Electrolyte shifts across the artificial lung in patients on extracorporeal membrane oxygenation: interdependence between partial pressure of carbon dioxide and strong ion difference.

Abstract

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 ∆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.

• Authors: Thomas Langer, Eleonora Scotti, Eleonora Carlesso, Alessandro Protti, Loredana Zani, Monica Chierichetti, Pietro Caironi, Luciano Gattinoni
• Journal: Journal of critical care (J Crit Care) Vol. 30 Issue 1 Pg. 2-6 (Feb 2015) ISSN: 1557-8615 [Electronic] United States
• PMID: 25307980 (Publication Type: Journal Article, Research Support, Non-U.S. Gov't)
• Copyright: Copyright © 2014 Elsevier Inc. All rights reserved.

Chemical References

• Anions
• Chlorides
• Electrolytes
• Carbon Dioxide
• Hemoglobin A
• Sodium
• Oxygen

Topics

• Acid-Base Equilibrium
• Adult
• Anions (blood)
• Carbon Dioxide (blood)
• Chlorides (blood)
• Electrolytes
• Extracorporeal Membrane Oxygenation
• Female
• Hemoglobin A (metabolism)
• Humans
• Hydrogen-Ion Concentration
• Male
• Oxygen (blood)
• Partial Pressure
• Sodium (blood)