Cardiovascular · Year 1 · from Cardiovascular
Case 3: Septic Shock with Distributive Physiology
Patient Presentation
Demographics: 72-year-old male
Chief Complaint: Fever, confusion, and low blood pressure
History of Present Illness: A 72-year-old male with history of diabetes and recent UTI (treated with oral antibiotics 5 days ago) presents with fever, confusion, and weakness for 1 day. His wife reports he has been "not himself" and has had difficulty urinating. He has had shaking chills and decreased oral intake.
Physical Examination:
- Vital Signs: BP 75/40 mmHg (MAP 52), HR 125 bpm, RR 26/min, SpO2 92% on room air, Temp 39.2°C
- General: Confused, flushed, appears ill
- Cardiovascular: Tachycardic, warm extremities despite hypotension, bounding pulses
- Lungs: Clear
- Abdomen: Suprapubic tenderness
- Extremities: Warm, well-perfused, no edema
Workup
- Labs:
- WBC: 22,000/μL with 15% bands (left shift)
- Lactate: 5.2 mmol/L
- Creatinine: 2.8 mg/dL (baseline 1.2)
- Procalcitonin: 25 ng/mL (markedly elevated)
- Urinalysis: Pyuria, bacteriuria
- Blood cultures: Pending (later grew E. coli)
- Invasive hemodynamics (after resuscitation):
- Cardiac index: 4.8 L/min/m² (elevated)
- SVR: 450 dynes·s/cm⁵ (severely reduced, normal 800-1200)
- PCWP: 8 mmHg (low-normal)
- CVP: 6 mmHg
Diagnosis
Septic shock secondary to urosepsis with distributive physiology
Cardiac Output Correlation: MAP = CO × SVR
In septic shock (distributive):
- SVR severely reduced: Inflammatory mediators (NO, cytokines) cause profound vasodilation
- Cardiac output increased: Compensatory increase to maintain perfusion (hyperdynamic state)
- Despite high CO, hypotension: MAP = CO × SVR; if SVR drops dramatically, MAP falls despite high CO
- Tissue hypoperfusion: Maldistribution of blood flow → elevated lactate despite high CO
Contrast with cardiogenic shock:
| Parameter | Cardiogenic | Septic (early) |
|---|---|---|
| CO | ↓↓ | ↑ |
| SVR | ↑↑ | ↓↓ |
| PCWP | ↑↑ | Normal/↓ |
| Extremities | Cold | Warm |
Late septic shock: Myocardial depression may develop → CO falls → mixed picture
Treatment
- Aggressive fluid resuscitation: 30 mL/kg crystalloid within first 3 hours
- Broad-spectrum antibiotics: Ceftriaxone + metronidazole (started within 1 hour)
- Vasopressors: Norepinephrine (α1 agonist) to increase SVR and MAP
- Target MAP ≥65 mmHg
- Foley catheter (may need urology consult for obstruction)
- Source control: Remove any obstructed catheter, drainage if abscess
- Stress-dose steroids if vasopressor-refractory
Clinical Image
Image Description: Diagram illustrating the hemodynamic profile of septic shock showing decreased systemic vascular resistance (SVR) with compensatory increased cardiac output, resulting in warm shock physiology with hypotension.
Source: Wikimedia Commons - Septic shock physiology License: CC BY-SA 4.0 URL: https://commons.wikimedia.org/wiki/File:Septic_shock.svg