[Pathophysiology of metabolic acidosis in patients with reduced glomerular filtration rate according to Stewart-Fencl theory].
OBJECTIVE
Metabolic acidosis is a regular sign of renal insufficiency. Conventional assessment of acid-base balance using Henderson-Hasselbalch equation does not make identification of the cause of metabolic disorders possible as the serum HCO3- concentration might only reflect changes to the overall plasma ion spectrum. Therefore, we used the Stewart-Fencl approach that is based on a more detailed physical and chemical analysis and that showed that changes to serum HCO3- concentration are closely related to parameters not usually monitored in connection to acid-base balance. PATIENT GROUP AND METHODOLOGY: We performed a single measurement of arterial or capillary blood pH and pCO2 in 69 non-dialysed patients with glomerular filtration rate ranging from 0.04 to 0.88 ml/s/1.73 m2 according to MDRD, standard calculation of serum HCO3- concentration using Henderson-Hasselbalch equation was carried out, and serum albumin and ion concentrations (Na+, K+, Cl, Pi) plus creatinine and urea concentrations were determined from venous blood.


RESULTS
Metabolic acidosis was present in 47 patients ([S-HCO3-] < 22 mmol/l) with the mean [S-HCO3-] value of 19.6 mmol/l for the entire group. We proved a statistically significant correlation between [S-HCO3-] and [SID] (p < 0.001), and between [S-HCO3-] and the individual [SID] determining factors: [Na+-Cl-], [UA- ], [Pi-], [K+] (p < 0.01).


CONCLUSIONS
Reduction in [S-HCO3-] in non-dialysed patients with reduced glomerular filtration is predominantly associated with a decrease in [Na+-Cl-] difference, the quantitative contribution of which to metabolic acidosis is more significant than the strong acids retention. In addition to [S-Cl-] increase, [S-Na+] reduction too has a major role in reducing the [Na+-Cl-] difference.
Havlín
J
J
Interní klinika 2. lékarské fakulty UK a FN Motol Praha. havlin.jan@post.cz
Matousovic
K
K
Schück
O
O
Horácková
M
M
Charvát
J
J
Kotaska
K
K
Králová
D
D
D000136:Acid-Base Equilibrium; D000138:Acidosis / Q000378:metabolism*; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001639:Bicarbonates / Q000097:blood; D005260:Female; D005919:Glomerular Filtration Rate; D006801:Humans; D006863:Hydrogen-Ion Concentration; D008297:Male; D008875:Middle Aged; D051437:Renal Insufficiency / Q000150:complications / Q000378:metabolism* / Q000503:physiopathology; D012709:Serum Albumin / Q000032:analysis; D055815:Young Adult
D001639:Bicarbonates; D012709:Serum Albumin