Shock - Pathology - Allied health sciences

Course: first year MLT, MIT, ATOT, RDT
Faculty: Pathology
Kanachur Institute of Medical Sciences

1. SHOCK Dr. Salman Ansari Dept. of Pathology Kanachur Institute of Medical Sciences

2. Contents Definition Types of shock with examples Hypovolemic shock Cardiogenic shock Septic shock Stages of shock: non-progressive, progressive and irreversible

3. Shock Definition : pathological process characterised by intense failure of the circulatory system to maintain an appropriate blood supply to the microcirculation This results in life-threatening hypoperfusion to vital organs

4. Types of shock Cardiogenic Hypovolemic Septic Less common types: neurogenic shock, anaphylactic shock

5. Type Causes Cardiogenic MII Ventricular rupture Arrhythmia Cardiac tamponade Pulmonary embolism Hypovolemic Fluid loss(bleeding, vomiting, diarrhoea, burns) Septic Severe bacterial or fungal infections Less common: neurogenic, anaphylactic Spinal cord injury, anesthetic accident

6. Cardiogenic shock Definition : Shock due to low cardiac output as a result of: myocardial damage external compression of the heart obstruction to outflow of blood from ventricles Causes : MI Ventricular rupture Arrhythmia Cardiac tamponade Pulmonary embolism

7. Pathogenesis of cardiogenic shock Various causes of cardiogenic shock(e.g: MI) ↓ LV dysfunction ↓ Decreased cardiac output ↓ Decreased perfusion of tissues

8. Hypovolemic shock Hypovolemia=abnormal decrease in volume of circulating blood Definition : Shock due to low cardiac output as a result of: Loss of blood: massive hemorrhage Loss of plasma: severe burns Loss of fluid: vomiting, diarrhoea, severe gastroenteritis Causes : Fluid loss due to: Hemorrhage Vomiting Diarrhoea burns

9. Pathogenesis of hypovolemic shock Inadequate blood or plasma volume and fluid loss ↓ hypovolemia ↓ low cardiac output ↓ hypotension ↓ inadequate perfusion of tissue.

10. Septic shock Definition : Shock due to severe sepsis with hypotension Causes : Infection by Gram-positive bacteria most commonly. E.g: Staphylococcus aureus, Streptococcus pneumoniae Gram-negative bacteria fungi

11. Main factors contributing to septic shock Inflammatory response : Activation of neutrophils, macrophages and cytokine release Endothelial cell activation and injury : Increased vascular permeability → widespread edema Pro-coagulant state : endotoxin activates factor XII → activation of coagulation system → thrombosis of small vessels - complication called Disseminated intravascular coagulation(DIC)

12. 4. Metabolic abnormalities : hyperglycemia, insulin resistance - Decreased glucocorticoid production - due to adrenal gland insufficiency - life-threatening complication called Waterhouse-Friderichsen syndrome(WFS) 5. Organ dysfunction : decreased contractility of the heart and cardiac output → failure of multiple organs like liver, lung, kidneys and heart → death 6. Immune suppression : hyperinflammatory state leads to suppression of immune system

13. Pathogenesis of septic shock(short version) Major factors contributing to septic shock are: Inflammatory response : Activation of neutrophils, macrophages and cytokine release Endothelial cell activation and injury : Increased vascular permeability → widespread edema Pro-coagulant state : endotoxin causes activation of coagulation system → Disseminated intravascular coagulation(DIC)

14. 4. Metabolic abnormalities : hyperglycemia, insulin resistance, adrenal gland insufficiency 5. Organ dysfunction : decreased cardiac output → failure of multiple organs like liver, lung, kidneys and heart → death 6. Immune suppression

15. Activation of host’s immune system: neutrophils and cytokines released Endothelial cell injury Vasodilation and pooling of blood in peripheries ↑ permeability: widespread edema Decreased tissue perfusion Multi-organ failure Endotoxin Activation of coagulation Micro-thrombi - Disseminated intravascular coagulation(DIC) Tissue ischemia Microbial products

16. Stages of shock 3 phases Non-progressive (compensated/reversible) phase Progressive phase Irreversible phase

17. Nonprogressive/compensated/reversible phase Various compensatory mechanisms are activated Blood is redistributed to maintain perfusion to vital organs

18. 2. Progressive phase If the underlying cause of shock is not corrected, shocks passes into the progressive phase Widespread tissue hypoperfusion, hypoxia and blood pools in the microcirculation Cardiac output worsens and there will be widespread hypoxic damage to vital organs and they begin to fail

19. 3. Irreversible phase If there is no intervention, shock enters into irreversible stage Widespread cell injury further worsens shock Acute renal failure Death

20. Morphology Kidney : acute tubular necrosis(acute renal failure) Lungs : diffuse alveolar damage - acute respiratory distress - “shock lung” Disseminated intravascular coagulation(DIC) : widespread deposition of micro-thrombi, especially in brain, heart, lungs, kidney, adrenal glands and GI tract

21. Prognosis Hypovolemic shock : can survive with appropriate management Septic shock, cardiogenic shock with massive MI : poorer prognosis

22. References: Ramadas Nayak - Textbook of Pathology for Allied Health Sciences Questions: [email protected]