Sacamay T E, Bolton W K
Division of Nephrology, University of Virginia School of Medicine, Charlottesville, USA.
Kidney Int. 1998 Sep;54(3):986-91. doi: 10.1046/j.1523-1755.1998.00060.x.
Classically, urea (molecular wt = 60) is used to determine the urea reduction ratio (URR) or clearance, based on volume of distribution (Kt/V). These methods are subject to many errors. The purpose of this study was to determine whether iohexol (Io; molecular wt = 821) could be used instead of urea and provide better information as well as middle molecule clearance data.
Ten hemodialysis (HD) patients were evaluated. All were dialyzed for three hours, and a single bolus of 100 ml of Io was injected immediately post-HD. For direct dialysis quantification (DDQ), the spent dialysate was collected in a drum, and urea and iodine (I) determined immediately prior to, at the end of, and 30 minutes post-HD. As routinely used, DDQ measures clearance directly rather than estimates the levels.
Calculated Kt/V urea (1.21+/-0.05) significantly overestimated DDQ Kt/V urea (0.78+/-0.04, P < 0.001) whereas calculated and DDQ Kt/V Io were similar (1.44+/-0.10 vs. 1.36+/-0.05). The URR and iohexol reduction ratio (IoRR) were also different (0.63+/-0.02 vs. 0.69+/-0.02; P < 0.002) with a urea but not Io rebound (URR30 min 0.59+/-0.02, P < 0.05). Calculated urea clearance (C(urea)), 247+/-21 ml/min, significantly overestimated DDQ C(urea) (157+/-10 ml/min P < 0.001). Calculated CIo and DDQ CIo, however, were similar (109+/-8 vs. 104+/-7 ml/min). Total body clearance (TBC) in six anuric subjects was 2.5+/-0.3 ml/min, and in four oliguric subjects was 5.2+/-0.5 ml/min. In 10 additional patients, direct urine measurements demonstrated a non-renal clearance (NRC) of 2.97+/-0.18 ml/min, which was 4.0+/-0.3% of body wt. Use of this factor allowed an estimation of residual renal function (RRF) that accurately reflected measured RRF (1.32+/-0.53 vs. 1.42+/-0.55 ml/min)
A single injection of Io can be used to determine Kt/V, RR, and RRF without rebound or the inconvenience of urine collection. It may also represent middle molecule clearance better than urea kinetics, and may serve as a superior method for determining HD delivered and dialysis adequacy.
传统上，尿素（分子量 = 60）用于根据分布容积（Kt/V）来测定尿素清除率（URR）或清除量。这些方法存在许多误差。本研究的目的是确定碘海醇（Io；分子量 = 821）是否可替代尿素使用，并能提供更好的信息以及中分子清除数据。
对10名血液透析（HD）患者进行评估。所有患者均透析3小时，并在透析结束后立即静脉注射100 ml的碘海醇。为进行直接透析定量（DDQ），将用过的透析液收集到桶中，并在透析前、结束时和结束后30分钟立即测定尿素和碘（I）。按照常规使用方法，DDQ直接测量清除率而非估算水平。
计算得出的Kt/V尿素（1.21±0.05）显著高估了DDQ的Kt/V尿素（0.78±0.04，P < 0.001），而计算得出的和DDQ的Kt/V碘海醇相似（1.44±0.10对1.36±0.05）。URR和碘海醇清除率（IoRR）也有所不同（0.63±0.02对0.69±0.02；P < 0.002），存在尿素但不存在碘海醇的反跳现象（URR30分钟为0.59±0.02，P < 0.05）。计算得出的尿素清除率（C(尿素)）为247±21 ml/分钟，显著高估了DDQ的C(尿素)（157±10 ml/分钟，P < 0.001）。然而，计算得出的CIo和DDQ的CIo相似（109±8对104±7 ml/分钟）。6名无尿患者的全身清除率（TBC）为2.5±0.3 ml/分钟，4名少尿患者的为5.2±0.5 ml/分钟。在另外10名患者中，直接尿液测量显示非肾清除率（NRC）为2.97±0.18 ml/分钟，占体重的4.0±0.3%。使用该因素可估算残余肾功能（RRF），其准确反映了测量的RRF（1.32±0.53对1.42±0.55 ml/分钟）
单次注射碘海醇可用于测定Kt/V、RR和RRF，不存在反跳现象或尿液收集的不便。它可能比尿素动力学更能代表中分子清除情况，并且可能是确定HD剂量和透析充分性的更优方法。
