N-Methyl-D-Aspartate Antagonists and Steroids for the Prevention of Persisting Post-Surgical Pain After Thoracoscopic Surgeries: A Randomized Controlled, Factorial Design, International, Multicenter Pilot Trial

Purpose: We conducted a feasibility 2×2 factorial trial comparing N-methyl-D-aspartate (NMDA) antagonists (intravenous ketamine and oral memantine) versus placebo and intravenous steroids versus placebo, in patients having elective video-assisted thoracic surgery lobectomies, at St. Joseph's Hamilton, Canada, and Cleveland Clinic, Cleveland, USA. Our feasibility objectives were: 1) recruitment rate/week; 2) recruitment of ≥90% of eligible patients; and 3) >90% follow-up. Secondary objectives were incidence and intensity of persistent post-surgical pain (PPSP) and other clinical and safety outcomes.

Methods: Using computerized randomization, patients were allocated to one of four groups: NMDA active with steroid placebo; NMDA placebo with steroid active; both NMDA and steroid active; both NMDA and steroid placebo. Patients, health providers, and data analysts were blinded to allocation. Patients were followed for 3 months after randomization.

Results: The trial was initiated in May 2017 at Hamilton and, after subsequent regulatory and ethics approval, in April 2018 at Cleveland. The trial had to be stopped after only 1 month of recruitment in Cleveland because the packaged study medications (memantine) expired and we were unable to procure the dosage required. Among 41 eligible patients, 27 (66%) were randomized. The recruitment rate/week was 0.63, 95% confidence interval (CI): 0.47-0.79 in Hamilton; and 1, 95% CI: 0.83-1.17 in Cleveland. Follow-up was complete for all 24 patients (100%) in Hamilton, and 3 of 4 patients in Cleveland. In total, only 4 patients (15%), and 2 patients (7%) had persistent pain at rest and with movement, respectively. There were no significant differences between groups for other outcomes.

Conclusion: The trial had to be stopped prematurely due to non-availability of study medications. Trial feasibility objectives of recruiting 90% of eligible patients and recruiting at least one patient/week per site were not met. Consideration for protocol changes will be necessary for the full trial.

Trial Registration: NCT02950233.