Percutaneous extracorporeal arteriovenous carbon dioxide removal improves survival in respiratory distress syndrome: A prospective randomized outcomes study in adult sheep

Objective: Arteriovenous carbon dioxide removal (AVCO(2)R) uses a simple ar teriovenous shunt for CO, removal to minimize barotrauma/volutrauma from me chanical ventilation. We performed a prospective randomized outcomes study of AVCO(2)R in our new, clinically relevant model of respiratory distress s yndrome. Methods: Adult sheep (n = 18) received an LD50 severe smoke inhalation and 40% third-degree burn. When respiratory distress syndrome developed (Pao(2) /FIO2 < 200 at 40 to 48 hours), animals were randomized to the AVCO(2)R (n = 9) or sham group (n = 9) for 7 days. Ventilator management protocols mand ated reductions in minute ventilation, first tidal volume to peak inspirato ry pressure less than 30 cm H2O, then respiratory rate when Pace, was less than 40 mm Hg. Pao, was kept above 60 mm Hg by adjusting FIO2. When FIO2 wa s 0.21, animals were weaned. Results: The study required 2946 animal-hours of critical care with 696 AVC O(2)R hours. One died in each group during model development, AVCO(2)R flow from 820 mL/min to 970 mL/min (11% to 14% cardiac output) removed CO2 at a rate of 92 to 116 mL/min (mean 103 mL/min; 93%-97% of CO2 production). Hea rt rate, mean arterial pressure, cardiac output, and pulmonary arterial wed ge pressure remained relatively constant. Within 48 hours, AVCO(2)R allowed significant ventilator reductions versus baseline in the following measure ments: tidal volume (420 to 270 mL), peak inspiratory pressure (25 to 14 cm H2O), minute ventilation (13 to 5 L/min), respiratory rate (26 to 16 breat hs/min), and Fret (0.88 to 0.35). Ventilator-free days with AVCO(2)R were 3 .9 versus 0.2 (P < .01) for sham animals, and ventilator-dependent days wit h AVCO(2)R were 2.4 versus 6.2 (P < .01) for the 3 sham survivors. All 8 AV CO(2)R animals and 3 of 8 sham animals survived 7 days after randomization. Conclusions: Percutaneous AVCO(2)R achieved significant reduction in airway pressures, increased ventilator-free days, decreased ventilator-dependent days, and improved survival in a sheep model of respiratory distress syndro me.