my father was recently in the hospital with severe pain in his hip. the cause was fluid in the joint. they gave him morphine to relieve the pain. after this when the pain was lessened, the nurse began to take blood. he began to get very groggy and break out in a sweatand his heart rate dropped down very low, they began to prepare crash carts and asked my mother to leave. a few minutes later his heart rate came up and he is fine. the doctors said this is common for men who have been dealing with severe pain and the pain is greatly reduced and called it something.