Fluids, Electrolytes & Nutrition: Fluid Replacement

Intravenous Fluids

Crystalloid Fluids

Definition: Aqueous Solutions Containing Mineral Salts & Small Molecules
Types of Crystalloid:
- Lactated Ringer (LR)/Hartmann’s Solution
  - Sodium (Na): 130 mEq/L
  - Chloride (Cl): 109 mEq/L
  - Potassium (K): 4 mEq/L
  - Calcium (Ca): 2.7 mEq/L
  - Lactate: 28 mEq/L
    - Metabolization Releases Bicarbonate (Alkalinize)
    - Overall pH: 6.5
- 0.9% Normal Saline (NS)
  - Sodium (Na): 154 mEq/L
  - Chloride (Cl): 154 mEq/L
- Hypertonic Saline (3% NS)
  - Sodium (Na): 513 mEq/L
  - Chloride (Cl): 513 mEq/L
- 0.45% Normal Saline (1/2 NS)
  - Sodium (Na): 77 mEq/L
  - Chloride (Cl): 77 mEq/L
Additives:
- Dextrose
  - D5 (5%) or D10 (10%)
  - D5W – 5% Dextrose in Water
- Potassium Chloride (KCl)

Colloid Fluids

Definition: Aqueous Solutions Containing Large Molecules
Types of Colloids:
- Packed Red Blood Cells (PRBC)
- Platelets (Plt)
- Plasma (FFP)
- Albumin
Synthetic Colloids: Hydroxyethyl Starch, Dextran or Gelatins
- Rarely Used Now
- Side Effect: Coagulopathy (From Impaired Platelet Function) & AKI
*See Hematology & Oncology: Blood Products

Resuscitation Fluids

Fluid Choice: Lactated Ringer (LR) or Normal Saline (NS)
- Avoid Crystalloids in Hemorrhagic Shock (*See Hemorrhagic Shock & Damage Control Resuscitation)
Resuscitation Rate:
- General Peds: 20 cc/kg
  - Blood Products – 10 cc/kg
- General Adult: 30 cc/kg
- Trauma: 2 L Wide Open
- Burns: *See Trauma: Burns

Maintenance Fluids (mIVF)

Fluid Choice:
- Neonate (< 10 kg): D10 1/4-NS + 10 mEq KCl
- Peds: D5 1/4-NS + 20 mEq KCl
  - *More Hypotonic Fluid Preferred in Peds Due to Ineffective Ability of the Distal Nephrons to Concentrate Urine (GFR About 25% that of an Adult)
- Adult: D5 1/2-NS + 20 mEq KCl
Maintenance Rate: Mn

- *Each Step is Added to the Prior Steps
- *Ex: 23 kg > 10×4 + 10×2 + 3×1 = 63
May Need to Decrease Infusion Rate Below the Calculated Maintenance Rate Once Patients Begin Mobilizing Third-Space Fluid
- Often Occurs Around Post-Operative Day #3
Goal Urine Output (UOP):
- Infant (< 1 Year): > 2.0 cc/kg/hr
- Peds: 1.0-2.0 cc/kg/hr
- Adult: 0.5-1.0 cc/kg/hr

Fluid Replacement Sequestration

Crystalloid – Only 1/3 Remains Intravascular
Albumin – Stays Intravascular Longer (Does Not “Pull” Fluids In)
- Benefits & Indications are Poorly Defined

Easy Way to Calculate Hourly Maintenance Fluid Requirements