MethodsThe animals used in these studies were females of the Sprague Dawley strain which had been fasted IS hours before use. Water was allowed during the fast. At the time of the experiment, the animals weighed 175 to 225 Gm. Sodium pentobarbital (40 mg./Kg. intraperitoneally) was used as the anesthetic.Two levels of hemorrhage were employed, 10 ml./Kg -. and 21 to 25 ml./Kg. The smaller hemorrhages were accomplished by withdrawal of blood from the femoral vein after the intravenous administration of 1 ing. heparin per rat. The larger hemorrhages were, in most cases, accomplished similarly. In some cases, the femoral artery and vein were cut together with a razor blade and the lost blood absorbed and weighed on cotton pledgets; bleeding usually stopped spontaneously after the loss of 21 to 25 nil. of blood/ Kg'. In a few cases, the hemorrhage was from a catheter in the carotid artery. The route of hemorrhage had no discernible effect on the results.

No abstract

Rats anesthetized with ethyl ether were compared with rats anesthetized with sodium pentobarbital from the standpoint of cardiac output, peripheral resistance and regional blood flow. Cardiac output was measured by the indicator-dilution technic; regional blood flow was determined by the indicator-fractionation technic employing Rb 86 or I 131 -antipyrine. The cardiac output is one and a half times as great in ether anesthesia as in pentobarbital anesthesia; the peripheral resistance is about two-thirds as great with ether. Compared to pentobarbital, ether increases myocardial, cerebral, and carcass blood flow, while decreasing renal, splanchnic and cutaneous blood flow. The pronounced difference in the cardiovascular effects of the two agents indicates the need for caution in the interpretation of experiments in which cardiovascular measurements are made under anesthesia.