Answer:

According to the MHAUS website under “FAQs: General MH Questions: How is MH Treated?” cold isotonic saline for IV infusion and gastric, peritoneal or rectal irrigation is recommended.

If all you had at hand to emergently cool a patient was cold IV lactated ringers solution, it could certainly be used (at least until you could get some isotonic saline to give).

However, would not make a special effort to stock it in an MH cart. Keep things simple and have cold IV saline 0.9% available. Also, LR has a bit more potassium in it than saline and the possibility that a patient may receive a large volume of IV fluid during an MH event could exacerbate the hyperkalemia that often occurs during MH.