With aging population, more older patients will receive major surgery for cancer. Older patients are at increased risk of postoperative neurocognitive complications including delayed neurocognitive recovery (dNCR), which is associated with prolonged hospital stay, raised complications, and impaired quality of life. Intraoperative hypothermia occurs in 57.1%-78.6% of patients undergoing major cancer surgery, especially in the elderly. Studies show that intraoperative hypothermia suppresses immune function, interferes with anesthetic metabolism, and delays anesthesia emergence. All these may be correlated with the occurrence of early postoperative dNCR. This study aims to verify whether intraoperative targeted temperature management (target core temperature: 36.8°C) compared with conventional temperature management (core temperature: 35.5°C) can reduce the incidence of dNCR in older patients undergoing major cancer surgery.

With aging population, more older patients will undergo major surgery for cancer. Due to age-related cognitive decline, cancer-related frailty, as well as impacts from surgical trauma and anesthesia, older patients are at increased risk of postoperative neurocognitive complications including delayed neurocognitive recovery (dNCR), which refers to new-onset cognitive decline within 30 days after surgery. Studies reported that the incidence of dNCR within 7 days ranges from 23.2% to 41.4% in older patients after non-cardiac surgery. Patients with dNCR tend to have prolonged hospital stay, impaired quality of life, and even increased long-term cognitive disorders, and thus imposing a heavy burden on patients, their families, and the healthcare system.

The occurrence of dNCR after surgery results from the combined effects of predisposing factors (e.g., advanced age, preoperative cognitive impairment, comorbidities, malnutrition) and precipitating factors (e.g., anesthetic management, surgical stress, residual drug effects, postoperative complications). Among modifiable precipitating factors, unintended intraoperative hypothermia (core temperature <36 °C) is a common yet long underappreciated clinical issue. Due to prolonged operative duration, extensive body cavity exposure, and massive intraoperative fluid and blood transfusion, patients undergoing major cancer surgery have an incidence of intraoperative hypothermia between 57.1% and 78.6%.

Previous studies demonstrated that a core temperature below 35.5 °C is associated with multiple adverse events, including higher risks of intraoperative bleeding and blood transfusion and postoperative surgical site infections. The international multicenter randomized controlled PROTECT trial enrolled 5,056 patients over 45 years undergoing major non-cardiac surgery but found no significant differences in postoperative myocardial injury, surgical site infection, and blood loss between the routine management group (core temperature 35.5 °C) and the active warming group (core temperature 37 °C); these indicated that maintaining core temperature at 35.5 °C is safe with regard to these complications. However, neurocognitive function was not assessed in the PROTECT trial. Whether an intraoperative temperature of 35.5 °C is safe for the neurocognitive outcomes requires further investigation.

The pathogenesis of neurocognitive complications is complex, involving multiple pathological processes such as neuroinflammation, blood-brain barrier disruption, oxidative stress, and hippocampal neuronal injury. Perioperative hypothermia may trigger similar pathophysiological changes. Studies showed that hypothermia suppresses the immune function and promotes the release of peripheral pro-inflammatory cytokines including IL-6 and IL-1β, and thereby exacerbating central neuroinflammation, which is one of the core mechanisms underlying dNCR. Animal experiments demonstrated that hypothermia-induced cognitive dysfunction is associated with damage to hippocampal neurons and reduced expression of proteins related to synaptic plasticity. Furthermore, hypothermia impairs the metabolism of anesthetics and prolongs emergence time, which may contribute to the early manifestations of postoperative cognitive dysfunction.

There is still a lack of definitive evidence regarding whether intraoperative targeted temperature management can reduce dNCR in older patients undergoing major cancer surgery. Meanwhile, there remains debate over the hypothermia threshold and optimal target temperature range. We are currently conducting a multicenter randomized trial to verify whether intraoperative targeted temperature management (36.8 °C) reduces the incidence of delirium within 4 days in older patients after major cancer surgery. Based on patients enrolled at our institution, this study aims to verify whether intraoperative targeted temperature management (target core temperature: 36.8°C) compared with conventional temperature management (core temperature: 35.5°C) can reduce the incidence of delayed neurocognitive recovery in older patients undergoing major cancer surgery.

Inclusion Criteria:

1. Age ≥ 65 years.
2. Planned potentially curative initial cancer surgery with an expected duration of 2 hours or longer under general anesthesia.

Exclusion Criteria:

1. Preoperative fever (tympanic temperature ≥ 38℃).
2. Known or suspected preoperative infection.
3. Previous schizophrenia, epilepsy, Parkinson's disease, myasthenia gravis, or preexisting delirium.
4. Inability to communicate due to coma, severe dementia, or hearing or speech impairment.
5. Critically ill patients, defined as NYHA functional class > III or LVEF < 30%, Child-Pugh class C, preoperative dialysis dependence, ASA physical status > IV, or expected survival < 24 hours.
6. Surgery for breast cancer, intracranial tumors, or rare cancers.
7. Planned to undergo therapeutic hypothermia.
8. Body mass index > 30 kg/m² (to facilitate temperature management).
9. Previous enrollment in this study.
10. Other conditions deemed unsuitable for study participation.