78 



HANDBOOK OF PHYSIOLOGY 



CIRCULATION I 



however, was due to an increase of heart rate, the 

 stroke volume decreasing significantly. For this reason 

 right ventricular stroke work during hypovolemic 

 anemia was not significantly increased over the control 

 period. The results suggested that the increase of right 

 atrial transmural pressure was not an important 

 mechanism for increasing cardiac output, stroke vol- 

 ume, or cardiac stroke work in these experiments. 



The mechanism by which the cardiac output is in- 

 creased with acute anemia produced by dextran in- 

 fusion is still uncertain. Justus and co-workers (64) 

 made dogs anemic by bleeding and dextran infusion. 

 Transfusion of blood from these anemic dogs into 

 other dogs without producing anemia in the recipient 

 animals was associated with increased cardiac output 

 in the recipient dogs. These observations suggested 

 that a humoral substance may be important in medi- 

 ating the increase of cardiac output associated with 

 acute anemia. 



PHYSIOLOGIC EFFECTS OF COLLOIDAL INFUSION 

 IN OLIGEMIC ANIMALS 



We should now like to consider the effect of plasma 

 substitutes in animals made hypovolemic by bleeding. 

 Wasserman & Mayerson (108) lowered the blood 

 pressure of dogs to 40 mm Hg by bleeding. Four hours 

 after the infusion of 6 % clinical dextran, there was 

 an expansion of plasma volume, as measured by P'^' 

 human serum albumin, equivalent to 80% of the in- 

 fused volume. In unbled dogs the plasma volume was 

 expanded only 25% of the infused volume at this 

 time. Dextran levels in thoracic duct lymph remained 

 below plasma dextran levels. The dextran plasma- 

 lymph concentration gradient remained for at least 

 24 hours and was higher than that for albumin and 

 globulin. It was suggested that dextran leaked into 

 interstitial fluid more slowly than plasma protein and 

 was therefore a good plasma expander. Parkins and 

 associates (84) bled dogs and then reinfused them with 

 dextran, cxypolygelatin, modified fluid gelatin, or 

 saline. In one test procedure where reinfusion was 

 immediate there was no significant difference in the 

 three colloids. All were slightly less effective than 

 heparinized blood and more effective than saline. 

 When hypotension was prolonged for i hour, modified 

 fluid gelatin was almost as effective as blood. Dex- 

 tran and oxypolygelatin were less effective, but were 

 still considerably more so than saline. Padhi and co- 

 workers (83) bled dogs up to 35 % of their total blood 

 volume and replaced the blood which had been re- 



moved with dextran in equal volume. Blood pressure 

 and pulse rate responded equally well to blood or dex- 

 tran; however, all the animals replaced with dextran 

 showed a tendency to bleed, and three of six died the 

 following day. Waud (i 10) bled dogs to a blood pres- 

 sure level of 50 mm Hg and then transfused them with 

 an equal volume of 6'^c de.xtran (Intradex) (average 

 mol wt 75,000). Blood pyruvate and lactate rose after 

 bleeding and then fell with dextran. Blood sugar re- 

 mained unchanged. The blood pressure returned to 

 near normal with dextran. Heart and respiratory 

 rates, which rose following bleeding, fell with dextran. 

 Following dextran, there was a fall in hematocrit, in 

 the red blood cell count and white blood cell count, 

 and in rectal temperature, with a rise in the sedi- 

 mentation rate of erythrocytes. Twenty dogs given 

 dextran all lived; 8 not infused with dextran died. 

 Morrison and associates (78) compared the effects 

 of various replacement agents in bled rats, guinea 

 pigs, and dogs. After bleeding rats 3.5 ml/ 100 g body 

 weight, none survived without infusion; with iso- 

 tonic saline replacement, i o % survived ; with dex- 

 tran, 70% survived; with 3.5 ">c PVP, 8o';'c survived; 

 with 5% bovine osseous gelatin, 80% survived; with 

 serum albumin, 90% survived; with heparinized rat 

 blood, looS'o survived. In guinea pigs that were bled 

 followed by blood volume replacement with plasma 

 expanders, none survived with saline infusion; 50% 

 survived with dextran; with 3.5% P\'P, 60% sur- 

 vived ; with 5 % bovine osseous gelatin, 80 % survived ; 

 with serum albumin or heparinized guinea pig blood, 

 all survived. In dogs, dextran was more efficient than 

 other substitutes and approximately as efTective as 

 human plasma. Bollman and associates (16) studied 

 the effects of various plasma substitutes as plasma vol- 

 ume expanders in rabbits who were bled 20 ml/kg of 

 body weight, reducing the blood volume to 60% of 

 control. Dextran of 24,000 molecular weight did not 

 maintain blood volume better than saline; however, 

 dextran of molecular weight 120,000 maintained 

 blood volume with but slight fall during a 24-hour 

 period. Without bleeding 20 ml kg body weight of 

 dextran increased the blood volume to 120% in 30 

 min and at 6 hours; the blood volume returned to 

 control levels at 24 hours. Five per cent PVP in vol- 

 ume equal to the blood removed in bled rabbits main- 

 tained the blood volume at 95 % of the original for 24 

 hours. Two and a half per cent and 3.5% PVP main- 

 tained the blood volume at about 85% of control. 

 Three to 8% gelatin in saline maintained the blood 

 volume at 85 to 90 % for 6 hours with a decline to 70 

 to 75^ at 24 hours. Nine per cent acacia in saline 



