The pregnant and postpartum stomach

Abstract

For pulmonary aspiration to occur, sufficient gastric content must be present in the stomach, the protective function of the lower oesophageal sphincter has to be overcome and upper airway reflexes must be suppressed or absent. The basal gastric secretion and acidity is not changed in pregnancy. Overall, the evidence indicates that there is a delay in gastric emptying of water in the first trimester compared with the nonpregnant state, but no difference with water or solids in the second and third trimesters of pregnancy. In patients scheduled for elective caesarean delivery, the pre-operative ingestion of a carbohydrate drink, as advocated as part of enhanced recovery after caesarean delivery, leads to no difference in the cross-sectional area of the gastric antrum. Further, the Sip Til Send approach has been found to be noninferior to standard fasting with regard to the cross-sectional area of the gastric antrum and results in beneficial patient reported effects. In women in labour without systemic opioids and without epidural analgesia, gastric emptying was delayed with water and solids, and it was slowed even more with water in the presence of systemic opioids. Importantly, the use of epidural analgesia in labour increased gastric emptying, but not to levels observed in the nonpregnant phase. Clear fluids are likely to be well tolerated in labour, but the intake of solid food remains a concern. In the postpartum period, relative to the nonpregnant state, no difference in gastric emptying with water has been shown. Gastric ultrasound can be performed with the indication, acquisition, interpretation and medical management (I-AIM) framework. The indications for gastric ultrasound in obstetrics include caesarean delivery under general anaesthesia. Once past the first trimester of pregnancy, acquisition involves the semirecumbent and right lateral semirecumbent positions and an awareness of the differences on gastric ultrasound between nonpregnant and pregnant women. The contents of the stomach can be interpreted with qualitative and quantitative evaluation. In qualitative examination, the Perlas system of grading may be used. In quantitative examination, using the threshold of 1.5 ml kg−1, measurement of the gastric cross-sectional area as more than 608 mm2 in the semirecumbent position, 719 mm2 in the right lateral position and 960 mm2 in the right lateral semirecumbent position suggest the presence of a full stomach. In elective caesarean delivery with general anaesthesia, the observation of high-risk gastric contents on ultrasound may influence obstetric anaesthetists to postpone the caesarean delivery or reconsider the anaesthetic technique should the indication for general anaesthesia be relative rather than absolute. If no high-risk stomach contents are seen on gastric ultrasound, this may influence obstetric anaesthetists in their choice of induction method: either a modified rapid sequence induction; a standard general anaesthetic induction; full rapid sequence induction and secure the airway with a supraglottic airway rather than tracheal tube. In elective and emergency caesarean deliveries, the information gained from gastric ultrasound might be useful in the setting of failed tracheal intubation.