Authors: Nienke M. G. Rorije, M.D. et al
Anesthesiology 2 2018, Vol.128, 352-360.
Background: Sodium-induced microcirculatory changes, endothelial surface layer alterations in particular, may play an important role in sodium-mediated blood pressure elevation. However, effects of acute and chronic sodium loading on the endothelial surface layer and microcirculation in humans have not been established. The objective of this study was to assess sodium-induced changes in blood pressure and body weight as primary outcomes and also in microvascular permeability, sublingual microcirculatory dimensions, and urinary glycosaminoglycan excretion in healthy subjects.
Methods: Twelve normotensive males followed both a low-sodium diet (less than 50 mmol/day) and a high-sodium diet (more than 200 mmol/day) for eight days in randomized order, separated by a crossover period. After the low-sodium diet, hypertonic saline (5 mmol sodium/liter body water) was administered intravenously in 30 min.
Results: Both sodium interventions did not change blood pressure. Body weight increased with 2.5 (95% CI, 1.7 to 3.2) kg (P < 0.001) after dietary sodium loading. Acute intravenous sodium loading resulted in increased transcapillary escape rate of 125I-labeled albumin (2.7 [0.1 to 5.3] % cpm · g−1 · h–1; P = 0.04), whereas chronic dietary sodium loading did not affect transcapillary escape rate of 125I-labeled albumin (−0.03 [−3.3 to 3.2] % cpm · g−1 · h–1; P = 1.00), despite similar increases of plasma sodium and osmolality. Acute intravenous sodium loading coincided with significantly increased plasma volume, as assessed by the distribution volume of albumin, and significantly decreased urinary excretion of heparan sulfate and chondroitin sulfate. These changes were not observed after dietary sodium loading.
Conclusions: Our results suggest that intravenous sodium loading has direct adverse effects on the endothelial surface layer, independent of blood pressure.
What We Already Know about This Topic
- Tissue glycosaminoglycans influence sodium homeostasis vianonosmotic storage of sodium
- Impairment of the microcirculatory endothelial surface layer, which consists of different glycosaminoglycans, decreases its vascular barrier function
What This Article Tells Us That Is New
- Twelve healthy males followed both a low-sodium diet and a high-sodium diet for eight days each in a randomized crossover study and received intravenous hypertonic saline infusion over the course of 30 min after the low-sodium diet
- Despite similar increases in plasma sodium, chloride, and osmolality, chronic dietary sodium loading did not affect microvascular permeability, but hypertonic saline infusion increased it
- Increased microvascular permeability after saline infusion coincided with decreased urinary glycosaminoglycan excretion, indicating damage to the endothelial surface layer