Gastrointestinal System

Gastrointestinal System

Gastric Function

Anatomical changes and hormonal effects on smooth muscle tone promote gastric contents to reflux into the esophagus during pregnancy. The enlarging uterus increases gastric reflux in two ways. Firstly, the stomach is shifted upwards, and the lower intra-abdominal segment of the oesophagus is displaced up into the thorax, which reduces the effectiveness of the lower oesophageal sphincter, also known as the lower oesophageal high-pressure zone (LEHPZ). Secondly, the uterus compresses the intra-abdominal contents and increases intra-gastric pressure. Progesterone is a smooth muscle relaxant, and it also reduces the tone of the LEHPZ Delayed gastric emptying will increase the residual volume in the stomach. There is no delay in gastric emptying during pregnancy and early labour, but some dealt occurs just before delivery. However, gastric emptying is considerably slowed down by the use of opiate pain relief during labour. The risk of regurgitation decreases post delivery and should be normal 48 hours postpartum.

Clinical Implications

Pulmonary aspiration of gastric contents can occur after vomiting or passive regurgitation, resulting in significant morbidity and mortality. All pregnancy women should be considerable to have a full stomach, with increased risk of aspiration from the end of the first trimester. During general anesthesia, the airway needs to be protected with a cuffed tracheal tube. A rapid sequence induction should be performed with pre-oxygenation, cricoid pressure, and avoiding positive pressure ventilation until the airway is secured with a tracheal tube. The use of regional anesthesia for caesarean section avoids the risks of aspiration associated with general anesthesia.