Notes on Nausea

Prodromal phase of emesis: Salivation increases, sometimes a lot, pupils dilate, heart races, blood vessels constrict, cold sweat. Attention and focus go down, and fatigue starts to set in. Stomach has electrical activity, and relaxes to prevent emptying. Oesophagus contracts to pull the stomach into the chest through the diaphragm (like a funnel). Retrograde giant contraction: small intestine pushes contents back to the stomach. In the lower small intestine, contents are pushed to the colon.

Vomiting act: Retching involves muscles of the abdomen, oesophagus and respiratory system, but nothing comes out. During expulsion, intense pressure is generated in the stomach after the diaphragm and the abdomen contract

Nausea: From the Greek word meaning ship. Intensely aversive, used in behavioural change therapy (rather controversially). Aside: potatoes during pregnancy is a bad idea, unless you want your child to have a neural disease. Pregnancy nausea as a evolutionary defence mechanism, because the embryo is sensitive to toxins in food. Women with moderate to severe emesis during pregnancy have lesser miscarriages than women with mild to no emesis. But we don’t know why nausea happens with motion sickness.

Motion sickness happens when the motion that we experience is not the motion that we are expecting. No convincing explanation for why anxiety, or the sight of blood, or the sight of vomit causes nausea. Injury from sever vomiting can occur: rupture of the oesophagus, lung collapse, tearing of the spleen. Some doctors think pregnancy sickness is due to unconscious rejection of pregnancy (originally touted by Freud). Vomiting and nausea are not connected always, you can have one without the other, considering how common this is, we still don’t have a good antiemetic drug.