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Erschienen in: Wiener klinische Wochenschrift 7-8/2014

01.04.2014 | original article

Evaporation of free water causes concentrational alkalosis in vitro

verfasst von: Gregor Lindner, MD, Daniel Doberer, MD, Christoph Schwarz, MD, Bruno Schneeweiss, MD, Assoc. Prof. Georg-Christian Funk, MD

Erschienen in: Wiener klinische Wochenschrift | Ausgabe 7-8/2014

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Summary

Background

The development of metabolic alkalosis was described recently in patients with hypernatremia. However, the causes for this remain unknown. The current study serves to clarify whether metabolic alkalosis develops in vitro after removal of free water from plasma and whether this can be predicted by a mathematical model.

Materials and methods

Ten serum samples of healthy humans were dehydrated by 29 % by vacuum centrifugation corresponding to an increase of the contained concentrations by 41 %. Constant partial pressure of carbon dioxide at 40 mmHg was simulated by mathematical correction of pH [pH(40)]. Metabolic acid–base state was assessed by Gilfix’ base excess subsets. Changes of acid–base state were predicted by the physical–chemical model according to Watson.

Results

Evaporation increased serum sodium from 141 (140–142) to 200 (197–203) mmol/L, i.e., severe hypernatremia developed. Acid–base analyses before and after serum concentration showed metabolic alkalosis with alkalemia: pH(40): 7.43 (7.41 to 7.45) vs 7.53 (7.51 to 7.55), p = 0.0051; base excess: 1.9 (0.7 to 3.6) vs 10.0 (8.2 to 11.8), p = 0.0051; base excess of free water: 0.0 (− 0.2 to 0.3) vs 17.7 (16.8 to 18.6), p = 0.0051. The acidifying effects of evaporation, including hyperalbuminemic acidosis, were beneath the alkalinizing ones. Measured and predicted acid–base changes due to serum evaporation agreed well.

Conclusions

Evaporation of water from serum causes concentrational alkalosis in vitro, with good agreement between measured and predicted acid–base values. At least part of the metabolic alkalosis accompanying hypernatremia is independent of renal function.
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Metadaten
Titel
Evaporation of free water causes concentrational alkalosis in vitro
verfasst von
Gregor Lindner, MD
Daniel Doberer, MD
Christoph Schwarz, MD
Bruno Schneeweiss, MD
Assoc. Prof. Georg-Christian Funk, MD
Publikationsdatum
01.04.2014
Verlag
Springer Vienna
Erschienen in
Wiener klinische Wochenschrift / Ausgabe 7-8/2014
Print ISSN: 0043-5325
Elektronische ISSN: 1613-7671
DOI
https://doi.org/10.1007/s00508-013-0486-0

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