Electrolyte solutions with small molecules that can diffuse freely from intravascular to interstitial fluid compartments
25% will stay intravascularly, and 75% will be in the interstitial compartment
0.9% saline
Differs from plasma - higher sodium and chloride concentrations, higher osmolality, lower pH
Cause interstitial oedema more than CSL due to higher sodium load
Produces a hyperchloraemic metabolic acidosis in large volumes
Ringer's lactate (CSL/Hartmann's)
Essentially 0.9% NaCL with sodium lactate, potassium and ionised calcium added
Doesn't change pH
Doesn't change serum lactate in healthy patients, and the impact on unwell patients is unknown, but is thought to be negligible, unless the bloods are taken from downstream
5% dextrose
Does provide some calories - 3L = 510kcal/day, although this is less important now that we have TPN and enteral feeding
Causes a disproportionate cellular swelling due to uptake of dextrose; conversely, causes cellular dehydration in patients with impaired cellular glucose uptake
Encourages anaerobic metabolism in critically unwell patients - causes a significant rise in serum lactate
Causes hyperglycaemia
Therefore, don't use it for critically ill patients
A particulate solution with particles that do not dissolve completely. In clinical terms, this is a fluid with solutes that cannot pass into the interstitium, and hence create a colloid osmotic pressure/oncotic pressure to hold water in the vascular compartment.
Albumin solutions
Usually given as 250mL of 5%, or 50-100mL of 25%
Volume effect begins to dissipate at 6 hours, and can be lost after 12 hours
5% is safe to use as a resuscitation fluid, and may outperform crystalloids where hypovolaemia is secondary to blood loss (although, should just give blood)
The 25% solution draws fluid intravascularly from interstitial space, and therefore shouldn't be used for volume resuscitation, but may be useful in situations where hypovolaemia is the result of hypoalbuminaemia
