When you get a chance, would you please create a profile, similar to mine below, so we know your difficult child's age, dxes and medications if any? Simply go to "User CP" (above left tab) and click on "Edit Profile." It makes answering your questions easier when we have context.
My difficult child 1 has long had a terrible time with blood draws, immunizations and dentists. The last time he had blood drawn, we did it when he was sedated for an MRI. We have also used Ativan (an anti-anxiety medication) for blood draws. He is actually behind on his immunizations, but we will deal with that soon, probably with Ativan. We are exploring the option of having his teeth cleaned under sedation at the children's hospital in our area. Some pediatric dentists will use "laughing gas" with their patients to get them to relax during examinations. You may have to ask around to figure out your options.
Good luck -- I know how hard this situation can be.