Stomach contents can regurgitate up the gullet into the wind pipe and enter the lungs when there is no cough reflex, e.g. during general anaesthesia. Solid food can block airways and cause breathing difficulties. The acidic liquid from the stomach can damage the lungs. This is called aspiration pneumonitis or Mendelsohn’s syndrome. It can lead to serious illness or even death. Many caesarean sections now are undertaken using epidural or spinal anaesthesia, and here the risk is much lower because the woman stays awake and the cough reflex remains intact. A breathing tube, which provides a seal, is normally placed in the windpipe when setting up a general anaesthetic to try to prevent this problem. However, aspiration can still occur before the tube is inserted and when it is removed. It is thought that both the acidity and amount of fluid inhaled contribute to how much damage occurs in the lungs in the event of inhalation of the fluid into the lungs and how sick people become.
This review found 22 studies involving 2658 women looking at interventions given prior to caesarean section for reducing the risk of aspiration. There were several different drugs and drug combinations being considered and the studies were generally of poor or questionable quality. Antacids (like sodium citrate), H2 receptor antagonists (like ranitidine), proton pump antagonists (like omeprazole), all reduced the acidity of the stomach contents. An antacid plus an H2 receptor antagonist also reduced acidity. In theory, a combination like this, where the antacid acts quickly and the H2 receptor antagonists takes a little longer, should protect at periods of greatest risk, i.e. the beginning and end of the procedure (i.e. intubation and extubation). More research is needed to identify the best combination of drugs and to check for possible adverse effects.