Blood Pressure and Diurnal Variation in Sodium, Potassium, and Water Excretion

This study has been completed.
Sponsor:
Information provided by:
National Heart, Lung, and Blood Institute (NHLBI)
ClinicalTrials.gov Identifier:
NCT00005204
First received: May 25, 2000
Last updated: June 23, 2005
Last verified: November 2001
  Purpose

To determine if hypertensives and normotensives of similar ages had, on average, different ratios of 24-hour to overnight excretion of sodium, potassium, and water. Also, to determine the number of 24-hour collections needed to characterize individuals with respect to the ratios of 24-hour to overnight excretion and to determine if the ratios of 24-hour to overnight excretion vary by age and other factors related to blood pressure.


Condition
Cardiovascular Diseases
Heart Diseases
Hypertension

Study Type: Observational
Study Design: Observational Model: Natural History

Resource links provided by NLM:


Further study details as provided by National Heart, Lung, and Blood Institute (NHLBI):

Study Start Date: August 1987
Estimated Study Completion Date: July 1989
Detailed Description:

BACKGROUND:

For decades excess sodium intake has been implicated in the etiopathogenesis of high blood pressure. Data from epidemiological, clinical, and animal experimental studies all suggest a direct casual association between excess salt intake and hypertension. Several investigators suggest that hypertension is the result of an inability of the kidney to excrete salt and water normally. It is hypothesized that the development of chronic blood pressure elevation results from the kidney's need to increase urine volume and sodium excretion -- in the presence of habitual high sodium intake -- in order to maintain homeostasis of the extracellular fluid volume.

Diurnal variations in excretion of sodium, chloride, potassium and water have been observed in several studies. Water and electrolyte excretion in normal individuals generally reaches a maximum sometime around midday with a minimum toward the end of the sleep period. These studies suggest that the daytime excretion rate exceeds the nighttime rate by 50 to 100 percent. Overnight urine collections have been used in many studies since they are easier to obtain, but they do not provide a direct estimate of the actual intake of sodium or potassium. In order to estimate actual intake, overnight values must be corrected to 24-hour values, that is, by multiplying the overnight values by previously determined ratios of 24-hour to overnight excretions. Preliminary studies by this group of investigators in hypertensives were the first which computed 24-hour to overnight ratios for excretion of sodium, potassium and creatinine in a definite way. This study in hypertensives showed a reversal of the diurnal cycle of sodium excretion. What is not clear in this study and others is whether the reversal is associated with hypertension or reflects decreased renal function with age or whether deterioration of renal function is due to the kidney readjusting its output of salt and water to maintain homeostasis in the face of both an excess sodium intake and a highly variable day to day intake. In addition, it may be that an abnormal diurnal pattern of sodium excretion may indicate that one is at risk of development of hypertension.

DESIGN NARRATIVE:

Each participant provided three 24-hour urine collections, divided into daytime and overnight specimens for the assessment of sodium, potassium, creatinine, and water excretion. Four blood pressure measurements were made. Height and weight were measured. Information was collected on demographic variables, alcohol intake, history and treatment of blood pressure, medication use, family history of high blood pressure, cigarette use, and changes in dietary habits. Analysis of variance was the primary method of data analysis.

  Eligibility

Genders Eligible for Study:   Male
Accepts Healthy Volunteers:   No
Criteria

No eligibility criteria

  Contacts and Locations
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No Contacts or Locations Provided
  More Information

No publications provided

ClinicalTrials.gov Identifier: NCT00005204     History of Changes
Other Study ID Numbers: 1083
Study First Received: May 25, 2000
Last Updated: June 23, 2005
Health Authority: United States: Federal Government

Additional relevant MeSH terms:
Cardiovascular Diseases
Heart Diseases
Hypertension
Vascular Diseases

ClinicalTrials.gov processed this record on July 28, 2014