We've done it. The only problem sometimes is finding another Bair Hugger that isn't in use. Most frequently for our heart cases that are done without cardiopulmonary bypass and will need x-ray imaging- our TAVIs and daVinci CABGs that are combined with stents. We have gel water circuit underbody hyper/hypothermia blankets, but they interfere with image quality. Some of the other robotics specialties use both as well, and occasionally a trauma that doesn't require more than abdominal surgery.
I have worked at a few places where we have used upper and lower (spine), as well as under and lower (breast) with NO issues. In fact, the anesthesiologists mandated it!!! I am at a different facility today and the anesthesiologist went crazy on the team for the under and the lower (breast/TRAM). He said that manufacturer recommendations clearly state that more than one unit should never be used on a patient simultaneously. I may call the Co. tomorrow. Gotta love it!!!
We use under and over body bair hugger's together for our long neuro cases, Endoscopic Endonasal Approach and Crani for Tumors. It keeps our patients temp up much better than just having one over them.
jwk- ours have channels that are outside the patient that allows are flow to circulate. So there is a purpose.