Interventions for preventing nausea and vomiting in women undergoing regional anaesthesia for caesarean section.

BACKGROUND

Nausea and vomiting are distressing symptoms which are experienced commonly during caesarean section under regional anaesthesia and in the postoperative period.  OBJECTIVES: To assess the efficacy of pharmacological and non-pharmacological interventions versus placebo or no intervention given prophylactically to prevent nausea and vomiting in women undergoing regional anaesthesia for caesarean section.

SEARCH METHODS

For this update, we searched Cochrane Pregnancy and Childbirth's Trials Register, ClinicalTrials.gov and the WHO International Clinical Trials Registry Platform (ICTRP) (16 April 2020), and reference lists of retrieved studies.

SELECTION CRITERIA

We included randomised controlled trials (RCTs) of studies and conference abstracts, 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. Our primary outcomes are intraoperative and postoperative nausea and vomiting. Data entry was checked. Two review authors independently assessed the certainty of the evidence using the GRADE approach.

MAIN RESULTS

Eighty-four studies (involving 10,990 women) met our inclusion criteria. Sixty-nine studies, involving 8928 women, contributed data. Most studies involved women undergoing elective caesarean section. Many studies were small with unclear risk of bias and sometimes few events. The overall certainty of the evidence assessed using GRADE was moderate to very low. 5-HT antagonists: We found intraoperative nausea may be reduced by 5-HT antagonists (average risk ratio (aRR) 0.55, 95% confidence interval (CI) 0.42 to 0.71, 12 studies, 1419 women, low-certainty evidence). There may be a reduction in intraoperative vomiting but the evidence is very uncertain (aRR 0.46, 95% CI 0.29 to 0.73, 11 studies, 1414 women, very low-certainty evidence). There is probably a reduction in postoperative nausea (aRR 0.40, 95% CI 0.30 to 0.54, 10 studies, 1340 women, moderate-certainty evidence), and these drugs may show a reduction in postoperative vomiting (aRR 0.47, 95% CI 0.31 to 0.69, 10 studies, 1450 women, low-certainty evidence). Dopamine antagonists: We found dopamine antagonists may reduce intraoperative nausea but the evidence is very uncertain (aRR 0.38, 95% CI 0.27 to 0.52, 15 studies, 1180 women, very low-certainty evidence). Dopamine antagonists may reduce intraoperative vomiting (aRR 0.41, 95% CI 0.28 to 0.60, 12 studies, 942 women, low-certainty evidence) and postoperative nausea (aRR 0.61, 95% CI 0.48 to 0.79, 7 studies, 601 women, low-certainty evidence). We are uncertain if dopamine antagonists reduce postoperative vomiting (aRR 0.63, 95% CI 0.44 to 0.92, 9 studies, 860 women, very low-certainty evidence). Corticosteroids (steroids): We are uncertain if intraoperative nausea is reduced by corticosteroids (aRR 0.56, 95% CI 0.37 to 0.83, 6 studies, 609 women, very low-certainty evidence) similarly for intraoperative vomiting (aRR 0.52, 95% CI 0.31 to 0.87, 6 studies, 609 women, very low-certainty evidence). Corticosteroids probably reduce postoperative nausea (aRR 0.59, 95% CI 0.49 to 0.73, 6 studies, 733 women, moderate-certainty evidence), and may reduce postoperative vomiting (aRR 0.68, 95% CI 0.49 to 0.95, 7 studies, 793 women, low-certainty evidence). Antihistamines: Antihistamines may have little to no effect on intraoperative nausea (RR 0.99, 95% CI 0.47 to 2.11, 1 study, 149 women, very low-certainty evidence) or intraoperative vomiting (no events in the one study of 149 women). Antihistamines may reduce postoperative nausea (aRR 0.44, 95% CI 0.30 to 0.64, 4 studies, 514 women, low-certainty evidence), however, we are uncertain whether antihistamines reduce postoperative vomiting (average RR 0.48, 95% CI 0.29 to 0.81, 3 studies, 333 women, very low-certainty evidence). Anticholinergics: Anticholinergics may reduce intraoperative nausea (aRR 0.67, 95% CI 0.51 to 0.87, 4 studies, 453 women, low-certainty evidence) but may have little to no effect on intraoperative vomiting (aRR 0.79, 95% CI 0.40 to 1.54, 4 studies; 453 women, very low-certainty evidence). No studies looked at anticholinergics in postoperative nausea, but they may reduce postoperative vomiting (aRR 0.55, 95% CI 0.41 to 0.74, 1 study, 161 women, low-certainty evidence). Sedatives: We found that sedatives probably reduce intraoperative nausea (aRR 0.65, 95% CI 0.51 to 0.82, 8 studies, 593 women, moderate-certainty evidence) and intraoperative vomiting (aRR 0.35, 95% CI 0.24 to 0.52, 8 studies, 593 women, moderate-certainty evidence). However, we are uncertain whether sedatives reduce postoperative nausea (aRR 0.25, 95% CI 0.09 to 0.71, 2 studies, 145 women, very low-certainty evidence) and they may reduce postoperative vomiting (aRR 0.09, 95% CI 0.03 to 0.28, 2 studies, 145 women, low-certainty evidence). Opioid antagonists: There were no studies assessing intraoperative nausea or vomiting. Opioid antagonists may result in little or no difference to the number of women having postoperative nausea (aRR 0.75, 95% CI 0.39 to 1.45, 1 study, 120 women, low-certainty evidence) or postoperative vomiting (aRR 1.25, 95% CI 0.35 to 4.43, 1 study, 120 women, low-certainty evidence). Acupressure: It is uncertain whether acupressure/acupuncture reduces intraoperative nausea (aRR 0.55, 95% CI 0.41 to 0.74, 9 studies, 1221 women, very low-certainty evidence). Acupressure may reduce intraoperative vomiting (aRR 0.52, 95% CI 0.33 to 0.80, 9 studies, 1221 women, low-certainty evidence) but it is uncertain whether it reduces postoperative nausea (aRR 0.46, 95% CI 0.27 to 0.75, 7 studies, 1069 women, very low-certainty evidence) or postoperative vomiting (aRR 0.52, 95% CI 0.34 to 0.79, 7 studies, 1069 women, very low-certainty evidence). Ginger: It is uncertain whether ginger makes any difference to the number of women having intraoperative nausea (aRR 0.66, 95% CI 0.36 to 1.21, 2 studies, 331 women, very low-certainty evidence), intraoperative vomiting (aRR 0.62, 95% CI 0.38 to 1.00, 2 studies, 331 women, very low-certainty evidence), postoperative nausea (aRR 0.63, 95% CI 0.22 to 1.77, 1 study, 92 women, very low-certainty evidence) and postoperative vomiting (aRR 0.20, 95% CI 0.02 to 1.65, 1 study, 92 women, very low-certainty evidence). Few studies assessed our secondary outcomes including adverse effects or women's views.

AUTHORS' CONCLUSIONS: This review indicates that 5-HT antagonists, dopamine antagonists, corticosteroids, sedatives and acupressure probably or possibly have efficacy in reducing nausea and vomiting in women undergoing regional anaesthesia for caesarean section. However the certainty of evidence varied widely and was generally low. Future research is needed to assess side effects of treatment, women's views and to compare the efficacy of combinations of different medications.