Measurements
Ambulatory BP Monitoring
Ambulatory BP monitoring was performed either after the first or midweek hemodialysis session for 44 hours. Ambulatory BP was recorded every 20 minutes during the day (6 AM to 10 PM) and every 30 minutes during the night (10 PM to 6 AM) using a Spacelab 90207 ambulatory blood pressure monitor (SpaceLabs Medical, Inc) in the nonaccess arm, as reported previously.13 Awake and sleep readings were calculated for each patient by self-reported sleep and wake
times by means of a diary. Even limited number of ambulatory BP are useful for prognostic purposes in the general population; therefore,we did not exclude any patients based on the number of ambulatory BP recordings.