The Role of Left Ventricular Outflow Tract (LVOT) Velocity-time Integral (VTI) and Respiratory Variability at Peak Rate (Vpeak) in Predicting Hypotension After General Anesthesia Induction

Preoperatively, patients will undergo transthoracic echocardiography measurements approximately 15-30 minutes before induction. TTE will be performed on all patients by an experienced observer; the echocardiography device will be equipped with an S4-2 transducer (4-2 MHz frequency range) in the left lateral decubitus position. VTI and Vpeak values of the LVOT were measured from manually drawn contours using pulsatile wave Doppler technique in the apical five-chamber view. The Doppler beam was aligned with the aortic blood flow, and the signal was captured at an appropriate angle (\<20°). The maximum (VTImax) and minimum (VTImin) VTI, as well as the maximum (Vpeakmax) and minimum (Vpeakmin) Vpeak values, were determined over three respiratory cycles. ΔVTI was calculated with the following formula: ΔVTI = \[2 × (VTImax - VTImin) / (VTImax + VTImin)\] × 100%. ΔVpeak was calculated with the following formula: ΔVpeak = \[2 × (Vpeakmax - Vpeakmin) / (Vpeakmax + Vpeakmin)\] × 100%. These parameters were analyzed to evaluate the hemodynamic status of patients and estimate fluid responsiveness. Patients with a 30% decrease from baseline in SBP and a decrease in MAP below 60 mmHg in the first 10 minutes after anesthesia induction were considered to have hypotension. Patients were divided into two groups: "with" and "without" hypotension.