The death rate of patients with endstage renal disease (ESRD) on dialysis each year is 20%, with diseases related to the heart and blood vessels causing about half. About 60% of patients on hemodialysis have high blood pressure, which is poorly controlled in most. Normal blood pressure in these patients greatly improves the chance of living. Increased fluid in the body and bloodstream is a major cause of hypertension in patients with ESRD. Fluid removal during hemodialysis is often limited by symptoms of low blood pressure during the procedure. Therefore the increase in fluid and related high blood pressure is ongoing for many of these patients. Arginine vasopressin (AVP) is a hormone naturally produced by the body which has little effect on blood pressure in healthy people, but acts as a powerful vasoconstrictor (narrows the blood vessels) when blood pressure is threatened. Recent studies have shown when there is too little AVP, patients are more likely to have low blood pressure during dialysis that limits fluid removal, an effect that can be reversed by giving these patients low doses of AVP. This phase II trial will find out which of two doses of AVP (.15 or .30 mU kg-1 min-1), in combination with standard therapy, works best to change interdialytic 44-hour ambulatory systolic blood pressure after 2 weeks. Patients who enroll in this study will be divided into three groups. One group will be given a 0.15 mU kg-1 min-1 dose of AVP at each dialysis session over a 2-week period; the second group will be given AVP 0.3 mU kg-1 min-1 at the same interval; and a third group will be given normal saline (placebo) at the same interval. All patients will be closely monitored for side-effects.

This pilot study originally enrolled a group of 12 subjects (4 subjects per arm) in order to demonstrate feasibility with the primary outcome measure, interdialytic 44-hour ambulatory systolic blood pressure. Data on the original subjects is complete and results are posted.

The data from this study will be used to design and conduct additional study enrollment/extension (24 subjects) in order to make some initial statistical comparisons between groups, which will help establish greater confidence in our novel method for controlling blood pressure in dialysis patients.

Inclusion Criteria:

• End Stage Renal Disease on Hemodialysis greater than 3 months
• Hypertension (Predialysis systolic blood pressure (SBP) greater than 140 mmHg, averaged over preceding 6 dialysis treatments)
• Stable dry weight over preceding 6 dialysis treatments

Exclusion Criteria:

• Age less than 18 years
• Clinically significant vascular disease*
• Predialysis systolic blood pressure (SBP) greater than 200 mmHg or diastolic blood pressure (BP) >110
• Pregnancy
• Long QTc syndrome (an electrocardiogram (ECG) will be performed if unavailable within the last 3 months)

Clinically significant vascular disease is defined as any of the following occurring in the preceding three months: angina, claudication, transient ischemic attack, myocardial infarction, cerebrovascular accident, or decompensated heart failure. Furthermore, patients will be excluded if they have any history of ischemic colitis or Raynaud's disease.