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Communications to the Editor |

Metabolic Alkalosis and Cystic Fibrosis FREE TO VIEW

J. Scott Baird, MD; Patricia Walker, MD; Agnes Urban; Maria Berdella, MD
Author and Funding Information

Cystic Fibrosis Center Saint Vincent Catholic Medical Centers New York, NY

Correspondence to: J. Scott Baird, MD, 36 7th Ave, Ste. 509, New York, NY 10011; e-mail: jsbaird@dnamail.com



Chest. 2002;122(2):755-756. doi:10.1378/chest.122.2.755-a
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Published online

To the Editor:

Metabolic alkalosis is not uncommon in patients with cystic fibrosis. It has been associated with chloride depletion and avid urinary chloride retention in infants and children,12 suggesting appropriate renal tubular handling of chloride in this setting. We report urinary chloride excretion values for several patients with cystic fibrosis and metabolic alkalosis, and compare these values to previous reports.

We reviewed medical records of our patients with cystic fibrosis hospitalized during the last 4 years, looking for patients with metabolic alkalosis as well as urine chloride and creatinine concentrations. Three patients hospitalized on four occasions were identified (Table 1 ). Metabolic alkalosis—simple or mixed—was defined using the results of an arterial blood gas analysis with reference to the acid-base diagram of Stinebaugh and Austin,3 while the molar urinary chloride/creatinine ratio was used to indicate urinary chloride excretion (low, < 8.4; normal, 8.4 to 50.1; elevated, > 50.1).12

Consistent with previous reports12 of children with metabolic alkalosis and cystic fibrosis, the molar urinary chloride/creatinine ratio was low in our pediatric patient, while it was normal or elevated in our adult patients. If metabolic alkalosis in our adult patients was the result of respiratory alkalosis superimposed on respiratory acidosis (posthypercapnic metabolic alkalosis), urinary chloride excretion would be low. Inability to conserve chloride in the urine during metabolic alkalosis is associated with hyperaldosteronism, hypokalemia, refeeding syndrome, and diuretic therapy. Aldosterone levels were low in all episodes involving adult patients. Hypokalemia and refeeding syndrome were not present. None of the patients was receiving diuretic therapy. Alternative explanations for the lack of appropriate urinary chloride retention in adults with cystic fibrosis and metabolic alkalosis, such as an age-related change in renal tubular function or the renal expression of defective cystic fibrosis transmembrane conductance regulator, have not been described.

Whatever the cause, metabolic alkalosis may have a deleterious impact on ventilation and density of mucus secretions.1 We suggest that some adults with cystic fibrosis and metabolic alkalosis lack avid urinary chloride retention, that the etiology of this process is unknown, and that chloride repletion may be warranted.

Table Graphic Jump Location
Table 1. Hospitalized Patients With Cystic Fibrosis and Metabolic Alkalosis
* 

Successfully treated with chloride repletion.

 

Simple metabolic alkalosis.

Pedroli, G, Liechti-Gallati, S, Mauri, S, et al (1995) Chronic metabolic alkalosis: not uncommon in young children with severe cystic fibrosis.Am J Nephrol15,245-250
 
Mauri, S, Pedroli, G, Rudeberg, A, et al Acute metabolic alkalosis in cystic fibrosis: prospective study and review of the literature.Miner Electrolyte Metab1997;23,33-37
 
Stinebaugh, BJ, Austin, WH Acid-base balance: common sense approach.Arch Intern Med1967;119,182-188
 

Figures

Tables

Table Graphic Jump Location
Table 1. Hospitalized Patients With Cystic Fibrosis and Metabolic Alkalosis
* 

Successfully treated with chloride repletion.

 

Simple metabolic alkalosis.

References

Pedroli, G, Liechti-Gallati, S, Mauri, S, et al (1995) Chronic metabolic alkalosis: not uncommon in young children with severe cystic fibrosis.Am J Nephrol15,245-250
 
Mauri, S, Pedroli, G, Rudeberg, A, et al Acute metabolic alkalosis in cystic fibrosis: prospective study and review of the literature.Miner Electrolyte Metab1997;23,33-37
 
Stinebaugh, BJ, Austin, WH Acid-base balance: common sense approach.Arch Intern Med1967;119,182-188
 
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