Septic shock
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Harrison's Principles of Internal Medicine, Twenty First Edition
Page 8257
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septic shock management treatment antibiotics vasopressors fluid resuscitation
Harrison's Principles of Internal Medicine, Twenty First Edition
Page 8273
GradeResponse
GradeResponse
Septic Shock
Definition (Sepsis-3 Criteria)
Septic shock is defined as sepsis (suspected infection + acute organ dysfunction with SOFA score increase ≥2 from baseline) plus:
- Need for vasopressor therapy to maintain MAP ≥65 mmHg
- Serum lactate >2.0 mmol/L
- Despite adequate fluid resuscitation
(Harrison's, p. 8257)
Pathophysiology
The core mechanism is a dysregulated host response to infection leading to:
- Massive cytokine release (TNF-α, IL-1, IL-6) → systemic inflammation
- Vasodilation + capillary leak → distributive shock physiology (low SVR, high CO early)
- Endothelial dysfunction → impaired microvascular perfusion
- Mitochondrial dysfunction → cellular oxygen utilization failure despite adequate delivery
- Coagulopathy → disseminated intravascular coagulation (DIC) in severe cases
- Multi-organ dysfunction → renal, hepatic, pulmonary, cardiac failure
The result is tissue hypoperfusion despite often-normal or elevated cardiac output — distinguishing it from cardiogenic or hypovolemic shock.
Common Etiologies
| Source | Common Pathogens |
|---|---|
| Pneumonia (most common) | S. pneumoniae, Klebsiella, Staph aureus |
| Urinary tract / urosepsis | E. coli, Klebsiella, Pseudomonas |
| Intra-abdominal | E. coli, Bacteroides, Enterococcus |
| Skin/soft tissue | S. aureus (MRSA), Streptococcus |
| Bacteremia / line-related | S. aureus, coagulase-negative Staph, gram-negatives |
| Fungal | Candida spp. (immunocompromised) |
Clinical Presentation
- Hemodynamic: Hypotension, tachycardia, warm/flushed skin early (cold/clammy late)
- Respiratory: Tachypnea, hypoxia (ARDS in ~30%)
- Neurological: Altered mental status, confusion
- Renal: Oliguria, rising creatinine
- Metabolic: Elevated lactate, metabolic acidosis (high anion gap)
- Skin: Mottling, purpura (meningococcemia), petechiae
Diagnosis
No single diagnostic test — clinical diagnosis based on Sepsis-3 criteria.
Key investigations:
- Blood cultures ×2 (before antibiotics if possible, do not delay >45 min)
- Serum lactate (>2 mmol/L = high-risk; >4 mmol/L = severe)
- CBC, CMP, coagulation studies (PT/PTT, fibrinogen, D-dimer)
- Procalcitonin (supports bacterial infection; guides antibiotic de-escalation)
- ABG (assess oxygenation, acid-base)
- Cultures from suspected source (urine, sputum, wound)
- Chest X-ray / CT as clinically indicated
Bedside SOFA / qSOFA (quick screen: RR ≥22, altered mentation, SBP ≤100 — score ≥2 prompts full evaluation)
Management
Septic shock is a time-sensitive emergency. Management follows the Surviving Sepsis Campaign (SSC) Hour-1 Bundle:
Hour-1 Bundle
| Action | Detail |
|---|---|
| Measure lactate | Remeasure if initial >2 mmol/L |
| Blood cultures | Before antibiotics |
| Broad-spectrum antibiotics | Within 1 hour of recognition |
| IV fluid bolus | 30 mL/kg crystalloid |
| Vasopressors | If hypotension persists despite fluids; target MAP ≥65 mmHg |
1. Fluid Resuscitation
(Harrison's, p. 8273)
- 30 mL/kg IV crystalloid within first 3 hours
- Balanced crystalloids (e.g., lactated Ringer's) preferred over normal saline (reduces AKI/mortality)
- Guide ongoing resuscitation by lactate clearance, dynamic fluid responsiveness (pulse pressure variation, straight leg raise), or focused cardiac ultrasound
- Avoid hydroxyethyl starches and gelatins
2. Vasopressors
| Agent | Role |
|---|---|
| Norepinephrine | First-line vasopressor; target MAP ≥65 mmHg |
| Vasopressin | Add to reduce norepinephrine dose (up to 0.03 units/min) |
| Epinephrine | Second-line if MAP target not achieved |
| Dopamine | Avoid except in bradycardia or low tachyarrhythmia risk |
| Dobutamine | Add for myocardial dysfunction / low cardiac output |
3. Antimicrobials
- Administer within 1 hour of septic shock recognition
- Broad-spectrum empiric coverage based on likely source and local resistance patterns
- De-escalate based on culture results and clinical improvement (typically at 48–72 hours)
- Procalcitonin-guided de-escalation reduces antibiotic duration
Common empiric regimens:
| Source | Typical Regimen |
|---|---|
| Unknown/community | Pip-tazo or carbapenems ± vancomycin (if MRSA risk) |
| Pneumonia (CAP) | β-lactam + macrolide or fluoroquinolone |
| Urosepsis | Ceftriaxone or fluoroquinolone (adjust for local resistance) |
| Intra-abdominal | Pip-tazo or carbapenem |
| MRSA/line infection | Add vancomycin or daptomycin |
| Candida risk | Add echinocandin (anidulafungin/micafungin) |
4. Source Control
- Identify and control the infectious source within 6–12 hours: drain abscess, remove infected catheter/device, debride necrotic tissue
5. Corticosteroids
- Hydrocortisone 200 mg/day (continuous infusion or 50 mg q6h) for refractory septic shock (MAP not maintained despite adequate fluids + vasopressors)
- Reduces vasopressor duration; no clear mortality benefit in unselected patients
- Consider fludrocortisone 50 mcg/day if using hydrocortisone (APROCCHSS trial)
6. Ventilatory Support (if ARDS)
- Lung-protective ventilation: tidal volume 6 mL/kg IBW, plateau pressure <30 cmH₂O
- FiO₂ titration to SpO₂ 92–96%
- Prone positioning for P/F ratio <150
7. Additional Supportive Care
| Intervention | Target/Detail |
|---|---|
| Glucose control | 140–180 mg/dL (avoid hypoglycemia) |
| DVT prophylaxis | LMWH preferred |
| Stress ulcer prophylaxis | PPI or H2 blocker in high-risk patients |
| Renal replacement therapy | For refractory AKI, acidosis, or fluid overload |
| Blood transfusion | Hgb <7 g/dL (restrictive strategy); <9 g/dL with active MI/severe hypoxia |
| Nutrition | Early enteral nutrition if hemodynamically stable |
Complications
- Acute Respiratory Distress Syndrome (ARDS)
- Acute Kidney Injury (AKI) / renal failure
- Disseminated Intravascular Coagulation (DIC)
- Septic cardiomyopathy
- Shock liver / hepatic failure
- Critical illness neuropathy/myopathy
- Post-intensive care syndrome (PICS)
Prognosis
- Hospital mortality: ~25–50% (higher with more organ dysfunction)
- SOFA score correlates with mortality risk
- Lactate clearance (<10% at 2 hours) associated with worse outcomes
- Survivors face long-term cognitive, physical, and psychological sequelae
Key Sources: Harrison's Principles of Internal Medicine, 21st Ed. (pp. 8257, 8273); Surviving Sepsis Campaign International Guidelines 2021
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