Causes of Shock
Shock is defined as inadequate tissue perfusion resulting in cellular hypoxia. Classification into five types guides targeted resuscitation — treating the wrong type of shock with the wrong fluid can be fatal.
✦ The Mnemonic
"CHORD Classifies All Shock Types"
Cardiogenic · Hypovolaemic · Obstructive · Redistributive (septic/anaphylactic/neurogenic) · Distributive
Clinical Breakdown
Haemorrhagic shock classification (ATLS): Class I (<15% blood loss, no symptoms), Class II (15–30%, anxiety, tachycardia), Class III (30–40%, confusion, hypotension), Class IV (>40%, lethargy, life-threatening). Normal BP is maintained until Class III — tachycardia is the earliest sign.
Cardiogenic vs obstructive: both have raised JVP. Distinguishing features: tamponade = pulsus paradoxus + muffled heart sounds + Beck's triad; tension pneumothorax = tracheal deviation + absent breath sounds + hyperresonance; cardiogenic = pulmonary oedema + S3 gallop.
Septic shock (Sepsis-3 definition): sepsis + vasopressor requirement to maintain MAP ≥65 mmHg despite adequate fluid resuscitation, and serum lactate >2 mmol/L. Hour-1 bundle: blood cultures → antibiotics → 30 mL/kg IV crystalloid → lactate reassessment.
⭐ Clinical Pearl
Anaphylaxis: IM adrenaline 0.5 mg (1:1000) is the first and most important treatment — given immediately, into the lateral thigh, through clothing if needed. Antihistamines and steroids are adjuncts, NOT first-line. Biphasic reactions occur in up to 20% of cases — observe for minimum 6 hours. Prescribe an adrenaline auto-injector on discharge.