To be upset at this?

[SpeedbirdSquawker]

I've recently had a restructure at work and as a result my workload has increased and I have more responsibilities.

One such responsibility is something which is time sensitive.

I asked a senior manager to review something I've done before it goes public and gave a deadline. It has not come back to me and so I asked if they could get it back to me tomorrow and if they could give me an approx time they could complete by so I can start the next process, which includes more people having to do more things.

I got an email back basically saying they couldn't give me a time and more things which I thought was patronising.

Aibu to be so upset? I've had a cry. I'm so depressed at the moment and my anxiety is off the scale.

I think getting upset about work issues is generally a little pointless (but we all do it from time to time). The main question from me would be, was getting an approval from a senior manager is an essential part of the process. If yes, then missed deadline would be their responsibility and you have an email trail to demonstrate that.
If getting their approval was not an essential step and you did it "just in case", then I can see why the manager would have been a bit put out by having extra workload. It's not great management to refuse support but it's hard to say without seeing the context of their email whether they were truly patronising or whether they were gently (or not so gently) encouraging you to be more independent with the task.