Intravenous Fluids

Intravenous fluids can be classified into:

Crystalloids
Can pass freely through a semipermeable membrane. Can be further classified into:
- ECF replacement solutions
  Have a [Na⁺] similar to ECF, such that they are confined mostly to the ECF.
- Maintenance solutions
  Designed to distribute throughout TBW.
- Special solutions
  These solutions don't fit into the above two categories, and include:
  - Hypertonic saline
  - Mannitol
  - 8.4% Sodium Bicarbonate
Colloids
Substance evenly dispersed throughout another solution in which it is insoluble. Can be classified into:
- Naturally occurring
  - Albumin
    Heat-treated human albumin.
    - Produced at low pH but not technically sterile
      Use within 3 hours of opening.
    - Contributes to plasma oncotic pressure
    - Contributes to drug and endogenous substance binding
- Synthetic
  - Dextrans
    High molecular weight sugars synthesised from sucrose by bacteria.
    - Interfere with haemostasis due to vWF inhibition
    - Interfere with blood crossmatch
    - Risk of anaphylaxis
  - Gelatins
    High molecular weight proteins produced by collagen hydrolysis.
    - Greatest anaphylaxis risk
    - Do not interfere with clotting
  - Hydroxyl-ethyl starches
    - Risk of anaphylaxis
    - Risk of renal impairment
    - Accumulate in the reticuloendothelial system

Comparison of Crystalloids

Contents (mmol.L^-1)	0.9% NaCl	Hartmann's	Plasmalyte
Na⁺	154	130	140
Cl^-	154	109	98
K⁺		4	5
Ca²⁺		3
Mg²⁺			1.5
Lactate		28
Acetate			27
Gluconate			23
pH	5.0	6.5	5.5

Last updated 2020-10-09