Effect of an Intravenous Sodium Chloride Load

T HAT most hypertensive patients excrete more water, sodium, and chloride than do normotensive patients when given sodium chloride has been well established since the studies of Farnsworth and Barker.1-3 They pointed out that during diuresis a higher percentage of filtered chloride is excreted by hypertensive individuals. Green, Wedell, Wald, and Learned4 found water and sodium excretion to be directly related to blood pressure when water and sodium were administered. Using osmotic loading, Brodsky and Graubarth5 demonstrated a 2 to 21/2 times greater sodium chloride excretion in hypertensive than in normotensive patients. Birchall, Tuthill, Jacobs, Trautman, and Findley6 found a lack of antidiuretic response following hypertonic sodium chloride administration during water diuresis in hypertensive patients which they concluded was not due to a reduction in the release of antidiuretic hormone. Thompson, Silva, Kinsey, and Smithwick7 showed that hypertensive patients reject a higher proportion of infused sodium than do normotensive patients and that sodium excretion roughly correlates with the mean arterial blood pressure. Studies by Green and