The Effects of Low-Flow and Normal-Flow Sevoflurane Anesthesia on Frontal QRS-T Angle and TP-e Interval

This prospective observational study is designed to investigate the electrophysiological effects of different fresh gas flow rates during sevoflurane anesthesia in patients undergoing elective laparoscopic cholecystectomy. Laparoscopic procedures involving pneumoperitoneum and volatile anesthetics are known to influence autonomic nervous system balance and cardiovascular stability. While the impact of inhalation agents on myocardial repolarization is documented, the specific effects of Low-Flow Anesthesia (LFA)-an environmentally and economically favorable technique-on markers of electrical instability remain to be fully elucidated. The primary objective is to evaluate and compare the effects of low-flow and normal-flow sevoflurane techniques on the Frontal QRS-T angle and the Tp-e interval, which serve as critical non-invasive biomarkers for predicting malignant arrhythmia risk and reflecting the transmural distribution of ventricular repolarization.

The study protocol involves 128 patients, a sample size determined by power analysis (80% power, 0.05 alpha) to account for a predicted 35% difference between groups and potential dropouts. Patients are observationally assigned to either the Low-Flow Group (LFG) or the Normal-Flow Group (NFG) according to routine clinical practice. Following a standardized induction and an initial stabilization phase at 4-6 L/min, flow rates are adjusted once the target concentration (MACage +1) is reached: the LFG is reduced to 0.5 L/min, while the NFG is maintained at 2 L/min. Ventilation is managed to keep EtCO2 between 35-45 mmHg. Data collection is performed via high-resolution ECG recordings at four time points: preoperative baseline (T1), 5 minutes post-intubation (T2), 15 minutes post-intubation (T3), and 15 minutes postoperatively (T4).

Another key focus of this research is the detailed analysis of secondary outcomes, including the monitoring of hemodynamic stability (mean arterial pressure and heart rate) across all time points. Furthermore, the study aims to characterize the electrophysiological profile of each technique by analyzing the Tp-e/QT ratio and calculating time-dependent variations in repolarization parameters, specifically the delta changes from baseline to intraoperative stages (ΔT1-T2 and ΔT1-T3). Additionally, a cost-effectiveness analysis will be conducted by determining the total volume of volatile anesthetic consumed in both techniques. Statistical analysis will involve independent samples t-tests for inter-group comparisons, while repeated measures ANOVA with Bonferroni correction will evaluate time-dependent changes. Pearson correlation analysis will be utilized to assess the relationships between continuous variables, providing a comprehensive assessment of the safety and efficacy of low-flow versus normal-flow anesthesia management.

Inclusion criteria

• Patients aged 18 years and older.
• Patients scheduled for elective or semi-elective laparoscopic cholecystectomy.
• Patients who provide written voluntary informed consent.
• Patients with a predicted surgical duration between 60 and 180 minutes.

Exclusion criteria

• Patients with heart failure.
• Patients with valvular heart disease or pathology.
• Patients with hemodynamic instability.
• Patients requiring blood transfusion.
• Patients with a preoperative corrected QT (QTc) interval > 450 ms.
• Patients with a known history of cardiac arrhythmia.
• Patients scheduled for emergency surgery.
• Patients with a known risk or family history of malignant hyperthermia.
• Use of medications associated with QT interval prolongation (e.g., ketamine, 5-HT3 antagonists, quetiapine, etc.).