Prophylaxis of opioid-induced nausea in helicopter emergency medical service: a prospective quasi-experimental study

Objective In prehospital emergency medicine, opioids are usually used to treat acute traumatic pain. A common side effect of opioids is nausea. To prevent this, the prophylactic administration of 5-HT ₃ antagonists such as ondansetron has become established in clinical practice, even though there is currently no evidence to support its use. Aromatherapy is also used as an alternative non-pharmacological method for the treatment of nausea. We therefore investigated whether the prophylactic administration of ondansetron or prophylactic aromatherapy after opioid administration is beneficial to the patient. Methods Patients over the age of 16 who received opioid therapy due to acute traumatic pain by the crews of a total of six HEMS bases between February 2024 and April 2025 were prospectively included. Nausea prophylaxis after opioid-based pain therapy was performed according to a fixed rotating 7-day schedule: no nausea prophylaxis, medication-based nausea prophylaxis with ondansetron 4 mg intravenously, and aromatherapy-based nausea prophylaxis by inhalation of isopropanol. A nausea score was evaluated at the time of opioid administration and upon handover at the destination hospital, using a numeric rating scale (NRS) between 0 (no nausea) and 10 (maximum nausea). Primary endpoint was the change in NRS between the time before opioid administration and the time of patient handover at the emergency department. Secondary endpoints were incidence of moderate and severe nausea (defined as an NRS > 3), the incidence of vomiting during prehospital patient care and need of rescue medication (ondansetron for therapeutic use). Results A total of 205 patients were included in the analysis. Eighty-six in the “no prophylaxis” group, 64 in the ondansetron group, and 55 in the aromatherapy group. There was no difference between the groups in terms of changes in nausea before opioid administration compared to the time of hospital admission as well as in the incidence of moderate and severe nausea. Therapeutic administration of ondansetron was necessary in 4 patients in the “no prophylaxis” group and in one patient in the aromatherapy group. None of the patients experienced any improvement in nausea as a result, three of these patients from the “no prophylaxis” group vomited after ondansetron administration. Conclusion Neither the prophylactic administration of ondansetron nor aromatherapy seem to be beneficial for the prevention of opioid-induced nausea in unselected patients in the setting of prehospital emergency medicine. Larger randomized controlled trials are needed to clarify whether certain subgroups may benefit. Trial registration: not applicable