Intravenous Fluids

Chandler Montgomery

Indications for IV fluid

  • Restoration or maintenance of tissue perfusion
  • Correction of electrolyte abnormalities
  • Nutritional supplementation in those without reliable enteric access

Categorized into crystalloids and colloids

  • Crystalloid = water + electrolytes
  • Colloid = water + proteins/large molecules

Terms

  • Osmolality: osmoles of solute per L of solution
  • Tonicity: ability to induce movement of water across a membrane (i.e., effective osmolality)
  • Buffer: anions such as lactate, acetate, gluconate which are metabolized to bicarbonate in vivo with the goal of sustaining normal plasma pH

Crystalloids

  • Isotonic fluids used for volume resuscitation
    • After ~ 30 mins, redistribute such that only 25% remains w/in intravascular space
  • Balanced solutions (e.g. Lactated Ringer’s [LR], Plasma-Lyte)= have electrolytes concentrations similar to plasma
    • NS may lead to renal vasoconstriction, AKI, hemodynamic instability, increased mortality
      • SMART and SALT-ED: balanced solutions had lower rates of death, new renal replacement therapy, or persistent renal dysfunction compared to NS
    • Situations where NS may be preferred
      • Cerebral edema/traumatic brain injury
      • Hypovolemic hyponatremia
      • Pre-existing hypochloremic metabolic alkalosis (e.g. after vomiting or over diuresis)
    • Notes on LR
      • The small amount of K in LR (~4 mEq/L) is unlikely to significantly exacerbate hyperkalemia
      • Lactate in LR is sodium lactate. No hydrogen ions are being added to plasma

Common crystalloid solution

Fluid

Na

Cl

K

Ca

Mg

Glucose

Buffer

Osmolarity

Tonicity
Plasma ~140 ~100 ~4 ~2.4 1.0 ~0.85 Bicarb ~24 ~290 N/A
Normal 0.9% saline 154 154 0 0 0 0 0 308 Isotonic
Lactated Ringer’s 130 109 4.0 2.7 0 0 Lactate 28 273 Isotonic
Plasma-Lyte/Normosol 140 98 5.0 0 3.0 Gluconate 23
Acetate 27		 Lactate 28 295 Isotonic
D5W + 150 mEq HCO3- 150 0 0 0 0 50 Bicarb 150 300 Isotonic
3% Saline 513 513 0 0 0 0 0 1026 Hypertonic
DSW 0 0 0 0 0 50 0 252 Hypertonic

Colloids

  • Albumin: extracted from human plasma
    • 5%: use after plasma exchange
    • 25%: more concentrated; raises oncotic pressure and restores intravascular volume
      • Uses: post-LVP, diagnosis and treatment of hepatorenal syndrome, SBP (see Hepatology section)
      • Evidence base for use outside of above indications is poor (SAFE trial)
  • Blood products: packed RBCs, FFP, cryoprecipitate
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