When is the peripartum stomach safe?

1. When is the peripartum stomach safe? Jo Davies MBBS FRCA Department of Anesthesia UWMC April 2002

2. Surgery in the Peripartum period • Obstetric & non-obstetric surgery may be necessary at any time during the antepartum and early postpartum periods • there is an increased risk of acid aspiration during pregnancy & for some time post delivery • there is also an increased risk of failed intubation • regional anesthesia is the technique of choice • GA may be unavoidable • when should we consider the patient to have a full stomach?

3. Factors involved in Acid Aspiration • Gastric emptying • pH & volume of gastric contents • gastro-esophageal reflux

4. ANTEPARTUM • gastric emptying is unchanged in pregnant cf. nonpregnant women • plasma gastrin levels may be increased >20 weeks • pH of gastric contents & gastric volumes in pregnant women are not significantly different cf. controls < 20 weeks • lower esophageal sphincter integrity is compromised early in pregnancy (15-18wks) (especially in patients with symptomatic reflux) with increased risk of aspiration • progesterone relaxes the sphincters smooth muscle, with mechanical factors increasing gastric pressures later in pregnancy

5. POSTPARTUM - Gastric emptying • Gin et al showed rapid gastric emptying one day postpartum, with results unchanged on 3rd day & 6 weeks later • Sandhar et al used applied potential tomography & showed that the mean time to 50% emptying is the same in the 3rd trimester & 2-3 days postpartum as in the same group of women 6 weeks after delivery

6. POSTPARTUM - pH & volume of gastric contents • Gastrin levels causing hypersecretion of acid during pregnancy, fall within 30 mins of delivery • Blouw et al showed no significant difference in pH or volume of gastric contents when comparing a group of postpartum women (mean time from delivery 19.5 hrs) with controls • Lam et al confirmed this in women ranging from 12 to 120 hrs after delivery • James showed no significant difference in incidence of pH < 2.5, pH 1.4 or >25 ml in gastric aspirates of women 1 -8 hrs postpartum cf. controls

7. Postpartum - pH & gastric volume (2) • BUT - these studies highlight an alarming issue! • >50% patients involved, postpartum or controls, had gastric pH < 2.5 • many of these had gastric volumes > 0.4ml/kg • do all these patients have “dangerous” gastric contents, despite the very low incidence of acid aspiration? • OR - is a competent gastro-esophageal junction more important?

8. Postpartum - Gastro-esophageal reflux • Reported by 80% of women at term • monitoring of lower esophageal pH demonstrated reflux in asymptomatic women at term • reflux due to: • mechanical effect of gravid uterus increasing gastric pressure • relaxant effect of progesterone on smooth muscle of lower esophageal sphincter • plasma progesterone concs decrease within 24hrs of delivery • external pressure on stomach relieved at delivery • when does reflux resolve?

9. Postpartum - gastro-esophageal reflux • Vanner & Goodman investigated reflux in a group of conscious women at term and 24-80hrs postpartum used lower esophageal pH monitoring • 5 of 25 postpartum women refluxed • 17 of 25 term women refluxed • 2 of 3 studied < 26hrs postpartum refluxed • NO episodes of reflux > 48hrs

10. RECOMMENDATIONS • ANTEPARTUM • any pregnant patient should be considered at risk of aspiration >18- 20weeks , or earlier if symptomatic, & full precautions taken. • POSTPARTUM • 48 hrs after delivery anti aspiration measures including RSI should not be necessary • ANY woman with symptomatic reflux peripartum should receive full prophylaxis & a RSI if GA unavoidable • further investigation of gastric emptying & reflux in the first 24hrs postpartum is needed