Extracorporeal Carbon Dioxide Removal Enhanced by Lactic Acid Infusion in Spontaneously Breathing Conscious Sheep

Abstract

AbstractAbstract In a study of six spontaneously breathing conscious sheep connected to a minimally invasive circuit, extracorporeal blood acidification with lactic acid (acid load carbon dioxide removal) increased extracorporeal carbon dioxide removal by 50% compared with standard extracorporeal carbon dioxide removal. Although lactic acid infusion increased overall energy expenditure, feasibility safety and efficiency of acid load carbon dioxide removal were proved. Supplemental Digital Content is available in the text. Background The authors studied the effects on membrane lung carbon dioxide extraction (VCO 2 ML), spontaneous ventilation, and energy expenditure (EE) of an innovative extracorporeal carbon dioxide removal (ECCO 2 R) technique enhanced by acidification (acid load carbon dioxide removal [ALCO 2 R]) via lactic acid. Methods Six spontaneously breathing healthy ewes were connected to an extracorporeal circuit with blood flow 250 ml/min and gas flow 10 l/min. Sheep underwent two randomly ordered experimental sequences, each consisting of two 12-h alternating phases of ALCO 2 R and ECCO 2 R. During ALCO 2 R, lactic acid (1.5 mEq/min) was infused before the membrane lung. Caloric intake was not controlled, and animals were freely fed. VCO 2 ML, natural lung carbon dioxide extraction, total carbon dioxide production, and minute ventilation were recorded. Oxygen consumption and EE were calculated. Results ALCO 2 R enhanced VCO 2 ML by 48% relative to ECCO 2 R (55.3 ± 3.1 vs. 37.2 ± 3.2 ml/min; P less than 0.001). During ALCO 2 R, minute ventilation and natural lung carbon dioxide extraction were not affected (7.88 ± 2.00 vs. 7.51 ± 1.89 l/min, P = 0.146; 167.9 ± 41.6 vs. 159.6 ± 51.8 ml/min, P = 0.063), whereas total carbon dioxide production, oxygen consumption, and EE rose by 12% each (223.53 ± 42.68 vs. 196.64 ± 50.92 ml/min, 215.3 ± 96.9 vs. 189.1 ± 89.0 ml/min, 67.5 ± 24.0 vs. 60.3 ± 20.1 kcal/h; P less than 0.001). Conclusions ALCO 2 R was effective in enhancing VCO 2 ML. However, lactic acid caused a rise in EE that made ALCO 2 R no different from standard ECCO 2 R with respect to ventilation. The authors suggest coupling lactic acid–enhanced ALCO 2 R with active measures to control metabolism.