Is this anxiety or something more?

I am posting this on behalf of my husband. About 2.5 weeks ago he had, what he described as a panic attack at work. He is a respiratory therapist, was working in the ER (something he has done 100s of times) suddenly he got tunnel vision, was shaking, and panicking. This panic feeling basically never went away (going on almost 3 weeks). He went to his doctor who ran some labs, did an EKG, and started him on lexapro 5 mg (to increase to 10 mg at 2 week mark) and hydroxyzine as needed. The strange thing is, his anxiety symptoms peak at about 1 AM, he wakes up every single night in a complete panic and basically cannot go back to sleep. They then persist and slowly taper throughout the morning until he is “ok” around noon. Then it starts all over. Every night. His dad and brother have anxiety but don’t describe it anything like this. He has Xanax as needed that he can take in the middle of the night that calms him down a bit but he hardly sleeps. The hydroxyzine does nothing. He is taking the lexapro at night.

He is scheduled to see psych the end of this month.
He is on medical leave as he cannot function at work on hardly any sleep and his anxiety/panic is absolutely peaking during crucial work hours. Since people’s lives depend on him, he decided to take a month off to try to figure this out.

He is so frustrated and getting more depressed by the day.

Any other ideas? Is something being missed? He has otherwise never had anxiety/panic attacks. Would he benefit from some testing in his cortisol levels or adrenal gland issues?

Thanks for any insight or recommendations.