Antacids for LSCS

Roberts RB, & Shirley MA. Reducing the risk of acid aspiration during cesarean section. Anesthesia & Analgesia 1974; 53: 859-868.

RHH Journal Club. June 6th, 2013. Dr Susan Yeung

Full-text article (if available)

This paper from 1974 highlights the increased risk of aspiration in pregnant women undergoing caesarean section (CS). This has led to a change in practice whereby all women prior to elective or emergency section are given antacid prophylaxis.

Study design

This was single centre, prospective interventional trial at Mount Sinai Hospital in New York.

Methodology

100 randomly selected patients undergoing elective or emergency CS were recruited. Some received antacid prophylaxis (hexitol-stabilised mixture of magnesium and aluminium hydroxide) and all had a NasoGastric Tube (NGT) inserted post intubation. The volume and pH of gastric content was recorded and ‘at risk’ patients were identified.

  • Population: 100 parturients undergoing CS were randomly selected. Patients’ age, weight, expected delivery date and time from ingestion of antacid to CS were recorded.
  • Intervention: 57 patients received antacid prophylaxis and the rest 43 were used as controls. An NGT was inserted in all patients and volume as well as pH of gastric contents recorded.
  • Primary outcome: To indentify the ‘at risk’ group of patients using an arbitrary definition (gastric volume >25 mls and pH<2.5).
  • Secondary outcome: Determination of the ideal timing of antacid prophylaxis

Validity

This is a single centre trial with a small population group. The paper states that the patients were randomly selected although there is no explanation of how this was achieved. The study was not blinded. There may be a bias in the choice of the control group as these were patients who already underwent GA prior to the authors’ arrival in theatre, suggesting greater urgency for CS or out-of-hours surgery. There is no mention of statistical analysis of the results.

Results

  • Primary outcome: The study showed that use of antacid prophylaxis reduced the ‘number at risk’ by 10 and it became their standard of practice to administer it to all parturients.
  • Secondary outcome: The study showed that antacid prophylaxis may increase the gastric volume if given too late and become ineffective if given too early. Therefore this is given every 3 hours in all labouring women.

Take home message:

The physical and physiological changes of pregnancy undoubtedly put this group of women at high risk of aspiration during CS. The findings of this study are not surprising although the population group may not be representative of today’s pregnant population. The use of antacids and sodium citrate is the standard of practice currently.

 

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