The predictive values of platelet mitochondrial mass and quantity during the perioperative period in elderly patients on the occurrence of postoperative delirium

Abstract

Objective: To investigate the changes of platelet mitochondrial mass and quantity during perioperative period in elderly patients, and assess their predictive values on the occurrence of postoperative delirium (POD). Methods: In this prospective study, 162 elderly patients scheduled for abdominal surgery under general anesthesia were enrolled from November 2021 to January 2022 in Nanjing Drum Tower Hospital Affiliated to Nanjing University Medical School. Among them, 20 patients [10 males, 10 females, aged (71.4±6.8) years] developed POD within 3 days after surgery (POD group), and another 20 patients[12 males, 8 females, aged (67.7±5.3) years] who did not develope POD were selected as controls (control group) using propensity score matching method. Blood samples were collected preoperatively, at the end of surgery and on the first postoperative day. Platelets were extracted and mitochondrial mass was detected with flow cytometry. Transmission electron microscopy was used to determine mitochondrial quantity. The receiver operating characteristic (ROC) curve was drawn to analyze the value of mitochondrial mass and quantity in predicting the occurrence of POD. Results: The mean fluorescence intensities of platelet mitochondrial mass were 193±46, 236±61, 264±53 preoperatively, at the end of surgery and on the first postoperative day in the POD group, respectively. The corresponding values were 209±61, 191±67 and 201±56 in the control group. The platelet mitochondrial mass of patients in the POD group was significantly increased on the first postoperative day compared to preoperative levels (P<0.001). In contrast, there was no significant difference in the control group (P=0.410). Patients in the POD group had higher platelet mitochondrial mass than patients in the control group on the first postoperative day(P=0.002). Meanwhile, platelets from patients in the POD group showed significantly higher number of mitochondria than platelets from patients in the control group [3 (2, 4) vs 2 (1, 2), P<0.001]. According to the ROC curve of platelet on the first postoperative day, at a mitochondrial mass cut-off value of>275.35, the sensitivity, specificity and area under the ROC curve to detect the occurrence of POD were 55%, 90% and 0.800 (95%CI: 0.666-0.934, P<0.001). At a mitochondrial quantity cut-off value of>2, the sensitivity, specificity and area under the ROC curve to detect the occurrence of POD were 53%, 78% and 0.680 (95%CI: 0.584-0.776, P<0.001). Conclusions: Patients who developed POD show higher platelet mitochondrial mass after surgery compared to preoperative levels. The mitochondrial mass of platelets on the first postoperative day has good predictive value on the occurrence of POD.