Physiology of Circulatory Shock PDF

Physiology of Circulatory Shock Dr. Sovan Bagchi Professor of Physiology www.gmu.ac.ae COLLEGE OF HEALTH SCIENCES  Learning Objectives Define Shock List the different types of shock Enlist the stage...

Physiology of Circulatory Shock Dr. Sovan Bagchi Professor of Physiology www.gmu.ac.ae COLLEGE OF HEALTH SCIENCES  Learning Objectives Define Shock List the different types of shock Enlist the stages of shock  Definition of Shock ▪ Inadequate oxygen delivery to tissues. ▪ Results in global tissue hypo-perfusion and metabolic acidosis ▪ Arterial pressure is usually low in shock  Types of Shock 1. Cardiogenic – failure of myocardial pump myocardial infarction, arrhythmias, and pulmonary embolism 2. Hypovolemic - inadequate blood/plasma volume hemorrhage fluid loss (vomiting, diarrhoea, burns, trauma) 3. Septic – vasodilation + endothelial injury Gram+, Gram- bacteria 4. Neurogenic - loss of vascular tone (vasodilation) spinal cord injury Distributive Shock 5. Anaphylactic – IgE–mediated hypersensitivity (Vasodilation)  Understanding the Shock Inadequate systemic oxygen delivery activates autonomic responses to maintain systemic oxygen delivery Goal of our body during shock is to maintain cerebral and cardiac perfusion Sympathetic nervous system Norepinephrine, epinephrine, dopamine, and cortisol release Causes vasoconstriction, increase in HR, and increase of cardiac contractility (cardiac output) Renin-angiotensin axis Water and sodium conservation and vasoconstriction Increase in blood volume and blood pressure  Understanding the Shock Cellular responses 1- ATP depletion → ion pump dysfunction 2- Cellular edema 3- Hydrolysis of cellular membranes and cellular death Endothelial inflammation and disruption Inability of O2 delivery to meet the metabolic demand Result: 1- Lactic acidosis 2- Cardiovascular insufficiency 3- Increased metabolic demands Multi-Organ Dysfunction Syndrome (MODS) Cardiac depression Respiratory distress Renal failure Result is end organ failure  Stages of Shock 1. Stage I: Non-progressive and compensated Compensatory mechanism (neurohumoral) activation 2. Stage II: Progressive and decompensated Tissue hypoperfussion – metabolic inbalancies 3. Stage III: Irreversible (is it +ve or –ve feedback ??) Incurred cellular damage + tissue injury Death  Learning Resources Textbook: Guyton and Hall Textbook of Medical Physiology, Chapter 24, 293-302 Fourteenth Edition. Link: https://www-clinicalkey-com.gmulibrary.com/#!/content/book/3-s2.0- B9780323597128000242?indexOverride=GLOBAL Power-point presentation in the moodle www.gmu.ac.ae COLLEGE OF HEALTH SCIENCES