Blood pressure changes during daytime sleep and comparison of daytime and nighttime sleep-related blood pressure changes in patients with chronic renal failure

Abstract

Blood pressure has a diurnal pattern primarily related to activity and sleep. Chronic renal failure patients may lack the normal nocturnal decline in blood pressure during sleep. In 33 subjects (14 with normal renal function and 19 with renal dysfunction), the relationship between depth of daytime sleep, as determined by electroencephalographic sleep phase, and change in mean arterial blood pressure (MAP) and heart rate measured oscillometrically, was correlated. In 15 chronic renal failure patients, the effect of daytime and nighttime sleep on MAP and heart rate was compared. The percent change in night asleep versus day awake MAP and heart rate was measured (with Space Labs ambulatory blood pressure monitors) and compared with the percent change in daytime sleep-related MAP and heart rate measured during a daytime sleep electroencephalographic study. During daytime sleep, MAP changes are not significantly different in the normal versus renal dysfunction groups. In the 33 study subjects, MAP declines progressively from the upright position to Phase 3/4 sleep (118 ± 3.3 to 106 ± 3.6 mm Hg). The largest decline occurs between the upright to recumbent position, before sleep. Heart rate declines moving from the upright to recumbent position, 76 ± 2.3 to 70 ± 2.1 beats/min, but does not decline further with sleep. In 15 chronic renal failure patients, heart rate (10.8 ± 2.8%; P< 0.05), but not MAP, declines during nighttime sleep. Both MAP (7.7 ± 3.3%) and heart rate (5.4 ± 1.9%) decline significantly during daytime sleep. The responses of MAP and heart rate to daytime and nighttime sleep were in opposite directions in 3 of 15 subjects. In conclusion, MAP declines progressively during daytime sleep with successively deeper levels of sleep. Movement from the upright to the recumbent position accounts for a large part of the decline. In patients with chronic renal failure, MAP and heart rate responses to daytime and nighttime sleep may be in opposite directions. Future physiologic studies are needed to explore the mechanisms of daytime and nighttime sleep-related hemodynamic changes.