Lecture on Sepsis

Jun 5, 2024

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Lecture on Sepsis

Definition

  • Sepsis: Life-threatening organ dysfunction caused by dysregulated host response to infection.
  • Consequence: Damage to organs leading to failure and death.
  • Not every infection leads to sepsis but any infection can potentially do so.

Pathophysiology

  • Organ Dysfunction: Results from increased metabolic demands and insufficient circulation.
    • Increased demand with reduced supply.
  • Normal Inflammatory Response: Localized involving cytokines, neutrophils, and macrophages.
  • Dysregulated Immune Response: Impairs normal functioning.

Circulation in Sepsis

  • Components:
    • Cardiac Output: Stroke volume * heart rate.
    • Systemic Vascular Resistance: Resistance in blood vessels (afterload).
  • Mechanics:
    • Determine mean arterial pressure affecting perfusion.
    • Vasodilation from nitric oxide reduces venous return and systemic vascular resistance.
    • Heart increases rate to maintain cardiac output but may eventually fail.
    • Reduced perfusion can lead to septic shock.
    • Nitric oxide also reduces myocardial contractility.
    • Increased vessel permeability leads to fluid extravasation.
    • Procoagulant factors rise; anticoagulants drop, causing coagulopathy.
    • Thrombi formation in small vessels; impairs capillary circulation.
    • Red blood cells less flexible, impairing oxygen delivery.

Causes

  • Primary Sources:
    • Bacterial infections, especially Staphylococcus aureus, Pseudomonas, and E. coli.
    • Other pathogens: Viruses, fungi, parasites.
    • Common infection sites: Lower respiratory tract (pneumonia), abdomen, urinary tract.
    • Elderly: Urinary tract is common source.
  • Terms:
    • Septicemia: Blood poisoning; blood doesn't need to be infected but is in ~15% of cases.
    • In up to 1/3 of cases, no infection source found.

Risk Factors

  • Older age (>65 years), very young age.
  • Immunocompromised states: Malignancy, anti-cancer meds, steroids.
  • Recent surgery, invasive procedures, indwelling catheters or lines, diabetes, hemodialysis, alcohol/drug use, pregnancy.

Presentation

  • Varied Symptoms: Depend on source of infection.
    • Example: Cough in pneumonia.
  • Fever common but not always present; hypothermia possible in elderly.
  • Symptoms: Tachycardia, altered mental status, reduced urine output.
  • Clinical Diagnosis: Based on infection and organ dysfunction.

Diagnostic Criteria

  • Old Criteria: SIRS (Systemic Inflammatory Response Syndrome) criteria: 2 or more symptoms like abnormal temperature, tachycardia, hyperglycemia, altered mental state, WBC count abnormalities.
  • New Criteria: SOFA Score (Sequential Organ Failure Assessment).
    • Used in ICUs to determine organ failure extent.
    • Score ≥2 indicates organ dysfunction; change of ≥2 also significant.
    • Based on 6 parameters: Cardiovascular, respiratory, renal, liver functions, conscious level, coagulation.
    • Initial score of 10: 50% mortality; score of 14: 95% mortality.
    • Quick SOFA (qSOFA): Simplified version.
      • Criteria: Tachypnea, altered mental status, systolic BP < 100 mmHg.
      • 2 out of 3 criteria suggest need for further investigation.

Specifics on Septic Shock

  • Definition: Sepsis + persistent hypotension needing vasopressors to keep mean arterial pressure > 65 mmHg + serum lactate > 2.
  • Management: Low threshold for treatment.

Management: Sepsis Six

  • Three Things to Take:
    • Blood cultures (preferably before antibiotics).
    • Blood tests (include lactate level).
    • Measure urine output (insertion of catheter).
  • Three Things to Give:
    • Empirical IV antibiotics.
    • IV fluids to restore preload and circulation.
    • Oxygen.
  • Additional Measures:
    • Vasopressors.
    • Inotropes if IV fluid resuscitation is inadequate.