All of the response posts make sense, dubbs.
You and your husband should have been informed (upon discharge) that depression following open heart surgery is almost a given, especially in men. Lorazepam and hydroxyzine will do absolutely nothing for his depression, in fact, such drugs might add to his depression. Of course, they help with anxiety...and sleeping a lot is not what he needs to be doing right now. Rest for sure. But he should have a cardiac rehab program in place or soon to be started to help in recovery. In fact, your medical center's cardiology department should offer programs/options to help their post-op cardiac patients do exactly this. Perhaps check into that. There are even support groups for open heart surgery post-op patients which he might greatly benefit from. In my opinion, your husband should not languish in depression. He needs help for this...hopefully short term. And genetically he might be prone to depression, complicating things. There are many, many medications for him to try...often it's trial and error. There is most certainly a drug that will work for him. Instead of SSRIs - he might respond better to SNRIs. And the best physician to prescribe such medications is not your surgeon/PCP/cardiologist but a psychiatrist. Ask for a referral for an evaluation for your husband.
Gradually, slowly your husband needs to recuperate from his surgery. He most certainly needs a full program in place. Sleeping a lot is not helpful to him, in fact it's detrimental for him in getting back on track with his life.
Cardiac programs are available for his physical, emotional and mental recovery. Antidepressions are serious medications but seem to be necessary right now. Help is available for him...be his strong advocate!
All the best to your husband and you...life post open heart surgery can/will get better for sure! Don't give up!