代謝性酸中毒合併較高陰離子間隙可預測慢性腎臟病人預後
Metabolic acidosis with higher anion gap predicts long term renal
outcome in chronic kidney disease patients
葉時孟 1
黃道揚 1
洪啟智 1
李佳蓉 1 蔡哲嘉 1,2 顧進裕 1,2 黃尚志 1,2
陳鴻鈞 1,2
Shih-Meng Yeh1, Daw-Yang Hwang1, Chi-Chih Hung1, Jia-Jung Lee1, Jer-Chia Tsai1,2,
Jinn-Yuh Guh1,2, Shang-Jyh Hwang1,2, Hung-Chun Chen1,2
高雄醫學大學附設醫院腎臟內科, 2 高雄醫學大學腎臟照護學系
1
Division of Nephrology, Department of Internal Medicine, Kaohsiung Medical University
Hospital 2Faculty of Renal Care, Kaohsiung Medical University
1
Background: Metabolic acidosis, either normal or high anion gap, are well known
complication as renal function deteriorating unable to handle all daily acid load.
However, the characteristics and consequences of metabolic acidosis are little known.
We tried to figure out the metabolic acidosis pattern among patients with chronic
kidney disease and the influence on long term survival and renal outcome.
Method: A total of 1740 patients with CKD stage 1 to 5 (63.3 ± 0.4 years, 56% male)
were investigated. Participants were recruited from November 2002 to December
2007 in single hospital. All biochemical data were the average of 3 months before and
after the enrollment. Corrected anion gap was defined as Na – HCO3 – Cl +
0.8*(4-Alb). Clinical outcomes, patient characteristics used were ascertained from
integrated CKD care program databases.
Result: We divided patients into quartiles by bicarbonate level (<17.4, 17.4-20.7,
20.7-23.8,>23.8) and into 3 tertiles by anion gap as low(<9.2), median(9.2-12.55) and
high( >12.55) anion gap (AG) group. In high AG group, patients tend to be younger,
more female, hypertension ,anemic, higher uric acid, higher phosphate, higher sodium,
lower chloride, lower bicarbonate, and poor GFR (all P<0.05). In marked metabolic
acidosis group (HCO3-<17.4), we found similar characteristics, but high anion gap
group seemed to have more proportion of diabetes mellitus patients.
In our study, we confirmed the importance of established risk factors, including
hematocrit (HR 0.851; 95% CI 0.837 to 0.866), albumin(HR 0.471; 95% CI 0.411to
0.540), Uric acid (HR 1.162; 95% CI 1.102 to 1.224), total calcium (HR 0.745; 95%
CI 0.648to 0.858), potassium (HR 1.893; 95% CI 1.786 to 2.007), BUN (HR 1.040;
95% CI 1.037 to 1.043), MDRDGFR (HR 0.888; 95% CI 0.876 to 0.899).
We also found anion gap (HR 1.026; 95% CI 1.003 to 1.050) instead of bicarbonate
(P=0.119 ,HR0.965; 95% CI 0.922 to 1.009) is a more reliable risk factors for
predicting long term renal outcome in CKD patients. Patients with less acidosis but
higher anion gap have poorer outcome than more acidosis but lower anion gap.
Multivariate linear regression showed only BUN correlates.
Conclusion: Anion gap is a more reliable and independent risk factors for predicting
long term renal outcome than bicarbonate alone.
Key words: Anion gap, chronic kidney disease, metabolic acidosis, renal outcome