my father is elderly (63) he just had his artificial hip replaced in a 6 1/2 hour extensive surgery we were told things worked out better than they thought and then he spent 5 hours in recovery. now 24 hours later his blood pressure is down to 54/50 and they say it is okay. he is on a deloted iv push. should we be worried about his blood pressure? what is normal? he usually has high blood pressure.