Using only about 1250 words and 6 references, he explains that infusing lactated ringers not only does not cause harm, it is actually superior to normal saline in patients with hyperkalemia, metabolic acidosis, and renal failure.
I highly recommend reading the post which should take you only a few minutes. If you're too lazy to do that, here's a summary.
Dr. Farkas found no evidence that lactated ringers cause or worsens hyperkalemia. In fact, he presents some solid evidence to the contrary.
If the serum potassium is 6 mEq/L, a liter of lactated ringers, which contains 4 mEq/L of potassium, will actually lower the potassium level.
Because almost all potassium (~98%) in the body is intracellular, the infusion of any fluid with a normal potassium content will result in prompt redistribution of potassium into the cells negating any of the almost negligible effect of the potassium infusion.
A normal saline infusion is acidic, resulting in potassium shifting out of cells and increasing the serum potassium level. Lactated ringers, containing the equivalent of 28 mEq/L of bicarbonate, does not cause acidosis.
There's a lot more in the post. Read it.
This issue is arguably the most misunderstood fluid and electrolyte concept in all of medicine.
In my opinion, the post should be displayed on the bulletin boards of intensive care units, emergency departments, and inpatient floors of every hospital in the world and should be read by every resident or attending physician who writes orders for IV fluids.
Disclosure: I've never been a fan of normal saline. Two years ago I wrote a post that discussed two papers showing that because of its negative effects on renal function, normal saline was inferior to lactated ringers in critically ill patients.