Relationship between circadian blood pressure variation and circadian protein excretion in CKD

Circadian blood pressure changes are blunted in patients with chronic kidney disease (CKD). Proteinuria is the most important correlate of hypertension in CKD. However, little is known about the influence of circadian blood pressure changes and variation in protein excretion rate. Furthermore, the impact of blood pressure components, e.g., mean arterial pressure and pulse pressure, on proteinuria has not been evaluated. To analyze the relationship of circadian changes in blood pressure on urinary protein excretion patterns, glomerular filtration rate was measured with iothalamate clearance and 24-h ambulatory blood pressure with SpaceLabs 90207 monitor in 22 patients with CKD. It was found that hourly protein excretion rates were 31% higher during the night. Excretion results of sodium, potassium, chloride, urea, and creatinine were also between 30 and 40% higher at night. Systolic, mean arterial, and pulse pressures but not diastolic pressure were related to daytime protein excretion rate. At night, the relationship of systolic, diastolic, and mean arterial pressures was significantly lower and essentially flat with respect to protein excretion rate, but the relationship of pulse pressure and proteinuria was not different from that seen during the day. Circadian variation in blood pressure did not impact circadian sodium excretion rate. In conclusion, these data suggest that patients with CKD have patterns of proteinuria that share different relationships with blood pressure components depending on the awake-sleep state. Pulse pressure is related to proteinuria independent of the awake-sleep state. Reducing mean arterial pressure during the day and pulse pressure during the day or night may be effective antiproteinuric strategies.