As fun as it would surely be to float around without gravity, it makes even simple tasks difficult. Think about trying to perform CPR, or cardiopulmonary resuscitation, where you push down on someone’s chest to help their heart beat. On Earth, you would use your weight to press down on the chest, but that doesn’t work in space. On the ISS, the patient has to be strapped into a special harness and the medical helper has a belt tied around them to keep them in place. European Space Agency astronaut Samatha Cristoforetti demonstrated this in a video posted to Twitter.
Then there are the effects of microgravity on the blood. In surgery, it’s often necessary to cut someone open or to deal with bleeding. According to Nina Purvis, a researcher in space medicine at King’s College London, that means complications. “Bodily fluids will also behave differently in space and on Mars,” Purvis writes. “The blood in our veins may stick to instruments because of surface tension. Floating droplets may also form streams that could restrict the surgeon’s view, which is not ideal.”
If a surgeon’s vision being impeded by blood droplets sounds unpleasant, be warned — it gets worse. Purvis writes that in experiments on performing open surgery on animals in microgravity, the intestines would float around and get in the way.