Intraoperative Multimodal Monitoring as a Means in Reducing the Duration of Mechanical Ventilation in High-Risk Patients Undergoing Major Abdominal Procedures - A Pilot Study

This study will include patients aged 50 and older scheduled for elective abdominal oncologic surgery, classified as ASA II and III due to increased anaesthetic and surgical risk. Gender will not be a stratification factor. Exclusion criteria include patient refusal, memory impairment, psychosis, known or suspected EEG abnormalities, chronic psychoactive medication use, urgent procedures, BMI below 18 kg/m² or above 35 kg/m², persistent arrhythmias, NYHA class III-IV heart failure, valvular disease, liver diseases, and anticipated surgery duration over six hours. Eligible patients must sign an informed consent form one day prior to surgery. Demographic data collected will include age, sex, operation type, comorbidities, ASA status, height, weight, and BMI. Randomisation will occur before the study begins with a sample size of 100 subjects based on a pilot study of 5 patients per group. Premedication and Monitoring: Patients will receive premedication per institutional protocol, which includes intramuscular midazolam. Intraoperative monitoring follows randomisation allocation. The control group will have standard measurements, including invasive pressure and ECG. Data collection will be handled by designated team members who will archive anaesthesia charts. After intubation, patients will be ventilated with 6-8 ml/kg of predicted body weight and a fresh gas flow of 1 L/min. Intervention Group Protocol: In the intervention group, monitoring will be established via radial artery cannulation under local anaesthesia, using LiDCOrapid®, Rainbow®, and Hb attachments. Baseline MAP and CO values will be recorded, with DO2 calculated automatically. Sensors will be positioned to monitor anaesthetic depth and rSO2 before pre-oxygenation. A noradrenaline infusion will maintain venous tone. Anaesthesia will use TCI with propofol and sufentanil, targeting specific values based on age groups. The primary goal is to maintain an rSO2 of at least 85% of baseline. If rSO2 falls below this threshold, a DO2 optimisation protocol will be initiated, adjusting conditions and administering fluids and medications as necessary. Control Group Protocol: In the control group, propofol and sufentanil will be administered as previously outlined with adjustments based on intraoperative responses and awareness. Rocuronium bromide will be used for neuromuscular blockade, with monitoring and administration of fluids managed by the attending anaesthesiologist. Data Recording: All data during procedures will be recorded digitally or manually, and post-procedure data will be downloaded for analysis. Patients will be transferred to the ICU for postoperative monitoring. Laboratory Analysis: Blood samples for routine analysis will be collected at three time points: prior to surgery, upon ICU admission, and 24 hours after. Parameters assessed include complete blood count, electrolyte levels, PT, aPTT, fibrinogen, blood gas parameters, lactate, troponin I, and NTproBNP. Outcome Measurements: Both groups will be monitored for duration of anaesthesia, drug administration, fluid volume, postoperative complications, mortality rates, and ICU length of stay (LOS). Continuous variables will be reported using descriptive statistics or interquartile ranges, while categorical variables will be shown as counts and percentages. Statistical analysis will be performed using Mann Whitney U test for continuous variables, repeated measures ANOVA for group comparisons, and chi-squared tests for categorical variables. ANCOVA will be employed to compare clinical outcomes with age as a covariate. The software package jamovi v2.5.3 will be utilized for statistical analysis with a significance level set at p \< 0.05.