# Haemorrhagic Shock: Pathophysiology and ATLS Management
> Master the classification, pathophysiology, and life-saving management of haemorrhagic shock with this comprehensive guide based on ATLS guidelines.

Tags: haemorrhagic-shock, trauma-management, atls, emergency-medicine, pathophysiology, hypovolaemic-shock, medical-education
## Haemorrhagic Shock: A Medical Overview

*   **Definition:** A form of hypovolaemic shock from acute blood loss leading to tissue hypoxia and cellular hypoxia.
*   **Impact:** Accounts for 30–40% of trauma deaths; it is the most common preventable cause of trauma death.

## Aetiology & Causes

*   **Trauma:** Blunt, penetrating, and crush injuries.
*   **Gastrointestinal:** Peptic ulcers and variceal bleeding.
*   **Obstetric:** Postpartum haemorrhage and ruptured ectopic pregnancy.
*   **Vascular/Surgical:** Aortic aneurysm rupture and intraoperative haemorrhage.

## Pathophysiology

*   **Mechanism:** Acute blood loss → ↓ Cardiac Output → ↓ Tissue Perfusion → Cellular Hypoxia → Lactic Acidosis → Multi-Organ Dysfunction.
*   **Warning:** Compensatory mechanisms (sympathetic activation) can temporarily maintain BP, masking the severity of the shock.

## ATLS Classification of Shock

*   **Class I (<15% loss):** Heart rate <100, normal BP, slightly anxious.
*   **Class II (15-30% loss):** HR 100-120, decreased pulse pressure, mildly anxious.
*   **Class III (30-40% loss):** HR 120-140, decreased systolic BP, anxious/confused.
*   **Class IV (>40% loss):** HR >140, negligible urine output, lethargic.

## Clinical Features & Diagnostic Workup

*   **Signs:** Tachycardia, hypotension, weak pulse, pallor, and prolonged capillary refill (>2 sec).
*   **Diagnostics:** FBC (↓ Haemoglobin), Arterial Blood Gas (↑ Lactate), and FAST ultrasound imaging for internal bleeding.

## Complications

*   Acute Kidney Injury (AKI) due to renal hypoperfusion.
*   Acute Respiratory Distress Syndrome (ARDS).
*   Disseminated Intravascular Coagulation (DIC).
*   Multi-Organ Dysfunction Syndrome (MODS).

## Management & Treatment

*   **Resuscitation:** ABCDE survey, high-flow O2, and two large-bore IVs.
*   **Circulation:** Massive Transfusion Protocol (1:1:1 ratio of RBC:FFP:Platelets) and Tranexamic Acid (TXA) within 3 hours.
*   **Control:** Direct pressure, tourniquets, or surgical haemostasis.
*   **Goals:** Prevent the 'Lethal Triad' of hypothermia, acidosis, and coagulopathy.
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