Hemodynamic stability during arteriovenous carbon dioxide removal (AVCO₂R) for ARDS: a prospective randomized study in adult sheep

The hemodynamic effects of standardized pressure controlled ventilation (SMV) were compared with the algorithm directed decreased ventilation of extracorporeal percutaneous AVCO₂R in adult sheep with smoke/burn induced ARDS. Adult Suffolk ewes (n = 16) received smoke inhalation (36 breaths) + 40% TBSA III⁰ flame burn, followed by mechanical ventilation. With development of RDS (PaO₂/FiO₂<200 at 40-48 hrs) animals randomized to AVCO₂R (n = 8) or SHAM (n = 8). In the AVCO₂R group, the carotid artery (10F) and jugular vein (14F) were cannulated under general anesthesia. SHAM received identical surgical and medical management, sparing the vessels. Ventilator management for both groups entailed algorithm directed reductions in tidal volume (TV) for peak inspiratory pressure (PIP) < 30 cm H₂O, then respiratory rate (RR) for PaCO₂ < 40mm Hg. PaO₂ was > 60mm Hg by adjusting FiO₂ at PEEP 5cm H₂O. Hemodynamic data (heart rate, cardiac output, mean arterial pressure, pulmonary arterial pressure, and central venous pressure) were recorded every 6 hours following injury. AVCO₂R shunt flow (Qb) ranged from 820 to 968 mL/min (mean 870 mL/min) (11% to 14% CO). At 96 hours no significant differences were seen in any hemodynamic parameters (p > 0.05, all values AVCO₂R vs. SHAM) for heart rate (122 +/- 8.2 vs. 114.7 +/- 6.9), mean arterial pressure (123 +/- 6.5 vs. 115.7 +/- 3.1), cardiac output (6.6 +/- 0.7 vs. 7.1 +/- 0.6), pulmonary arterial pressure (25 +/- 1.9 vs. 26 +/- 3.0), pulmonary arterial wedge pressure (15 +/- 1.0 vs. 18 +/- 4.0), and central venous pressure (6 +/- 1.4 vs. 7 +/- 1.4). Despite the 11% to 14% shunt flow, AVCO₂R maintained stable hemodynamics comparable to SHAM throughout the study and at 96 hours. AVCO₂R as an alternative to SMV for severe respiratory failure is a simple and effective method of CO₂ removal that is well tolerated without adverse hemodynamic effects.