The crusade against “Ab”Normal Saline continues. This is a non-physiologic fluid that can harm our patients in several ways; however, this post will focus on the harms associated with its Chloride (Cl-) content.
Our Extracellular Fluid (ECF) is dominated by Na+ whose positive charges are balanced by Cl- and HCO3-. Our Intracellular Fluid (ICF) is dominated by K+ and Mg2+ whose positive charges are balanced by anions on proteins and organic phosphates. The ECF and ICF both work together to maintain this electroneutrality. When we infuse Normal Saline, we introduce a high amount of Cl- into the ECF making it more negative. The ICF responds by taking up an anion that, in reality, we actually need to remain in our ECF, HCO3-. Progressive loss of HCO3- inevitably leads to Metabolic Acidosis.
Metabolic Acidosis (H+) is a problem. It disrupts the activities of essentially all our vital organs leading to derangements in function. As acidemia worsens and (H+) accumulates in the ECF, the ICF tries to help out by taking up H+ to buffer against the drop in pH. However, for the ECF and ICF to remain electrically neutral, the ICF must now lose a positive charge of its own so in exchange for H+, K+ leaves the ICF and enters the ECF to maintain electroneutrality in both compartments. This is concerning as a too much K+ in the ECF causes Hyperkalemia, a complication which can easily be fatal if not immediately addressed.
Normal saline has been associated with an increased risk of renal failure possibly requiring dialysis or CRRT. The high CL- content induces renal vasoconstriction of the afferent arteriole which reduces renal blood flow and perfusion. Studies have correlated this even in healthy volunteers showing reduced renal blood flow with saline infusions. Many of the patients we are all treating are far from healthy, I’ll leave it to your imagination then to think of the possible outcomes.
Balanced crystalloids like LR are safer, more physiologic, and thus easier to use. The only thing “Normal” about saline is when we take it off a patients MAR.
#foamed #criticalcare #management #diagnosis #treatment #pharmacology #physiology #crystalloids
Obiajulu Anozie
@icuexplained
· 4 years ago
