Nitrous oxide for pain and anxiety management in elderly patients after THA rehabilitation: a study protocol for a randomized controlled trial

BMC Geriatr. 2026 Jun 2. doi: 10.1186/s12877-026-07689-z. Online ahead of print.

ABSTRACT

BACKGROUND: With the increasing incidence of femoral neck fracture and necrosis of the femoral head, total hip arthroplasty is the ideal treatment due to its advantages of small damage and quick recovery. Pain is a decisive factor in determining the early and active participation of patients in rehabilitation after total hip arthroplasty. Nitrous oxide with its rapid analgesic effect is often used to reduce pain in minor procedures. The purpose of this study was to determine if nitrous oxide reduces pain during rehabilitation after total hip arthroplasty.

METHODS: This is a randomized, double-blind, controlled clinical study. Patients ≥ 65 years old undergoing rehabilitation training after total hip arthroplasty with acute pain (VAS ≥ 4) are included. Participants will be randomly assigned to nitrous oxide or placebo control group using randomization before rehabilitation training in a ratio of 1:1. Rehabilitation will be carried out by therapists. The two gases will be implemented by trained and qualified nurses. A total of 160 participants (80 per group) will be enrolled, accounting for an estimated 20% dropout rate. The primary endpoint is the between-group difference in pain intensity measured by Visual Analogue Scale (VAS) at T1 (during rehabilitation), with additional assessments at T0 (baseline) and T2 (post-rehabilitation). Longitudinal analyses using generalized estimating equations (GEE) will include T0, T1, and T2. Key secondary outcomes include anxiety score (VAS), Berg balance scale (BBS), functional ambulation category (FAC), side effects, satisfaction, and acceptance. Safety monitoring includes continuous assessment of oxygen saturation, vital signs, and predefined stopping criteria for adverse events.

CONCLUSION: This study is designed to generate evidence regarding the effectiveness and safety of nitrous oxide for analgesia in patients undergoing rehabilitation after total hip arthroplasty. This intervention has the potential to provide more effective support options for pain management in rehabilitation training for elderly patients, potentially improving patient satisfaction and quality of life. If proven effective, this intervention may provide preliminary evidence for a new analgesic option in hospital and rehabilitation settings.

TRIAL REGISTRATION: This trial was registered at the Chinese Clinical Trial Registry (ChiCTR), on August 6, 2024 (registration number ChiCTR2400087866).

PMID:42231201 | DOI:10.1186/s12877-026-07689-z