TOTAL ARTERIOVENOUS CO2 REMOVAL - SIMPLIFYING EXTRACORPOREAL SUPPORT FOR RESPIRATORY-FAILURE

Background. To reduce the complexity, complications, and cost of conve ntional extracorporeal membrane oxygenation, we have developed a techn ique of simplified arteriovenous extracorporeal CO2 removal (AVCO(2)R) with a low-resistance membrane gas exchanger for total CO2 removal to provide lung rest in the setting of severe respiratory failure. Metho ds. We initially used AVCO(2)R in healthy animals to quantify the gas exchange capabilities of the system and establish ventilator managemen t protocols for the subsequent studies of AVCO(2)R in a large animal m odel of respiratory failure secondary to a severe smoke inhalation inj ury. Results. In healthy sheep the maximum spontaneous arteriovenous f low ranged from 1,350 to 1,500 mL/min, whereas CO2 removal plateaued a t a blood flow of approximately 1,000 mL/min in which 112 +/- 3 mL/min CO2 was removed, allowing an 84% reduction in the minute ventilation of from 6.9 +/- 0.8 L/min to 1.1 +/- 0.4 L/min (p < 0.01) without trig gering hypercapnia. A subsequent reduction in extracorporeal flow at a reduced minute volume led to the development of hypercapnia only if i t decreased to less than 500 mL/min. We also applied AVCO(2)R in mecha nically ventilated sheep with a severe smoke inhalation injury and rem oved 95% (111 +/- 4 mL/min) of the total CO2 production. This allowed the minute ventilation to be reduced by 95% and the peak inspiratory p ressures by 52% (both p < 0.05) over 6 hours and produced no adverse h emodynamic effects. The partial pressure of arterial oxygen was mainta ined above 100 mm Hg at a maximally reduced minute volume. The mean AV CO(2)R now was 1,213 +/- 29 mL/min, averaging 27% +/- 1% of the cardia c output. Conclusions. We conclude that AVCO(2)R in a simple arteriove nous shunt is a less complicated technique than extracorporeal membran e oxygenation and is capable of total CO2 removal that allows a signif icant reduction in the minute ventilation and peak airway pressure dur ing severe respiratory failure. (C) 1997 by The Society of Thoracic Su rgeons.