Systemic Infectious and Immune Disorders
Core approach
Systemic infection and immune emergencies require early recognition and source control. Core topics include sepsis and septic shock, meningitis, pneumonia, endocarditis, toxic shock syndrome, neutropenic fever, anaphylaxis, angioedema, and transplant-related infection. For sepsis, obtain cultures when feasible, give broad-spectrum antibiotics promptly, and resuscitate with fluids and vasopressors as needed. For anaphylaxis, epinephrine is first-line and should not be delayed for antihistamines or steroids. Recognize angioedema, including ACE inhibitor-associated presentations.
Traps
Elderly and immunosuppressed patients may be afebrile or have normal white blood counts. A normal lactate does not exclude sepsis. Do not delay antibiotics in unstable sepsis to obtain cultures. Anaphylaxis can occur without skin findings, and biphasic reactions may occur. Do not give flumazenil or unnecessary medications that may worsen autonomic instability. In neutropenic fever, broad-spectrum coverage is urgent.
Worked example
A patient develops stridor, hypotension, and diffuse urticaria minutes after an antibiotic. Give IM epinephrine to the lateral thigh, oxygen, and rapid fluids; repeat epinephrine every 5 to 15 minutes if needed. Rule of thumb: intramuscular epinephrine is the first treatment for anaphylaxis, not an antihistamine.
Key concepts
Sepsis care includes early antibiotics, cultures when feasible, fluids, and vasopressors for persistent hypotension. Toxic shock syndrome is toxin-mediated and requires source removal.