Cardiogenic and obstructive shock

Overview & Definition

Shock is the failure of the cardiovascular system to deliver enough oxygen to the tissues to meet metabolic demand. It is not defined by a blood pressure reading — a child can be in shock with a normal blood pressure, because compensatory tachycardia and vasoconstriction keep the pressure up until late, and hypotension is a late and ominous sign.[1][17] Shock becomes decompensated when the blood pressure falls below the Pediatric Advanced Life Support hypotension thresholds for age — below 70 mmHg in infants, below 70 + (2 × age in years) mmHg from 1 to 10 years, and below 90 mmHg at 10 years and older.[17]

Paediatric shock is classified by its mechanism into four types: hypovolaemic (loss of volume), distributive (vasodilation, as in sepsis or anaphylaxis), cardiogenic (pump failure), and obstructive (mechanical obstruction to forward flow). This page owns the last two types. Cardiogenic shock is the failure of the heart to generate an adequate cardiac output because of impaired contractility, a structural lesion, or a pathological rhythm. Obstructive shock is the failure of forward flow because something mechanical is blocking the heart or the great vessels: cardiac tamponade, tension pneumothorax, or massive pulmonary embolism.[1][3]

The reason cardiogenic and obstructive shock are grouped together is that they share a cold, low-output phenotype and, crucially, they are the two shock types where aggressive fluid resuscitation can harm. Both demand early vasoactive support or physical decompression rather than the large-volume crystalloid boluses that rescue hypovolaemic and septic shock. Recognising the type within the first minutes of assessment is the skill that separates the safe from the dangerous resuscitation.[1]

References17Show ledgerHide ledger

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