I work night shift in a pediatric CICU. When I first started, I had a patient who had a heart defect repair during the day and came out of the OR around 1600. We always monitor our patients for what we call the "12 hour slump". Around 0400, my patient went into v-fib arrest. All you need to do is start compressions and CALL FOR HELP. Instinct definitely kicks in, and there are so many people around to help. Regardless of the outcome, you will do the best you can to save the patient.