Plasma Expanders

Intro & Classification - Fluid Fix Fundamentals

• Plasma Expanders: High molecular weight (MW) solutions that increase plasma volume by raising oncotic pressure.
• Primary Use: Rapid restoration of circulating volume in hypovolemia (e.g., shock, burns).
• Ideal Qualities:
  • Sustained intravascular presence.
  • Iso-oncotic with plasma.
  • Non-toxic, non-antigenic.
  • No blood group interference.
• Types:
  • Crystalloids: E.g., Normal Saline, Ringer's Lactate (initial fluid replacement).
  • Colloids:
    • Natural: Albumin, Plasma Protein Fraction (PPF).
    • Synthetic: Dextrans, Gelatins, Hydroxyethyl Starches (HES).

⭐ Albumin is the main protein contributing to plasma oncotic pressure, approximately 80%.

Crystalloid Solutions - Saline & Solutions Story

• Aqueous solutions of mineral salts/water-soluble molecules; rapidly distribute to ECF.

  ⭐ Crystalloids require 3-4x volume of colloids for same plasma expansion due to rapid ECF redistribution.

• Normal Saline (NS - 0.9% NaCl):
  • Isotonic; 154 mEq/L Na⁺ & Cl⁻.
  • Uses: Resuscitation, hyponatremia.
  • ⚠️ Risk: Hyperchloremic metabolic acidosis (HCMA) with large volumes.
• Ringer's Lactate (RL):
  • Balanced; lactate → bicarbonate.
  • Uses: Burns, trauma.
  • Caution: Hyperkalemia, liver disease.
• Hypertonic Saline (e.g., 3% NaCl):
  • ↓ ICP, severe hyponatremia.
  • ⚠️ Risk: Osmotic demyelination syndrome (ODS).
• Dextrose Solutions (e.g., D5W):
  • D5W: Isotonic in bag, hypotonic in vivo.
  • Provides free water; not for primary resuscitation.

Colloid Solutions - Big Molecules Boost

• Large molecules; remain intravascular longer than crystalloids, increasing plasma oncotic pressure.
• Mechanism: Draw fluid from interstitial space into intravascular space, leading to plasma volume expansion.
• Types:
  • Natural Colloids:
    • Albumin (Human Albumin 5%, 25%): Uses include hypoalbuminemia, burns, Spontaneous Bacterial Peritonitis (SBP), Hepatorenal Syndrome (HRS).
    • Plasma Protein Fraction (PPF)
    • Fresh Frozen Plasma (FFP): Primarily for clotting factor replacement.
  • Artificial Colloids:
    • Dextrans (Dextran 40, Dextran 70): Glucose polymers. SE: Anaphylaxis, renal failure, interference with coagulation (antiplatelet effect), rouleaux formation (interferes with blood cross-matching).
    • Gelatins (e.g., Polygeline, Modified Fluid Gelatin): Bovine origin. SE: Anaphylaxis (higher incidence).
    • Hydroxyethyl Starches (HES): e.g., Hetastarch, Pentastarch. SE: Anaphylaxis, coagulopathy (dose-dependent), pruritus. ⚠️ Black Box Warning: Increased mortality and severe renal injury in critically ill adult patients, including sepsis.
• Advantages: Smaller volume required for resuscitation compared to crystalloids; longer intravascular retention.
• Disadvantages: Higher cost, risk of anaphylactoid reactions, potential for coagulation disturbances (esp. Dextrans, HES), renal toxicity (HES).

⭐ Albumin administration in conjunction with antibiotics is recommended in patients with Spontaneous Bacterial Peritonitis (SBP) to reduce incidence of hepatorenal syndrome and mortality.

Clinical Application & Monitoring - Clinical Use & Caveats

• Clinical Uses:
  • Rapid volume restoration: Hypovolemic shock (hemorrhage, burns, trauma, surgery).
  • Acute Normovolemic Hemodilution (ANH).
  • Cardiopulmonary bypass (pump prime).
• Monitoring Strategy:

• Key Caveats:
  • ⚠️ Volume overload: High risk in cardiac/renal failure; watch for pulmonary edema.
  • ⚠️ Anaphylaxis: Dextrans (highest risk), HES, Gelatins.
  • Coagulopathy (dose-dependent): Dextrans (↓vWF, FVIII, platelets); HES (↓vWF, FVIII).
  • AKI: Esp. Dextran-40, older/high MW HES.
  • Dilutional: ↓Hct, ↓proteins, ↓platelets.
  • Interference: Dextrans with blood cross-matching.

⭐ Hetastarch (HES) products carry a black box warning for increased mortality and severe renal injury in critically ill patients (sepsis) and burn patients.

High‑Yield Points - ⚡ Biggest Takeaways

• Plasma expanders restore circulating volume in hypovolemia.
• Crystalloids (NS, RL) distribute widely; require larger volumes (approx. 3:1 to blood loss).
• Colloids (Albumin, Dextrans, HES) exert oncotic pressure for sustained intravascular expansion.
• Dextrans: Risk of anaphylaxis and impaired hemostasis.
• HES: Associated with renal dysfunction and coagulopathy.
• Albumin: Natural colloid for burns and severe hypoalbuminemia.
• Monitor for fluid overload, allergic reactions, and agent-specific toxicities.