ABSTRACT
BACKGROUND: Intradialytic hypotension is the most common and severe acute complication of hemodialysis therapy. In our previous study, infusion of 20 mL of 10% saline into the venous line of a dialyzer increased blood pressure during dialysis hypotension by stimulating arginine vasopressin (AVP) secretion, independent of its effect on plasma volume (PV). This study examines the mechanism by which a small amount of hypertonic solution stimulates AVP secretion. METHODS: Hemodialysis patients were infused with 20 mL of 2.5 M saline (100 mOsm) over 5 (Protocol 1) or 2 min (Protocol 2) or with isotonic saline (Protocol 3) into the venous line. RESULTS: Arterial plasma osmolality (Posm) increased by 28.1 and 16.0 (P < 0.0001), while peripheral venous Posm increased by only 8.6 and 8.9 mOsm/kg H(2)O (P < 0.001) in Protocols 2 and 1, respectively. Plasma AVP (P(AVP)) increased significantly by 18.6 and 5.6 pg/mL, PV by 7.2 and 5.5% and mean arterial pressure (MAP) by 15.0 and 7.2 mmHg in Protocols 2 and 1, respectively. Thus, there were large differences in Posm between arterial and peripheral venous blood; osmolar gap, P(AVP) and MAP increased in proportion to the infusion rate. Isotonic saline (30.8 mOsm) infusion increased PV by 8.7% and MAP by 7.2 mmHg. CONCLUSION: Our results indicate that by a mechanism similar to cardiopulmonary recirculation, hypertonic saline infusion caused a striking increase in arterial Posm that enhanced AVP secretion and raised blood pressure. The effect of hypertonic saline on PV was less than one-third of isotonic saline under similar osmolar loads.
Subject(s)
Arginine Vasopressin/metabolism , Hypotension/drug therapy , Hypotension/prevention & control , Renal Dialysis/adverse effects , Saline Solution, Hypertonic/administration & dosage , Adult , Aged , Aged, 80 and over , Arginine Vasopressin/drug effects , Cohort Studies , Dose-Response Relationship, Drug , Drug Administration Schedule , Female , Follow-Up Studies , Humans , Hypotension/etiology , Infusions, Intravenous , Kidney Failure, Chronic/diagnosis , Kidney Failure, Chronic/therapy , Male , Middle Aged , Osmolar Concentration , Prospective Studies , Reference Values , Renal Dialysis/methods , Risk Assessment , Treatment OutcomeABSTRACT
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 H(2)O; 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.
Subject(s)
Arginine Vasopressin/metabolism , Dialysis Solutions/adverse effects , Hypertonic Solutions/adverse effects , Hypotension/blood , Renal Dialysis/adverse effects , Aged , Aged, 80 and over , Arginine Vasopressin/blood , Blood Pressure , Blood Volume , Dialysis Solutions/therapeutic use , Female , Follow-Up Studies , Humans , Hypertonic Solutions/therapeutic use , Hypotension/etiology , Hypotension/physiopathology , Male , Middle Aged , Osmotic Pressure , Prognosis , Risk Factors , Time FactorsABSTRACT
BACKGROUND: Although attention has recently focused on electrolyte-free water clearance (E-CH2O) as a replacement for solute-free water clearance (CH2O), especially from the viewpoint of plasma sodium regulation, a thorough comparison of the two has yet to be conducted. METHODS: CH2O and E-CH2O were systematically compared in normal subjects in different diuretic stages, including furosemide-induced solute diuresis, and in patients with renal disease. RESULTS: The normal renal ability to conserve free water based on E-CH2O was only 41% of that based on CH2O. E-CH2O remained positive until the urinary osmolality exceeded 500 mosm/kg H2O, markedly different from the 300 mosm/kg H2O for CH2O. The difference between E-CH2O and CH2O could ultimately be attributed to urea osmolar clearance, i.e., urea excretion rate/plasma osmolality, which accounted for about 40% of the osmolar clearance. CH2O underestimated the free water clearance by about 1 ml/min on average at all diuretic stages. CONCLUSIONS: E-CH2O is a more correct parameter than CH2O with regard to the regulation of both plasma sodium and plasma osmolality. However, there is the opinion that the concept of E-CH2O is difficult to understand and that E-CH2O is still not a generally accepted parameter. It is expected that the results of the present study will lead to more general acceptance.
