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

The Effects of Low-Flow and Normal-Flow Sevoflurane Anesthesia on Frontal QRS-T Angle and TP-e Interval in Patients Undergoing Elective Laparoscopic Cholecystectomy

Laparoscopic cholecystectomy procedures involve pneumoperitoneum and volatile anesthetics, both of which can significantly influence cardiovascular physiology and autonomic balance. While volatile anesthetics are known to affect myocardial repolarization, the specific impact of Low-Flow Anesthesia (LFA)-a cost-effective and environmentally friendly technique-on these cardiac markers remains under-researched.

This prospective observational study aims to compare the effects of low-flow versus normal-flow sevoflurane anesthesia on two critical non-invasive biomarkers of ventricular repolarization: the Frontal QRS-T angle and the Tp-e interval. These parameters are essential for predicting electrical instability and the risk of malignant arrhythmias. The study will evaluate a total of 128 patients to determine whether different fresh gas flow rates lead to significant changes in cardiac electrophysiological stability during the perioperative and early postoperative periods.

Study Overview

• Status: Not yet recruiting
• Conditions: Anesthesia; Cardiac Arrhythmia
• Intervention / Treatment: Procedure: low flow anesthesia

Detailed Description

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.

• Study Type: Observational
• Enrollment (Estimated): 128

Participation Criteria

Eligibility Criteria

• Ages Eligible for Study: Adult; Older Adult
• Accepts Healthy Volunteers: Yes

• Sampling Method: Probability Sample

Study Population

The study population consists of adult patients (aged 18 years and older) scheduled for elective or semi-elective laparoscopic cholecystectomy at a tertiary care training and research hospital.

Description

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.).

Study Plan

How is the study designed?

Number of groups / cohorts

2

Cohorts and Interventions

Group / Cohort	Intervention / Treatment
Low-Flow Group (LFG); Anesthesia induction and initial stabilization (first 6-8 minutes at 4-6 L/min) follow standard hospital protocols. Fresh Gas Flow (FGF) reduced to 0.5 L/min after the target concentration (MACage +1) is reached. Ventilation parameters are adjusted to maintain end-tidal carbon dioxide (EtCO2) between 35-45 mmHg with a minimum FiO2 of 0.30. Volatile anesthetics are discontinued 15 minutes before the estimated end of surgery. Pre-oxygenation and wash-out are performed at 5-6 L/min with 80% oxygen prior to extubation.	Procedure: low flow anesthesia; Fresh Gas Flow (FGF) reduced to 0.5 L/min after the target concentration (MACage +1) is reached.
Normal-Flow Group (NFG); Anesthesia induction and initial stabilization (first 6-8 minutes at 4-6 L/min) follow standard hospital protocols. Fresh Gas Flow (FGF) maintained at 2 L/min during anesthesia maintenance. Ventilation parameters are adjusted to maintain end-tidal carbon dioxide (EtCO2) between 35-45 mmHg with a minimum FiO2 of 0.30. Volatile anesthetics are discontinued 15 minutes before the estimated end of surgery. Pre-oxygenation and wash-out are performed at 5-6 L/min with 80% oxygen prior to extubation.

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Frontal QRS-T angle	electrocardiogram	Pre-operative period, 5 minutes after induction, 15 minutes after induction, post operative 15th minute
Tp-e interval	electrocardiogram	Pre-operative period, 5 minutes after induction, 15 minutes after induction, post-operative 15th minute

Secondary Outcome Measures

Outcome Measure	Measure Description	Time Frame
blood pressure	Non-invasive blood pressure (NIBP) monitor	during peri-operative period
heart rate	electrocardiogram	during peri-operative period
Tp-e/QT ratio	electrocardiogram	Pre-operative period, 5 minutes after induction, 15 minutes after induction, post-operative 15th minute
Total amount of volatile anesthetic consumed	Mindray anesthesia machine	end of operation
Total amount of Remifentanil consumed	infusion pump	end of operation

Collaborators and Investigators

• Sponsor: Istanbul University

Publications and helpful links

General Publications

• Yildirim H, Adanir T, Atay A, Katircioglu K, Savaci S. The effects of sevoflurane, isoflurane and desflurane on QT interval of the ECG. Eur J Anaesthesiol. 2004 Jul;21(7):566-70. doi: 10.1017/s0265021504007112.
• Kim NY, Han DW, Koh JC, Rha KH, Hong JH, Park JM, Kim SY. Effect of Dexmedetomidine on Heart Rate-Corrected QT and Tpeak-Tend Intervals During Robot-Assisted Laparoscopic Prostatectomy With Steep Trendelenburg Position: A Prospective, Randomized, Double-Blinded, Controlled Study. Medicine (Baltimore). 2016 May;95(19):e3645. doi: 10.1097/MD.0000000000003645.
• Bingol Tanriverdi T, Tercan M, Patmano G, Tanriverdi Z, Gusun Halitoglu A, Kaya A. The Effect of Low-Flow and Normal-Flow Desflurane Anesthesia on the Frontal QRS-T Angle in Patients Undergoing Rhinoplasty Operation: A Randomized Prospective Study. Cureus. 2022 Sep 8;14(9):e28920. doi: 10.7759/cureus.28920. eCollection 2022 Sep.

Study record dates

Study Major Dates

• Study Start (Estimated): May 15, 2026
• Primary Completion (Estimated): May 15, 2027
• Study Completion (Estimated): August 15, 2027

Study Registration Dates

• First Submitted: April 30, 2026
• First Submitted That Met QC Criteria: April 30, 2026
• First Posted (Actual): May 7, 2026

Study Record Updates

• Last Update Posted (Actual): May 7, 2026
• Last Update Submitted That Met QC Criteria: April 30, 2026
• Last Verified: April 1, 2026

More Information

Terms related to this study

• Additional Relevant MeSH Terms: Cardiovascular Diseases; Pathologic Processes; Heart Diseases; Pathological Conditions, Signs and Symptoms; Arrhythmias, Cardiac
• Other Study ID Numbers: 96-2026

Drug and device information, study documents

• Studies a U.S. FDA-regulated drug product: No
• Studies a U.S. FDA-regulated device product: No