The topic of normal saline vs. lactated ringers can spark fierce debate, but are we asking ourselves the wrong question?

An Age-Old Debate

Few topics in the world of resuscitation and critical care generate as much controversy as the discussion over which is the “superior” intravenous fluid: normal saline (NS) or lactated ringer’s (LR). I myself, a budding intensivist and self-professed LR acolyte, have often overzealously argued in favor of my fluid of choice.

The SMART trial in 2018 helped fuel the fire, showing a benefit of balanced solution (Plasma-Lyte or LR) over normal saline in critically ill patients with respect to a composite outcome of death from any cause, new renal-replacement therapy, or persistent renal dysfunction at 30 days.¹ However within the last year two new trials (PLUS and BASICS) have been published that throw water on the results of SMART. Both trials were overwhelmingly negative, revealing no difference between balanced crystalloids and NS in their primary outcomes.^2,3

Suboptimal Choices

While there may still be situations which call for one fluid in particular (BASICS showed a clear advantage of normal saline in TBI patients, and much literature points to LR as the fluid of choice in DKA management), I think a more fundamental issue lies beneath this debate and is rarely addressed. While LR is commonly lauded as more physiologic, I think we have to consider that even it is far from “ideal.”

There is in fact no ideal “physiologic” IV fluid available to us. Comparing both NS and LR to physiologic conditions reveals lackluster results: while NS certainly comes out the loser (composed of only supraphysiological concentrations of sodium and chloride), LR compared to serum plasma is actually hypotonic, hyponatremic and hypocalcemic, and contains no magnesium.⁴ 

Fluid “Resuscitation”: A Misnomer?

With this in mind, perhaps we should ask ourselves if perhaps all IV fluids have long been overrated, or at the very least over-utilized. While we reflexively reach for a bag of crystalloid when a patient presents with undifferentiated shock, a basic understanding of physiology would tell us that this would only be effective in cases of hypovolemic shock when a patient presents with a fluid deficit, whether that be from GI losses, insensible losses, or poor PO intake. While many critically ill patients will present with some degree of dehydration, more often than not they will require more than IV fluids to resolve the underlying cause of their shock.