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Hypovolemic Shock: Pathogenesis, Complications, and Clinical Findings Authors: Dean Percy Miranda Schmidt Reviewers: Yan Yu Tristan Jones Frank Spence* Ben Campbell Ayaaz Sachedina* * MD at time of publication Progressive ↓ in level of consciousness Pulseless Electrical Activity Acute Kidney Injury ↑ Reabsorption of salt and water in the kidney Oliguria (↓ urine output) Inflammation (pancreatitis, cirrhosis, post-operative, etc.) Inflammatory mediators ­ vessel permeability and fluid leaks out Trauma Ruptured vessels leak fluid into potential spaces Hemorrhagic losses (GI bleed, postpartum hemorrhage, etc.) ↓ Intravascular volume ↓ Venous return to the heart ↓ Cardiac output (blood pumped from the heart) Hypovolemic Shock ↓ Oxygen delivery to tissues due to low blood volume Insufficient organ perfusion Non-Hemorrhagic losses (dehydration, GI losses, skin losses / burns, renal losses, etc.) ‘Third Spacing’ of fluid (fluid located outside the intravascular or intracellular space; large collections can occur in the pelvis, thorax, GI tract, long bones of children, intra-abdominally, retroperitoneally) P = Q x R; less ‘flow’ in the vessels (Q), with vessels not constricting enough to maintain resistance (R)à pressure (P) will drop ↓ Blood Pressure Caution: young, healthy individuals can maintain blood pressure during circulatory collapse with ­ cardiac output and ­ vasoconstriction; do not use blood pressure as an indicator of shock severity in children Carotid sinus baroreceptors sense low blood pressure ↓ Carotid sinus inhibition of sympathetic nervous system Release of sympathetic catecholamines (epinephrine and ↓ Pressure in venous circulation Brain Heart Kidneys ↓ Blood in the right internal jugular vein ↓ Oxygen delivery to the brain ↓ Myocardial contractility (from lactic acidosis) ↓ Blood flow to kidneys ↓ Jugular Venous Pressure Catecholamines bind to beta-1 receptors in the sinoatrial node of the heart Beta-1 receptor activation causes ↑ heart rate Tachycardia norepinephrine) Catecholamines bind to and stimulate alpha-1 receptors in peripheral vessels Vasoconstriction of peripheral vessels ↓ Blood flow to peripheral tissue Catecholamines bind to and stimulate beta receptors in sweat glands Diaphoresis (sweating) In all body tissues Inadequate oxygen delivery ↓ ATP production ↑ Anaerobic metabolism ↓ Body temperature Impaired neurological functioning Renal ischemia Activation of the renin-angiotensin aldosterone system ↓ Glomerular filtration rate ↓ Clearance of lactic acid by the kidney ↑ Lactic acid production ↓ Rate of activity of clotting enzymes Lactic Acidosis Unknown mechanism Coagulopathy Hypothermia Trauma Triad of Death ↑ Capillary Cold, mottled refill time extremities Legend: Pathophysiology Mechanism Sign/Symptom/Lab Finding Complications Published January 24, 2013, updated December 4, 2022 on www.thecalgaryguide.com