Effect of Hyperosmolality on Vasopressin Secretion in Intradialytic Hypotension: A Mechanistic Study

Background

Administration of a small volume of hypertonic solution has been used as an effective treatment for patients with intradialytic hypotension. Hypertonic solutions have been considered to act as plasma volume expanders. This clinical study examines whether arginine vasopressin (AVP) is involved in this mechanism of blood pressure control.

Study Design

Nonrandomized trial.

Setting & Participants

42 patients on long-term hemodialysis therapy at a single hospital.

Intervention

Effects of intravenous infusions of 20 mL of 10% saline, 20 mL of 50% glucose, 200 mL of 0.9% saline, or physiological doses of AVP were examined during intradialytic hypotension.

Outcomes & Measurements

Changes in plasma AVP levels, osmolality, plasma volume, and blood pressure were analyzed.

Results

Hypertonic saline infusion increased plasma osmolality (mean, 292.7 to 302.3 mOsm/kg H₂O; P < 0.001), plasma AVP levels (3.9 to 7.8 pg/mL; P = 0.03), and mean arterial pressure (66.6 to 71.8 mm Hg; P = 0.01). The increase in plasma volume (2.3%; P = 0.03) was too small to increase blood pressure because of volume alone. Hypertonic glucose infusion yielded similar results. Isotonic saline infusion increased blood pressure with an abrupt increase in plasma volume (12.7%; P < 0.001). AVP infusion increased blood pressure and plasma AVP to levels similar to those induced by the hypertonic solutions.

Limitations

There are limitations in accurately measuring changes in plasma volume during hemodialysis.

Conclusions

Results strongly suggest that the osmotic stimulation of AVP secretion by hypertonic solutions has an important role in increasing blood pressure in patients with intradialytic hypotension. Manipulating plasma AVP appropriately may help correct and prevent intradialytic hypotension.

Index Words: Hemodialysis, vasopressin, hypotension, osmolality, plasma volume