EFFECTS OF SEVERE PROGRESSIVE HEMODILUTION ON REGIONAL BLOOD-FLOW AND OXYGEN-CONSUMPTION

  • 1 January 1976
    • journal article
    • research article
    • Vol. 79  (3) , 299-305
Abstract
Electrolyte solutions are effective in the immediate treatment of hemorrhagic shock, but the acceptable limits of hemodilution are not well defined. In this study O2 consumption was measured in various tissues at rest and in maximally exercising skeletal muscle during progressive hemodilution. Splenectomized, anesthetized dogs (20) were studied (weight, 22.6 .+-. 2.0 kg). Measurements were made of cardiac output, capillary muscle blood flow in the hind limb and renal and superior mesenteric arterial blood flow. Arteriovenous O2 differences in the hind limb, kidney, gut and in the whole body were calculated from the O2 content of arterial and appropriate venous samples. Electrical stimuli were applied to hind limb to cause rhythmic muscle contraction and maximal blood flow. After control measurements the animals were bled and were saline-infused stepwise until the hematocrit was reduced to 11.5 .+-. 4.7%. Measurements were repeated at various hematocrit levels. With hemodilution there was a rise in cardiac output (2.50 .+-. 0.58-3.59 .+-. 1.17 l/min, P < 0.005) and a fall in total peripheral resistance. There was a slight fall in total O2 uptake (125 .+-. 36-100 .+-. 40 ml/min) and in splanchnic O2 uptake (12.8 .+-. 6.6-8.8 .+-. ml/min). Renal O2 uptake was not altered significantly, but there was a large decrease in the maximum O2 consumption of exercising muscle (6.38 .+-. 4.3-1.37 .+-. 1.2 ml/100 gm of muscle per min, P < 0.001) due to significant reduction of capillary perfusion in addition to the expected reduction of arteriovenous O2 difference. The total O2 consumption was unrelated to the hematocrit, but the positive correlation between the hematocrit and exercising muscle O2 consumption was highly significant (r = 0.66, P < 0.001). Resting O2 consumption in the whole body, kidney and gut remains adequate even with severe hemodilution, but in exercising muscle which has high O2 demand, normal function cannot be maintained.

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