The　letter　to　the　editor　was　written　in　response　to　the　recent　article　by　Wang　et　al.　＂The　influence　of　low-dose　s-ketamine　on　postoperative　delirium　and　cognitive　function　in　older　adults　undergoing　thoracic　surgery＂,　which　is　published　in　Journal　of　Cardiothoracic　Surgery.　2024;　19(1):324.　This　article　concludes　that　intravenous　low-dose　S-ketamine　during　thoracic　surgery　in　older　patients　significantly　reduces　the　incidences　of　postoperative　delirium　and　cognitive　dysfunction,　indicating　a　potential　neuroprotective　effect　of　intraoperative　low-dose　S-ketamine.　In　view　to　the　retrospective　nature　of　this　study　and　their　inconsistent　findings　with　the　results　of　a　recent　randomized　controlled　trial　performed　in　patients　undergoing　non-cardiac　thoracic　surgery,　we　believe　that　several　methodological　issues　and　potential　confounders　in　this　study　deserve　further　clarification　and　discussion　before　accepting　their　conclusions.　Our　main　concerns　include　lacking　the　times　and　number　of　delirium　monitoring　per　postoperative　day,　alone　use　of　the　Confusion　Assessment　Method　form　for　delirium　screening,　not　providing　the　factors　related　to　the　occurrence　of　postoperative　delirium　in　the　ICU　stay,　and　application　of　a　non-standard　definition　for　postoperative　cognitive　impairment.　We　believe　that　clarification　of　these　issues　is　useful　for　improving　the　transparency　of　their　methodology　and　facilitating　the　interpretation　of　their　results.