Metabolic alkalosis contributes to acute hypercapnic respiratory failure in adult cystic fibrosis.
BACKGROUND
and study objectives: Patients with end-stage cystic fibrosis (CF) develop respiratory failure and hypercapnia. In contrast to COPD patients, altered electrolyte transport and malnutrition in CF patients may predispose them to metabolic alkalosis and, therefore, may contribute to hypercapnia. The aim of this study was to determine the prevalence of metabolic alkalosis in adults with hypercapnic respiratory failure in the setting of acute exacerbations of CF compared with COPD.


METHODS
Levels of arterial blood gases, plasma electrolytes, and serum albumin from 14 consecutive hypercapnic CF patients who had been admitted to the hospital with a respiratory exacerbation were compared with 49 consecutive hypercapnic patients with exacerbations of COPD. Hypercapnia was defined as a PaCO(2) of > or = 45 mm Hg.


RESULTS
Despite similar PaCO(2) values, patients in the CF group were significantly more alkalotic than were those in the COPD group (mean [+/- SD] pH, 7.43 +/- 0.03 vs 7.37 +/- 0.05, respectively; p < 0.01). A mixed respiratory acidosis and metabolic alkalosis was evident in 71% of CF patients and 22% of COPD patients (p < 0.01). The mean concentrations of plasma chloride (95.1 +/- 4.9 vs 99.8 +/- 5.2 mmol/L, respectively; p < 0.01) and sodium (136.5 +/- 2.8 vs 140.4 +/- 4.5 mmol/L, respectively; p < 0.01) were significantly lower in the CF group, and the levels of serum albumin were significantly reduced (27.4 +/- 5.8 vs 33.7 +/- 4.8 mmol/L, respectively; p < 0.01).


CONCLUSIONS
Metabolic alkalosis contributes to hypercapnic respiratory failure in adults with acute exacerbations of CF. This acid-base disturbance occurs in conjunction with reduced total body salt levels and hypoalbuminemia.
Holland
Anne E
AE
Department of Physiotherapy, The Alfred Hospital, Melbourne, VIC, Australia. a.holland1@pgrad.unimelb.edu.au
Wilson
John W
JW
Kotsimbos
Thomas C
TC
Naughton
Matthew T
MT
D000142:Acidosis, Respiratory / Q000209:etiology* / Q000378:metabolism; D000328:Adult; D000368:Aged; D000471:Alkalosis / Q000453:epidemiology / Q000209:etiology* / Q000378:metabolism; D001784:Blood Gas Analysis; D015992:Body Mass Index; D016022:Case-Control Studies; D003550:Cystic Fibrosis / Q000145:classification / Q000150:complications* / Q000378:metabolism; D004573:Electrolytes / Q000097:blood*; D005260:Female; D006801:Humans; D006935:Hypercapnia / Q000209:etiology*; D017136:Ion Transport; D008297:Male; D015995:Prevalence; D029424:Pulmonary Disease, Chronic Obstructive / Q000145:classification / Q000150:complications* / Q000378:metabolism
D004573:Electrolytes