Routine prophylactic drugs in normal labour for reducing gastric aspiration and its effects

No good evidence for drugs, like antacids, in normal labour to reduce the small chance of inhaling some stomach contents if general anaesthesia is required.

Caregivers are often concerned that some woman in normal labour may go on to have a general anaesthetic, either for a caesarean section in labour, or to remove the placenta after birth should it be retained. The concern arises because there is a very small risk that the woman might regurgitate and possibly inhale some of the stomach contents into the lungs (gastric aspiration or Mendelsohn's syndrome) during the general anaesthetic. This can cause severe lung and breathing problems, especially if the stomach contents are acid (low pH), and extremely rarely (one in a million) a woman may die from an anaesthetic problem. Giving drugs to reduce the volume of the stomach contents, or to make them less acid may help to reduce the problem. The review of trials looked to see whether giving such drugs routinely to all women in normal labour was effective. The review identified three trials involving 2465 women but none assessed gastric aspiration, probably because it is a very rare event. Instead the trials all assessed the incidence of vomiting, although there is no proven link between vomiting in labour and gastric aspiration during general anaesthesia. The review found some limited evidence that 1) drugs like antacids may reduce the chance of vomiting in labour, 2) H2 receptor antagonist drugs (like ranitidine) appeared to have a similar impact on outcomes as antacids and 3) dopamine antagonists (like metoclopramide) may reduce the chance on vomiting in labour when given alongside pethidine. Overall, there was no evidence that any of these drugs reduced the incidence of gastric aspiration or Mendelsohn's syndrome.

Authors' conclusions: 

There is no good evidence to support the routine administration of acid prophylaxis drugs in normal labour to prevent gastric aspiration and its consequences. Giving such drugs to women once a decision to give general anaesthesia is made, is assessed in another Cochrane review.

[Note: The four citations in the awaiting classification section of the review may alter the conclusions of the review once assessed.]

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Background: 

Women in normal labour may sometimes go on to have general anaesthesia if labour becomes abnormal, for example if a caesarean section is required. General anaesthesia carries a very small risk of regurgitation and inhalation of stomach contents into the lungs. This can cause inflammation, particularly if the fluid is acidic, and can lead to severe morbidity and very occasionally mortality. Labour hormones increase the risk of gastric aspiration or Mendelsohn's syndrome, though the exact incidence is unknown. The routine administration of acid prophylaxis drugs to all women in normal labour is commonly practiced worldwide, to reduce gastric aspiration by reducing the volume and acidity of stomach contents.

Objectives: 

To assess the effectiveness of routine prophylaxis drugs for women in normal labour to reduce gastric aspiration and its effects.

Search strategy: 

We searched the Cochrane Pregnancy and Childbirth Group's Trials Register (December 2005), EMBASE (1974 to April 2005) and CINAHL (1982 to April 2005). We updated the search of the Cochrane Pregnancy and Childbirth Group's Trials Register on 1 October 2009 and added the results to the awaiting classification section.

Selection criteria: 

Randomised and quasi-randomised controlled trials of women in normal labour assessing the routine administration of drugs (antacids, H2 receptor antagonists, dopamine antagonists and proton-pump inhibitors) compared with placebo/no treatment, and compared with other drugs for reducing gastric aspiration.

Data collection and analysis: 

Two review authors independently assessed eligibility, quality, extracted data and performed double-data entry.

Main results: 

Three trials were included, involving 2465 women, assessing the effects of antacids, H2 receptor antagonists and dopamine antagonists. There were no trials on proton-pump inhibitors. None of the trials were of good quality, and none assessed the incidence of gastric aspiration, Mendelsohn's syndrome or their consequences. All the studies assessed vomiting, and there was limited evidence that vomiting may be reduced by antacids (relative risk (RR) 0.46, 95% confidence interval (CI) 0.27 to 0.77, n = 578, one trial) or by dopamine antagonists given alongside pethidine (RR 0.40, 95% CI 0.23 to 0.68, n = 584, one trial). Comparisons between different drugs showed no significant differences, though the number of participants was small. There was no evidence that H2 receptor antagonists improved outcomes compared with antacids, though only one trial addressed this issue.

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