Suspect your patient has an aortic dissection? Don't wait to lower the blood pressure.
A few considerations for the patient with suspected aortic dissection:
If the patient is hypertensive AND you really think they could have the disease, start the drip then. Don't wait until the CT is done. Every second that goes by with extremely elevated BP may increase the dissection length.
If you are really worried about a patient having a proximal aortic dissection, don't wait for the creatinine to come back...scan them without it. If you are really suspicious this is justified in many cases.
There is very little (to no) role in performing a dry CT (because the patient's creatinine comes back elevated). Dry CT is very insensitive. Instead get a transesophageal echo or an MRI.
