I had the same reaction to salt water enema just two days ago. I have been for many years on a low salt diet and I realize that my body absorbs a lot of salt from the salt water enema even though it is not supposed to do that.
I have found through experience that if my body has been on a low salt diet and my sodium level is somewhat lower than normal, it will absorb salt quite readily from a salt water enema. The only time I can tolerate a saline enema is when I take several large soapsuds enemas which I am sure somewhat dehydrates me. I do take a sale water enema after what I call a large volume coffee enema with Epsom salts. This enema is dehydrating. Refer to my blog, "My challenge", link below.