RESUMEN
The aim of this study was evaluate the effects of a single, 10 min, intravenous infusion of a hyperonic NaCl solution [2.400 mOsm/l; infused volume 0.35 ñ 0.03 ml (SEM) on the hamster cheek pouch microcirculation during normovolemia and after acute bleeding to a hypotension level of about 40 mmHg. Upon bleeding, the arterial pressure dropped to 39 µ 1 mmHg, arterioles > 40 -m constricted 12 ñ 3% (from their control value), arterioles < 40 µm dilated 6 ñ 2%, venules stayed largely unchanged, while RBC velocity and volume flow decreased 57 ñ 7% in all vessels. Durign the subsequent hypertonic NaCl infusion, the arterial pressure increased rapidly to a new steady state level of 66 ñ 3 mmHg. After the infusion, the large arterioles stayed constricted 11 ñ 1% and the small arterioles dilated 7 ñ 1% for a 1-h observation period. The venules constricted iniatially by 6 ñ 2% and returned to control diameter in 30-40 min. RBC velocity and calculated volume flow returned to the pre-hemorrhage cotrol values in about 10 min for the arterioles and in 40 min for the venules. An identical hypertonic infusion given to normovolemic hamsters caused no significant alterations of the measured variables