By a suitable pattern of saline infusion we established an equilibrium between input and renal output of sodium and water in the conscious animal, which was maintained for six hours. During this period of equilibrium we found an increase in GFR, plasma volume and functional ECFV of about 30% each, the amount of intravascular protein and albumin being unchanged. Under nitrous-oxide and thiopentone anaesthesia renal sodium and water excretion was unchanged compared with values of conscious animals. However there was a striking decrease in plasma volume as well as in circulating protein and albumin by approximately 20%. Similarly functional ECFV (sulphate space) was found to be reduced under thiopentone anaesthesia. Retention of sodium about 12 hours after the end of anesthesia amounted to 7% of the quantities infused (about 50 mval per animal), whilst the applied water load had been completely excreted.
Anesthesia Animals