# Shock Pathology > Shock pathology for MBBS Pathology: hypovolaemic, cardiogenic, obstructive and distributive types, stages, cellular mechanisms and MODS. - Canonical URL: https://prepelephant.com/topics/mbbs/pathology/shock-pathology - Exam / course: MBBS · Subject: Pathology - Publisher: PrepElephant (https://prepelephant.com) — Prepared and reviewed by the PrepElephant Academic Review Team - First published: 2026-10-02 - Last updated: 2026-10-02 - How to cite: "Shock Pathology", PrepElephant, https://prepelephant.com/topics/mbbs/pathology/shock-pathology ## Direct answer Shock, whatever its trigger, is systemic cellular hypoperfusion — oxygen and substrate delivery falling below cellular demand — and the four-type classification carries the therapeutics with it: hypovolaemic (haemorrhage, dehydration, burns), cardiogenic (infarction, failure), obstructive (tension pneumothorax, cardiac tamponade, massive pulmonary embolism) and distributive (septic, anaphylactic, neurogenic; low systemic vascular resistance with normal or high output). All converge on one cellular script: ATP depletion, sodium-pump failure, cellular swelling, anaerobic glycolysis with lactic acidosis, and finally membrane damage, lysosomal leakage and cell death. The course runs through three stages — non-progressive (compensated by sympathetic, renin-angiotensin and ADH responses), progressive (oliguria, confusion, metabolic acidosis) and irreversible (multi-organ dysfunction, disseminated intravascular coagulation) — and the stage, not the blood pressure alone, decides the hour's management. ## What you must remember - **Haemodynamic signatures:** hypovolaemic and cardiogenic shock — cold, vasoconstricted periphery with low cardiac output and high systemic vascular resistance; early septic shock — warm, vasodilated, high output with low resistance and a widened pulse pressure; neurogenic shock — warm hypotension without tachycardia, because sympathetic outflow is cut. - **Compensation arithmetic (ATLS classes):** class I haemorrhage under 15 per cent of blood volume with near-normal vitals; class II 15-30 per cent with tachycardia and narrowed pulse pressure; class III 30-40 per cent with hypotension and altered mentation; class IV above 40 per cent, life-threatening. Narrow pulse pressure, not hypotension, is the early sign. - **Stages with physiology:** non-progressive — baroreceptor-mediated vasoconstriction with renin-angiotensin and ADH salvage centralising flow; progressive — microvascular sludging, endothelial leak, tissue hypoxia with lactate above 2 mmol/L; irreversible — membrane injury, lysosomal rupture, DIC, apoptotic and necrotic death cascading into multi-organ dysfunction. - **Organ pattern of established shock:** oliguric acute kidney injury (acute tubular injury), acute respiratory distress syndrome, gut barrier failure with bacterial translocation, myocardial depressant factor effects, and liver dysfunction with transaminitis. - **Obstructive shock trio to memorise:** tension pneumothorax (trachea away, hyper-resonance, no breath sounds), cardiac tamponade (Beck triad — hypotension, raised JVP, muffled sounds; pulsus paradoxus), massive pulmonary embolism (raised JVP with clear lung fields). - **The cellular endpoint:** ischaemia-reperfusion injury can worsen the picture at resuscitation — xanthine oxidase-generated free radicals when oxygen returns. - **Indian relevance:** obstetric haemorrhage and sepsis remain leading causes of shock in Indian emergency practice, which is why the obstetric and septic variants dominate professional-exam scenarios. ## Reading the haemodynamics at the bedside Two patients, both with blood pressure 88/50. The first, a road-traffic victim, is cold, clammy, tachycardic at 128 with a thready pulse and a narrowed pulse pressure — the picture of compensated-then-progressing hypovolaemic shock; his problem is volume, and two large-bore cannulae, rapid transfusion protocol and a search for the bleeding source (chest, abdomen, pelvis, long bones) come before any inotrope. The second, a febrile patient with a urinary infection, is paradoxically warm and well perfused at the fingers with a bounding pulse and a widened pulse pressure — early distributive (septic) shock; here the priorities invert: cultures, broad-spectrum antibiotics within the hour, 30 mL/kg crystalloid, and early noradrenaline if pressure does not respond, with source control (the obstructed, infected urinary tract) deciding the outcome. Same number on the cuff, opposite physiology, opposite first moves — this bedside reading is precisely what short-case examiners probe. The teaching point stands: classify the shock before treating the number. ## Where students slip Waiting for hypotension to diagnose haemorrhagic shock is the classic error — tachycardia with a narrowing pulse pressure precedes it, particularly in young patients who compensate grimly. The second slip is missing neurogenic shock: a cord-injured patient is hypotensive and bradycardic or at least not appropriately tachycardic — the absence of the expected tachycardia is the clue. Third, do not fill a patient in cardiogenic shock into pulmonary oedema; the wedge pressure concept, if not the catheter, still guides the reasoning. And remember stage terminology: "irreversible" is a retrospective verdict, but the term is still examinable. ## Frequently asked questions ### What are the four physiological categories of shock? Hypovolaemic, cardiogenic, obstructive and distributive — defined by preload, pump function, outflow obstruction and vascular tone respectively. ### Which early sign precedes hypotension in haemorrhagic shock? A narrowed pulse pressure with tachycardia — compensation maintains systolic pressure while diastolic rises from vasoconstriction. ### Why is the septic shock patient warm rather than cold? Nitric oxide-mediated vasodilatation and high cardiac output characterise early distributive shock, with low systemic vascular resistance and warm peripheries. ### What defines multi-organ dysfunction syndrome? Physiological dysfunction of two or more organ systems in an acutely ill patient, the common endpoint of prolonged shock and uncontrolled inflammation. ### What triad suggests cardiac tamponade? Beck triad — hypotension, elevated jugular venous pressure and muffled heart sounds, often with pulsus paradoxus.