Effects of desmopressin on immersion diuresis and physcial and cognitive performance after long dives

Water immersion, in and of itself, causes a redistribution of blood volume and an increase in urine production which results in a loss of plasma volume (dehydration). Dehydration affects the blood flow to muscle and skin as well as generally affecting the distribution of blood volume. 1-Desamino-8-D-Arginine Vasopressin (DDAVP), an analog of endogenous vasopressin, inhibits urine production and is of use in preventing the loss in blood volume due to immersion. This study was conducted in two phases to examine the effect of DDAVP on immersion diuresis and subsequent physical and cognitive performance. Twenty U.S. Navy divers participated in long duration air dives, 10 in a pool study at 72°F and 10 in a field study at 80-82°F. Post dive hydration and physical and cognitive performance were measured. Dives lasted 3.5 hours at 10-15 feet sea water. Each diver completed a control (saline placebo) and an experimental dive. During the experimental dive the divers were given 40 micrograms of DDAVP intranasally prior to entering the water. Blood samples were taken before and after each dive. Exercise tests (Physical Work Capacity 170) and cognitive performance assessments were also performed before and after dives. Several urine, electrolyte and hematologic values were determined pre and post dive, with and without DDAVP, and compared. Changes in body weight were also determined. DDAVP effectively attenuated the immersion diuresis in both the pool and field studies. Total urine volume during the 3.5-hour dive was reduced from 1867±187ml to 663±142ml in the pool and from 1355±301 ml to 290±57ml in the field by the administration of DDAVP. The administration of DDAVP and attenuation of immersion diuresis neither impaired nor increased physical or cognitive performance at these warm water temperatures. DDAVP significantly reduced fluid loss by attenuating the immersion diuresis.