Effects of furosemide on body water compartments in infants with bronchopulmonary dysplasia.

We studied the effects of a single dose of intravenous furosemide on the body water compartments of nine infants with bronchopulmonary dysplasia. We measured total body water, extracellular water, and plasma volume using deuterium oxide, sodium bromide, and Evans blue dye, respectively. From the results of these measurements, we calculated cell water, interstitial water, red cell volume, and total blood volume. We performed these measurements on the first day of the study and again 28 h later, 4 h after an intravenous dose of furosemide (1 mg/kg). All infants had a brisk diuresis in the first hour after the dose, but urine output was no greater during the 24-h period after the dose than during the preceding 24-h period. Total body water, extracellular water, and interstitial water were significantly decreased 4 h after furosemide. There was no change in plasma volume, red cell volume, or total blood volume.

Circadian rhythm in sweating and cutaneous blood flow.

To characterize the changes in the control of the heat loss responses associated with the circadian variation in body temperature, we studied five men during 20 min of exercise in 25 degrees C on 6 separate days. Experiments were conducted at six times, equally spaced over the 24-h day. Esophageal temperature (Tes) and chest sweat rate (msw) were measured continuously, and forearm blood flow (FBF) was measured one to two times per minute. The thresholds for sweating and forearm vasodilation were significantly higher at 1600 and 2000 than at 2400 and 0400, averaging 0.57 and 0.65 degrees C higher, respectively, at 1600 than at 0400. Resting Tes and the Tes thresholds for cutaneous vasodilation and sweating during exercise all showed a similar circadian rhythm. The level at which core temperature is regulated therefore varies over the 24-h day with the zenith occurring around 1600 and the nadir at 0400. However, whereas the slope of the msw-to-Tes relation did not change over the 24-h day, the slope of the FBF-to-Tes relation tended to increase between 0400 and 2400, implying that the circadian rhythm may be more complex than just a shift in the central reference temperature.