Chocolate lab concerns

Question
I have a 9 month old chocolate lab who is around 8 to 9 days in her first heat cycle.  She is due to be spayed tomorrow.  She is an indoor dog but has been allowed to be outdoors alot prior to and during the cycle (we have invisible fencing).  Last night and today she has been breathing harder than usual (not excessive or panting--but just a little harder than normal).  She also seems to be sluggish in getting up.  I know as a female at my time of the month, I am sluggish too.  But, is she experiencing that during her heat cycle?  Or is the sluggishness and breathing a sign of heat?  Once I take her outside, she walks around, runs a little (not as fast as normal), and her bowel movements are fine--tight and regular looking with nothing that I would need be concerned about.  I don't think she has gotten into anything because she isn't vomitting or having any loose bowels at all.  She will wag her tail and lick me still if I sit on the floor.  We have been trying to break her of jumping all over people when they come to visit.  She's normally a very hyper dog.  Is it normal for a dog to change during heat?  I know labs suffer hip problems.  What should I be looking for if that were the case here?  She's an indoor dog and she's normally pretty active all of the time.  I don't know if the heat cycle has slowed her down or what is going on.  Any advice?

Answer
I would NOT recommend she be spayed tomorrow but instead she be examined carefully. First of all, spaying a dog in heat is risky because of excess bleeding. However, lethargy is not a sign of being in heat and she may have something else going on. Have her examined as soon as possible. Hip pain from dysplasia is a possibility and is easy enough to diagnose on xrays.

Dr. G.