Septicemia and Septic Shock

Definitions and Spectrum

Pathophysiology

1. Hypovolemia - both absolute (GI loss, sweating, tachypnea, reduced intake) and relative (increased venous capacitance + capillary leak into third spaces).
2. Myocardial depression - direct cardiac dysfunction occurs early, driven by circulating TNF-α, IL-1β, overproduction of NO via inducible nitric oxide synthase (iNOS), and mitochondrial oxidative phosphorylation impairment. Ejection fraction falls even in the "hyperdynamic" stage.
3. Systemic inflammation - widespread endothelial activation, vasodilation, edema, DIC, and metabolic derangements lead to multisystem organ failure through microvascular and mitochondrial dysfunction. This produces ARDS (capillary leak in lungs), acute kidney injury, and liver dysfunction. - Rosen's Emergency Medicine; Robbins Basic Pathology

Clinical Features and Workup

• WBC: leukocytosis (>12,000) or leukopenia (<4,000) or bandemia (≥5-10% bands) - all are imperfect indicators
• Lactate: elevated; target normalization as resuscitation end-point
• Procalcitonin (PCT): >0.5 ng/mL suggests bacterial infection; <0.1 ng/mL makes it less likely (but does NOT exclude severe infection)
• Anion gap metabolic acidosis: often lactic acidosis; low bicarbonate indicates inadequate perfusion
• Creatinine/GFR: elevated signals AKI and worsens prognosis
• Coagulation panel: thrombocytopenia, elevated PT/aPTT, low fibrinogen, elevated fibrin split products/D-dimer indicate DIC
• Blood cultures: obtain before antibiotics if possible, but do not delay antibiotics

Management

1. Volume Resuscitation

• 30 mL/kg IV crystalloid within the first hour (balanced crystalloid such as lactated Ringer preferred over normal saline - associated with lower rates of AKI and possibly improved mortality)
• Albumin shows no convincing benefit over crystalloid
• Hetastarch is contraindicated in septic shock
• Monitor volume responsiveness to avoid overload; excessive resuscitation is associated with increased mortality
• A restrictive vs. liberal fluid strategy results in similar mortality, but either requires careful monitoring - Goldman-Cecil Medicine

2. Vasopressors

• First line: Norepinephrine (1-50 μg/min) - preferred over dopamine (fewer arrhythmias, particularly atrial fibrillation); acts via α1 and β1 adrenergic receptors
• Second line: Vasopressin (up to 0.03 U/min) - may be added to norepinephrine when MAP target is not achieved; does not significantly outperform norepinephrine alone
• Angiotensin II (20-200 ng/kg/min) can reduce early norepinephrine requirements but does not reduce mortality
• Dobutamine (2-20 μg/kg/min) for patients with low cardiac index despite adequate filling pressures (low mixed venous O2 saturation with high CVP)
• Target MAP ≥65 mmHg (65-70 mmHg is as effective as 80-85 mmHg as a target) - Goldman-Cecil Medicine

3. Antimicrobials

• Start antibiotics immediately after blood cultures - delays in appropriate antibiotic therapy directly increase mortality
• Use broad-spectrum empirical coverage based on likely source and local resistance patterns
• Source control (e.g., drainage of abscess, debridement of necrotizing infection) as soon as reasonably possible - Washington Manual of Medical Therapeutics

4. Corticosteroids

• Not recommended if fluid + vasopressors can restore hemodynamic stability
• If refractory shock: hydrocortisone 200 mg/day IV (50 mg q6h) ± fludrocortisone (50 μg daily x7 days via NGT) may improve 90-day mortality
• Hydrocortisone alone shortens duration of shock but does not reduce 90-day mortality
• Risks: superinfection, neuromyopathy, hyperglycemia, immune suppression - Goldman-Cecil Medicine

5. Lactate Monitoring

• Lactate clearance is associated with improved mortality; current Surviving Sepsis guidelines recommend targeting lactate normalization during resuscitation

6. Glucose Control

• Hyperglycemia and insulin resistance are common
• Intensive insulin therapy is NOT recommended - associated with higher hypoglycemia rates and possibly increased mortality; standard glucose control is preferred

7. Red Blood Cell Transfusion

• Transfusion threshold: hemoglobin <7 g/dL (equivalent outcomes to 9-10 g/dL threshold with fewer transfusion-related complications)

8. Mechanical Ventilation / Sedation

• Daily sedation interruption decreases duration of ventilation and ICU stay
• Brain natriuretic peptide-guided weaning results in more ventilator-free days
• Fever reduction to normothermia (36.5-37°C) via external cooling can reduce vasopressor requirements and 14-day mortality, especially with high vasopressor doses or marked tachycardia

Scoring Tools Summary

Recent Evidence (2024-2026)

• A 2024 JAMA meta-analysis (PMID: 38864162) found that prolonged infusions of beta-lactam antibiotics (vs. intermittent dosing) may improve outcomes in adults with sepsis/septic shock.
• A 2024 systematic review (PMID: 38904978) examined methylene blue in septic shock - a potential adjunct for refractory vasoplegic states, though evidence is still emerging.
• The Surviving Sepsis Campaign 2026 Pediatric Guidelines (PMID: 41869844) have been published, updating recommendations for children.