Thomas Langer1, Eleonora Scotti2, Eleonora Carlesso3, Alessandro Protti4, Loredana Zani3, Monica Chierichetti2, Pietro Caironi4, Luciano Gattinoni4. 1. Dipartimento di Fisiopatologia Medico-Chirurgica e dei Trapianti, Università degli Studi di Milano, Milano, Italy; Dipartimento di Anestesia, Rianimazione ed Emergenza Urgenza, Fondazione IRCCS Ca' Granda-Ospedale Maggiore Policlinico, Milano, Italy. Electronic address: tom.langer@hotmail.it. 2. Dipartimento di Anestesia, Rianimazione ed Emergenza Urgenza, Fondazione IRCCS Ca' Granda-Ospedale Maggiore Policlinico, Milano, Italy. 3. Dipartimento di Fisiopatologia Medico-Chirurgica e dei Trapianti, Università degli Studi di Milano, Milano, Italy. 4. Dipartimento di Fisiopatologia Medico-Chirurgica e dei Trapianti, Università degli Studi di Milano, Milano, Italy; Dipartimento di Anestesia, Rianimazione ed Emergenza Urgenza, Fondazione IRCCS Ca' Granda-Ospedale Maggiore Policlinico, Milano, Italy.
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.
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: Alberto Zanella; Thomas Langer; Pietro Caironi; Luciano Gattinoni; Antonio Pesenti Journal: Am J Respir Crit Care Med Date: 2020-09-15 Impact factor: 21.405
Authors: Manu L N G Malbrain; Thomas Langer; Djillali Annane; Luciano Gattinoni; Paul Elbers; Robert G Hahn; Inneke De Laet; Andrea Minini; Adrian Wong; Can Ince; David Muckart; Monty Mythen; Pietro Caironi; Niels Van Regenmortel Journal: Ann Intensive Care Date: 2020-05-24 Impact factor: 6.925