In SMA, breathing rates are usually higher than normal. In a healthy person, the rate of breathing should be 12-14 times a minute. In SMA, breathing rates can range from 20 times a minute on up. When the rate of breathing is so high you lose a lot of water from inspiration and expiration. Water replacement helps keep the lungs moist and you are less likely to get atelectasis. In SMA, there is a lot of water lost via breathing fast, open mouth breathing, and sweating. I highly recommend you give lots of water for hydration. Secretions should be thin not tacky. The recommendation from dieticians for a 1-3 year old is 115-125 cc/kg of water. At the age of 4 ½, Hannah got almost 53 ounces a day of liquids in her diet consisting of juice, water and/or breastmilk. At 8 ½ years of age, Hannah gets almost 80 ounces of liquid a day. When it is hot outside or when Hannah sweats or has fever she gets more water.
In SMA, the older the child the more water they need. I have never heard of water intoxication from giving to much water to an SMA individual. I am sure it is possible but you would have to give a HUGE amount of water