Black Stars coach Goran Stevanovic is close to finalising his 23-man squad for the tournament, which is to be hosted by Gabon and Equatorial Guinea in January and February.
And Adomah's form for City in the Championship this season means he is in prime position to make the final cut.
Arguably the team's most consistent and effective attacking player, the Londoner is considered a key component in City's fight against relegation and manager McInnes dislikes losing him.
But the reality is that the Robins could be without Adomah for up to a month and McInnes is already putting contingency plans in place.
Should Adomah make the squad and Ghana reach the final on February 12, the winger could be away for four weeks from mid-January and miss five Championship games.
Jamal Campbell-Ryce and Yannick Bolasie can fill in on the right wing, but McInnes is not ruling out making a loan signing to plug the gap.
The Scot said: "The fact Albert has an opportunity to go away and play in such a high-profile tournament is a good thing for him. In the long-term, I'm sure he will learn a lot from an experience like that.
"Obviously, we would like to send him on his way with our best wishes with us being in a much better position.
"But our position is still not so good and Albert is a key player for us. As much as he wants to go to the Africa Cup of Nations and take part in it, he also knows he has a responsibility to Bristol City and he wants to do well for us.
"It's a difficult one and we'll just have to wait and see what develops when the squad is announced."
Commenting on the possibility of finding a short-term replacement, McInnes said: "I'm not saying I'm definitely going to do that, but it would be wrong not to look.
"Like anything in football management, you are constantly trying to cover yourself and I'm aware of what might happen.
"We also have good players within the club who can come in and play a part, but we also have to plan ahead for every eventuality."
If called up by the Black Stars, Adomah could potentially miss City's trip to Brighton on January 14 and subsequent Championship games against Doncaster, Reading, Leeds and Hull.