Perioperative IL-33 is Associated with the Early Stage of Postoperative Neurocognitive Dysfunction After Major Abdominal Surgery

A total of 150 patients scheduled for Abdominal surgery gave written informed consent and were enrolled in this study.

Common demographic factors were collected when the patients were admitted to the hospital, for example, age, gender, body mass index (BMI), and education level. Moreover, the hemocyte indexes, hepatic and renal functions were assessed by blood routine examination 1 day before and 3 days after the surgery.

To evaluate the patients'neurocognitive levels, a well-trained investigator performed a questionnaire to roundly assess their neurocognitive functions 1 day before and 3 days after the surgery. The questionnaire included: (1) Mini-Mental State Examination (MMSE); (2) Hopkins Verbal Learning Test-Revised, testing ability of Verbal learning and memory skills; (3) Brief Visuospatial Memory Test-Revised, testing ability of Visuospatial memory; (4) Trail Making Test; (5) Digital Scope Test; (6) Word Delayed Recall Test, testing ability of long-memory; (7) Word Delayed Interference Test;(8) Image Delayed Recall Test, testing ability of delay recall; (9) Verbal Fluency Test, testing fluency and executive function. At the very beginning, patients with severe cognitive dysfunction were excluded by the lower MMSE score than we required. Each qualified patient gets scores of these tests preoperatively and postoperatively. The investigators collected all of these scores and then obtained the standard deviation (SD) of every preoperative test. The investigators defined a worse test performance as a negative changed score, with an absolute value larger than 1.5 times SD. Patients with no less than two nega- tive changed scores, except for MMSE, were diagnosed as PND . According to this standard, the investigators divided the participants into the PND group and the non-PND group. Finally, the investigators defined two decreased scores as mild PND and more than two decreased scores as severe PND.

Patients got the same preoperative preparation, including ECG monitoring, blood oxygen saturation monitoring, arterial blood pressure, and central venous pressure monitoring. As for the anesthesia method, the investigators took combined anesthesia of inhalation and intravenous. The main anesthetic included sevoflurane, propofol, cisatracurium besylate or rocuronium bromide , and lidocaine for topical anesthesia. During the surgery, the patients were given mechanical ventilation at 12 times/min, with a tidal volume of 6-8ml/kg. Systemic arterial blood pressure was measured via radial artery catheterization. After induction of anesthesia, a central venous catheter was inserted for monitoring central venous pressure (CVP) and fluid management.

At the end of the operation peripheral venous blood was sampled to measure IL-33 expression in peripheral blood monocytes.After the surgery, the surgery time and the anesthesia time were recorded.