You should never, ever sign the medical release that is sent to you by the at-fault driver's insurance company. While releases are sometimes important to the claim every release that I have ever seen from an insurance company is overbroad: contains no time limit, can be sent to anyone at all, and allows the insurance company to re-release the information to others. There is no requirement that you sign their release.
While you're still going to the doctor treating your accident injuries there is no good reason for the at-fault driver's insurance company to be monitoring your medical records. The only reason they want to see your medical records is so they can look for things to use against you and ways they can weaken your injury case. I can't count the number of times I've been called and told me the at-fault driver's insurance adjuster is telling an injury victim that they should have been healed by now and they weren't really hurt that bad in the car accident. Don't fall for this tactic. Your doctor is the expert on the severity of your injury and how much treatment you need to recover.
My advice to you is that if an insurance adjuster calls you requesting you to sign anything, tell them to mail you the form and you'll be happy to review it with your attorney.
Or better yet order my free book "The Guide to Washington Injury Cases" by clicking here. The book will give you some good information about the whole car accident injury claim process before you speak with that pushy insurance adjuster.