Lecture on Sepsis

Definition of Sepsis

• Sepsis is a life-threatening condition caused by a dysregulated host response to infection.
• Results in organ dysfunction from the body's response to infection, leading to organ failure and potentially death.
• Not all infections cause sepsis, but any infection can potentially lead to it.

Pathophysiology

• Organ Dysfunction: Caused by increased metabolic demands and insufficient circulation (increased demand, reduced supply).
• Normal Inflammatory Response: Localized, involves innate response, release of cytokines, recruitment of inflammatory cells (neutrophils, macrophages).
• Sepsis Response: Dysregulated, impairs normal body functioning.

Circulation and Sepsis

• Cardiac Output: Stroke volume x heart rate.
• Systemic Vascular Resistance: Resistance blood encounters in vessels (afterload).
• Mean Arterial Pressure: Product of cardiac output and systemic vascular resistance; determines perfusion.
• Vasodilation in Sepsis: Caused by nitric oxide, results in systemic vasodilation (arteries and veins), reduced venous return (preload), reduced stroke volume, and cardiac output.

Physiological Effects

• Heart attempts to compensate by increasing heart rate.
• Hypotension: Reduced mean arterial pressure, can lead to septic shock (form of distributive shock).
• Myocardial Contractility: Reduced by nitric oxide, affects heart's ability to pump effectively.
• Increased Vessel Permeability: Fluid extravasation, reduced circulating volume.
• Coagulopathy: Increased procoagulant factors, reduced anticoagulants, thrombi formation in small vessels.
• Red Blood Cells: Less flexible, impaired oxygen delivery.

Causes

• Bacterial Infections: Most common (Staphylococcus aureus, Streptococcus pneumoniae, E. coli).
• Sources: Lower respiratory tract (most common), abdomen, urinary tract.
• Septicemia: Blood infection in about 15% of cases.
• No Source: In up to 1/3 of cases, no infection source found.

Risk Factors

• Older age (>65), very young, immunocompromised states (malignancy, anti-cancer medication, steroid use).
• Recent surgery, invasive procedures, indwelling catheters/lines.
• Chronic conditions: Diabetes mellitus, hemodialysis.
• Lifestyle factors: Alcohol, drug use, pregnancy.

Clinical Presentation

• Varied presentation with infection source features (e.g., cough in pneumonia).
• Common Symptoms: Fever (may be absent in elderly), tachycardia, tachypnea, altered mental status, reduced urine output.
• Diagnosis: Clinical, based on infection presence and organ dysfunction.

Diagnostic Criteria

• SIRS Criteria: Previously used, includes temperature, heart rate, respiratory rate, white blood cell count.
• SOFA Score: Current method, Sequential Organ Failure Assessment; score of 2+ indicates organ dysfunction.
• Quick SOFA (qSOFA): Condensed version, includes tachypnea, altered mental status, systolic blood pressure <100 mmHg.

Septic Shock

• Definition: Sepsis with persistent hypotension, requiring vasopressors to maintain mean arterial pressure >65 mmHg, serum lactate >2.

Management: Sepsis Six

• Three Things to Take:
  • Blood cultures (before antibiotics but shouldn't delay treatment).
  • Blood tests, including lactate level.
  • Measure urine output (via urinary catheter).
• Three Things to Give:
  • Empirical intravenous antibiotics.
  • Intravenous fluids (restore preload, circulation).
  • Oxygen.
• Additional Measures: Vasopressors, inotropes if blood pressure not maintained with IV fluids.