Hong Kong Journal of Nephrology

Volume 6 Number 1, 2004

Urea Kinetics and Clinical Chemistry Parameters in Patients on Twice-Weekly Hemodialysis

Yuk-Lun Cheng, Koon-Shing Choi, Chee-Unn Yung, Kim-Ming Wong, Ka-Foon Chau, Chun-Sang Li, Kwong-Yuen Tsang, Chi-Kwan Wong, Yee-Tuen Tsui, Alex W.Y. Yu

Background: Despite the fact that thrice-weekly hemodialysis is regarded as the standard for maintenance dialysis, prescription of twice-weekly hemodialysis with a longer treatment time is common in Hong Kong to allow more renal failure patients to receive treatment. In an attempt to assess whether clinical and biochemical parameters differ between hemodialysis with different interdialytic intervals, we investigated the urea kinetics and blood biochemistry parameters in patients undergoing two dialysis sessions per week.
Methods: Data were collected for 16 anuric stable maintenance dialysis patients for two dialyses in the same week.
Results: Compared with hemodialysis after a short interdialytic interval (HDSII), hemodialysis after a long inter-dialytic interval (HDLII) led to significantly greater interdialytic weight gain. Predialysis plasma potassium, urea and creatinine concentrations were significantly higher for HDLII. On the other hand, there were no significant differences in predialysis plasma sodium, chloride, total carbon dioxide, albumin, calcium and phosphorus concentrations and anion gap between HDSII and HDLII. Both immediate postdialysis and 30-minute postdialysis plasma urea concentrations were significantly higher for HDLII. Urea removal, creatinine removal, modified urea reduction ratio (mURR), single-pool Kt/V (spKt/V) and equilibrated Kt/V (eKt/V) were significantly greater for HDLII. Moreover, there was a good linear relationship between mURR for HDSII and HDLII. Similar findings were noted for both spKt/V and eKt/V. However, there were no differences between the two dialyses in urea reduction ratio, normalized protein equivalent of total nitrogen appearance and postdialysis urea rebound.
Conclusion: Our findings suggest that there are differences in some dialysis indices and blood biochemistry parameters between HDSII and HDLII. Standardization of dialysis sessions (HDSII or HDLII) for blood sampling schedules is needed to permit meaningful comparison of dialysis indices and biochemistry parameters within and between dialysis patients.

Key words: urea kinetics, biochemistry parameters, hemodialysis schedule, twice-weekly hemodialysis

背景: 長期血液透析的頻率一般建議為一週 3 次,然而為了讓更多的腎衰竭患者接受治療,在香港有不少病人正接受一週 2 次時間較長的透析。本研究對一週 2 次的透析接受者作出研究,調查了透析間隔(interdialytic interval) 的長短對尿素動力學及血液生化指標的影響。 方法: 研究數據來自 16 位正在接受一週 2 次長期血液透析的無尿症患者。
結果: 相比於透析間隔較短的病人(HDSII),間隔較長者(HDLII)的體重出現明顯增加﹔HDLII 之透析前血漿鉀、尿素、及肌酸酐濃度亦較高。兩組之間在其他指標上則相同,包括透析前血漿鈉、氯、總二氧化碳、白蛋白、鈣、磷、及陰離子間隙。在透析剛完成及 30 分鐘後,HDLII 的血漿尿素濃度顯著高於 HDSII;尿素清除量、肌酸酐清除量、修正後之尿素下降比率(mURR)、單一體積(single-pool)之 Kt/VspKt/V)、及平衡後(equilibrated)之 Kt/VeKt/V) 亦以 HDLII 較高。HDSIIHDLII 組中在 mURR 上呈現良好的線性關係;同樣的情形亦可見於 spKt/VeKt/V。然而,兩組之間在尿素下降比率、總氮出現量之正常化蛋白質當量(nPNA)(normalized protein equivalent of total nitrogen appearance)、及透析後之尿素反彈上相似。

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