# **Circulatory Shock – Detailed Notes** *(Exam-oriented for MBBS, B.Sc. OTT, Nursing, and Allied Health Sciences)* --- # Definition **Shock** is a life-threatening state of **circulatory failure** in which the cardiovascular system cannot deliver sufficient oxygen and nutrients to meet the metabolic demands of tissues. The hallmark of shock is **inadequate tissue perfusion**, leading to: * Cellular hypoxia * Anaerobic metabolism * Lactic acidosis * Cellular dysfunction * Multiple Organ Dysfunction Syndrome (MODS) * Death if untreated --- # Classification of Shock 1. Hypovolemic Shock 2. Cardiogenic Shock 3. Obstructive Shock 4. Distributive (Vasodilatory) Shock * Septic Shock * Anaphylactic Shock * Neurogenic Shock --- # 1. HYPOVOLEMIC SHOCK ## Definition Hypovolemic shock occurs due to a **significant reduction in circulating blood volume**, causing inadequate preload and decreased cardiac output. It is the **most common type of shock**. --- # Causes ## A. Hemorrhagic causes Loss of whole blood Examples * Trauma * Road traffic accidents * Gunshot injuries * Gastrointestinal bleeding * Ruptured ectopic pregnancy * Postpartum hemorrhage * Major surgery * Ruptured abdominal aortic aneurysm --- ## B. Non-Hemorrhagic causes Loss of plasma or body fluids Examples * Severe dehydration * Cholera * Persistent vomiting * Severe diarrhea * Heat stroke * Excessive sweating * Diabetic ketoacidosis * Diabetes insipidus * Burns * Pancreatitis * Intestinal obstruction --- # Pathophysiology ## Step 1 Blood loss ↓ Reduced circulating blood volume ↓ Reduced venous return (Preload) ↓ Reduced ventricular filling ↓ Reduced stroke volume ↓ Reduced cardiac output ↓ Fall in Mean Arterial Pressure (MAP) ↓ Reduced organ perfusion ↓ Tissue hypoxia ↓ Anaerobic glycolysis ↓ Lactic acid accumulation ↓ Metabolic acidosis ↓ Cellular dysfunction ↓ Multiple organ failure --- ## Compensatory Mechanisms The body activates: ### Sympathetic Nervous System Releases * Adrenaline * Noradrenaline Effects * Tachycardia * Vasoconstriction * Sweating * Cold skin --- ### Renin-Angiotensin-Aldosterone System (RAAS) Renin ↓ Angiotensin II ↓ Vasoconstriction ↓ Aldosterone ↓ Sodium and water retention --- ### ADH Release Water reabsorption ↓ Maintains blood volume --- # Clinical Features ### Early * Anxiety * Restlessness * Tachycardia * Tachypnea * Thirst * Pale skin * Cold extremities ### Late * Severe hypotension * Weak pulse * Oliguria * Confusion * Cyanosis * Loss of consciousness --- # Investigations * CBC * Blood grouping * Cross matching * ABG * Serum lactate * Electrolytes * FAST ultrasound * CT scan (if stable) --- # Management ## Airway Maintain airway Intubation if needed --- ## Breathing 100% oxygen Mechanical ventilation if required --- ## Circulation Two large-bore IV cannulas Continuous BP monitoring ECG Urine catheter --- ## Fluid Replacement Crystalloids * Normal saline * Ringer Lactate Blood transfusion * Packed RBC * Fresh frozen plasma * Platelets --- ## Treat Cause Stop bleeding Emergency surgery Control burns Treat diarrhea --- # Complications * Acute kidney injury * DIC * MODS * Death --- # 2. CARDIOGENIC SHOCK ## Definition Cardiogenic shock occurs when the **heart fails to pump enough blood** despite normal blood volume. --- # Causes ## Myocardial Causes * Acute MI (most common) * Cardiomyopathy * Myocarditis --- ## Electrical Causes * Ventricular tachycardia * Ventricular