Millie is a 1 year-old intact female West Highland white ter…

Millie is a 1 year-old intact female West Highland white terrier that has a two-week history of waxing and waning episodes of lethargy.  She is now in examination room 1 and is very lethargic.  Your veterinarian suspects that she may have hypoadrenocorticism based on her breed and history.  What is the best type of crystalloid fluid to give an animal during episodic crises of this disease?