Clinical Autonomic Research

, Volume 8, Issue 4, pp 231–235 | Cite as

Early effects of oral salt on plasma volume, orthostatic tolerance, and baroreceptor sensitivity in patients with syncope

  • Benjamin L. Mtinangi
  • Roger Hainsworth
Research Paper


Salt loading of patients with orthostatic-related syncope has been shown to increase plasma volume and orthostatic tolerance and to decrease baroreceptor sensitivity. This study aims to define the time course of these changes and reveal indications as to the likely mechanisms involved. We measured plasma volume by Evans blue dilution, orthostatic tolerance by time to presyncope in a test of combined head-up tilt and lower body suction, and baroreceptor sensitivity as the cardiac interval prolongation to neck suction. Tests were carried out in patients with poor orthostatic tolerance and low initial urinary salt excretion, before and after 7 or 3 days of salt loading (120 mmol/d). In both groups after salt loading plasma volume and orthostatic tolerance increased and baroreceptor sensitivity decreased. These results confirm the beneficial effects of salt in some patients and show that all these changes occur within 3 days.


salt orthostasis baroreceptors plasma volume syncope 


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  1. 1.
    Day SC, Cook EF, Funkenstein H, Goldman L. Evaluation and outcome of emergency room patients with transient loss of conciousness.Am J Med 1982;73:15–23.CrossRefPubMedGoogle Scholar
  2. 2.
    Wahbha MMAE, Morley CA, Al-Shamma YMH, Hainsworth R. Cardiovascular reflex responses in patients with unexplained syncope.Clin Sci 1989;77:547–553.PubMedGoogle Scholar
  3. 3.
    El-Bedawi KM, Hainsworth R. Combined head-up tilt and lower body suction: a test of orthostatic tolerance.Clin Auton Res 1994; 4:41–47.CrossRefPubMedGoogle Scholar
  4. 4.
    Hainsworth R, El-Bedawi KM. Orthostatic tolerance in patients with unexplained syncope.Clin Auton Res 1994;4:239–244.CrossRefPubMedGoogle Scholar
  5. 5.
    El-Bedawi KM, Hainsworth R. Cardiac pacing does not change orthostatic tolerance in patients with vasovagal syncope.Clin Auton Res 1994;4:233–237.CrossRefPubMedGoogle Scholar
  6. 6.
    El-Sayed H, Hainsworth R. Salt supplement increases plasma volume and orthostatic tolerance in patients with unexplained syncope.Heart 1996;75:134–140.PubMedGoogle Scholar
  7. 7.
    El-Sayed H, Goodall SR, Hainworth R. Re-evaluation of Evans blue dye dilution method of plasma volume measurement.Clin Lab Haem 1995;17:189–194.Google Scholar
  8. 8.
    Stevens PM. Cardiovascular dynamics during orthostasis and influence of intravascular instrumentation.Am J Cardiol 1996;17: 211–218CrossRefGoogle Scholar
  9. 9.
    O'Connor WJ. Normal sodium balance in dogs and in man.Cardiovasc Res 1997;11:375–408.Google Scholar
  10. 10.
    Gupta BN, Linden RJ, Mary DASG, Weatherill D. The influence of high and low sodium intake on blood volume in dogs.Q J Exp Physiol 1981;66:117–128.PubMedGoogle Scholar
  11. 11.
    Rocchini AP, Cant JR, Barger AC, Carotid sinus reflex in dogs with low-to-high sodium intake.Am J Physiol 1997;233:H196-H202.Google Scholar
  12. 12.
    Lyons RH, Jacobson SD, Avery NL. Increases in the plasma volume following the administration of sodium salts.Am J Med Sci 1944;208:148–154.Google Scholar
  13. 13.
    Romero JC, Stoneloni RJ, Duf MC, et al. Changes in fluid compartments, renal haemodynamics, plasma renin and aldosterone secretion induced by low sodium intake.Metabolism 1968;17:10–19.PubMedGoogle Scholar
  14. 14.
    Brown WJ, Brown FK, Krishon I. Exchangeable sodium and blood volume in normotensive and hypertensive humans on high and low sodium intake.Circulation 1971;43:508–519.PubMedGoogle Scholar
  15. 15.
    El-Sayed H, Hainsworth R. Relationship between plasma volume, carotid baroreceptor sensitivity and orthostatic tolerance.Clin Sci 1995;88:463–470.PubMedGoogle Scholar
  16. 16.
    Intersalt Cooperative Research Group. Intersalt: an international study of electrolyte excretion and blood pressure.Br Med J 1988;297:319–328.Google Scholar
  17. 17.
    Vatner SF, Boettcher DH, Hayndrickx GR, McRitchie RJ. Reduced baroreflex sensitivity with volume loading in conscious dogs.Circ Res 1975;37:236–242.PubMedGoogle Scholar
  18. 18.
    Billman GE, Dickey DT, Zeho KK, Stone HL. Effects of central venous blood volume shifts on arterial baroreflex control of heart rate.Am J Physiol 1982;241:H571-H575.Google Scholar

Copyright information

© Lippincott Williams & Wilkins 1998

Authors and Affiliations

  • Benjamin L. Mtinangi
    • 1
  • Roger Hainsworth
    • 1
  1. 1.Institute for Cardiovascular ResearchUniversity of LeedsLeedsUK

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