DOI: 10.1097/pr9.0000000000001473 ISSN: 2471-2531

Randomized trial of intraoperative nitrous oxide for postoperative pain reduction in cervical spinal cord injury

Mayu Hoshina, Takao Kato, Yuki Shiko, Yohei Kawasaki, Kunihide Okubo, Akiko Kimura, Madoka Yokotani, Yusuke Mazda, Tadashi Yahata, Koichi Inokuchi, Hideaki Obata
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Abstract

Introduction:

Neuropathic pain after cervical spinal cord injury (SCI) is common and difficult to manage.

Objectives:

To evaluate whether intraoperative nitrous oxide (N 2 O) influences acute postoperative pain and long-term neuropathic pain after cervical SCI surgery.

Methods:

This single-center, randomized study enrolled adults (≥20 yr) undergoing emergency surgery for traumatic cervical SCI (American Spinal Injury Association Impairment Scale C or D). Patients were randomly assigned to receive intraoperative N 2 O or Air. The primary outcome was resting pain intensity on postoperative day 1 (D1), measured using the Numeric Rating Scale (NRS). Secondary outcomes included global pain and neuropathic pain assessments up to 6 months (6M) after surgery.

Results:

Of 80 randomized patients, 59 were analyzed (mean [SD] age 70.34 [12.07] years; 46 [78%] male). Baseline characteristics were similar between groups (Air, n = 29; N 2 O, n = 30). The primary outcome was higher in the N 2 O group, indicating no acute analgesic effect (NRS on D1: 3.27 [2.69] vs 5.10 [3.06]; P = 0.021). By contrast, at 6M, resting NRS was lower in the N 2 O group (1.72 [2.64] vs 0.53 [1.25]; P = 0.030), and numbness-related symptoms also improved. No serious adverse events occurred.

Conclusion:

Intraoperative N 2 O did not reduce acute postoperative pain after cervical SCI surgery. However, exploratory secondary analyses suggested a potential reduction in chronic neuropathic pain at 6 months, supporting the hypothesis that early perioperative modulation of central sensitization may influence pain chronification after SCI.

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