Introduction Previous research establishes that patients often experience inadequate pain relief following acute traumatic injury. The aim of this secondary analysis of data from the PACKMaN trial is to explore the contributing factors and impact of sub-optimal pain relief on short to long term outcomes.

Methods PACKMaN was a randomised controlled trial comparing ketamine and morphine when used by paramedics treating severe pain following trauma. We dicotomised all patients into two groups, those who reported moderate to severe pain (NRS pain score ≥ 4) at hospital arrival and those who reported mild pain at hospital arrival (NRS pain score < four), irrespective of which treatment they had received. We explore the contributing factors to analgesic efficacy, hospital, short (3 month) and long-term (6 month) pain outcomes.

Results Final pain score was available in 446 (99%) participants. In our analysis population 175 (39%) had a final pain score below 4 and 271 (61%) had a final pain score of 4 or above. Significant differences were found in the Sum of Pain Intensity Difference (SPID), Total Pain Relief (TOTPAR) scores, percentage of maximum dose in milligrams, patient global impression of change, time to perceptible analgesia, time to meaningful analgesia, and duration of analgesia, participants being admitted to hospital in the adjusted analysis, and both short and long-term pain outcomes on the brief pain inventory.

Conclusion Participants still experiencing moderate to severe pain at hospital arrival report greater pain severity scores at both 3- and 6-months post randomisation as well as higher pain interference scores.

Trial Registration ISRCTN14124474

The authors have declared no competing interest.

EudraCT 2020-000154-10 ISRCTN14124474

https://warwick.ac.uk/fac/sci/med/research/ctu/trials/packman/

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Ethical approval was provided by the West of Scotland Research Ethics Committee (20/WS/0126).

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