Caracterização dos distúrbios ácido-base na doença renal crônica avançada : correlação dos seus determinantes com albumina e paratormônio

Abstract

Chronic kidney disease (CKD) is known to cause a progressive reduction in serum bicarbonate levels. Most patients with CKD-associated metabolic acidosis present a high serum anion gap, due to the accumulation of unmeasured anions; however, in other patients, CKD is associated with hyperchloremic acidosis. According to the quantitative approach to acid-base disorders, hyperchloremia can lead to metabolic acidosis due to a reduction in strong ion difference (SID). Hyperchloremia is known to play a role in metabolic acidosis in up to 43% of CKD patients. Metabolic acidosis is detrimental to nutritional status and contributes to the pathogenesis of secondary hyperparathyroidism. Several studies have found serum bicarbonate to be correlated with serum albumin and serum intact parathyroid hormone (iPTH). The purpose of this study was to assess the relationship between each of the two main components of metabolic acidosis (unmeasured anions and reduced SID due to hyperchloremia) and serum albumin and iPTH, respectively. The final sample consisted of 383 patients (57.4% male) from a large emergency hospital (HGF) in Fortaleza (Brazil). The vast majority (n=333, 87%) had metabolic acidosis and only 1.8% had metabolic alkalosis. Among the former, 153/333 (46%) had metabolic acidosis exclusively due to unmeasured anions and 180/333 (54%) had a hyperchloremic component (142 with mixed metabolic acidosis - unmeasured anions and hyperchloremia - and 38 with pure hyperchloremic metabolic acidosis). As expected, patients with metabolic acidosis had reduced serum albumin levels (3.5 ± 0.6 vs. 3.2 ± 0.6 g/dL, p=0.026) and increased serum iPTH levels, in comparison with those without acidosis (222,8 ± 52.1 vs. 134,2 ± 46.3 pg/mL, p=0.006). Acidosis severity was similar in patients with metabolic acidosis exclusively due to unmeasured anions and patients with a hyperchloremic component. Serum albumin levels were lower in patients with metabolic acidosis exclusively due to unmeasured anions, and PTH levels were higher in patients with a hyperchloremic component - reduced SID. A detailed understanding of the components of metabolic acidosis can help establish a diagnosis and identify patients most likely to respond to alkali therapy in different clinical scenarios.