Dexamethasone for prophylaxis of postoperative nausea and vomiting. A meta-analysis of randomized controlled studies

OBJECTIVE: Randomised controlled trials investigating the efficacy of dexamethasone alone or in combination with other antiemetics to prevent postoperative nausea and vomiting (PONV) were included in a meta-analysis to estimate the relative efficacy of these treatments. METHODS: Studies were systematically searched using Medline, EMBASE, the Cochrane-Library, and by manual screening the reference lists and current issues of locally available anaesthesia journals. Studies identified were divided into four different groups. For each subgroup an independent analysis was performed: 1. Dexamethasone vs. placebo, 2. Dexamethasone + other antiemetic vs. other antiemetic alone, 3. Dexamethasone + other antiemetic vs. dexamethasone alone, 4. Dexamethasone vs. other antiemetics. The main end point in each study was defined as complete absence of nausea, retching, and vomiting after prophylactic antiemetic treatment. The pooled odds-ratios, the relative risk (RR) and the numbers-needed-to-treat (NNT) with their corresponding 95%-confidence intervals (given in parentheses) were calculated using a random effects model. RESULTS: A total of 26 studies with 2561 patients were analysed. 1. As a sole antiemetic agent dexamethasone is superior to placebo to prevent PONV (RR: 0.49 (0.15-0.42); NNT: 3.4 (2.5-5.3)). 2. When dexamethasone and an other antiemetic (e.g. a 5-HT3-antagonist) are combined this drug combination is significantly more effective than the single antiemetic without dexamethasone (RR: 0.60 (0.46-0.78); NNT: 7.3 (5.7-10.2)). 3. A similar result was obtained when the dexamethasone combination was compared with dexamethasone alone. The combination is statistically superior (RR: 0.16 (0.08-0.32); NNT: 3.2 (2.2-6.3)). 4. Dexamethasone was usually compared with 5-HT3-antagonist and to a less extends also with dopamine antagonists. Summarising these studies, there was no significant difference concerning effectiveness (RR: 1.35 (0.99-1.85); NNT: 10.6 (5.6-92.6)). CONCLUSION: Dexamethasone has antiemetics effects that are superior to placebo treatment and are comparable with conventional antiemetic agents (e.g. 5-HT3-antagonist, dopamine antagonists). The drug is especially useful in combination with other antiemetics and increases the efficacy of the antiemetic partner drug.