I would say his iv bag was still in him so I think he could have lasted about a wek but in the flash back it shows shane trying to rescue rick but the power goes.out but the out break seems to have already gone global ande the zombie were already im huge numbers and because they live in a somewhat remote area it may have tooken time to get thete so the hospital could have kept him alive as the infection continued to ravage the state so he could have been kept alive for month as the infection started then woke up shortly after the power went out
