Give me five causes of hypotension in pediatric age group.
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Five Causes of Hypotension in the Pediatric Age Group
Hypotension in children is defined as a systolic BP below the 5th percentile for age (estimated as SBP < 70 + age in years × 2 mmHg). It is a late and ominous sign in most pediatric illnesses, as children can maintain BP through tachycardia and vasoconstriction for longer than adults before decompensating.
The causes are classically organized by the mechanism of shock:
1. Hypovolemic Shock (most common in children)
Loss of intravascular volume is the leading cause of pediatric hypotension. Common scenarios include:
- Gastroenteritis with dehydration - diarrhea/vomiting causing fluid losses (most common worldwide)
- Hemorrhage - trauma (motor vehicle collisions, falls, sports injuries are leading causes of pediatric blunt trauma)
- Burns - large surface area burns with plasma loss
Volume depletion reduces preload, cardiac output falls, and BP drops.
2. Distributive Shock (Sepsis / Anaphylaxis)
Sepsis is the leading cause of death in children worldwide. It causes hypotension via massive vasodilation, increased nitric oxide production, and myocardial depression. Importantly, in pediatric septic shock, hypotension may be absent early - it is a late finding, unlike in adults. Key signs preceding hypotension include tachycardia, poor capillary refill, and altered mental status. - Rosen's Emergency Medicine, p. 3113
Anaphylaxis (to foods, insect stings, medications) causes acute massive histamine-mediated vasodilation, leading to distributive shock and hypotension.
3. Cardiogenic Shock
Pump failure leads to reduced cardiac output and hypotension. Causes in children include:
- Acute myocarditis (viral, most often)
- Dilated cardiomyopathy and hypertrophic cardiomyopathy
- Congenital structural heart disease - e.g., critical aortic stenosis, hypoplastic left heart syndrome presenting neonatally when the ductus arteriosus closes
- Arrhythmias - long QT syndrome, Brugada syndrome, catecholaminergic polymorphic VT causing ventricular tachycardia or fibrillation
Harriet Lane Handbook, 23rd ed. lists electrical and structural cardiac etiologies as important life-threatening causes of pediatric hemodynamic compromise.
4. Obstructive Shock
Mechanical obstruction to blood flow:
- Tension pneumothorax - impairs venous return
- Cardiac tamponade - pericardial effusion or hemopericardium compresses the heart
- Massive pulmonary embolism - less common in children but can occur in hypercoagulable states or with central venous catheters
5. Neurogenic / Other Distributive Causes
- Vasovagal syncope with hypotension - accounts for ~50% of pediatric syncope; transient but significant drop in BP via increased parasympathetic tone
- Orthostatic hypotension - volume depletion, autonomic dysfunction, or prolonged bed rest
- Toxic ingestion / Drug overdose - medications causing hypotension include antihypertensives, beta-blockers, calcium channel blockers, opioids, tricyclic antidepressants, and clonidine - all important in the pediatric toxicology context
- Adrenal insufficiency - congenital adrenal hyperplasia crisis or acute adrenal suppression (e.g., sudden steroid withdrawal) causing mineralocorticoid and glucocorticoid deficiency
Quick Summary Table
| Mechanism | Example Causes |
|---|---|
| Hypovolemic | Dehydration, hemorrhage, burns |
| Distributive (septic) | Sepsis, anaphylaxis |
| Cardiogenic | Myocarditis, congenital heart disease, arrhythmia |
| Obstructive | Tension pneumothorax, tamponade |
| Neurogenic / Toxic | Vasovagal, toxin ingestion, adrenal crisis |
Key clinical pearl: In children, hypotension is a late sign of shock. Tachycardia, prolonged capillary refill, mottled skin, and altered mental status precede hypotension - do not wait for low BP to begin resuscitation.
Sources: Rosen's Emergency Medicine, 9th ed., p. 3112-3113 | The Harriet Lane Handbook, 23rd ed., p. 259-260
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