Treatment of Perioperative Neurocognitive Disorders With Olfactory Enrichment

Treatment of Perioperative Neurocognitive Disorders With Olfactory Enrichment: Study Protocol for a Randomized Controlled Trial

Perioperative neurocognitive disorder (PND) is one of the most common postoperative complications among elderly patients. However, the mechanism and targeted intervention of PND remains unclear. Our previous clinical studies demonstrated the association between olfactory impairment and PND. Moreover, our translational studies showed that anesthesia/surgery induced olfactory impairment and caused cognitive impairment in mice and olfactory enrichment could prevent the anesthesia/surgery-induced cognitive impairment. However, there was no clinical investigation to determine whether olfactory enrichment can mitigate PND in elderly patients. Therefore, we propose determining whether olfactory enrichment can prevent and/or treat PND in elderly patients.

The study will be a double-blinded, randomized controlled trial. Participants (65 years old or older) undergoing scheduled orthopaedic surgery (≥2 hours, under general anesthesia) will be randomized to either olfactory enrichment group or sham group. Participants in olfactory enrichment group will receive olfactory enrichment with a dispenser twice sessions per day on preoperative day 1-3 and postoperative day 1-3 (30 min per session, 4 odors for each session) while participants in sham group will be equipped with the same pattern except that water will be used in the dispenser. Participants will be assessed twice daily by a research assistant blinded to allocation. The primary outcome will be the incidence of postoperative delirium measured by the Confusion Assessment Method on postoperative days 1, 2 and 3. The secondary outcomes will be the severity of postoperative delirium, cognitive function, plasma Tau-PT217 level, and olfactory function.

Inclusion Criteria:

1. Age ≥65 years old.
2. Having a scheduled surgery (≥2 hours, general anesthesia) (e.g., total hip replacement, toal knee replacement, open reduction and internal fixation of hip and lumbar spine).
3. Being able to complete neuropsychological tests, 3D-CAM and CAM-S.
4. Chinese Mandarin as their native language.
5. Edmonton frailty scale (EFS) score ≥ 6.

Exclusion Criteria:

1. Having delirium, assessed by 3D-CAM, before surgery.
2. Having a brain tumour, stroke or mental disorders (eg, major depressive disorder or dementia).
3. Participating in other clinical studies at the time of screening.
4. Unwillingness to comply with the protocol or procedures.