Reducing nausea and vomiting in women receiving regional anaesthesia for caesarean section

Caesarean section is a commonly performed operation for the birth of a baby when difficulties arise either for the mother or for the baby. Women may be either awake for the procedure (regional anaesthesia) or asleep (general anaesthesia). Nausea and vomiting are common and distressing symptoms, which can occur during the procedure if the woman is awake or they can also occur after the procedure. Low blood pressure and some of the medications administered during the procedure may contribute to the nausea and vomiting.

A wide range of medications are commonly used either to reduce the chance of symptoms occurring, or are given as a treatment if symptoms do occur. In addition, a number of non-drug approaches have been tried such as using acupuncture or acupressure; giving extra oxygen; or giving extra intravenous fluids. We aimed to study the effectiveness of the various treatments to reduce the occurrence of nausea and vomiting during elective or emergency caesarean section using regional anaesthesia. We found 41 studies (involving 5046 women) that met our inclusion criteria and provided data which we could analyse. These were mainly small studies of unclear or poor quality.

Nevertheless, we found that many drugs, such as 5-HT3 antagonists (e.g. ondansetron), dopamine antagonists (e.g. metoclopramide, droperidol) and sedatives (mainly propofol) were effective in reducing the occurrence of nausea and vomiting either during surgery under regional anaesthesia or afterwards. Other effective interventions for some nausea and vomiting included corticosteroids (e.g. dexamethasone), antihistamines (e.g. cyclizine) and anticholinergics (e.g. scopolamine). In addition, acupressure was effective in reducing some nausea but not vomiting.

Few studies assessed the possible side effects such as headaches, dizziness, low blood pressure, skin rashes and breathing difficulties.

In addition to this review, there will be two further reviews on nausea and vomiting at caesarean section. The first will look at interventions given to reduce nausea and vomiting after general anaesthesia (as opposed to regional anaesthesia). The second will explore interventions given as a treatment to women who do suffer nausea and vomiting during regional anaesthesia.

Authors' conclusions: 

This review indicates that many different interventions have efficacy in preventing nausea and vomiting in women undergoing regional anaesthesia for caesarean section. There is little evidence that combinations of treatment are better than single agents.

Read the full abstract...
Background: 

Nausea and vomiting are distressing symptoms which are experienced commonly during caesarean section under regional anaesthesia and can also occur in the period following the procedure. 

Objectives: 

To assess the efficacy of pharmacological and non-pharmacological interventions given prophylactically to prevent nausea and vomiting in women undergoing regional anaesthesia for caesarean section.

Search strategy: 

We searched the Cochrane Pregnancy and Childbirth Group’s Trials Register (27 February 2012) and reference lists of identified studies.

Selection criteria: 

We included randomised controlled trials (RCTs) and excluded quasi-RCTs and cross-over studies.

Data collection and analysis: 

Review authors independently assessed the studies for inclusion, assessed risk of bias and carried out data extraction. Data entry was checked.  

Main results: 

Fifty-two studies met the inclusion criteria but only 41 studies, involving 5046 women, provided useable data for the review involving women having caesareans under regional anaesthesia. The majority of the studies involved women undergoing elective caesarean section. Only two studies included emergency surgery, however, they did not stratify data according to type of surgery. The studies covered numerous comparisons, but the majority of studies involved 5-HT3 receptor antagonists, dopamine receptor antagonists, corticosteroids or acupressure. Studies were mainly small and of unclear quality.

Three classes of intervention were found to be effective in at least three out of four of our primary outcomes (intraoperative nausea, intraoperative vomiting, postoperative nausea and postoperative vomiting). These interventions were 5-HT3 antagonists, dopamine antagonists and sedatives. Other classes of intervention were effective for fewer than three of our primary outcomes.

With 5-HT antagonists, we found a reduction in intraoperative nausea (average risk ratio (RR) 0.64, 95% confidence interval (CI) 0.46 to 0.88, eight studies, 720 women). There were also reductions in postoperative nausea (average RR 0.40, 95% CI 0.25 to 0.64, four studies, 405 women) and vomiting (average RR 0.50, 95% CI 0.32 to 0.77, five studies, 565 women). We did not detect a significant reduction in intraoperative vomiting (average RR 0.56, 95% CI 0.31 to 1.00, seven studies, 668 women).

Dopamine antagonists demonstrated a reduction in intraoperative nausea (average RR 0.38, 95% CI 0.25 to 0.57, nine studies, 636 women) and intraoperative vomiting (average 0.39, 95% CI 0.24 to 0.64, eight studies, 536 women), with similar reductions in postoperative nausea (average RR 0.60, 95% CI 0.40 to 0.91, five studies, 412 women) and vomiting (average RR 0.57, 95% CI 0.36 to 0.91, six studies, 472 women). These differences were observed with both metoclopramide and droperidol.

Sedatives (most commonly propofol) demonstrated a reduction in intraoperative nausea (average RR 0.71, 95% CI 0.52 to 0.96, four studies, 285 women) and intraoperative vomiting (average RR 0.42, 95% CI 0.26 to 0.68, four studies, 285 women), also with a reduction in postoperative nausea (average RR 0.25, 95% CI 0.09 to 0.71, two studies 145 women) and vomiting (average RR 0.09, 95% CI 0.03 to 0.28, two studies, 145 women).

Acupressure was found to be effective for intraoperative nausea (average RR 0.59, 95% CI 0.38 to 0.90, six studies, 649 women) but not postoperative nausea (average RR 0.83, 95% CI 0.68 to 1.00, three studies, 429 women). Acupressure was not effective at reducing vomiting either intraoperatively (average RR 0.74, 95% CI 0.46 to 1.18, six studies, 649 women) or postoperatively (average RR 0.69, 95% CI 0.45 to 1.06, three studies, 429 women).

Other effective intervention classes included corticosteroids, antihistamines, and anticholinergics.

There were insufficient data to demonstrate any class of intervention was superior to another. There were no significant differences observed in the comparison of combined versus single interventions.

Few studies assessed our secondary outcomes or the incidence of adverse effects. However, one study showed an increase in respiratory depression with sedation (midazolam) compared with dopamine antagonists.