fibrillation * Complete heart block --- ## Mechanical Causes * Papillary muscle rupture * Ventricular septal rupture * Acute mitral regurgitation * Acute aortic regurgitation --- ## Others * Severe heart failure * Drug overdose --- # Pathophysiology Heart muscle damage ↓ Reduced contractility ↓ Reduced stroke volume ↓ Reduced cardiac output ↓ Hypotension ↓ Poor coronary perfusion ↓ More myocardial ischemia ↓ Further pump failure ↓ Vicious cycle ↓ Multi-organ hypoperfusion --- ## Backward Failure Blood accumulates in lungs ↓ Pulmonary venous pressure rises ↓ Pulmonary edema ↓ Dyspnea ↓ Hypoxia --- ## Forward Failure Less blood reaches organs ↓ Kidney failure ↓ Brain hypoxia ↓ Metabolic acidosis --- # Clinical Features * Severe hypotension * Chest pain * Cold clammy skin * Tachycardia * Pulmonary edema * Raised JVP * Crackles * Altered sensorium --- # Investigations * ECG * Troponin * Echocardiography * BNP * Chest X-ray * ABG --- # Management Treat MI immediately Primary PCI or Thrombolysis --- ### Inotropes * Dobutamine * Milrinone Increase cardiac contractility --- ### Vasopressors Norepinephrine if BP remains low --- ### Mechanical Support * Intra-aortic balloon pump * VA ECMO * LV assist device --- ### Treat arrhythmias Pacemaker Cardioversion Antiarrhythmics --- # Complications * Pulmonary edema * Cardiac arrest * Renal failure * MODS --- # 3. OBSTRUCTIVE SHOCK ## Definition Obstructive shock results from **physical obstruction to blood flow**, preventing adequate cardiac filling or emptying. --- # Causes ## Cardiac Tamponade Fluid compresses heart --- ## Tension Pneumothorax Air compresses mediastinum ↓ Reduced venous return --- ## Massive Pulmonary Embolism Large clot blocks pulmonary artery ↓ Right ventricular failure --- ## Rare Causes * Constrictive pericarditis * Cardiac tumors --- # Pathophysiology Mechanical obstruction ↓ Reduced venous return or Markedly increased right ventricular afterload ↓ Reduced preload ↓ Reduced stroke volume ↓ Reduced cardiac output ↓ Hypotension ↓ Organ hypoperfusion ↓ Anaerobic metabolism ↓ Lactic acidosis --- # Clinical Features General * Hypotension * Tachycardia * Elevated JVP --- ### Cardiac Tamponade Beck's Triad * Hypotension * Raised JVP * Muffled heart sounds --- ### Tension Pneumothorax * Tracheal deviation * Hyperresonance * Absent breath sounds * Respiratory distress --- ### Pulmonary Embolism * Sudden dyspnea * Chest pain * Syncope * Hypoxia --- # Investigations * ECG * Chest X-ray * Echocardiography * CT Pulmonary Angiography * Ultrasound --- # Management ### Cardiac Tamponade Emergency pericardiocentesis --- ### Tension Pneumothorax Immediate needle decompression ↓ Chest tube insertion --- ### Pulmonary Embolism Thrombolysis Heparin Surgical embolectomy if indicated --- # 4. DISTRIBUTIVE SHOCK ## Definition Distributive shock occurs because of **widespread vasodilation**, causing decreased systemic vascular resistance (SVR) and maldistribution of blood flow despite an adequate or increased cardiac output early in the course. --- # A. SEPTIC SHOCK ## Causes Common organisms Gram-negative bacteria * *Escherichia coli* * *Klebsiella* * *Pseudomonas* Gram-positive bacteria * *Staphylococcus aureus* * *Streptococcus* species Fungi * *Candida* species Common sources * Pneumonia * Urinary tract infection * Abdominal infections * Catheter-related bloodstream infections --- ## Pathophysiology Infection ↓ Pathogen-associated