The Effects of Anesthesia on Postoperative Cognitive Functions in Patients Undergoing Sleeve Gastrectomy

The aim of this study is to investigate the effects of TIVA (Total Intravenous Anesthesia) and inhalational anesthesia on postoperative cognitive functions in patients undergoing sleeve gastrectomy as a bariatric surgery, to determine the residual effects of anesthetic drugs and to determine recovery times, to observe mental changes caused by the anesthesia method and surgical intervention, to evaluate postoperative cognitive functions with neurocognitive tests, and to try to determine the most appropriate anesthesia method for the patient as the method with faster recovery, better patient comfort and less cognitive function changes. The investigators think that they can safely choose inhalation anesthesia, like TIVA, in patients who will undergo obesity surgery.

The relationships between the choice of anesthesia method and the recovery in obese patients remain unclear. Obesity-related physiological changes, such as increased cardiac output, may affect the pharmacokinetics of anesthetic agents by increasing the volume of distribution and clearance of the drug. However, it is difficult to assess the extent of these changes. In fact, no significant clinical difference has been shown in terms of recovery times between obese and non-obese patients anesthetized with inhalation agents in clinical studies.

TIVA and inhalational anesthesia have been used safely up to date, and both are routinely used in patients undergoing laparoscopic bariatric surgery. Although TIVA was once seen as a promising alternative to inhalational anesthesia; in morbidly obese patients with different clinical and metabolic profiles, the high lipid solubility and slow metabolic elimination of intravenous anesthetics, in addition to manual administration of these drugs, are limited even in computer-controlled automated systems such as TCI (Target Controlled Infusion) devices and CLADS (Closed Loop Anesthesia Delivery System) designed to provide predefined plasma concentrations based on patient response and multi-compartmental pharmacokinetic algorithms.

In another study conducted to determine the optimum anesthesia method in obese patients, TIVA and inhalational anesthesia were applied in sleeve gastrectomy, and TIVA showed better recovery, lower pain scores, lower incidence of postoperative nausea and vomiting, and shorter PACU (Post Anesthesia Care Unit) stay.

A consensus group was formed to develop terminology similar to that used in cognitive classifications of the general population to be used in the investigation of cognitive function changes after anesthesia and surgery. This working group suggested using the term "POND"(Perioperative Neurocognitive Disorders) as a comprehensive term for cognitive disorders defined in the preoperative and postoperative periods, and decided to call the cognitive decline present in the preoperative period "NCD" (Neurocognitive Disorder), the form defined as a clear and acute event within the first 7 days after the effects of postoperative surgery and anesthesia excluded as "Postoperative Delirium", the cognitive decline observed in the time period up to 30 days after surgery "Delayed Neurocognitive Recovery" and the form observed up to 12 months "POCD" (Postoperative Cognitive Dysfunction).

Since there are differences in the definition and measurement parameters of postoperative cognitive dysfunction, neurophysiological examination is required. However, both preoperative and postoperative cognitive functions can be evaluated with some mini tests. For this purpose, we planned to apply MMST (Mini Mental State Examination) and ACE (Addenbrooke's Cognitive Examination) tests to our patients at certain intervals in our study.

After the approval decision numbered 2024/226 of the Scientific Research Ethics Committee of Sancaktepe Sehit Prof. Dr. Ilhan Varank Training and Research Hospital, we trained residents in our clinic to perform MMST and ACE tests. The patients who will undergo sleeve gastrectomy, have been evaluated by the multidisciplinary council for obesity surgery at the General Surgery Clinic of Sancaktepe Sehit Prof. Dr. Ilhan Varank Training and Research Hospital and they will be informed about the study by a randomly selected anesthesia resident during the preoperative visit one day before the surgery, and patients verbal and written informed consents will be obtained in accordance with the informed consent forms.

After the consents are taken, a randomly assigned resident will perform MMST and ACE tests on the patients the day before surgery. Patients will be administered inhalational anesthesia or TIVA according to the preference of a random anesthesia specialist physician who is going to work at that day in the operating room of general surgery.

The study will not interfere with the selection of anesthesia method and equal numbers of patients in both groups enrolled. All intraoperative data will be obtained primarily from the hospital information system, medical records and devices, anesthesia follow-up documents, patient follow-up forms and test forms.

The power analysis was performed using the G*Power (v3.1.7) programme to determine the sample size. The power of the study is expressed as 1-β (β =Type II error probability). The effect size was calculated as d=2.954 and it was calculated that in order to obtain 99% power at the α=0.01 level, there should be 20 patients in each group and at least 40 patients in total. Considering that there may be losses during the study process, it was decided to exceed this number and 60 patients were included in the study.

The data will be analyzed using the SPSS 25.0 package program. The Kolmogorov Smirnov test will be used to check whether the distribution of the data is normally distributed, and descriptive statistical methods (Mean, Standard Deviation, Median, IQR, frequency, ratio) will be used when evaluating the study data. Independent t test will be used for two group comparisons showing parametric distribution, and One Way Anova Test analysis methods will be used for more than two group comparisons. Mann-Whitney U test will be used for two group comparisons not showing parametric distribution, and Kruskal Wallis test will be used for more than two group comparisons. Spearman correlation and Pearson correlation analysis will be used to determine the relationship between them. Chi-Square test will be used in the evaluation of categorical data. Significance will be evaluated at p<0.05 levels for all values.