Jakić Marko
Odjel za dijalizu, Klinika za internu medicinu, Klinicka bolnica Osijek.
Lijec Vjesn. 2009 Sep-Oct;131(9-10):243-7.
Body water volume (BWV) equals urea distribution volume (UDV), crucial for accurate calculation of dialysis dosage from urea clearance in patients treated with peritoneal dialysis. BWV is precisely determined only by monitoring tritium--or deuterium--labeled water concentration in patient plasma. These are not routine methods, thus a number of alternative methods and anthropometric formulas have been used instead trying to determine BWV from patient body weight and body height, age and sex. These methods are relatively simple but not fully reliable. In the present study, BWV being mostly determined by use of Watson formula at the time of peritoneal dialysis and upon switching to hemodialysis or undergoing kidney transplantation, was monitored in peritoneal dialysis patients to demonstrate that it significantly exceeded the value obtained by the formula. Immediately before switching to hemodialysis or undergoing kidney transplantation, 39 patients (14 female, 25 male) without dialysate in the abdomen had a mean body weight of 74.60 +/- 12 kg and mean BWV of 37.90 +/- 5.80 L according to Watson formula. In the first month of switching to another dialysis method, all patients reduced their body weight by a mean of 3.35 +/- 2.55 kg. Now, their mean body weight was 71.25 +/- 11.45 kg and mean BWV 36.80 +/- 5.50 L. However, differences in the mean body weight and BWV did not reach statistical significance (t body weight = 1.25; t body water = 0.84; p>0.05). The body weight reduction during the period of observation could have almost certainly been ascribed to the accumulated fluid elimination. This in turn implies that immediately before switching to hemodialysis or undergoing kidney transplantation, peritoneal dialysis patients had a total body water greater by a mean of 3.35 +/- 2.55 L than the figure obtained by Watson formula. Thus, their BWV was not 37.90 +/- 5.80 L (50.80 +/- 7.75% of body weight) but 41.25 +/- 6.85 L (55.16 +/- 9.15% of body weight). According to t-test, then their true BWV statistically significantly (by 8.83%) exceeded the figure yielded by the formula (t=2.39; p<0.05), the Kt/V was falsely higher by approximately the same percentage, and the BWV reduction upon switching from peritoneal dialysis to another dialysis method or undergoing kidney transplantation was statistically significant (41.25 +/- 6.85 vs. 36.80 +/- 5.50 L; t=3.20; p<0.01). In conclusion, retrograde assessment of BWV in patients treated by peritoneal dialysis showed the BWV calculated by the most widely used anthropometric formula to be considerably underestimated and urea clearance overestimated for the same reason.
机体水量（BWV）等于尿素分布容积（UDV），这对于根据腹膜透析患者的尿素清除率准确计算透析剂量至关重要。只有通过监测患者血浆中氚或氘标记水的浓度才能精确测定BWV。这些并非常规方法，因此人们使用了许多替代方法和人体测量公式，试图根据患者的体重、身高、年龄和性别来确定BWV。这些方法相对简单但并不完全可靠。在本研究中，对腹膜透析患者在进行腹膜透析时、转为血液透析或接受肾移植时主要使用Watson公式测定的BWV进行监测，结果表明其显著超过公式计算所得值。在即将转为血液透析或接受肾移植前，39例（14例女性，25例男性）腹腔内无透析液的患者，根据Watson公式计算，平均体重为74.60±12kg，平均BWV为37.90±5.80L。在转为另一种透析方法的第一个月，所有患者体重平均减轻了3.35±2.55kg。此时，他们的平均体重为71.25±11.45kg，平均BWV为36.80±5.50L。然而，平均体重和BWV的差异未达到统计学显著性（体重t值 = 1.25；机体水量t值 = 0.84；p>0.05）。观察期间体重减轻几乎肯定归因于蓄积液体的清除。这反过来意味着，在即将转为血液透析或接受肾移植前，腹膜透析患者的总体水量比Watson公式计算所得值平均多3.35±2.55L。因此，他们的BWV不是37.90±5.80L（占体重的50.80±7.75%），而是41.25±6.85L（占体重的55.16±9.15%）。根据t检验，他们的真实BWV在统计学上显著超过公式计算值（高8.83%）（t = 2.39；p<0.05），Kt/V也因同样原因被错误高估了约相同的百分比，并且从腹膜透析转为另一种透析方法或接受肾移植时BWV的降低具有统计学显著性（41.25±6.85L对36.80±5.50L；t = 3.20；p<0.01）。总之，对腹膜透析患者BWV的回顾性评估表明，最广泛使用的人体测量公式计算出的BWV被大幅低估，并且由于同样原因尿素清除率被高估。
