Sepsis Pathophysiology Overview

Sepsis

• Sepsis is a life-threatening condition triggered by an existing infection.
• It causes a chain of physiological reactions throughout the body.
• The normal physiology changes in a step-by-step process.

Pathophysiology

• Step 1: Infection (e.g., a cut).
• Step 2: Immune response is triggered, leading to inflammation and swelling in the glands in the neck.
• Step 3: Hyperactive immune response occurs, resulting in an overproduction of white blood cells (leukocytes), which fight infection.
• Step 4: The immune response becomes systemic (throughout the body) instead of local.
• Step 5: Capillaries become more dilated and permeable, allowing fluid to leak out of the blood vessels. This results in a decrease in intravascular volume.
• Step 6: Decreased blood flow to organs and tissues, and a drop in intravascular volume.
• Step 7: Abnormal clotting cascade (DIC) is triggered by the loss of blood volume and tissue damage from metabolic acidosis and vascular permeability.
• Step 8: Micro clots form, further restricting oxygen availability to tissues.
• Step 9: Lack of oxygen leads to anaerobic metabolism, producing lactic acid, which can be deadly.

Shock

• Shock occurs when there is inadequate tissue and organ perfusion (blood flow).
• The three main components for effective blood flow are an effective pump (heart), an effective circulatory system (blood vessels), and adequate blood volume (fluid).

Shock Types

• Hypovolemic: Due to blood loss or other fluid loss.
• Cardiogenic: Due to heart problems like a heart attack or arrhythmia
• Distributive: Related to blood vessel issues like neurogenic, septic, or anaphylactic shock
• Obstructive: Caused by physical obstructions like tension pneumothorax or cardiac tamponade.
• Dissociative: Related to issues with blood oxygen-carrying capacity, like severe anemia.

Blood Gas Values

• pH: 7.23 (normal 7.35-7.45), indicating acidosis
• PaO2: 9.85 kPa (normal 11-13 kPa) (slightly low)
• PaCO2: 3.2 kPa (normal 4.7-6.0 kPa) (low)
• HCO3: 12.6 mmol/L (normal 22-26 mmol/L), low bicarbonate
• Lactic Acid: 6.2 mmol/L (<2 mmol/L), high lactate

Red Flag Criteria for Sepsis

• Systolic BP 40 mm Hg less than baseline
• Respiratory rate >25/min
• Heart rate >130
• Altered consciousness, new confusion
• Limited urine output
• SpO2 <91%

Important Considerations

• Sepsis is a serious condition requiring immediate medical attention.
• Fluids (IV fluids) and antibiotics are crucial interventions, as are addressing underlying causes and monitoring organ systems to preserve their function.