Cardiology

Background

Distributive shock is a type of circulatory shock characterized by severe peripheral vasodilation and relative hypovolemia, leading to inadequate tissue perfusion despite normal or increased cardiac output. It results from a failure of vascular tone due to underlying pathophysiological processes such as inflammation, neurogenic disruption, or anaphylaxis. 

II) Classification/Types 

By Etiology: 

• Septic Shock: Caused by systemic infection triggering widespread inflammatory response and vasodilation. 

• Anaphylactic Shock: Severe allergic reaction leading to histamine-mediated vasodilation and increased vascular permeability. 

• Neurogenic Shock: Disruption of sympathetic pathways (e.g., spinal cord injury), leading to unopposed parasympathetic tone and vasodilation. 

• Endocrine Shock (e.g., adrenal crisis): Cortisol or thyroid hormone deficiency impairing vascular response to stress. 

By Onset: 

• Acute: Rapid onset (e.g., anaphylaxis, spinal trauma). 

• Subacute to Chronic: Seen in evolving sepsis or endocrine dysfunction. 

III) Epidemiology 

• Sex: Slight male predominance in septic and neurogenic shock. 

• Age: Older adults and immunocompromised individuals are more susceptible to septic shock. 

• Geography: Higher incidence of septic shock in hospital/ICU settings globally. 

• Comorbidities: Diabetes, chronic kidney disease, immunosuppression, recent surgery, trauma. 

Etiology

I) What Causes It 

• Sepsis (most common): Bacterial (gram-negative > gram-positive), viral, fungal infections. 

• Anaphylaxis: Food, drugs (e.g., penicillin), insect stings, contrast media. 

• Neurogenic Injury: Spinal cord trauma (above T6), anesthesia, brain injury. 

• Adrenal Crisis: Addison’s disease, steroid withdrawal, pituitary insufficiency. 

II) Risk Factors 

• Recent infection or surgery 

• Immunosuppression (chemotherapy, HIV) 

• Spinal cord trauma 

• Allergies (food, medications) 

• Adrenal insufficiency 

• ICU hospitalization, indwelling catheters 

Clinical Presentation

I) History (Symptoms) 

• Fever or hypothermia (sepsis) 

• Rash, urticaria, angioedema, or wheezing (anaphylaxis) 

• Bradycardia and warm skin (neurogenic) 

• Confusion, dizziness, decreased urine output 

• Lightheadedness or syncope 

• Nausea, vomiting (especially in adrenal crisis) 

II) Physical Exam (Signs) 

Vital Signs: 

• Hypotension (MAP <65 mmHg) 

• Tachycardia (except in neurogenic shock) 

• Fever or hypothermia 

Skin: 

• Warm, flushed (early sepsis/neurogenic), later cool and mottled 

• Hives or angioedema in anaphylaxis 

Cardiac Exam: 

• Bounding pulse in early shock, weak pulse in late stages 

Pulmonary: 

• Tachypnea, possible wheezing or rales 

Neurologic: 

• Altered mental status 

• Flaccid paralysis in spinal cord injury 

Peripheral: 

• Capillary refill may be brisk initially 

• Dry mucous membranes in adrenal crisis 

Differential Diagnosis (DDx)

• Hypovolemic shock (e.g., hemorrhage, dehydration) 

• Cardiogenic shock (e.g., MI, arrhythmia) 

• Obstructive shock (e.g., PE, cardiac tamponade) 

• Acute adrenal insufficiency 

• Autonomic dysreflexia 

• Vasovagal syncope (transient) 

Diagnostic Tests

Initial Tests: 

• CBC: Leukocytosis or leukopenia (sepsis) 

• Lactate: Elevated (>2 mmol/L) indicates tissue hypoperfusion 

• Blood Cultures: Prior to antibiotic initiation (septic shock) 

• Procalcitonin: Elevated in bacterial infections 

• CMP: Electrolytes, renal function, liver enzymes 

• Arterial Blood Gas (ABG): Metabolic acidosis with high anion gap 

• Serum Cortisol: Low in adrenal crisis 

• Serum Tryptase: Elevated in anaphylaxis 

• ECG: Rule out arrhythmias, MI 

• CXR: Evaluate for pneumonia or ARDS 

• Urinalysis: Source of infection 

• Echocardiogram: To assess cardiac function 

Treatment

I) Medical Management 

Septic Shock: 

• Broad-spectrum IV antibiotics within 1 hour 

• IV fluids (30 mL/kg crystalloid bolus) 

• Vasopressors (norepinephrine 1st-line) if hypotension persists 

• Corticosteroids if refractory to vasopressors 

Anaphylactic Shock: 

• IM Epinephrine (0.3–0.5 mg) immediately 

• IV fluids 

• Antihistamines (H1: diphenhydramine; H2: ranitidine/famotidine) 

• Corticosteroids (methylprednisolone) 

• Bronchodilators (albuterol) 

Neurogenic Shock: 

• IV fluids 

• Vasopressors (norepinephrine or phenylephrine) 

• Atropine for symptomatic bradycardia 

• Maintain spinal precautions 

Endocrine Shock (Adrenal Crisis): 

• IV hydrocortisone (100 mg) 

• IV fluids with dextrose 

• Electrolyte correction 

II) Supportive Care: 

• ICU monitoring 

• Oxygen therapy or mechanical ventilation if needed 

• Glycemic control 

• DVT prophylaxis 

• Nutritional support 

Patient Education, Screening, Vaccines

• Recognize early signs of infection or allergic reaction 

• Avoid known allergens (carry epinephrine auto-injector) 

• Adrenal insufficiency patients should wear medical ID and carry emergency steroids 

• Adherence to immunization schedules: 

• Influenza annually 

• Pneumococcal vaccine 

• COVID-19 vaccination 

• Sepsis education post-discharge: “Time = Tissue” awareness 

Consults

• Critical Care/ICU: All distributive shock cases 

• Infectious Disease: Source control, antimicrobial stewardship 

• Allergy/Immunology: Evaluation for anaphylaxis 

• Endocrinology: Adrenal insufficiency management 

• Neurology/Neurosurgery: Neurogenic shock due to spinal cord injury 

• Primary Care/Internal Medicine: Long-term follow-up and prevention 

Follow-Up

• Septic Shock: 

• Repeat cultures, de-escalation of antibiotics 

• Monitor for long-term sequelae (e.g., post-sepsis syndrome) 

• Anaphylactic Shock: 

• Allergen testing and education 

• Epinephrine auto-injector training 

• Follow-up with allergist 

• Neurogenic Shock: 

• Neurological rehab 

• Long-term BP and autonomic monitoring 

• Adrenal Crisis: 

• Steroid replacement titration 

• Regular endocrinology review 

• Sick-day rule education