Lane 2012.
| Methods | 3‐group RCT comparing peppermint spirit vapour with inert placebo or standard antiemetics | |
| Participants | 35 women post‐cesarean section delivery. (22 peppermint/8 placebo/5 standard antiemetic). Mean age 31.3 years (range 22‐43) Inclusion criteria: "scheduled for a nonemergency C‐section, English speaking, at least 18 years of age, nonsmoker, and became nauseated post C‐section". Exclusion criteria: allergy to peppermint or food colorings, diagnosed with persistent vomiting such as hyperemesis, receiving magnesium sulphate therapy or had a condition in which the contraction of abdominal muscles during vomiting would have been contraindicated such as infected wound. Setting: community hospital, USA |
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| Interventions | Zip‐lock bag containing either pharmacy‐grade peppermint spirits ("Humco Peppermint Spirit USP: ethyl alcohol 82%, peppermint oil, purified water, peppermint leaf extract") or green‐coloured, sterile water on cotton balls. Participants in aromatherapy groups instructed to hold opened bag 2 inches under their nose and take 3 deep breaths. Standard antiemetic group received either IV ondansetron or PR promethazine depending on surgeon protocol. | |
| Outcomes | Nausea severity at initial complaint, 2, 5 min, as measured by 6‐point ordinal nausea scale (0 = no nausea, 6 = vomiting) measured by 'staff nurse' | |
| Notes | Unequal group sizes caused by allocation prior to complaints of nausea/ failure to recruit sufficient participants to account for the majority not experiencing nausea/ protocol violations and large amounts of missing/ accidentally destroyed data. Additional information requested. No information on funding source | |
| Risk of bias | ||
| Bias | Authors' judgement | Support for judgement |
| Random sequence generation (selection bias) | Unclear risk | "...blocked systematic random assignment" method used Comment: unclear how sequence was generated |
| Allocation concealment (selection bias) | Low risk | "The AD [admitting department] staff performed random assignment" i.e. allocation to groups done by administrative staff in separate department. Comment: probably done |
| Blinding of participants and personnel (performance bias) All outcomes | High risk | Although the intervention and placebo were stored in identical bags and appeared identical, unblinding would have occurred on opening the bags due to the odour of the peppermint. Nurses became unblinded to the intervention and chose not to implement if it was the placebo (Quote: "nurses...did not implement the research protocol for participants in the placebo aromatherapy group.") Comment: probably not done |
| Blinding of outcome assessment (detection bias) All outcomes | High risk | Clinical staff who delivered the intervention also measured the outcomes. Although the intervention and placebo were stored in identical bags and appeared identical, unblinding would have occurred on opening the bags due to the odour of the peppermint. Nurses became unblinded to the intervention and chose not to implement if it was the placebo (Quote: "nurses...did not implement the research protocol for participants in the placebo aromatherapy group.") Comment: probably not done |
| Incomplete outcome data (attrition bias) All outcomes | High risk | Large attrition/missing data from study due in part to unblinding of intervention ("nurses...did not implement the research protocol for participants in the placebo aromatherapy group.") Some data destroyed by accident. Incomplete data recorded for several participants. Comment: likely attrition bias |
| Selective reporting (reporting bias) | Low risk | Comment: reporting appears comprehensive, within constraints of large amounts of lost data |
| Other bias | Unclear risk | Comment: unequal group sizes likely to be a problem for statistical inference. |