What I read was that as a precaution they decided to give him an adrenalin injection prior to the operation to increase his heart rate.
His heart rate didn't increase so they used an epidural injection rather than a general anaesthetic.
He had heart checks between operations and they found no problems.
The only thing they could put the lack of response to the adrenalin was his superb fitness levels
He wasn't happy being awake during the op but listened to an ipod to distract him.