Gonzalez J, Morrissey T, Byrne T, Rizzo R, Wilmore D
Laboratories for Surgical Metabolism and Nutrition, Harvard Medical School, Boston, Mass., USA.
J Thorac Cardiovasc Surg. 1995 Jul;110(1):111-8. doi: 10.1016/S0022-5223(05)80016-9.
Excessive fluid accumulation is associated with increased morbidity and prolonged convalescence after cardiopulmonary bypass. However, water fluctuations are difficult to assess solely on the basis of changes in body weight and fluid balance. Bioelectric impedance analysis is a simple, rapid, noninvasive bedside technique that measures the resistance of the body to a weak alternating current (50 kHz). The change in resistance is inversely proportional to the change in total body water. To investigate the relationship between body weight, fluid balance, and resistance, 18 patients who had cardiopulmonary bypass (9 men, 9 women, aged 61 +/- 3 years, weighing 80 +/- 4 kg, with ejection fraction 54% +/- 3% and bypass time 113 +/- 8 minutes [mean plus or minus standard error of the mean]) were followed up for 7 postoperative days. Body weight, fluid balance, and whole body and regional resistance were determined at 24-hour intervals. In the immediate postoperative period, fluid retention was accurately detected by simultaneous measurements of weight gain and decreased resistance (p < 0.001). Both measurements detected the initiation of diuresis by postoperative day 2 (p < 0.01). Whole body resistance returned to baseline values by day 7 (p > 0.05), and body weight returned to baseline on day 4 (p > 0.05). Change in weight and change in whole body resistance were highly correlated with cumulative fluid balance (r = 0.84, p < 0.001, and r = -0.81, p < 0.001, respectively), and these two measures were also related to each other throughout the study (r = -0.89, p < 0.001). The initial change in resistance was the best measurement associated with postoperative outcome (p < or = 0.01). The data suggest that the measurement of electric resistance across the body can accurately detect acute changes in total body water and in fluid redistribution through the body. However, determining the relative day-to-day change in whole body resistance seems more appropriate than calculating absolute fluid changes over time. Bioelectric impedance offers a simple, rapid, noninvasive method to monitor serial changes in total body water. This technique can be useful in situations in which rapid alterations in water compartments occur, and it may be useful in predicting outcome after cardiopulmonary bypass.
体外循环后过多的液体蓄积与发病率增加及恢复期延长相关。然而，仅根据体重和液体平衡的变化很难评估水分波动情况。生物电阻抗分析是一种简单、快速、无创的床旁技术，可测量身体对弱交流电（50 kHz）的电阻。电阻的变化与总体液量的变化成反比。为研究体重、液体平衡与电阻之间的关系，对18例行体外循环的患者（9名男性，9名女性，年龄61±3岁，体重80±4 kg，射血分数54%±3%，体外循环时间113±8分钟[均值±均值的标准误]）进行了术后7天的随访。每隔24小时测定体重、液体平衡以及全身和局部电阻。在术后即刻，通过同时测量体重增加和电阻降低准确检测到液体潴留（p<0.001）。两种测量方法均在术后第2天检测到利尿开始（p<０.01）。全身电阻在第7天恢复到基线值（p>0.05），体重在第4天恢复到基线（p>0.05）。体重变化和全身电阻变化与累积液体平衡高度相关（分别为r = 0.84，p<0.001和r = -0.81，p<0.001），并且在整个研究过程中这两种测量方法也相互关联（r = -0.89，p<0.001）。电阻的初始变化是与术后结果相关的最佳测量指标（p≤0.01）。数据表明，测量身体的电阻可以准确检测总体液量的急性变化以及液体在体内的重新分布。然而，确定全身电阻的相对每日变化似乎比计算随时间的绝对液体变化更合适。生物电阻抗提供了一种简单、快速、无创的方法来监测总体液量的系列变化。该技术在体液快速变化的情况下可能有用，并且可能有助于预测体外循环后的结果。
