The effect of augmented hemodynamics on blood flow during arteriovenous carbon dioxide removal

Arteriovenous carbon dioxide removal (AVCO(2)R) as an alternative treatment for acute respiratory distress syndrome uses a low resistance gas exchanger in a simple arteriovenous shunt to achieve total CO2 removal and allow lung rest. We have previously shown in our clinically relevant LD40 ovine model of smoke/burn induced acute respiratory distress syndrome that AVCO(2)R allows significant decreases in respiratory rate, tidal volume, peak airway pressure, and FiO(2), as compared with standard mechanical ventilation. In addition, we have shown in a prospective randomized outcomes study that AVCO(2)R increases ventilator free days, decreases ventilator dependent days, and significantly improves survival. The purpose of this study is to further define the limits of AVCO(2)R through hemodynamic augmentation and evaluation of peak end expiratory pressure (PEEP). Administration of an alpha agonist (phenylephrine) and a beta agonist (isoproterenol) increased mean arterial pressure (MAP) and cardiac output (CO), respectively. MAP increases ranged from 2.4% to 94.4% and CO increases ranged from 33% to 146%. Phenylephrine caused elevations in MAP (2.4-94.4%) and AVCO(2)R flow (9-67%), and CO never decreased more than 10%. lsoproterenol administration increased CO (33-146%), decreased MAP (9-54%), and decreased AVCO(2)R flow (11-42%). In a second group, PEEP was increased stepwise from 0 (baseline) to 20 cm H2O. Increasing PEEP did not result in significant hemodynamic changes (<10% change from baseline PEEP) for MAP, CO, or AVCO(2)R flow. In conclusion, alpha agonist administration increased AVCO(2)R blood flow, whereas beta agonist administration decreased MAP and AVCO(2)R blood flow, despite CO elevation. Various levels of PEEP are well tolerated and thus allow a range of options during AVCO(2)R.