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Extracorporeal Carbon Dioxide Removal Enhanced by Lactic Acid Infusion in Spontaneously Breathing Conscious Sheep
Vittorio Scaravilli1, Stefan Kreyer, Slava Belenkiy
1From the Dipartimento Scienze della Salute, Università Milano-Bicocca, Monza, Italy (V.S., A.Z.); Comprehensive Intensive Care Research Task Area (V.S., S.K., S.B., K.L., Y.L., L.C.C., A.I.B.) and Damage Control Resuscitation Task Area (M.A.D.), United States Army Institute of Surgical Research, Fort Sam Houston, Texas; National Research Council, National Academies, Washington, D.C. (V.S., S.K.); Department of Anesthesiology and Intensive Care Medicine (S.K.) and Pediatric Department (K.L.), University Hospital Bonn, Bonn, Germany; and Dipartimento di Fisiopatologia Medico-Chirurgica e dei Trapianti, Università Degli Studi di Milano and Dipartimento di Anestesia, Rianimazione ed Emergenza Urgenza, Fondazione IRCCS Ca' Granda, Ospedale Maggiore Policlinico, Milan, Italy (A.P.).
Background:
The authors studied the effects on membrane lung carbon dioxide extraction (VCO2ML), spontaneous ventilation, and energy expenditure (EE) of an innovative extracorporeal carbon dioxide removal (ECCO2R) technique enhanced by acidification (acid load carbon dioxide removal [ALCO2R]) 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 ALCO2R and ECCO2R. During ALCO2R, lactic acid (1.5 mEq/min) was infused before the membrane lung. Caloric intake was not controlled, and animals were freely fed. VCO2ML, natural lung carbon dioxide extraction, total carbon dioxide production, and minute ventilation were recorded. Oxygen consumption and EE were calculated.
Results:
ALCO2R enhanced VCO2ML by 48% relative to ECCO2R (55.3 ± 3.1 vs. 37.2 ± 3.2 ml/min; P less than 0.001). During ALCO2R, 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:
ALCO2R was effective in enhancing VCO2ML. However, lactic acid caused a rise in EE that made ALCO2R no different from standard ECCO2R with respect to ventilation. The authors suggest coupling lactic acid-enhanced ALCO2R with active measures to control metabolism.
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