Effects of intraoperative body temperature, blood pressure, cerebral tissue oxygenation, and anesthesia type on postoperative cognitive functions in geriatric arthroplasty surgery for hip fracture.

Objectives: This study aimed to explore the effects of cerebral oxygenation, body temperature, hemodynamic changes, and anesthesia type on postoperative cognitive dysfunction (POCD) in geriatric patients undergoing hip fracture surgery.

Patients and methods: One hundred five elderly patients (59 males, 46 females; mean age: 76.7±8.8 years; range, 65 to 95 years) who were scheduled for hip fracture surgery under general or spinal anesthesia between March 2021 and March 2023 were enrolled in the prospective observational study. The cognitive functions were evaluated using the Mini-Mental State Examination (MMSE). Postoperative MMSE values <24 were considered indicative of POCD. Cerebral oxygenation was evaluated before and during the operation using near-infrared spectroscopy (NIRS), and body temperature was measured using a tympanic thermometer, with values <36℃ considered hypothermia. The relationship between decreases in blood pressure ≥30% and POCD was investigated. The relationship between decreases in NIRS of 25% and POCD was also investigated.

Results: Postoperative cognitive dysfunction was observed in 29 (27.25%) of the 105 patients. The MMSE value was 24 in 67.06% of 29 patients, and all these patients developed POCD. The incidence of POCD in patients with a preoperative MMSE1 score of 30 was 12.30% (p=0.001). No relationship was identified between MMSE changes and anesthesia type, hypotension, and decreases in the NIRS (p=0.439, p=0.399). Hypothermia was found to be significantly related to POCD (p=0.013). The degree of hypothermia decreased the postoperative MMSE value at different rates. A 1°C body temperature decrease caused a 16.7%, 44.4%, and 50% decrease in MMSE scores of one, one, and two patients, respectively.

Conclusion: Hypothermia was found to be significantly related to POCD. The same degree of hypothermia caused different MMSE changes. Since the number of patients with POCD was very low, the effect of amounts of body temperature changes on clinically significant MMSE changes could not be supported by logistic regression. The preoperative MMSE values, MMSE change rates, and age were found to be effective in POCD. Maintaining the body temperature throughout the operation will ensure the preservation of postoperative cognitive functions.