Factors Influencing Acute Pain Trajectories after Lower Extremity Trauma: A Pilot Study

Title: Factors influencing acute pain trajectories after lower extremity trauma:  A pilot study.

Introduction: Up to 62% of patients report chronic pain at the site of injury six to twelve months after blunt trauma, with pain from lower extremity (LE) fractures exceeding those from other injury sites. Factors reported to correlate with the development of post-trauma chronic pain include older age, being female, untreated preinjury anxiety or depression, fewer years of education, and high pain intensity at the time of injury. It is currently not clear what trauma patient characteristics, the minimum pain intensity level, or severity of unrelieved pain leads to chronic pain for patients with LE trauma. Plotting pain scores over time – trajectories - allows for the classification of patients into groups of those whose pain improved and did not improve during hospitalization, which can then be used to predict chronic pain status particularly when associated with pre-hospital trauma patient characteristics and in-hospital factors.

Objective: The purpose of this pilot study was to examine differences in LE trauma patient characteristics classified by those who have improvement in pain scores during hospitalization compared with those who do not have improvement in pain scores.

Method: This descriptive study retrospectively reviewed medical records of 18 randomly chosen patients admitted to a large academic urban trauma center. Pre-hospital variables collected included gender, age, race, abbreviated injury scale (AIS) scores, toxicology screen, smoking status and height and weight for body mass index (BMI). In-hospital variables consisted of pain scores recorded in the trauma resuscitation unit (TRU), the patient care daily record (PCDR), pain medication administered with associated pain scores, acute pain management consult (APMS) and patient controlled analgesia (PCA). The PCDR pain scores were used to calculate the pain trajectory. The intercept was the first pain score recorded and the slope was the pain scores over time. A patient was classified, as having improved pain when the slope (pain trajectory) decreased over time and the 50% confidence interval did not include zero.

Results: The study sample was mostly white (67%), male (72%) and with a mean of 41 years (SD = 15). Patients’ sustained injuries in motor vehicle and motorcycle accidents 61% of the time. The shortest length of stay was 1.7 days and the longest was 5.7 days with an average length of stay 3.7 (SD = 1.2) days. Pain scores did not improve during hospitalization in 55% of patients. Pre-hospital factors associated with patients whose pain did not improve included, younger age, current smoker, positive toxicology screen and normal weight. In-hospital factors associated with not improved pain included slightly shorter hospital stay; higher mean pain scores in the TRU (6.4 vs. 8.3), PCDR (4.6 vs. 6.4) and a higher opioid equianalgesic dose averaged over 24 hours (61.3 mg vs. 57.7 mg).

Discussion: Despite the emphasis on frequent pain assessment and pain control in patient care, half of patients with LE trauma in this sample had no improvement or worsening pain during hospitalization. Further exploration of certain trauma patient characteristics such as admission pain score, positive toxicology screen, BMI and amount of opioid received is warranted, as these may be predictive of in-hospital pain thus influencing pain management strategies. Phase two of this study will follow patients after discharge to examine factors leading to chronic pain.