Regional blood acidification enhances extracorporeal carbon dioxide removal: a 48-hour animal study.
BACKGROUND
Extracorporeal carbon dioxide removal has been proposed to achieve protective ventilation in patients at risk for ventilator-induced lung injury. In an acute study, the authors previously described an extracorporeal carbon dioxide removal technique enhanced by regional extracorporeal blood acidification. The current study evaluates efficacy and feasibility of such technology applied for 48 h.


METHODS
Ten pigs were connected to a low-flow veno-venous extracorporeal circuit (blood flow rate, 0.25 l/min) including a membrane lung. Blood acidification was achieved in eight pigs by continuous infusion of 2.5 mEq/min of lactic acid at the membrane lung inlet. The acid infusion was interrupted for 1 h at the 24 and 48 h. Two control pigs did not receive acidification. At baseline and every 8 h thereafter, the authors measured blood lactate, gases, chemistry, and the amount of carbon dioxide removed by the membrane lung (VCO2ML). The authors also measured erythrocyte metabolites and selected cytokines. Histological and metalloproteinases analyses were performed on selected organs.


RESULTS
Blood acidification consistently increased VCO2ML by 62 to 78%, from 79 ± 13 to 128 ± 22 ml/min at baseline, from 60 ± 8 to 101 ± 16 ml/min at 24 h, and from 54 ± 6 to 96 ± 16 ml/min at 48 h. During regional acidification, arterial pH decreased slightly (average reduction, 0.04), whereas arterial lactate remained lower than 4 mEq/l. No sign of organ and erythrocyte damage was recorded.


CONCLUSIONS
Infusion of lactic acid at the membrane lung inlet consistently increased VCO2ML providing a safe removal of carbon dioxide from only 250 ml/min extracorporeal blood flow in amounts equivalent to 50% production of an adult man.
From the Dipartimento di Scienze della Salute, Università di Milano-Bicocca, Ospedale San Gerardo Nuovo dei Tintori, Monza, Italy (A.Z., P.M., S.R., V.S., M.G., D.F., N.P., and A.P.); Dipartimento di Patologia animale, Igiene e Sanità pubblica veterinaria, sez. di Biochimica e Fisiologia, Università degli studi di Milano, Milan, Italy (F.P. and M.A.); and Dipartimento di Scienze Farmacologiche e Biomolecolari (DiSFeB), Scuola di Scienze del Farmaco, Università degli studi di Milano, Milan, Italy (D.S.).
Alberto
A
Zanella
Paolo
P
Mangili
Sara
S
Redaelli
Vittorio
V
Scaravilli
Marco
M
Giani
Daniela
D
Ferlicca
Diletta
D
Scaccabarozzi
Federica
F
Pirrone
Mariangela
M
Albertini
Nicolò
N
Patroniti
Antonio
A
Pesenti
D000818:Animals; D001774:Blood Chemical Analysis; D002245:Carbon Dioxide / Q000097:blood*; D016207:Cytokines / Q000097:blood; D004573:Electrolytes / Q000097:blood; D004912:Erythrocytes / Q000378:metabolism; D005112:Extracorporeal Circulation; D015199:Extracorporeal Membrane Oxygenation; D005240:Feasibility Studies; D006863:Hydrogen-Ion Concentration; D007262:Infusions, Intravenous; D019344:Lactic Acid / Q000008:administration & dosage / Q000097:blood / Q000494:pharmacology*; D045726:Metalloproteases / Q000032:analysis / Q000378:metabolism; D012121:Respiration, Artificial; D013552:Swine
D016207:Cytokines; D004573:Electrolytes; D002245:Carbon Dioxide; D019344:Lactic Acid; D045726:Metalloproteases