What happens in hospital when someone arrests?

A cardiac arrest team will be called in, and the staff will start CPR immediately, they will use a BVM and Defib (if necessary) to attempt to resus the patient the cardiac arrest team will then move in and perform ALS on the patient.

Usually the patient will go into respiratory arrest and then cardiac arrest, their heart rhythm will normally go from normal synas rhythm into VF (Ventiricualr Fibrillation) where a shock will be nececerry to stop the heart, and shock it back into normal rhythem.

If the patient receives early CPR and early Defib they have a fairly good chance of surviving if they go into VF.

Hope this helps.