Rescuing Severe ARDS Patients
A new study from Harborview Medical Center in Seattle published in Critical Care Medicine explores whether a longer-term survival benefit accrues to those who receive rescue therapies for severe acute respiratory distress syndrome (ARDS).1
For many severe respiratory infections, including those due to emerging respiratory viruses like SARS, H5N1 influenza, and MERS, the final common pathway to death often includes severe ARDS with refractory hypoxemia not amenable to conventional ventilation. In such dire situations, various “rescue” therapies are often initiated. The efficacy of these therapies as well as the optimum timing of their use has been a matter of some debate in the critical care literature. This new study sheds some light on the long-term survival of patients with severe ARDS who have been treated with these approaches as a last resort.
Rescue therapies included in this study were prone-positioning, inhaled epoprostenol, or inhaled nitric oxide (NO). During the 2009 H1N1 influenza pandemic, these modalities saw increased use and a renewed interest in them emerged. The same is true of extracorporeal membrane oxygenation (ECMO)2, although this modality was excluded from this study. Since that time, rescue therapies have been used with increasing frequency, although (with the exception of prone position ventilation3) strong mortality benefit data is lacking, though transfer to a center adept at the management of ARDS has been shown to be beneficial.4
428 Patients Studied
The study retrospectively analyzed adults treated in the ICU between 2008-2011 who had severe ARDS. Rescue therapies were employed in 62 while conventional ventilation was used in 366. Sepsis and/or pneumonia were the most common primary diagnoses.
Several statistical differences were noted among those treated with rescue therapies:
- They were younger
- They were more likely to have sepsis and/or pneumonia
- Their oxygenation status was worse
The rescue therapies employed included inhaled therapy (NO or epoprostenol) in 58%, prone positioning in 21%, and a combined approach in 21%.1
Survival at 3 years
The primary endpoint of the study was 3-year survival. For the whole cohort, the probability of survival at 3 years was 56% and those treated with a rescue therapy had an increased risk of death. This was not surprising because the patients who received rescue therapies tended to be sicker by some measures and the authors acknowledge a likely selection bias. Almost all deaths occurred during hospitalization and few occurred post-discharge conferring a survival rate of 85% in those who made it to discharge.
Median ICU length of stay, median hospital length of stay, and cost was not significantly different in those who received rescue therapies1.
The Future of Rescue Therapies
This study highlights the fact that rescue therapies are often employed in the most severely ill patients—an element of selection bias—who, no matter the intervention, have a very high chance of death. However, if a person can be supported with rescue therapies and make it to hospital discharge their 3-year mortality is similar to those who are not treated with rescue therapies. Future work should try to look at specific subgroups such as influenza patients and bacterial pneumonia patients apart from other subgroups such as trauma in order to disentangle effects. Also, studying the use of rescue therapies as a bridge to venous-venous ECMO may also prove to be an important avenue of study. Finally, as an accompanying editorial suggests, perhaps rescue therapies should not be used exclusively in salvage situations as use earlier in the course of illness may alter the illness trajectory more dramatically.5
- Khandelwal N, Hough CL, Bansal A, et al. Long-Term Survival in Patients With Severe Acute Respiratory Distress Syndrome and Rescue Therapies for Refractory Hypoxemia. Crit Care Med 2014;42:1610–1618.
- Adalja AA, Watson M, Waldhorn RE, et al. A conceptual approach to improving care in pandemics and beyond: severe lung injury centers. J Crit Care 2013; 318:e9-e15.
- Guérin C, Reignier J, Richard JC, et al.PROSEVA Study Group. Prone positioning in severe acute respiratory distress syndrome. N Engl J Med 2013;368:2159–2168.
- Noah MA, Peek GJ, Finney SJ, et al. Referral to an extracorporeal membrane oxygenation center and mortality among patients with severe 2009 influenza A(H1N1). JAMA 2011. 306: 1659-1668.
- Keriwala RD, Rice TW. The ongoing challenge of evaluating rescue therapies in acute respiratory distress syndrome. Crit Care Med 2014; 42: 1727-1728.