Spleen removal in dog..?

Hi just looking for some information my 9 year old lab is in the vet he just had his spleen removed .. He is now having some heart Arrhythmias they are treating started with the low end now in the medium range .. it hasnt even been 24 hrs is this normal or something i should be concerned about.. They gave him a blood transfusion he lost 27% blood loss... I just hope hes not suffering and i am doing the right thing .. the vet seems really calm .. which im sure they have to be ... Please any advice would be helpfull...