The effect of fentanyl compared to morphine on pain score and cardiorespiratory vital signs in out-of-hospital adult stemi patients

Objective: ST-elevation myocardial infarction (STEMI) is a leading cause of mortality in Australia. Paramedics treating adults with STEMI in the out-of-hospital environ-ment can use fentanyl or morphine to manage the patient's pain, although there is little research comparing the efficacy and safety of these drugs. Therefore, the objec-tive of this study was to compare the effects of fentanyl to morphine on cardiac chest pain and cardiorespiratory vital signs in adult STEMI patients in the out-of-hospital environment. Methods: We conducted a retrospective analysis of records of 1902 STEMI cases attend-ed by Queensland Ambulance Service paramedics during the 4-year interval from 2013 to 2016. We compared pain score, blood pressure, respiratory rate, and pulse rate between patients administered intravenous fentanyl and intravenous morphine. We used a two-way mixed effects model (drug, time) to assess for main and interaction effects, and where the interaction effect was significant, applied Mann-Whitney U tests to further analyze between-group differences at each time point. Results: We observed a significant main effect of time on pain score (p < 0.001), respiratory rate (p < 0.05), and pulse rate (p = 0.025), such that these variables all decreased over time. Additionally, we observed a significant drug-time interaction for systolic and diastolic blood pressures (both p < 0.01), such that blood pressures decreased over time in the morphine, but not fentanyl, group. Conclusion: We compared the effects of fentanyl to morphine on cardiac chest pain and cardiorespiratory vital signs in out-of-hospital adult STEMI patients and observed differences in blood pressures only. Morphine appeared to have a depressive effect on systolic and diastolic blood pressure, whereas fentanyl did not. An unanticipated behavioural finding of this research is that, in the absence of a definitive guideline, paramedics appear to use fentanyl when patients may be at risk of developing hypo-tension.