Sepsis, Infection, and Immunocompromise
Definitions and bundles
Sepsis is life-threatening organ dysfunction from dysregulated host response to infection, operationalized as a SOFA rise ≥2. Septic shock is vasopressor-requiring hypotension with lactate >2 mmol/L despite fluids. qSOFA is a bedside prompt, not a rule-out. The high-yield bundle elements are cultures before antibiotics when it does not delay therapy, broad antibiotics within one hour for shock, 30 mL/kg crystalloid for hypoperfusion, lactate measurement, and source control.
Vasopressors and fluids
Start norepinephrine early; peripheral administration is acceptable while access is obtained. Add vasopressin for escalating norepinephrine. Consider hydrocortisone for shock refractory to vasopressors. Fluids should be reassessed dynamically; over-resuscitation causes edema, abdominal hypertension, and worsened oxygenation.
Immunocompromise
Febrile neutropenia requires empiric antipseudomonal beta-lactam within one hour, with addition of coverage for resistant organisms based on history. Consider fungal infection in prolonged neutropenia, Pneumocystis in prolonged steroids or HIV, and CMV in transplant recipients. Reduce immunosuppression when possible in severe infection, in consultation with the transplant team.
Traps
- Delaying antibiotics in shock to obtain cultures.
- Using qSOFA to exclude sepsis.
- Withholding pressors until a central line is placed.
- Giving steroids to all septic patients rather than refractory shock.
- Using procalcitonin to justify withholding antibiotics in a sick patient.
Worked example
A patient on norepinephrine 0.3 µg/kg/min with lactate 5 despite 30 mL/kg: give antibiotics and source control, add vasopressin, consider hydrocortisone, and reassess fluid responsiveness rather than repeating blind boluses.
Rule of thumb
Antibiotics and source control are the only interventions that reliably alter sepsis mortality; everything else is supportive.