Introduction

Hemorrhagic shock is a form of hypovolemic shock caused by acute blood loss resulting in inadequate circulating volume, reduced tissue perfusion and insufficient oxygen delivery to meet cellular metabolic requirements.

In a young polytrauma patient, occult hemorrhage may occur into the chest, abdomen, pelvis, retroperitoneum and long-bone fractures.

Definition

Shock is a state of circulatory failure in which tissue perfusion and oxygen delivery are inadequate for cellular metabolic demands.

In hemorrhagic shock:

Blood loss
   ↓
↓ Circulating blood volume
   ↓
↓ Venous return / preload
   ↓
↓ Stroke volume
   ↓
↓ Cardiac output
   ↓
↓ Tissue oxygen delivery
   ↓
Cellular hypoxia
   ↓
Anaerobic metabolism
   ↓
Lactate + acidosis
   ↓
Organ dysfunction

A. Pathophysiology of Hemorrhagic Shock

1. Reduction in Circulating Volume

Acute blood loss decreases venous return to the heart, causing reduced preload and stroke volume.

Cardiac output = Heart rate × Stroke volume

As stroke volume falls, cardiac output decreases unless initially compensated by tachycardia.

2. Compensatory Neuroendocrine Response

Reduced…