Hemorrhage in Normal Man

Abstract

A study of hemorrhage has been conducted in 10 normal male volunteer subjects. Blood loss by phlebotomy over a 20-min. period totalled 10.5-14.3% of blood volume. After a 4 hr. period without treatment, 6 of the subjects received saline infusions totalling approximately 3.5 ml/ml of blood lost. This infusion, 2,000 ml was given over a 4 hr. period. Measurement of phase volumes was carried out, including those for extracellular water, by repeated Injections of radiobromlde. Three of the subjects were fasted, rather than being treated by infusion; 1 of these 3 maintained a total fast and thirst throughout the experiment. The resting ratio of plasma volume to interstitial water [PV: IF] was 0.230 for the group, with a range of 0.180-0.298. Hemorrhage lowers the PV:IF ratio acutely through bulk removal of plasma. Plasma volume refill raises this ratio to a value above normal (0.30), where it remains for as long as 40 hr. if no fluids are given to restore interstitial fluid volume to normal. Continued losses of water and salt by skin, lungs and urine contribute further to the reduction in interstitial fluid volume. The infusion of balanced salt solution over a period of 4 hr. resulted in a transient restoration of plasma volume above normal; interstitial fluid volume and blood volume both returned to normal. The PV: IF ratio was restored to a normal value. The incremental PV: IF ratio in the bled subjects had a mean value of 0.43, indicating a retention of the infused solution to an extent greater than that predicted from the resting PV: IF ratio of 0.23. Administration of fluids by mouth had a similar effect. Subjects who remained fasting and thirsting demonstrated a prolonged rise of PV: IF, as interstitial fluid volume remained low and was not restored by any route. The 1 subject who was kept totally fasting and thirsting, and whose blood loss was 14.3% of blood volume, at the end of the study still had a PV: IF ratio of 0.28, with a plasma volume 13% below normal, a blood volume 15% below normal and an extracellular fluid volume 11% below normal with an unrepaired deficit of 1,600 ml. This deficit was accountable largely on the basis of plasma volume removal plus continued losses by kidney, lungs, and skin. Discrepancy between the observed changes in extracellular water volume and the sum of plasma volume and urine losses averaged about 370 ml or less than 2% of the initial extracellular fluid volume-discrepancies that were well within the range of error of the method. Albumin concentrations were not significantly lowered during the 4 hr. following hemorrhage, and the effect of the saline infusion was to lower globulin concentrations and hematocrit more than albumin. Alterations in renal function were not remarkable, either as a result of the hemorrhage alone or the subsequent infusion. The infusion produced a brisk increase in Na excretion rate and some tendency to retain K. The exponential slope of radiobromide disappearance following equilibrium showed a diminution during the posthemorrhagic state, with restoration to normal by salt infusion.