Comparison of the Effects of Spinal and General Anesthesia on Frontal QRS Axis in Patients Undergoing Total Knee Arthroplasty: A Prospective Observational Study

This is a single-center, prospective, observational, non-interventional clinical study to be conducted in the Department of Anesthesiology and Reanimation at Elazig Fethi Sekin City Hospital. The study population consists of adult patients scheduled for elective total knee arthroplasty under either spinal anesthesia or general anesthesia in routine clinical practice. Patients will not be assigned to an intervention by protocol; instead, they will be observed according to the anesthesia technique selected during standard care.

Eligible participants will be patients aged 18 years or older with ASA physical status I to III who undergo elective total knee arthroplasty under spinal or general anesthesia. Exclusion criteria include the presence of a pacemaker, known cardiac conduction abnormalities, technically inadequate preoperative electrocardiograms, active preoperative electrolyte abnormalities, acute coronary syndrome, heart failure, and bilateral knee arthroplasty performed in the same session.

For each participant, demographic and perioperative data will be collected, including age, sex, ASA class, comorbidities, intraoperative fluid volume, arterial blood pressure, oxygen saturation, heart rate, and tourniquet duration. Standard 12-lead electrocardiography will be recorded before surgery and again in the postoperative period before mobilization. Frontal QRS axis values will be obtained from the automatic measurements reported by the ECG device.

The primary outcome measure is the preoperative-to-postoperative change in frontal QRS axis. The main analysis will compare this change between the spinal anesthesia group and the general anesthesia group. Secondary analyses will examine perioperative and demographic factors that may be associated with changes in frontal QRS axis. According to the protocol, approximately 140 to 150 patients are planned for inclusion, taking into account possible loss to follow-up or incomplete data.

Statistical analyses will be performed using IBM SPSS Statistics version 25. Descriptive statistics will be presented as mean and standard deviation, median, or percentage, as appropriate. Between-group comparisons will be performed using the independent samples t test or Mann-Whitney U test depending on data distribution. Within-group preoperative and postoperative comparisons will be assessed using the paired samples t test or Wilcoxon signed-rank test. A p value below 0.05 will be considered statistically significant.