Minutolo R, Andreucci M, Balletta M M, Russo D
Department of Nephrology, School of Medicine, University Federico II, Naples, Italy.
Am J Kidney Dis. 2000 Oct;36(4):719-27. doi: 10.1053/ajkd.2000.17616.
It is well known that posture affects natriuresis in cirrhosis and heart failure. This study evaluates the role of posture on spontaneous urinary salt excretion (U(Na)V) and diuretic-induced natriuresis in nephrotic patients with mild renal impairment. U(Na)V and plasma concentrations of the main hormones involved in sodium regulation were evaluated at baseline (Baseline) and after furosemide administration (20 mg intravenously at 8:00 AM [Diuretic]) in seven nephrotic patients with mild renal impairment (creatinine clearance, 68.5 +/- 7.6 mL/min) in either the supine or upright position for 6 hours (from 8:00 AM to 2:00 PM). At baseline, U(Na)V was greater in the supine than upright position (sodium, 51.8 +/- 6.2 versus 38.3 +/- 6.1 mEq/d; P: < 0.01). Similarly, furosemide was more effective in increasing U(Na)V in the supine (sodium, 51.8 +/- 6.2 to 87.4 +/- 9.1 mEq/d; P: < 0.005) than upright position (sodium, 38.3 +/- 6.1 to 59.0 +/- 6.8 mEq/d; P: = not significant). Consequently, body weight decreased in the supine but not the upright position (-0.73 +/- 0.15 versus -0.17 +/- 0.22 kg; P: < 0. 05). Peripheral renin activity (PRA) and plasma aldosterone (Aldo) concentrations were greater in the upright than supine position at both Baseline and Diuretic. A similar pattern was observed for hematocrit, used as an index of plasma volume. In addition, a positive correlation was detected between hematocrit and PRA (r = 0.89; P: < 0.001) in the upright position. Postural changes did not influence plasma concentrations of atrial natriuretic peptide. These data indicate that in nephrotic patients with mild impairment of glomerular filtration rate, the upright position causes a reduction in plasma volume; this hypovolemia activates the renin-Aldo system responsible for sodium retention in unstimulated conditions and a blunted natriuretic response to furosemide.
众所周知，姿势会影响肝硬化和心力衰竭患者的利钠作用。本研究评估姿势对轻度肾功能损害的肾病患者自发性尿钠排泄（U(Na)V）及利尿剂诱导的利钠作用的影响。在7例轻度肾功能损害（肌酐清除率为68.5±7.6 mL/min）的肾病患者中，于上午8:00（基线）及静脉注射呋塞米（上午8:00静脉注射20 mg [利尿剂]）后，分别在仰卧位和直立位持续6小时（从上午8:00至下午2:00），评估U(Na)V及参与钠调节的主要激素的血浆浓度。在基线时，仰卧位的U(Na)V高于直立位（钠，51.8±6.2对38.3±6.1 mEq/d；P：<0.01）。同样，呋塞米在仰卧位增加U(Na)V方面比直立位更有效（钠，从51.8±6.2增至87.4±9.1 mEq/d；P：<0.005），而直立位（钠，从38.3±6.1增至59.0±6.8 mEq/d；P：无显著差异）。因此，仰卧位体重下降，而直立位体重未下降（-0.73±0.15对-0.17±0.22 kg；P：<0.05）。在基线和利尿剂使用后，直立位的外周肾素活性（PRA）和血浆醛固酮（Aldo）浓度均高于仰卧位。作为血浆容量指标的血细胞比容也观察到类似模式。此外，在直立位，血细胞比容与PRA之间检测到正相关（r = 0.89；P：<0.001）。姿势变化不影响心房利钠肽的血浆浓度。这些数据表明，在肾小球滤过率轻度受损的肾病患者中，直立位会导致血浆容量减少；这种血容量不足会激活肾素 - 醛固酮系统，该系统在未受刺激的情况下负责钠潴留，并导致对呋塞米的利钠反应减弱。
