Shock in Orthopaedic Patients
DNB Orthopaedics • October 2024 • Paper III • 10 Marks
Introduction
Shock is an acute state of circulatory failure resulting in inadequate tissue perfusion and oxygen delivery to meet cellular metabolic requirements. If untreated, cellular hypoxia progresses to anaerobic metabolism, lactic acidosis, cellular dysfunction, multiple-organ dysfunction and death.
Orthopaedic relevance
In an orthopaedic patient, shock should immediately raise the possibility of occult haemorrhage from pelvic, femoral or associated thoracoabdominal injuries. However, neurogenic, septic, cardiogenic and obstructive shock must also be recognised.
Physiological Basis
Oxygen delivery (DO₂) = Cardiac Output × Arterial Oxygen Content
Cardiac Output = Heart Rate × Stroke Volume
Shock develops when effective circulating volume, cardiac pump function or vascular tone becomes inadequate to maintain tissue oxygen delivery.
Physiological Classification of Shock
1. Hypovolaemic Shock
Reduced circulating intravascular volume.
2. Distributive Shock
Pathological vasodilatation and maldistribution of blood flow.
Septic • Neurogenic • Anaphylactic
3. Cardiogenic Shock
Failure of the heart as a pump.
4. Obstructive Shock
Mechanical obstruction to cardiac filling or outflow.
Easy mnemonic: “Tank – Pipes – Pump –…