I think everyone got messed up with your mom in the hospital. Tests, delays, waiting for doctors….and she's in her 70s and was totally run down and dehydrated. Hospitals are notoriously terrible places to get any rest so she was probably sleep-deprived from all the beeping of machines and activity with staff in and out of the room and going down the halls. Did anyone talk to you about how disoriented the elderly can get in the hospital? Even if they are lucid at home, they can get all discombobulated in the hospital.
You were exhausted too - you even slept for 3 hours on Christmas, from noon to 3. You agreed to have Christmas with your own family, and your brother with his. You did that, at least until you went to sleep.
Meantime, everyone else was all upset too, worried, and making contingency plans.
Your mother somehow let you down and didn't make all kinds of arrangements to call you. Your brother did the same - he had Christmas with his own family, then your parents were going over at the last minute. He just thought it was for a meal, but then they decided at the last minute to bring presents.
Still, you are ripping mad. Instead of acknowledging that you felt lousy (start of a cold) and no bout the exhaustion of worrying about your mother's overall health, and instead of being kind about the confusion that can easily result after days of upheaval with a hospital visit, you decided to tear your brother apart. His wife probably made some of the arrangements, thinking she was being helpful and to take some of the stress off your brother, since he was probably starting to think about the long term parental care situation too.
As a woman with an elderly mother and an absolutely impossible brother, I can tell you I would dearly love to have a brother who lived 2 miles from my parents and who knew how to apologize. I can also tell you that dealing with aging parents who may have to leave their home and deal with health problems is so very difficult - parents can be stubborn, in denial, and overwhelmed. You and your brother have to talk directly, and you have to put your egos aside. You have to be the grown-up here, not the child of these people who are getting older and who have health problems. People in their 70s can be old or young, depending on their medical condition, medications, attitudes, and family history.
Your parents have been through a scare, and both are exhausted. They are probably worrying about their own future. They really don't need to be worrying about forgetting to call their adult daughter in the confusion of a holiday hospital stay. You were going to see them shortly anyway for your dad's birthday.
You really have to rise above this, or future conversations are going to center on not offending you. People will start to leave you out of the discussions. Be a big enough person to see the big picture here. And you absolutely need to model for your children a mature attitude, a willingness to cooperate with siblings, and greater regard for their grandparents.