title: Hypocapnic but not metabolic alkalosis impairs alveolar fluid reabsorption.
abstract: Acid-base disturbances, such as metabolic or respiratory alkalosis, are relatively common in critically ill patients. We examined the effects of alkalosis (hypocapnic or metabolic alkalosis) on alveolar fluid reabsorption in the isolated and continuously perfused rat lung model. We found that alveolar fluid reabsorption after 1 hour was impaired by low levels of CO2 partial pressure (PCO2; 10 and 20 mm Hg) independent of pH levels (7.7 or 7.4). In addition, PCO2 higher than 30 mm Hg or metabolic alkalosis did not have an effect on this process. The hypocapnia-mediated decrease of alveolar fluid reabsorption was associated with decreased Na,K-ATPase activity and protein abundance at the basolateral membranes of distal airspaces. The effect of low PCO2 on alveolar fluid reabsorption was reversible because clearance normalized after correcting the PCO2 back to normal levels. These data suggest that hypocapnic but not metabolic alkalosis impairs alveolar fluid reabsorption. Conceivably, correction of hypocapnic alkalosis in critically ill patients may contribute to the normalization of lung ability to clear edema.
authors.affiliation: Division of Pulmonary and Critical Care Medicine, 240 East Huron, McGaw 2-2300, Northwestern University, Chicago, IL 60611, USA.
authors.forename: Pavlos M
authors.initials: PM
authors.lastname: Myrianthefs
authors.forename: Arturo
authors.initials: A
authors.lastname: Briva
authors.forename: Emilia
authors.initials: E
authors.lastname: Lecuona
authors.forename: Vidas
authors.initials: V
authors.lastname: Dumasius
authors.forename: David H
authors.initials: DH
authors.lastname: Rutschman
authors.forename: Karen M
authors.initials: KM
authors.lastname: Ridge
authors.forename: George J
authors.initials: GJ
authors.lastname: Baltopoulos
authors.forename: Jacob Iasha
authors.initials: JI
authors.lastname: Sznajder
mesh_terms: D000042:Absorption; D000472:Alkalosis, Respiratory / Q000150:complications / Q000378:metabolism* / Q000503:physiopathology; D000818:Animals; D002245:Carbon Dioxide / Q000378:metabolism; D004195:Disease Models, Animal; D016857:Hypocapnia / Q000209:etiology / Q000378:metabolism* / Q000503:physiopathology; D008168:Lung / Q000201:enzymology / Q000503:physiopathology; D008297:Male; D010313:Partial Pressure; D011650:Pulmonary Alveoli / Q000378:metabolism* / Q000503:physiopathology; D051381:Rats; D017207:Rats, Sprague-Dawley; D000254:Sodium-Potassium-Exchanging ATPase / Q000378:metabolism
chemical_list: D002245:Carbon Dioxide; D000254:Sodium-Potassium-Exchanging ATPase