Which of the following intravenous solutions are hypotonic?
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0.45% saline and 5% dextrose are hypotonic fluids. The osmolality of half-strength or 0.45% saline is 155 milliosmoles/L, dextrose is 252 mOsm/L (and the dextrose is quickly metabolized, leaving free water).
The calculated serum osmolality is 280-310 mOsm/kg in healthy animals.
Hetastarch and Vetstarch are colloids composed of high molecular weight starches in saline, they are isotonic.
Normosol-R ® and lactated Ringer’s are balanced isotonic crystalloids, at 296 and 272 mOsm/L, respectively.
Normosol-M ® is somewhat hypertonic at 364 mosm/L. It is not typically used in veterinary medicine. It has low levels of sodium and chloride and more potassium than replacement type fluids.
Check out these helpful tables on the different types of crystalloids and colloids.