molecular patterns (e.g., endotoxin/LPS) ↓ Macrophage activation ↓ TNF-α IL-1 IL-6 ↓ Nitric oxide release ↓ Generalized vasodilation ↓ Marked decrease in SVR ↓ Hypotension ↓ Capillary leak ↓ Fluid moves into tissues ↓ Relative hypovolemia ↓ Reduced tissue perfusion ↓ Lactic acidosis ↓ MODS --- ### Early Phase Warm shock * Warm skin * Bounding pulse * High cardiac output * Low SVR --- ### Late Phase Cold shock * Low cardiac output * Cold extremities * Severe hypotension --- # Management * Broad-spectrum antibiotics within 1 hour * Aggressive IV crystalloids (commonly 30 mL/kg initially in adults) * Blood cultures before antibiotics if feasible * Source control (drain abscess, remove infected devices) * **Norepinephrine** is the first-line vasopressor * Vasopressin or epinephrine may be added if needed --- # B. ANAPHYLACTIC SHOCK ## Causes * Penicillin * Bee sting * Latex * Nuts * Seafood --- # Pathophysiology Allergen ↓ IgE antibody ↓ Mast cell activation ↓ Histamine release ↓ Massive vasodilation * Increased capillary permeability * Bronchospasm ↓ Hypotension ↓ Airway edema ↓ Shock --- # Clinical Features * Urticaria * Angioedema * Wheezing * Stridor * Hypotension * Tachycardia --- # Management * **Intramuscular epinephrine** (first-line) * High-flow oxygen * IV crystalloids * Antihistamines * Corticosteroids * Nebulized bronchodilators if bronchospasm persists --- # C. NEUROGENIC SHOCK ## Causes * Cervical spinal cord injury * High thoracic spinal cord injury (above T6) * Spinal anesthesia * Severe brain injury --- # Pathophysiology Spinal cord injury ↓ Loss of sympathetic outflow ↓ Unopposed vagal activity ↓ Peripheral vasodilation ↓ Reduced SVR ↓ Hypotension * Bradycardia ↓ Reduced cardiac output ↓ Organ hypoperfusion --- # Clinical Features * Hypotension * **Bradycardia** * Warm, dry skin * Flaccid paralysis (depending on injury) * Loss of temperature regulation --- # Management * Airway stabilization * Cervical spine immobilization * IV fluids * **Norepinephrine** or another appropriate vasopressor if hypotension persists * Atropine for symptomatic bradycardia * Definitive management of the spinal injury --- # Summary Table | Type | Primary Problem | Skin | Heart Rate | CVP/JVP | Main Treatment | | ---------------- | ------------------------------- | --------------------- | ----------------- | ---------- | ---------------------------------------------------------------------------- | | **Hypovolemic** | Low blood volume | Cold, clammy | ↑ Tachycardia | ↓ | IV fluids, blood transfusion, control bleeding | | **Cardiogenic** | Pump failure | Cold, clammy | Usually ↑ | ↑ | PCI, inotropes, treat cause | | **Obstructive** | Mechanical obstruction | Cold, clammy | ↑ | ↑ | Relieve obstruction (needle decompression, pericardiocentesis, thrombolysis) | | **Septic** | Vasodilation + capillary leak | Warm early, cold late | ↑ | Variable | Fluids, antibiotics, norepinephrine | | **Anaphylactic** | Histamine-mediated vasodilation | Warm, flushed | ↑ | ↓/Variable | IM epinephrine, oxygen, IV fluids | | **Neurogenic** | Loss of sympathetic tone | Warm, dry | **↓ Bradycardia** | ↓/Normal | Fluids, vasopressors, atropine if needed | These notes align with current clinical practice and are suitable for detailed theory answers, viva examinations, and OT/anesthesia coursework. :- explain in detailed overview

explain in detailed overview

explain in detailed overview