Characterisation of pragmatic postoperative PAin Trajectories over seven days and their association with CHronicity after 3 months: a prospective, pilot cohort study (PATCH study)

Background: Reliable outcome measurement providing information both on early and late postoperative pain outcomes are still lacking. The purpose of this study was: 1) to characterise postoperative pain trajectories according to an innovative pragmatic concept: ideal pain trajectory (rapid and sustained pain relief) vs non-ideal pain trajectories (late, transient, or no pain relief); and 2) to assess the incidence of persistent post-surgical pain (PPSP) and the potential association between non-ideal pain trajectories and PPSP.

Methods: This prospective observational pilot cohort study was performed from March until June 2016. A total of 344 patients undergoing major general surgery were invited to complete a self-assessment of pain intensity using numerical rating scale (NRS; 0 = no pain to 10 = worst pain) from day 1 until day 7 after surgery, in order to establish their pain trajectory. Three months after surgery, patients were screened for PPSP.

Results: Rest pain score was analysed in 308 participants. Among them, 210 (68% - 95% CI: 63-73) had an "ideal" pain trajectory, while 98 (32% - 95% CI: 27-37) had "non-ideal" pain trajectories. Three months after surgery, 31% (95% CI: 26-37) reported PPSP. Multivariable analysis showed that "non-ideal" pain trajectories [OR 2.25; (95% CI: 1.26-4.01) P = 0.006] were significantly associated with PPSP.

Conclusions: The present study proposes an innovative pragmatic concept of postoperative pain trajectories: ideal vs non-ideal pain trajectories, providing information both on acute postoperative pain resolution and early identification patients at risk for developing PPSP.

Trial registration: NCT02599233; November, 6, 2015, with clinicaltrials.gov.