Twelve human near-drowning victims were treated, and their clinical courses were studied with particular attention given to electrolyte and blood gas changes. Ten of these patients made complete uneventful recoveries. The primary pathophysiological disturbance which necessitated emergency therapy was acute asphyxia with persistent arterial hypoxemia and acidosis. Initially the hypoxia appeared to be due to perfusion of nonventilated alveoli. Persistent arterial hypoxemia was present, however, even after a significant intrapulmonary shunt could no longer be demonstrated. The plan of management for each patient should be determined by individual laboratory and clinical studies.During the past few decades, considerable em¬ phasis has been placed on the serum elec¬ trolyte changes that occur during drowning.' '* In a retrospective study published in 1963, however, Fuller was unable to document significant electro¬ lyte changes in human near-drowning victims.7 Recent experiments with animals have shown that the electrolyte changes following aspiration of both fresh water8 and sea water" are related directly to the quantity of water aspirated. In untreated ani¬ mals which survived these experiments, electrolyte values spontaneously returned to normal. The com¬ mon denominator in all animals, regardless of the composition or volume of fluid aspirated, was the onset of acute asphyxia with persistent arterial hypoxemia and acidosis.'" The following clinical study was undertaken to correlate laboratory find¬ ings of studies of animals with changes observed in human near-drowning victims.Methods.-Twelve human near-drowning victims, six who had aspirated chlorinated fresh water, and six who had aspirated sea water, have been treated during the past three years at the University of Miami-Jackson Memorial Hospital. The sea-water victims were retrieved from the Atlantic Ocean beaches of southeastern Florida, and the fresh wa¬ ter victims were rescued from chlorinated fresh wa¬ ter pools. For all patients who had nearly drowned in fresh water, a sample of pool water was obtained and analyzed for electrolyte concentrations. Medi¬ cal therapy was supervised by the authors for 11 patients from the moment they first entered the hospital. Consultation was not obtained until 18 hours after admission for the 12th victim (case 4). Initial emphasis was on immediate therapy, and the data were obtained without compromising the clinical course of the patients. Aliquots of venous blood were drawn within min¬ utes of each patient's arrival to the emergency room and were placed in tubes containing sodium citrate for whole blood studies, or in dry tubes for serum studies. Whole blood was analyzed for hemo¬ globin concentration by the cyanmethemoglobin method, and for hematocrit value with a GuestWeichselbaum microcapillary centrifuge. The blood was then centrifuged, and the plasma was removed and analyzed for hemoglobin content by a modifica¬ tion of the Bing and Baker technique." Serum concentrations of sodium and potassium were deter¬ mined o...