(1794) Nebulized Epinephrine for Improvement of Oxygenation in Sheep With Severe ARDS on ECMO

Introduction: Extracorporeal membrane oxygenation (ECMO) is the final option for severe acute respiratory distress syndrome (ARDS) refractory to optimal medical management, including prone positioning and protective ventilation strategies. However, since ECMO has the potential for undesirable complications, the duration of ECMO should be minimized. In this study, we aimed to test the hypothesis that nebulized epinephrine improves oxygenation in sheep with severe ARDS on ECMO.

Methods: Adult female sheep (35-49 kg) were surgically prepared five days prior to the study. The sheep were then subjected to smoke inhalation injury to induce severe ARDS under anesthesia and analgesia. Veno-venous ECMO was initiated when the sheep's PaO2/FiO2 (P/F) ratio fell below 150 mmHg, 24 hours after smoke inhalation. Prior to ECMO initiation, sheep were placed on a mechanical ventilator with settings: APVcmv mode, respiratory rate 20 breaths/min, tidal volume 12 mL/kg, PEEP 5 cm H2O. After ECMO initiation, sheep were provided with lung-protective ventilation (tidal volume < 6 mL/kg). Immediately after ECMO initiation, the sheep were divided into two groups: control and treatment (4 mg epinephrine nebulized every 4 hours) groups. The sheep were monitored in a conscious state for 72 hours (total 96 hours study period).

Results: 21-23 Fr drainage cannulas were inserted through the right jugular vein and 19-21 Fr return cannulas were inserted through the right femoral vein. ECMO blood flow was maintained at 2.5-3.0 L/min in all sheep. In the control group, none of the sheep (0 out of 5) survived beyond 48 hours after ECMO initiation. In contrast, in the treatment group, 4 out of 5 sheep survived, with 2 surviving for 72 hours. No differences were observed between the two groups in terms of respiratory mechanics, hemodynamics, and oxygenation up to 48 hours after ECMO initiation. However, an improvement in the P/F ratio was observed in the treatment group after 48 hours. Additionally, a strong correlation between the P/F ratio and time for 72 hours was observed in the treatment group.

Conclusions: Nebulized epinephrine for severe ARDS requiring ECMO can improve oxygenation after 48 hours. This may potentially reduce the duration of ECMO.