The purpose of this study is 1) to determine what physiologic factors (extracellular fluid overload or vasoconstriction) contribute more to increased blood pressure levels between dialysis treatments in hemodialysis patients whose blood pressure increases and decreases during hemodialysis and 2) to determine whether carvedilol provides better control of blood pressure between dialysis treatments than prazosin in patients whose blood pressure increases during dialysis.

Inclusion Criteria (for Aims 1 and 2):

• age more than 18 years
• Hypertension defined as systolic blood pressure more than 140 mmHg before dialysis or more than 130 mmHg after dialysis
• For case subjects with intradialytic hypertension: systolic blood pressure increase more than 10 mmHg from pre to post dialysis in at least 4 out of 6 screening treatments
• For control subjects: systolic blood pressure decrease more than 10 mmHg from pre to post dialysis in at least 4 out of 6 screening treatments

Inclusion criteria for Aim 3 includes the case subjects described above.

Exclusion Criteria:

For Aims 1 and 2:

• Hemodialysis vintage less than 1 month
• Amputated arm or leg
• Presence of cardiac defibrillator or pacemaker
• Presence of large metal prosthesis
• Failure to achieve dry weight

For Case subjects participating in Aim 3:

• Patients with a specific indication for beta blocker therapy including systolic heart failure, history of myocardial infarction, history of tachyarrhythmia or angina being managed with beta blocker therapy.
• Patients with contraindications to beta blockade including bradycardia (heart rate less than 60 beats per minute) while not on a pulse lowering drug, severe reactive airway disease, prior intolerance to beta blocker therapy
• Prior intolerance to alpha blocker therapy

This study population includes hypertensive hemodialysis patients.