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

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?

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

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

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

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 25 ml in gastric aspirates of women 1 -8 hrs postpartum cf. controls

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?

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?

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

RECOMMENDATIONS ANTEPARTUM –any pregnant patient should be considered at risk of aspiration > weeks, 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