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 Pulmonary Vasodilators in COVID-19 Infection: A Systematic Review and Meta-Analysis

Introduction: Inhaled pulmonary vasodilators (IPVD) have been previously studied in patients with non-coronavirus disease-19 (COVID-19) related acute respiratory distress syndrome (ARDS). The use of IPVD has been shown to improve the partial pressure of oxygen in arterial blood (PaO₂), reduce fraction of inspired oxygen (FiO₂) requirements, and ultimately increase PaO₂/FiO₂ (P/F) ratios in ARDS patients. However, the role of IPVD in COVID-19 ARDS is still unclear. Therefore, we performed this meta-analysis to evaluate the role of IPVD in COVID-19 patients. Methods: Comprehensive literature search of PubMed, Embase, Web of Science and Cochrane Library databases from inception through April 22, 2022 was performed for all published studies that utilized IPVD in COVID-19 ARDS patients. The single arm studies and case series were combined for a 1-arm meta-analysis, and the 2-arm studies were combined for a 2-arm meta-analysis. Primary outcomes for the 1-arm and 2-arm meta-analyzes were change in pre- and post-IPVD P/F ratios and mortality, respectively. Secondary outcomes for the 1-arm meta-analysis were change in pre- and post-IPVD positive end-expiratory pressure (PEEP) and lung compliance, and for the 2-arm meta-analysis the secondary outcomes were need for endotracheal intubation and hospital length of stay (LOS). Results: 13 single arm retrospective studies and 5 case series involving 613 patients were included in the 1-arm meta-analysis. 3 studies involving 640 patients were included in the 2-arm meta-analysis. The pre-IPVD P/F ratios were significantly lower compared to post-IPVD, but there was no significant difference between pre- and post-IPVD PEEP and lung compliance. The mortality rates, need for endotracheal intubation, and hospital LOS were similar between the IPVD and standard therapy groups. Conclusion: Although IPVD may improve oxygenation, our investigation showed no benefits in terms of mortality compared to standard therapy alone. However, randomized controlled trials are warranted to validate our findings.

Role of low-dose tissue plasminogen activator in patients with refractory hypoxia due to presumed microthrombi in pulmonary vasculature in coronavirus disease 2019: A case series and review of the literature

Severe hypoxia due to coronavirus disease 2019 (COVID-19) is challenging in the intensive care unit (ICU). It is often unresponsive to mechanical ventilation at high positive end-expiratory pressure and the fraction of inspired oxygen combination. The cause of such worsening hypoxia may be microvascular thrombosis in the pulmonary vascular system because of the procoagulant nature of COVID-19 infection. Confirming the diagnosis with computed tomographic pulmonary angiography is not always possible, as the patients are too sick to be shifted. Tissue plasminogen activator (tPA) is recommended for pulmonary thromboembolism with hypotension and worsening hypoxia, as confirmed by computed tomography pulmonary angiography. However, its role in worsening hypoxia because of presumed microthrombi in the pulmonary vasculature in COVID-19 is unclear. We present six cases from our ICU where we used low-dose tPA in COVID-19 refractory hypoxia with presumed microthrombi in the pulmonary vasculature (oligemic lung field, refractory hypoxia, increased D dimer, electrocardiographic features of pulmonary embolism, and right ventricular strain on echocardiography). Oxygenation improved within 6 h and was maintained for up to 48 h in all patients. Therefore, there is a possible role of microthrombi in the mechanism of hypoxia in this setting. An early decision to start low-dose tPA may improve the outcome. However, all patients finally succumbed to sepsis and multiorgan failure later in their course. A systematic review of the literature has also been performed on the mechanism of thrombosis and the use of tPA in hypoxia due to COVID-19.

Effects of Extracorporeal Membrane Oxygenation Initiation on Oxygenation and Pulmonary Opacities

Introduction

There is limited data on the impact of extracorporeal membrane oxygenation (ECMO) on pulmonary physiology and imaging in adult patients. The current study sought to evaluate the serial changes in oxygenation and pulmonary opacities after ECMO initiation.

Methods

Records of patients started on veno-venous, or veno-arterial ECMO were reviewed (n=33; mean (SD): age 50(16) years; Male: Female 20:13). Clinical and laboratory variables before and after ECMO, including daily PaO₂ to FiO₂ ratio (PFR), were recorded. Daily chest radiographs (CXR) were prospectively appraised in a blinded fashion and scored for the extent and severity of opacities using an objective scoring system.

Results

ECMO was associated with impaired oxygenation as reflected by the drop in median PFR from 101 (interquartile range, IQR: 63-151) at the initiation of ECMO to a post-ECMO trough of 74 (IQR: 56-98) on post-ECMO day 5. However, the difference was not statistically significant. The appraisal of daily CXR revealed progressively worsening opacities, as reflected by a significant increase in the opacity score (Wilk’s Lambda statistic 7.59, p=0.001). During the post-ECMO period, a >10% increase in the opacity score was recorded in 93.9% of patients. There was a negative association between PFR and opacity scores, with an average one-unit decrease in the PFR corresponding to a +0.010 increase in the opacity score (95% confidence interval: 0.002 to 0.019, p-value=0.0162). The median opacity score on each day after ECMO initiation remained significantly higher than the pre-ECMO score. The most significant increase in the opacity score (9, IQR: -8 to 16) was noted on radiographs between pre-ECMO and forty-eight hours post-ECMO. The severity of deteriorating oxygenation or pulmonary opacities was not associated with hospital survival.

Conclusions

The use of ECMO is associated with an increase in bilateral opacities and a deterioration in oxygenation that starts early and peaks around 48 hours after ECMO initiation.