Questions about cardiac CT's

Our hospital has recently started doing heart scans. Since I am new to radiology, I would like to hear from nurses with experience in this test. We currently give 100mg Lopressor po 2 hours prior to scan to lower HR. If this does not lower HR to less than 65, we give IV Lopressor 5 mg Q5 minutes X3 doses. Recently, we had a patient with known cardiac prob's (MI and stents 5 years ago), who was already on a beta blocker, so he did not take the po Lopressor we normally give. We ended up giving him 3 doses of IV (15 mg total). The problem is, his HR was still in the high 60's, although it REALLY dropped his BP (80/50) post procedure!! We do not have a "recovery room" so I monitored him in our treatment room for 45 minutes. Of course his BP was better, and he went home. I have 2 questions: Does anyone use anti-anxiety meds(Ativan, Valium, etc) po prior to scan to lower HR? 2nd question: Does anyone use po Calcium channel blockers for someone with asthma instead of a beta blockers? When I asked one of our cardiologists, he said he would still use a beta blocker on someone with asthma because it "is in and out so quickly". By the way, when we scan, I am the only nurse and I have a radiologist with me and the tech. Our radiologist reads the heart scan. Is this common practice else where? Thanks in advance!