Great post from emcrit.org on the myths of using LR in renal failure, specifically pointing out the physiology then backing it up with clinical trials:
the primary reason that this myth is wrong has to do with potassium shifting between the cells and the extracellular fluid. About 98% of the potassium in the body is present inside the cells, with an intracellular potassium concentration of ~140 mEq/L. Therefore, even a tiny shift of potassium out of the cellular compartment will have a major effect on extracellular potassium levels. NS causes a non-anion gap metabolic acidosis, which shifts potassium out of cells, thereby increasing the potassium level. On the other hand, LR does not cause an acidosis, but instead may have a mild alkalinizing effect given that it contains the equivalent of 28 mEq/L of bicarbonate. Potassium shifts have a greater effect on the serum potassium than the actual concentration of potassium in the infused solution.
The trials were quite excellent, with one comparing LR vs NS use in patients undergoing renal transplant.. the trial was actually stopped early as the LR patients were doing so much better than the NS patients:
They performed a prospective, randomized, double-blind controlled trial of NS versus LR among 52 patients undergoing renal transplant surgery. The mean change in serum potassium during the procedure was +0.5 mEq/L in the NS group compared to -0.5 mEq/L in the LR group (p < 0.001; figure below). Patients in the NS group also had lower pH levels following surgery.0
More detailed explanation at EMCRIT ( http://emcrit.org/pulmcrit/myth-busting-lactated-ringers-is-safe-in-hyperkalemia-and-is-superior-to-ns/ )
Another common myth associated with LR has to do with blood transfusions, according to this the calcium in LR can cause clots by overwhelming the chelating capability of the citrate in stored blood. But as a trial from 1998 demonstrated, this is also false and blood banks should recommend using LR for its advantages during trauma resuscitation vs. NS. See: http://www.aafp.org/afp/1998/0801/p502.html
So next time someone tells you to use NS for whatever reason in the OR or elsewhere, let them know LR is the best!