Snapshot A 56-year-old man presents after a bee sting half an hour ago. He reports sudden onset of an itchy rash, swelling, and difficulty breathing. His blood pressure is 88/58 mmHg, pulse is 104/min, and respirations are 24/min. On exam, he has swollen lips and generalized erythematous urticarial plaques over his face and chest. There are wheezes audible with each breath. He is given intramuscular epinephrine and fluid bolus. (Anaphylactic shock) Introduction Clinical definition shock secondary to severe peripheral vasodilation Epidemiology Risk factors infection exposure to allergens trauma Etiology Pathogenesis an underlying event (such as infection or anaphylaxis) causes severe peripheral vasodilation → ↓↓ systemic vascular resistance (SVR) → hypotension interruption of autonomic pathways (e.g., from traumatic brain injury) → decreased SVR ↓ SVR → compensatory ↑ cardiac output (CO) initially in severe cases, ↓ CO Septic shock (most common type) non-septic shock systemic inflammatory response syndrome (SIRS) (e.g., burns or air embolism) neurogenic shock (e.g., traumatic brain injury) anaphylactic shock mediated by IgE toxin-induced shock (e.g., snake bites) endocrine shock (e.g., adrenal failure) Presentation Symptoms typically presents with features of the underlying cause (e.g., pneumonia or spinal trauma) Physical exam hypotension warm or dry skin may have fever Studies Labs serum lactate may help guide management in septic shock Pulmonary artery catheterization findings ↓ pulmonary capillary wedge pressure (PCWP < 15 mmHg) ↑ or ↓ cardiac output ↓ systemic vascular resistance Making the diagnosis most cases are clinically diagnosed Differential Different Types of Shock Shock Type Skin Wedge Pressure (PCWP) (Preload) Systemic Vascular Resistance (SVR) (Afterload) Cardiac Output Hyovolemic Cold and clammy skin ↓↓ ↑ ↓ Cardiogenic ↑ ↑ ↓ Obstructive ↑ or ↓ ↑ ↔ or ↓↓ Distributive Warm or dry skin ↔ or ↓ ↓↓ ↓ or ↑ Treatment Management approach treat underlying cause Medical intravenous fluid boluses indications for all patients vasopressors indication for all patients refractory to fluids drugs norepinephrine mechanism of action vasoconstriction of peripheral vessels side effects digital ischemia (due to vasospasm) arrhythmias epinephrine/vasopressin second line vasopressor phenylephrine Complications Death Acute renal failure Prognosis Septic shock is associated with 40-50% mortality rate