TY - JOUR
T1 - Electrolyte shifts across the artificial lung in patients on extracorporeal membrane oxygenation
T2 - Interdependence between partial pressure of carbon dioxide and strong ion difference
AU - Langer, Thomas
AU - Scotti, Eleonora
AU - Carlesso, Eleonora
AU - Protti, Alessandro
AU - Zani, Loredana
AU - Chierichetti, Monica
AU - Caironi, Pietro
AU - Gattinoni, Luciano
PY - 2015/2/1
Y1 - 2015/2/1
N2 - Purpose: Partial pressure of carbon dioxide (Pco2), strong ion difference (SID), and total amount of weak acids independently regulate pH. When blood passes through an extracorporeal membrane lung, Pco2 decreases. Furthermore, changes in electrolytes, potentially affecting SID, were reported. We analyzed these phenomena according to Stewart's approach. Methods: Couples of measurements of blood entering (venous) and leaving (arterial) the extracorporeal membrane lung were analyzed in 20 patients. Changes in SID, Pco2, and pH were computed and pH variations in the absence of measured SID variations calculated. Results: Passing from venous to arterial blood, Pco2 was reduced (46.5 ± 7.7 vs 34.8 ± 7.4 mm Hg, P <.001), and hemoglobin saturation increased (78 ± 8 vs 100% ± 2%, P <.001). Chloride increased, and sodium decreased causing a reduction in SID (38.7 ± 5.0 vs 36.4 ± 5.1 mEq/L, P <.001). Analysis of quartiles of {increment}Pco2 revealed progressive increases in chloride (P <.001), reductions in sodium (P <.001), and decreases in SID (P <.001), at constant hemoglobin saturation variation (P = .12). Actual pH variation was lower than pH variations in the absence of measured SID variations (0.09 ± 0.03 vs 0.12 ± 0.04, P <.001). Conclusions: When Pco2 is reduced and oxygen added, several changes in electrolytes occur. These changes cause a Pco2-dependent SID reduction that, by acidifying plasma, limits pH correction caused by carbon dioxide removal. In this particular setting, Pco2 and SID are interdependent.
AB - Purpose: Partial pressure of carbon dioxide (Pco2), strong ion difference (SID), and total amount of weak acids independently regulate pH. When blood passes through an extracorporeal membrane lung, Pco2 decreases. Furthermore, changes in electrolytes, potentially affecting SID, were reported. We analyzed these phenomena according to Stewart's approach. Methods: Couples of measurements of blood entering (venous) and leaving (arterial) the extracorporeal membrane lung were analyzed in 20 patients. Changes in SID, Pco2, and pH were computed and pH variations in the absence of measured SID variations calculated. Results: Passing from venous to arterial blood, Pco2 was reduced (46.5 ± 7.7 vs 34.8 ± 7.4 mm Hg, P <.001), and hemoglobin saturation increased (78 ± 8 vs 100% ± 2%, P <.001). Chloride increased, and sodium decreased causing a reduction in SID (38.7 ± 5.0 vs 36.4 ± 5.1 mEq/L, P <.001). Analysis of quartiles of {increment}Pco2 revealed progressive increases in chloride (P <.001), reductions in sodium (P <.001), and decreases in SID (P <.001), at constant hemoglobin saturation variation (P = .12). Actual pH variation was lower than pH variations in the absence of measured SID variations (0.09 ± 0.03 vs 0.12 ± 0.04, P <.001). Conclusions: When Pco2 is reduced and oxygen added, several changes in electrolytes occur. These changes cause a Pco2-dependent SID reduction that, by acidifying plasma, limits pH correction caused by carbon dioxide removal. In this particular setting, Pco2 and SID are interdependent.
KW - Acid-base equilibrium
KW - Electrolyte shift
KW - Extracorporeal membrane oxygenation
KW - Gas exchange
KW - Respiratory failure
KW - Stewart approach
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U2 - 10.1016/j.jcrc.2014.09.013
DO - 10.1016/j.jcrc.2014.09.013
M3 - Article
C2 - 25307980
AN - SCOPUS:84920679632
VL - 30
SP - 2
EP - 6
JO - Journal of Critical Care
JF - Journal of Critical Care
SN - 0883-9441
IS - 1
ER -