Renal Medicine, Leeds Teaching Hospitals, Leeds, United Kingdom.
School of Medicine, Faculty of Medicine and Health Sciences, Keele University, United Kingdom.
Physiol Meas. 2022 Aug 3;43(8). doi: 10.1088/1361-6579/ac80e8.
. With growing recognition of the benefits of preserving residual kidney function (RKF) and use of incremental treatment regimes, the incentive to measure residual clearance in haemodialysis patients is increasing. Interdialytic urine collections used to monitor RKF in research studies are considered impractical in routine care, partly due to the requirement for blood samples before and after the collection. Plasma solute levels can be estimated if patients are in 'steady state', where urea and creatinine concentrations increase at a constant rate between dialysis sessions and are reduced by a constant ratio at each session. Validation of the steady state assumption would allow development of simplified protocols for urine collections in HD patients.. Equations were derived for estimating plasma urea and creatinine at the start or end of the interdialytic interval for patients in steady state. Data collected during the BISTRO study was used to assess the agreement between measured and estimated plasma levels and the effect of using estimated levels on the calculated glomerular filtration rate (GFR).. The mean difference between GFR calculated with estimated plasma levels for the HD session after the collection and a full set of measured levels was 2.0% (95% limits of agreement -10.7% to +14.7%, = 316). Where plasma levels for the session before the collection were estimated, the mean difference was 1.2% (limits of agreement -10.3% to +7.9%, = 275).. Using estimated levels for one session led to a clinically significant difference in the calculated GFR for less than 3% of the collections studied. This indicates that the steady state assumption can be used to estimate solute levels when determining GFR from timed urine collections. A pragmatic approach to monitoring RKF in HD would be for patients to collect for approximately 24 h before routine bloods are taken.
随着人们越来越认识到保留残余肾功能（RKF）和使用递增治疗方案的好处，测量血液透析患者残余清除率的动力也在增加。在研究中，间歇性尿液收集用于监测 RKF，但在常规护理中被认为不切实际，部分原因是收集前后需要采集血液样本。如果患者处于“稳态”，即尿素和肌酐浓度在透析间隔之间以恒定速率增加，并且在每次透析时以恒定比例降低，那么可以估计血浆溶质水平。稳态假设的验证将允许为血液透析患者的尿液收集开发简化方案。
推导出了用于估计稳态患者在间歇性透析间隔开始或结束时的血浆尿素和肌酐的方程。使用 BISTRO 研究中收集的数据评估了测量和估计的血浆水平之间的一致性，以及使用估计水平对计算肾小球滤过率（GFR）的影响。
在用收集后的血液透析 session 的估计血浆水平计算 GFR 与用完整的测量血浆水平计算的 GFR 之间的平均差异为 2.0%（95%一致性界限为-10.7%至+14.7%，=316）。在估计 session 之前的血浆水平的情况下，平均差异为 1.2%（一致性界限为-10.3%至+7.9%，=275）。
在研究的不到 3%的采集情况下，使用一个 session 的估计水平会导致计算出的 GFR 出现临床显著差异。这表明在使用定时尿液采集来确定 GFR 时，可以使用稳态假设来估计溶质水平。在血液透析中监测 RKF 的实用方法是让患者在常规采血前收集大约 24 小时的尿液。
