Extracorporeal Carbon Dioxide Removal With the Hemolung in Patients With Acute Respiratory Failure: A Multicenter Retrospective Cohort Study*

Abstract

Objectives: Extracorporeal carbon dioxide removal (ECCO2R) devices are effective in reducing hypercapnia and mechanical ventilation support but have not been shown to reduce mortality. This may be due to case selection, device performance, familiarity, or the management. The objective of this study is to investigate the effectiveness and safety of a single ECCO2R device (Hemolung) in patients with acute respiratory failure and identify variables associated with survival that could help case selection in clinical practice as well as future research. Design: Multicenter, multinational, retrospective review. Setting: Data from the Hemolung Registry between April 2013 and June 2021, where 57 ICUs contributed deidentified data. Patients: Patients with acute respiratory failure treated with the Hemolung. The characteristics of patients who survived to ICU discharge were compared with those who died. Multivariable logistical regression analysis was used to identify variables associated with ICU survival. Interventions: None. Measurements and Main Results: Of the 159 patients included, 65 (41%) survived to ICU discharge. The survival was highest in status asthmaticus (86%), followed by acute respiratory distress syndrome (ARDS) (52%) and COVID-19 ARDS (31%). All patients had a significant reduction in Paco2 and improvement in pH with reduction in mechanical ventilation support. Patients who died were older, had a lower Pao2:Fio2 (P/F) and higher use of adjunctive therapies. There was no difference in the complications between patients who survived to those who died. Multivariable regression analysis showed non-COVID-19 ARDS, age less than 65 years, and P/F at initiation of ECCO2R to be independently associated with survival to ICU discharge (P/F 100–200 vs <100: odds ratio, 6.57; 95% CI, 2.03–21.33). Conclusions: Significant improvement in hypercapnic acidosis along with reduction in ventilation supports was noted within 4 hours of initiating ECCO2R. Non-COVID-19 ARDS, age, and P/F at commencement of ECCO2R were independently associated with survival.

Is It Time to Put Low-Flow Extracorporeal Carbon Dioxide Removal to REST?*

“…However, the conduct of ECCO 2 R is not just the process of cannulation and device initiation but comprises a bundle of interventions including sedation and ventilatory management, hemostatic management, manipulation of blood flow, and sweep gas flow rates along with high-quality supportive intensive care. In REST, less than 10% of patients underwent adjunctive prone positioning, compared with around 33% in the current registry study by Tiruvoipati et al (13). If the fewer complications reported by Tiruvoipati et al ( 13) are a true reflection of the Hemolung system in practice, one cannot misinterpret the absence of harm, as the presence of benefit.…”

“…The former study used an arteriovenous ECCO 2 R system with blood flow in the range of 1-2 L/min, with ECCO 2 R patients demonstrating a significant increase in ventilator-free days at day 28 versus controls, whereas in-hospital mortality in the intervention arm was just 17.5% (14). Anticoagulation was delivered for a target activated partial thromboplastin time (aPTT) of 40-50 seconds in the Xtravent study, compared with a target aPTT of 50-70 seconds in the current Registry study by Tiruvoipati et al (13). A single cannulation complication was noted among 148 patients, and median transfusion was extraordinarily low at just 1 (0.0-4.0) in the survivor group and 0 (0.0-3.0) in nonsurvivors.…”

“…Tiruvoipati et al (13) in their analysis, published in this issue of Critical Care Medicine, of the Hemolung Registry data confirm the lack of survival benefit with low-flow ECCO 2 R but report no significant differences in complication rate between survivors and nonsurvivors. This Registry is a voluntary data repository maintained by the device manufacturer; thus, selection bias may not be excluded.…”

“…The overall complication rate they report was much lower than suggested by randomized controlled trials of ECCO 2 R in ARDS/AHRF. Although the complication rates reported based on observational data from Hemolung Registry (159 patients, 57 centers) by Tiruvoipati et al (13) are very encouraging, how does one interpret this in the wake of the REST trial that reported a 25.3% adverse event rate while using the same device, of which approximately half were deemed serious? (10) The REST trial recruited 410 patients from 51 centers of whom 202 were randomized to receive ECCO 2 R using the Hemolung device.…”

“…If the fewer complications reported by Tiruvoipati et al ( 13) are a true reflection of the Hemolung system in practice, one cannot misinterpret the absence of harm, as the presence of benefit. Unfortunately, there are insufficient granular data presented by Tiruvoipati et al (13) to compare treatment efficacy (e.g., on driving pressure and respiratory rate reduction) and other relevant outcomes meaningfully with the REST cohort. Although much can be learned from observational data, the inherent biases involved in such studies must be supplanted by that gleaned from well-constructed RCTs, especially when reflecting on the potential patient harms posed by current low-flow ECCO 2 R devices.…”