Myth: Normal Saline Is the IV Fluid of Choice
Which fluid is superior, normal (0.9%) saline or balanced crystalloids (ie, lactated Ringer’s)? Balanced fluids, in theory, are defined as fluids that are more physiologic in several parameters when compared to normal saline (NS).
It appears we have a critical mass of sufficient evidence suggesting NS needs to take a back seat to lactated Ringer’s (LR).
LR has been criticized for being physiologically hypotonic, (reduced “actual osmolality” or tonicity) and thus may diffuse to extravascular spaces too quickly, limiting their effectiveness for volume expansion. Such diffusion results from osmotic pressure (ie, solutes and their associated osmotic coefficients).1 As an example, sodium and chloride only partially dissociate when dissolved and thus the solutes are only partially osmotically active (osmotic coefficient 0.926). The osmolarity of NaCl 0.9% is 308 mOsmol/L, but its actual osmolality is 286 mOsmol/kg H2O. The osmolarity of LR is 273 mOsm/L, but its osmolality is 254 mOsm/kg.1 This difference in tonicity may result in a shorter half-life for LR.| | | Next → | Single Page