Abstract
PurposePartial 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. MethodsCouples 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. ResultsPassing 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). ConclusionsWhen 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.
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Disclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.