Effect of Hemorrhage on the Cardiac Output and Distribution in the Rat

Abstract

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.

Effects of Hemorrhage on Regional Blood Flow Distribution in Dogs and Primates

“…There are several possible explanations for the discrepancy between the conclusion of previous investigations, indicating intense renal vasoconstriction with hemorrhage (18)(19)(20)(21)(22)(23)(24)(25)(26)(27), and those in the present one, demonstrating sparing of the renal bed. Three important features of the present investigation were (a) renal blood flow was measured in the conscious animal, (b) these measurements were instantaneous and continuous, and (c) hemorrhage was not severe or prolonged, i.e., hemorrhagic shock did not develop.…”

“…When hemorrhage -was continued in the anesthetized animals to 26 ml/kg, renal flow had fallen and renal resistance had risen substantially. This effect has been observed by others with equivalent levels of hemorrhage in anesthetized animals (19,20,22,(24)(25)(26)(27). In contrast, in the present study renal dilatation occurred uniformly in the normal conscious animals with similar degrees of hemorrhage.…”

“…While measurements were recorded continuously during hemorrhage, two points were chosen to compare with control values; the first occurred before a reduction in arterial pressure, which occurred after 14±2 ml/kg of hemorrhage and is designated as the mild nonhypotensive hemorrhage response, while the second point was chosen after a sustained [20][21][22][23][24][25][26][27][28][29][30] ied hypoten-iliac flow had fallen by 58±5% to 46±4 ml/min and iliac resistance had risen from 0.88+0.05 to 1.72±0.11 -onary blood mm Hg/ml/min. These changes were all significant and transi-(P < 0.01) ( %) resistances were significantly less than without blockade (P < 0.01).…”

“…In contrast, the concept that the renal bed responds to hemorrhage with constriction is widely accepted (1, 2, 18-27). In fact, there are several studies which indicate the renal bed has the most intense constriction of all peripheral beds studied (25,26).…”

“…Three important features of the present investigation were (a) renal blood flow was measured in the conscious animal, (b) these measurements were instantaneous and continuous, and (c) hemorrhage was not severe or prolonged, i.e., hemorrhagic shock did not develop. Studies indicating intense renal vasoconstriction with hemorrhage were generally conducted in animals after general anesthesia and surgical manipulation of the kidney (19,20,22,26,27) or in man and experimental animals utilizing intermittent techniques to measure blood flow (18,23,25).…”