It is not uncommon, but an unwelcome development which, depending upon the time of onset , requires investigation.
A reaction to morphine is often a post surgery resulting in an alarming drop of BP is well reported.
It's something that affects me after surgery. They keep me in recovery until it returns to normal.... many hours sometimes. I've never had an explanation.
Oh, I was probably unclear in how I worded my post...the rash is known to be due to one of his medications.
I'll be emailing him later and hopefully the blood pressure situation is under control.