Microgravity always looks really fun. It’s all fun and games until someone gets hurt, right?
In space and in micro-gravity we lose the constant of gravity to prevent items from moving in a specific direction. If you let go of a wrench while you’re moving it, it falls to the ground and friction stops its movement on Earth. In space, that wrench will continue in the direction you let go of it and bonk someone in the head.
This is when you’d need to do a little surgery to suture up your mistake. Surgery in space is going to be even more difficult because of a number of reasons.
Without gravity, we don’t have blood being pushed downwards. Instead, blood pools in the center of your body. If this happened on Earth, it would mean you have too much blood! So your body will try to remove liquid, thus lowering your blood volume significantly. This brings your standard blood volume in space to a pretty low level already. If you add a wrench to the head, though, you lose even more blood, putting you at a critical level quickly.
Wound healing in microgravity is also an unknown - we’ve done almost no research on how wounds will heal in space. It’s likely that there will be trouble because of the lack of gravity pushing downwards. This is made worse by the fact that your immune system will be heavily suppressed and poorly prepared to fight off infections from being in the microgravity. Bacteria grows in even more interesting ways - instead of growing in two-dimensions because gravity holds it down, it can grow in 3 dimensions.
Without gravity, water will be held together not by gravity, but instead by surface tension. Surface tension will cause the blood to pool together, obscuring the view of surgeons. You’ll need to constantly be clearing the field of view, but given weightlessness and possible bacteria infections it’s difficult to decide what to do with that excess. That’s also an unknown.
Suffice it to say - we probably aren’t prepared for this yet.