creation date: 2026-09-01 16:35
tags: Pathologies
Distributive Shock
Background
Definitions
Shock is defined as a life-threatening condition of circulatory failure. It is a state of cellular tissue hypoxia due to inadequate oxygen delivery for the metabolic demands.
The effects of shock are initially reversible but can deteriorate to an irreversible state with multiorgan failure and death.
Four types of shock are recognized, of which multifactorial shock is possible. The specifics of each type are described in their respective pages:
- Distributive (66% – 62% septic shock, 4% other)
- Cardiogenic (16%)
- Hypovolemic (16%)
- Obstructive (2%)
The general approach to undifferentiated shock is described separately. This articles describes specific findings and treatment of this type of shock.
Etiology
Distributive shock is characterized by severe peripheral vasodilation. Capillary leakage may cause redistribution of fluid from intravascular to extravascular compartment. The molecules that mediate vasodilation vary based on etiology.
Cardiac output may increase initially but with drop in preload and cardiac depression, CO decreases. Cellular hypoxia occurs in a positive feedback cycle and anaerobic metabolism results in elevated lactate levels.
Septic shock
- A subset of sepsis, which is defined as a dysregulated host response to infection resulting in capillary leakage and systemic vasodilation
- Circulating inflammatory cytokines causes myocardial depression
- Types of pathogens varies and ranges from:
- Gram-positive bacteria (eg. Pneumococcus, Enterococcus)
- Gram-negative organisms (eg. Pseudomonas, Klebsiella, Enterobacter)
- Antibiotic-resistant organisms (eg. MRSA)
- Fungi (eg. Candida)
Systemic inflammatory response syndrome (SIRS)
- Characterized by robust inflammatory response
- Induced by infectious (similar to septic shock) or noninfectious (eg. pancreatitis, blunt trauma, air/fat/fluid embolism)
Neurogenic shock
- Interruption of autonomic pathways due to severe brain and/or spinal cord injury results in unopposed vagal tone
- Vagal tone causes peripheral vasodilation and pooling of peripheral blood
Anaphylactic shock
- Severe immunoglobulin-E mediated allergic reaction resulting in degranulation of mast cell
- Massive histamine release causes vasodilation and capillary leakage
Drug and toxin-induced shock
- SIRS-like syndrome can be induced by drug overdoses (eg. narcotics), snake/insect/spider bites, heavy-metal poisoning, transfusion reactions
- Cyanide and carbon monoxide causes shock from mitochondrial dysfunction
Endocrine shock
- Addisonian crisis (due to mineralocorticoid deficiency) and myxedema
- In mineralocorticoid deficiency, vascular tone is altered
- In myxedema, link to thyroid hormone unclear
Risk Factors
Septic shock:
- Suppressed immune system
- Extremes of age (infants or elderly)
- Procured organ (transplant)
- Surgical procedure
- Indwelling devices
- Sickness
Clinical Presentation
Signs & Symptoms
Vitals:
- Tachycardia (unless neurogenic shock or on beta blocker)
- Hypotension (unless early sepsis)
- Tachypnea (unless severe shock)
- SpO2 usually normal (unless severe)
- Increased pulse pressure
Distributive shock presents with hypotension with reduced preload or fluid overload:
- Skin turgor is normal
- Mucous membranes are moist
- IVC normal on imaging
- Preserved or hyperdynamic left ventricle on echocardiography
- No peripheral edema
- No distended neck veins
- Central venous pressure is normal (8-12 mmHg)
- Mixed venous oxyhemoglobin saturation (SvO2) >70%
Septic shock
- Symptoms suggestive of source of infection
- Cutaneous manifestation of infective endocarditis
- Fever
Anaphylactic shock
- Flushing
- Urticaria
- Hoarseness of voice
- Oral and facial edema
- Exposure to common allergens
History & Physical Exam
History and physical should focus on finding a source of infection or anaphylactic reaction.
Diagnosis
Criteria
Shock is a clinical diagnosis.
Work-up
Work-up following diagnosis of distributive shock consist of finding potential source of infection or allergic reaction.