Metabolic acidosis in hemodialysis: a neglected problem in Brazil

ABSTRACT Introduction: Metabolic acidosis is associated with the high mortality seen in hemodialysis patients. The panorama of metabolic acidosis in hemodialysis in Brazil is unclear since 1996 when the analysis of bicarbonate levels was no longer a compulsory exam. We aimed to establish the prevalence of metabolic acidosis in a hemodialysis population and analyze the factors associated with low bicarbonate levels. Methods: A cross-sectional study was carried out to assess the prevalence of metabolic acidosis in adults undergoing regular hemodialysis from January to April 2017, in four dialysis centers from Niteroi, Rio de Janeiro, Brazil, and surroundings. For blood gas analysis, samples of 2 mL were collected in heparinized syringes before a midweek dialysis session. Results: 384 patients with a mean age of 58.1 ± 15.8 years (54.5% men and 63.0%, non-white) were included. Approximately 30% had diabetes and 48%, hypertension. Nearly 88% used primary arteriovenous fistula as vascular access. The pre-dialysis mean serum tCO2 in the midweek session was 22.7 ± 3.0 mEq/L. The prevalence rate of serum bicarbonate below DOQI recommendation (22 mEq/L or higher) was 40.3%, and 6.5% had serum bicarbonate < 18 mEq/L. The dialyzer use count and the use of low-flux dialyzers were negatively associated whereas age and the standard Kt/V values were positively associated with the serum bicarbonate levels. Conclusion: The findings were in agreement with global data reported in previous studies. However, because the sample was relatively small and non-representative of the Brazilian population, a more comprehensive study, addressing national data is necessary to substantiate our findings.

摘要 引言：代谢性酸中毒与血液透析患者的高死亡率密切相关。自1996年碳酸氢盐水平检测不再作为强制检查项目以来，巴西血液透析人群中代谢性酸中毒的流行全景尚不明确。本研究旨在明确血液透析患者群体中代谢性酸中毒的患病率，并分析与低碳酸氢盐水平相关的影响因素。方法：本研究为横断面研究，于2017年1月至4月在巴西里约热内卢州尼泰罗伊市及其周边地区的4家血液透析中心开展，评估接受规律血液透析的成年患者的代谢性酸中毒患病率。血气分析样本采集于周中透析治疗前的肝素化注射器中，每份样本容量为2 mL。结果：本研究共纳入384例患者，平均年龄为58.1±15.8岁，其中男性占54.5%，非白人患者占63.0%。约30%的患者合并糖尿病，48%合并高血压。近88%的患者采用自体动静脉内瘘作为血管通路。周中透析前的血清总二氧化碳（total carbon dioxide, tCO2）平均水平为22.7±3.0 mEq/L。血清碳酸氢盐水平低于透析预后质量倡议（Dialysis Outcomes Quality Initiative, DOQI）推荐的≥22 mEq/L标准的患者占比为40.3%，另有6.5%的患者血清碳酸氢盐水平＜18 mEq/L。透析器使用次数与低通量透析器的使用与血清碳酸氢盐水平呈负相关，而年龄与标准Kt/V值则与血清碳酸氢盐水平呈正相关。结论：本研究结果与既往研究报道的全球数据相符。但由于本研究样本量相对较小，且未能够代表巴西整体人群，因此需要开展一项纳入全国代表性数据的更全面的研究，以验证本研究的结论。