# Shock Classification and Management

> Shock classification for FMGE Surgery: hypovolaemic to distributive types, four haemorrhage classes, sepsis bundle and first-line vasopressor choices.

- Canonical URL: https://prepelephant.com/topics/fmge/surgery/shock-classification
- Exam / course: FMGE · Subject: Surgery
- 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 Classification and Management", PrepElephant, https://prepelephant.com/topics/fmge/surgery/shock-classification

## Direct answer

Shock is inadequate tissue perfusion for metabolic need, classified as hypovolaemic, cardiogenic, obstructive or distributive, and recognised early by tachycardia with a narrowed pulse pressure before blood pressure falls. Haemorrhagic shock is graded into four classes by blood loss, hypotension appearing only in class III and above. Management treats the cause: transfusion and haemostasis for bleeding, decompression for tension pneumothorax and tamponade, adrenaline for anaphylaxis, and antibiotics with fluids and noradrenaline for septic shock.

## What you must remember

- The four classes of haemorrhagic shock: class I, under about 750 mL, minimal findings; class II, 750 to 1500 mL, tachycardia with narrowed pulse pressure and a normal blood pressure; class III, 1500 to 2000 mL, hypotension with confusion — the first class needing blood; class IV, over 2000 mL, lethal.
- Septic shock follows the hour-one bundle: lactate, blood cultures, broad-spectrum antibiotics within an hour, 30 mL per kg crystalloid for hypotension or lactate of 4 mmol/L or more, and noradrenaline as first-line vasopressor to hold mean arterial pressure at 65 mmHg or above.
- Obstructive shock: tension pneumothorax — tracheal shift, absent unilateral breath sounds, distended neck veins — is needle-decompressed at the fifth intercostal space in the anterior axillary line, then given a chest tube; cardiac tamponade with Beck triad goes to pericardiocentesis or thoracotomy.
- Anaphylactic shock: intramuscular adrenaline 0.5 mg (0.5 mL of 1 in 1000) into the mid-outer thigh, repeated as needed, with airway support, oxygen, crystalloid and adjuncts.
- Neurogenic shock after high spinal injury: hypotension with bradycardia and warm dry extremities from lost sympathetic tone — fluids plus vasopressors, with atropine for symptomatic bradycardia.
- Haemorrhage management: early blood products over excessive crystalloid, tranexamic acid within three hours in trauma, permissive hypotension until control in selected patients, and calcium with warming to break the lethal triad.
- End points of resuscitation: urine output of 0.5 mL per kg per hour, mean pressure 65 mmHg or more, and improving lactate clearance.

## Common confusion

The exam exploits compensation: a narrow pulse pressure with tachycardia and a normal pressure means class II haemorrhage, not wellness. Candidates also mix the vasopressor situations — noradrenaline for septic, adrenaline for anaphylactic, vasopressors plus fluids for neurogenic. Cardiogenic shock resists fluids and needs inotropes, the opposite of the distributive pattern.

## Exam-focused takeaway

FMGE shock questions are classification-plus-intervention questions. Expect blood loss percentages mapped to pulse, pressure and mental status, where hypotension first appears in class III and blood becomes the answer. Then the emergency pairs: sepsis gets antibiotics within the hour, 30 mL per kg crystalloid and noradrenaline to a mean pressure of 65; anaphylaxis gets intramuscular adrenaline 0.5 mg; tension pneumothorax gets a needle before a tube; tamponade gets Beck triad and theatre; neurogenic shock gets vasopressors, bradycardia its signature. End haemorrhage answers with tranexamic acid timing and the lethal triad.

## Frequently asked questions

### What are the four physiological categories of shock?

Hypovolaemic, cardiogenic, obstructive and distributive — the last including septic, anaphylactic and neurogenic shock.

### In which class of haemorrhagic shock does hypotension appear?

Class III, roughly 30 to 40 per cent loss; classes I and II maintain blood pressure with tachycardia and narrowed pulse pressure.

### What is the first-line vasopressor in septic shock?

Noradrenaline, targeted to a mean arterial pressure of 65 mmHg or above after initial fluid and antibiotics.

### How is anaphylactic shock treated first?

Intramuscular adrenaline, 0.5 mg of 1 in 1000 into the mid-outer thigh, repeated as required, with airway and fluid support.

### Why does neurogenic shock cause bradycardia?

Loss of sympathetic outflow below a high spinal lesion leaves unopposed vagal tone, producing hypotension with bradycardia and warm dry limbs.

### What is the lethal triad of trauma?

Hypothermia, acidosis and coagulopathy — a self-reinforcing cycle in massive haemorrhage, broken by warming, blood products and calcium.