Johansen L B, Bie P, Warberg J, Christensen N J, Hammerum M, Videbaek R, Norsk P
Danish Aerospace Medical Centre of Research, Rigshospitalet 7805, Department of Medical Physiology, University of Copenhagen, Denmark.
Am J Physiol. 1997 Feb;272(2 Pt 2):R549-56. doi: 10.1152/ajpregu.1997.272.2.R549.
To test the hypothesis that hemodilution is a mediator of the renal responses to an isotonic saline infusion in the supine position, eight males underwent 1) intravenous infusion of 1.5 liter of saline over 21 min (Saline), 2) infusion of 1.5 liter of saline in combination with lower body negative pressure for 3 h (LBNP+Saline) to maintain central blood volume unchanged, and 3) a control study without infusion or LBNP. During the Saline series, central venous pressure (CVP) and left atrial diameter (LAD) increased by 4.4 +/- 0.6 mmHg and 2.6 +/- 0.4 mm (P < 0.05), respectively, whereafter they declined toward preinfusion levels. During LBNP+Saline, CVP and LAD were unchanged. Plasma colloid osmotic pressure remained unchanged during control and showed identical decreases by 5 mmHg (P < 0.05) in the Saline and LBNP+Saline series. During the 3rd h of LBNP, renal sodium excretion (U(Na)V) peaked at 296 +/- 55 micromol/min vs. a higher value of 383 +/- 54 micromol/min (P < 0.05) during Saline. The increase in U(Na)V above that of control during the 3rd h of LBNP+Saline constituted 48% of that during Saline. Plasma renin activity and plasma aldosterone concentration showed similar patterns of decrease after saline infusion irrespective of LBNP, whereas plasma norepinephrine was elevated late in the LBNP period compared with during Saline and control (P < 0.05). It is concluded that the maintenance of a constant CVP and LAD reduces the natriuresis of acute saline loading by about one-half. Thus hemodilution in conjunction with suppression of renin and aldosterone release (independent of change in CVP and LAD) might account for the remaining natriuresis of infusion.
为验证血液稀释是仰卧位时肾脏对等渗盐水输注反应的介导因素这一假说，8名男性受试者接受了以下操作：1）在21分钟内静脉输注1.5升盐水（盐水组）；2）输注1.5升盐水并结合下体负压3小时（下体负压+盐水组）以维持中心血容量不变；3）无输注或下体负压的对照研究。在盐水组中，中心静脉压（CVP）和左房直径（LAD）分别升高4.4±0.6 mmHg和2.6±0.4 mm（P<0.05），随后降至输注前水平。在下体负压+盐水组中，CVP和LAD未发生变化。在对照期间血浆胶体渗透压保持不变，在盐水组和下体负压+盐水组中均降低5 mmHg（P<0.05）。在下体负压第3小时，肾钠排泄（U(Na)V）峰值为296±55微摩尔/分钟，而在盐水组中为更高的383±54微摩尔/分钟（P<0.05）。在下体负压+盐水组第3小时，U(Na)V高于对照的增加值占盐水组增加值的48%。无论下体负压情况如何，盐水输注后血浆肾素活性和血浆醛固酮浓度均呈现相似的下降模式，而下体负压后期血浆去甲肾上腺素水平高于盐水组和对照组（P<0.05）。得出的结论是，维持恒定的CVP和LAD可使急性盐水负荷的利钠作用降低约一半。因此，血液稀释与肾素和醛固酮释放的抑制（独立于CVP和LAD的变化）可能是输注后剩余利钠作用的原因。
