pulmonary microvasculature is unclear, because sequestration occurs intensely in P falciparum, less so in P knowlesi, and has not been shown convincingly in P vivax. Because early markers of ALI/ARDS are lacking, fluid resuscitation in severe malaria should follow the old adage to "keep them dry." Bacteremia and hospital-acquired pneumonia can complicate severe malaria and may contribute to ALI/ARDS. Mechanical ventilation can save life in ALI/ARDS. Basic critical care facilities are increasingly available in tropical countries. The use of lung-protective ventilation has helped to reduce mortality from malaria-induced ALI/ARDS, but permissive hypercapnia in unconscious patients is not recommended because increased intracranial pressure and cerebral swelling may occur in cerebral malaria. The best antimalarial treatment of severe malaria is IV artesunate.

Inhaled epoprostenol improves oxygenation in severe hypoxemia

BACKGROUND

Epoprostenol (Flolan), an inhalational epoprostenol vasodilator, increases pulmonary arterial flow and decreases pulmonary pressures, thereby improving gas exchange and arterial oxygenation. We evaluated the benefits of inhaled epoprostenol as a less expensive alternative to nitric oxide in ventilated surgical intensive care patients with severe hypoxemia.

METHODS

After institutional review board approval was obtained, the records of mechanically ventilated surgical intensive care unit patients who received epoprostenol as a therapy for severe hypoxia (SaO₂ < 90%) in a tertiary care referral center were retrospectively reviewed. Initial PaO₂/FIO₂ (P/F) ratio and oxygen saturation were compared with values at 12 and 48 hours after the administration of epoprostenol. One-way repeated-measures analysis of variance compared improvements in oxygenation. Further subgroup analyses evaluated differences among trauma, nontrauma patient subgroups, time to initiation of epoprostenol, and age.

RESULTS

During a 20 month-interval beginning February 2009, 36 patients (23 trauma and 13 nontrauma; age, 15-80 years) were treated. Epoprostenol significantly improved both P/F ratio and oxygen saturation in both trauma and nontrauma patients. Therewas no difference between subgroups. Larger improvements in P/F ratiowere seen when epoprostenolwas started within 7 days. Response between age groups did not differ significantly. Subgroup analysis of mortality (trauma, 60.9% vs. nontrauma, 61.5%) failed to show any differences.

CONCLUSION

Treatment with inhaled epoprostenol improved gas exchange in severely hypoxemic surgical patients. Earlier intervention (within 7 days of intubation) was more efficacious at improving oxygenation.

[Decubitus prone position in patient with extracorporeal CO2 removal device Novalung(®)]

OBJECTIVE

To describe the course of a patient with the extracorporeal CO2 removal device and discover the effect of Novalung on ventilation, considering the patient's prone position and its influence on the device's blood flow. To develop a protocol of managing and specific care of a patient with Novalung.

MATERIAL AND METHODS

A case report of a patient with Novalung in a tertiary hospital ICU unit is reported. Parameters considered are hemodynamic, respiratory, pharmacological, analytical, neuromonitoring, managing of the Novalung and length of decubitus prone cycles. Anova Test, Student's T test, Wilcoxon-Mann Whitney and Spearman correlation. Significance p <0.05.

RESULTS

A 46-year old women with nosocomial pneumonia and acute respiratory failure with indication of Novalung to decrease hypercapnia and optimize ventilatory management of refractory hypoxemia. ICU Stay 26 days, MBP 82 ± 9 mmHg, HR 110 ± 6l pm during the admission, monitoring PICCO 5 days CI 3.2 ± 0.8 l/min/m2, ELWI 33 ± 4 ml, continuous hemofiltration 13.2 days with a median removal 50 cc/h. Norepinephrine dose 0.68 ± 0.79 μ/kg/min for 15 days. Respiratory parameters during the admission: PO2 59 ± 13 mmHg, PCO2 68 ± 35 mmHg, SatO2 85 ± 12%, PO2/FIO2 69 ± 35, tidal volume 389 ± 141 cc. Novalung® 13 days, heparin dose 181.42 ± 145 mIU/Kg/min, Cephalin time 57.56 ± 16.41 sec, O2 flow 7 ± 3 l/min, median blood flow 1030 cc/h, interquartile range 1447-612 cc/h. Prone cycles 4, duration 53 ± 27 hours. With Novalung® PCO2 decreased regardless of position 66 ± 21:56 ± 9, p=0.005. Tidal volume 512 ± 67:267 ± 72, p=0.0001. Blood flow on supine-prone position 1053 ± 82:113 ± 112, p=0.001. There was no link between blood flow and PCO2 (p=0.2) and between O2 and PO2 flow (p=0.05). Specific care: pedal and tibial pulse monitoring, keep circuit safe to prevent and detect signs of bleeding, femoral arterial and venous catheter care, coagulation monitoring.

COMMENTS

During the use of Novalung protective, ventilation, low tidal volumes, decreased pressure plateau, PEEP and hypercapnia were achieved. Blood flow decreased in prone position, but the PCO2 did not increase. The device did not coagulate.

Pathophysiology of pulmonary hypertension in acute lung injury

Acute lung injury (ALI) and acute respiratory distress syndrome are characterized by protein rich alveolar edema, reduced lung compliance, and acute severe hypoxemia. A degree of pulmonary hypertension (PH) is also characteristic, higher levels of which are associated with increased morbidity and mortality. The increase in right ventricular (RV) afterload causes RV dysfunction and failure in some patients, with associated adverse effects on oxygen delivery. Although the introduction of lung protective ventilation strategies has probably reduced the severity of PH in ALI, a recent invasive hemodynamic analysis suggests that even in the modern era, its presence remains clinically important. We therefore sought to summarize current knowledge of the pathophysiology of PH in ALI.

Hypoxic Pulmonary Vasoconstriction

It has been known for more than 60 years, and suspected for over 100, that alveolar hypoxia causes pulmonary vasoconstriction by means of mechanisms local to the lung. For the last 20 years, it has been clear that the essential sensor, transduction, and effector mechanisms responsible for hypoxic pulmonary vasoconstriction (HPV) reside in the pulmonary arterial smooth muscle cell. The main focus of this review is the cellular and molecular work performed to clarify these intrinsic mechanisms and to determine how they are facilitated and inhibited by the extrinsic influences of other cells. Because the interaction of intrinsic and extrinsic mechanisms is likely to shape expression of HPV in vivo, we relate results obtained in cells to HPV in more intact preparations, such as intact and isolated lungs and isolated pulmonary vessels. Finally, we evaluate evidence regarding the contribution of HPV to the physiological and pathophysiological processes involved in the transition from fetal to neonatal life, pulmonary gas exchange, high-altitude pulmonary edema, and pulmonary hypertension. Although understanding of HPV has advanced significantly, major areas of ignorance and uncertainty await resolution.