This study aims to evaluate the effect of low tidal volume (LTV) ventilation during cardiopulmonary bypass (CPB) on postoperative delirium. It is hypothesized that the risk of delirium, which negatively impacts recovery following cardiac surgeries, can be reduced by improving cerebral perfusion and oxygenation through LTV. The study is designed as a prospective, randomized, controlled trial comparing delirium incidence, ICU stay duration, and 30-day mortality/morbidity rates between LTV and apnea groups. Primary outcomes will be assessed using the 3D-CAM method, while secondary outcomes include ICU stay duration and mortality/morbidity rates.

Introduction and Objectives:

This protocol aims to evaluate the effect of low tidal volume (LTV) ventilation during cardiopulmonary bypass (CPB) on postoperative delirium. Postoperative delirium, commonly seen after cardiac surgeries, negatively impacts patient recovery. It is hypothesized that LTV reduces the risk of delirium by improving cerebral perfusion and oxygenation. The study objectives include comparing the incidence of delirium, ICU stay duration, and 30-day mortality/morbidity rates between groups.

Study Design and Methods:

This prospective, randomized, controlled trial will involve two groups: patients receiving LTV ventilation and those undergoing apnea during CPB. Inclusion criteria target CABG patients over 18 years of age, while exclusion criteria include emergent surgeries and cognitive impairments. Randomization will ensure balanced group allocation through computer-based methods. Mechanical ventilation parameters will follow standard protocols for both groups.

Measurements and Hypotheses:

The primary outcome is delirium, assessed using the 3D-CAM method, while secondary outcomes include ICU stay duration and 30-day composite mortality/morbidity rates. LTV ventilation is expected to reduce delirium incidence, shorten ICU stay, and lower mortality/morbidity rates. Statistical analyses will include multivariable models to account for potential confounding factors.

Substudies and Limitations:

The protocol includes two substudies to evaluate microcirculation and renal perfusion. Limitations may arise from the overlap of sedation effects with delirium symptoms, variations in surgical techniques, and potential data loss during patient follow-ups. Interim analyses are planned to assess the study's safety and effectiveness. The study will be conducted without external funding, adhering to routine clinical practices.

Inclusion Criteria:

• All male or female patients over the age of 18
• Patients undergoing planned cardiac surgeries including CABG
• Patients with an American Society of Anesthesiologists (ASA) physical status of II, III, or IV

Exclusion Criteria:

• Emergency surgeries will be excluded due to the high likelihood of non-compliance with the protocol and the potential lack of essential patient information.
• Surgeries requiring single-lung ventilation will be excluded as they may cause confusion in determining any effects of the intervention due to the inability to apply the study intervention and the differential treatment of the lungs.
• Patients who meet delirium criteria according to 3D-CAM measurements during the initial visit will be excluded.
• Patients with a life expectancy of less than 6 months or a history of psychiatric or neurological diseases (including depression, severe central nervous system depression, schizophrenia, epilepsy, Parkinson's disease, and Alzheimer's disease) will be excluded.
• Severe impairments such as blindness, severe deafness, or dementia that may hinder cognitive testing will be excluded.
• Patients using psychotropic or opioid medications, those with a history of delirium, or those with a history of alcohol abuse or withdrawal within the past 6 months will be excluded.