Lecture 25: Hemorrhage Flashcards Preview

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Flashcards in Lecture 25: Hemorrhage Deck (16)
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hemorrhagic shock

when 30-40% of blood volume is lost, cannot save animal from failure if transfusion is given too late. Assoc. with sudden withdrawal of sympathetic drive ("decompensation")


Arterial baroreflex to compensate for hemorrhage

rapid peripheral vasoconstriction via sympathetic drive triggered by low BP and unloading of baroreceptors. The most rapid compensatory mech.!


Which areas are vasoconstricted first in Arterial baroreflex?

non-vital vascular beds (skeletal, spleen, cutaneous, hepatic)


Chemoreflex compensatory mech. for hemorrhage

elicits increased vasoconstriction and hyperventilation. Stimulated by low O2 in blood due to low blood flow


Cerebral Ischemia compensatory mech. for hemorrhage

activates sympathoadrenal system for vasoconstriction. Prolonged activation may result in strong vagal stimulation and bradycardia


Reabsorption of Tissue fluids to compensate for hemorrhage

decreased capillary hydrostatic pressure promotes reabsorption of fluid. Cortisol increases capillary permeability to help this process


Endogenous vasoconstrictors compensatory mech. for hemorrhage

Increases circulating levels of E and NE


2 methods of renal conservation of water and salt in hemorrhage

1) vasopressin/ADH --> vasoconstrictor, promotes water reabsorption
2) angiotensin II --> vasoconstrictor, triggers release of more ADH


Aldosterone stimulated by

Ang II


Aldosterone fx

stimulates sodium reabsorption by the renal tubules


what causes decrease in hematocrit?

increase in fluid volume relative to red blood cell concentration


long term mechs. to increase blood volume: (2)

1) increased aldosterone release and decreased Na excretion
2) increased lvls of Ang II to stimulate thirst and salt appetite


final compensation for hemorrhage

restoration of lost plasma proteins and blood cells


where are plasma proteins and blood cells synthesized?

liver, bone marrow. proteins take few days, RBCs take 2-3 weeks


quick acting method of restoring volume post hemorrhage?

reabsorption of interstitial fluid back into capillaries


circulatory shock/hemorrhagic decompensation

progressive deterioration of CV function following extensive blood loss

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