ICU Advantage Lecture Notes

Introduction

• Presented by Eddie Watson
• Focus on critical care topics in the ICU.
• New series on fluid management strategies.
• Importance of managing fluid and electrolytes in ICU patients.

Fluid Management Overview

• Patients in ICU typically cannot manage their own fluid intake.
• Vital to maintain fluid and electrolyte balance in critical illness.

Types of IV Fluids

General Categories

• Crystalloids:

  • Contain water, electrolytes, and small water-soluble molecules.
  • Benefits: cost-effective, versatile, minimal immune response.

• Colloids:

  • Large insoluble molecules (often proteins).
  • Higher osmotic pressure, more expensive, potential immune complications.

Fluid Distribution in the Body

• Body composition: 50-60% water (varies by gender).
• Two major compartments:
  • Extracellular Fluid (ECF): 1/3 of total body fluid.
    • Plasma: 20% of ECF.
    • Interstitial Fluid: 80% of ECF.
  • Intracellular Fluid (ICF): majority of body fluid (inside cells).
• Water moves passively between compartments (osmotic/hydrostatic gradients).
• Major electrolytes: sodium, magnesium, potassium, calcium, chloride, bicarbonate.
• Importance of osmotic gradients and active transport for electrolyte distribution.
• Role of proteins (e.g., albumin) in maintaining osmotic pressure and fluid balance.
• Normal plasma osmolality: 285-295 mOsm/L.

Types of Crystalloids

Isotonic Solutions

• Normal Saline (0.9% NaCl):

  • Osmolality: 308 (slightly hypertonic).
  • Contains: 154 mEq/L sodium and chloride.
  • Risks: hyperchloremic metabolic acidosis, negatively affects GFR.

• Lactated Ringer's (LR):

  • Osmolality: 273 (slightly hypotonic).
  • Contains: sodium, potassium, chloride, calcium, lactate.
  • Considered a balanced fluid.
  • Caution: may worsen cerebral edema, issues with lactate metabolism in liver diseases.

• Plasmalite:

  • Osmolality: 295.
  • Composition: closely resembles plasma (sodium, potassium, chloride, magnesium, acetate, gluconate).
  • Balanced fluid, lower risk for hyperchloremic metabolic acidosis.

Hypertonic Solutions

• 3% Normal Saline:
  • Osmolality: 1030.
  • Commonly used for cerebral edema and severe hyponatremia.
  • Risks: hypernatremia, hyperchloremia, potential intravascular volume overload.

Hypotonic Solutions

• Half Normal Saline (0.45% NaCl):
  • Osmolality: 154.
  • Caution: potential for increased intracranial pressure, not for hypernatremia.

Dextrose-Containing Fluids

• D5W (5% Dextrose in Water):

  • Starts as isotonic but becomes hypotonic as dextrose metabolizes.

• D5 1/2 NS:

  • Starts hypertonic, shifts to hypotonic.

• D5 NS, D5 LR, D10W:

  • Similar properties as above, initially hypertonic, metabolizes to isotonic or hypotonic.

Colloids

• Albumin:

  • Available as 5% or 25%.
  • Preserves renal function; can be used for hypovolemia.

• Hydroxyethyl Starches (HES) and Dextran:

  • Less commonly used, potential complications in certain populations (e.g., hemorrhagic shock, sepsis).

Conclusion

• Understanding fluid types and their effects is crucial in ICU management.
• Next lesson will build on these foundational concepts.

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