Overview
This lecture covers distributive shock, focusing on sepsis and anaphylaxis, including their pathophysiology, recognition criteria, clinical features, prevention, and management strategies.
Distributive Shock Overview
- Distributive shock (vasodilatory shock) includes sepsis and anaphylaxis, both characterized by inappropriate vasodilation and maldistribution of blood volume.
- Leads to decreased cardiac output and tissue perfusion.
Sepsis: Pathophysiology & Recognition
- Sepsis starts with a precipitating infection causing local inflammation and can progress to SIRS (systemic inflammatory response syndrome).
- SIRS criteria: two or more of the following—fever (>38°C) or hypothermia (<36°C), tachycardia, tachypnea (RR >20 or PaCO2 <32), abnormal WBC count (<4,000 or >12,000, or >10% bands).
- Sepsis = SIRS + confirmed or suspected infection; severe sepsis = sepsis + organ dysfunction; septic shock = sepsis with refractory hypotension; MODS = failure of two or more organs.
Sepsis: Management & Prevention
- Prevention: scrub IV lines with alcohol, sterile dressing changes, timely removal of invasive devices, and early detection.
- Obtain two sets of blood cultures before antibiotics; draw from different sites 15 minutes apart.
- Remove or culture any indwelling lines before inserting new ones.
- Elevated lactic acid (>2 mmol/L = elevated, >4 mmol/L = poor prognosis); reassess after fluid bolus.
- Initiate with two large bore IVs, give 30 mL/kg fluid bolus; use vasopressors if hypotension persists.
- Fluid challenge: raise legs to assess BP response—if BP rises, fluid responsive; otherwise, consider vasopressors.
- Complete initial sepsis assessment ideally within 1 hour.
Anaphylaxis: Pathophysiology & Recognition
- Anaphylaxis is a severe allergic reaction, commonly triggered by foods, medications, insect stings, latex, or environmental factors.
- Mediated by IgE antibodies, which activate mast cells to release histamine (causes vasodilation, bronchospasm) and other mediators.
- Symptoms vary but may include hives, airway swelling, wheezing, and in severe cases, cardiovascular collapse.
- First exposure may cause little reaction; subsequent exposures may be more severe.
- Allergies can be hereditary; prevention includes avoiding triggers and carrying an EpiPen.
Anaphylaxis: Management
- Severity determines management; time of onset and amount/type of exposure affect severity.
- Mild: nasal congestion, hives, tingling, warmth within 2 hours.
- Moderate: above symptoms plus flushing, anxiety, coughing, airway swelling, and wheezing.
- Severe: rapid onset, includes airway closure, cyanosis, hypotension, diarrhea, vomiting, cardiac arrest.
- Monitor patients for recurrent reactions (may occur within 48 hours).
- Epinephrine: adults 0.3 mg IM (1:1,000), children 0.01 mg/kg IM; IV epinephrine only during cardiac arrest (1:10,000).
- Additional meds: corticosteroids (solu-medrol), antihistamines (diphenhydramine for H1, famotidine/pepsid for H2).
- Never give 1:1,000 concentration IV.
Key Terms & Definitions
- Distributive Shock — shock due to vasodilation and maldistribution of blood flow.
- SIRS (Systemic Inflammatory Response Syndrome) — clinical response to widespread inflammation with set criteria.
- MODS (Multi-Organ Dysfunction Syndrome) — dysfunction of at least two organ systems from severe illness or injury.
- Sepsis — life-threatening organ dysfunction due to a dysregulated body response to infection.
- Anaphylaxis — rapid, severe allergic reaction involving multiple body systems.
- IgE — antibody responsible for triggering allergic responses.
- Epinephrine — medication used as first-line treatment in anaphylaxis.
Action Items / Next Steps
- Practice recognizing SIRS criteria and early sepsis signs.
- Review proper technique for obtaining and culturing blood/line specimens.
- Learn and rehearse EpiPen use and allergy assessment protocols.
- Prepare for neurogenic shock in the next lecture.