Fluid Responsiveness Through the Corrected Carotid Flow Time, Before and After Sternotomy

Perioperative fluid management is used to maintain the perfusion of vital organs, prevent hypovolemia, inadequate tissue perfusion, and tissue edema, and cardiovascular complications caused by the infusion of large amounts of blood and blood products. Optimal fluid management improves postoperative outcomes. However, excessive or inadequate fluid infusion increases morbidity. Traditional fluid therapy strategies are divided into three groups: liberal fluid therapy, restrictive fluid therapy, and goal-directed therapy (GDT). Fluid responsiveness refers to a patient's hemodynamic response to intravenous fluid loading and is defined as an increase of 10% or more in stroke volume (SV) or cardiac output (CO). Various parameters are used to assess fluid responsiveness. Static parameters have limited accuracy in predicting fluid responsiveness. Dynamic parameters such as stroke volume variation (SVV), pulse pressure variation (PPV), passive leg raising test (PLR), and end-expiratory occlusion test (EEOT) have been found to be more reliable in assessing fluid responsiveness. The pulse contour analysis method (PCA) continuously measures cardiac output by analyzing the arterial pressure waveform. The ProAQT/PulsioFlex system measures cardiac output by analyzing the arterial waveform without requiring calibration. Lung recruitment maneuvers (LRM) are techniques used in mechanically ventilated patients to prevent atelectasis and improve oxygenation. They have also been shown to assist in assessing fluid responsiveness. LRM methods include sustained inflation (SI), increased PEEP pressure, increased tidal volume, and targeted recruitment. The temporary increase in intrathoracic pressure during LRM can affect stroke volume variation and be used to assess fluid responsiveness. Corrected carotid flow time (FTc) is a non-invasive parameter calculated by normalizing the systolic ejection time in the carotid artery to heart rate. FTc can be measured using Doppler ultrasound. It is thought that changes in FTc measured during passive leg raising (PLR) or lung recruitment maneuvers (LRM) may help identify fluid-responsive patients, and new studies are being conducted on this topic. Recent studies suggest that changes in FTc during lung recruitment maneuvers may be a reliable method for assessing fluid responsiveness. The optimal method for assessing fluid responsiveness during lung-protective ventilation remains unknown. In patients who have undergone sternotomy with an open chest wall, an ideal method for evaluating fluid responsiveness has not yet been determined. The primary objective of this study is to investigate the usability of changes in corrected carotid flow time induced by lung recruitment maneuvers during protective lung ventilation (6 ml/kg tidal volume) in patients undergoing elective Coronary Artery Bypass Graft (CABG) surgery to evaluate fluid responsiveness. The secondary objective is to determine the correlation between measurements taken before and after sternotomy. This study aims to reduce invasive procedures used for assessing fluid responsiveness and minimize the need for difficult-to-access devices for measurements. The study was conducted in the Cardiovascular Surgery Operating Room at the Ministry of Health Ankara Bilkent City Hospital. Fifty patients, aged 18-80 years, classified as ASA II-III, who were scheduled for elective coronary artery bypass graft surgery under general anesthesia, were included in the study. Three patients were excluded due to missing data, and two patients were excluded due to hemodynamic instability, leaving 45 patients in total. The study was designed as a single-center, prospective, observational study and was conducted between July 1, 2024, and November 1, 2024. All patients included in the study were monitored in the same standard way. Heart rate, intra-arterial monitoring, and PulsioFlex monitoring were performed. All patients were given the same induction and anesthesia maintenance. Fluid responsiveness was evaluated by measurements taken at specific intraoperative times. Hemodynamic parameters, including heart rate (HR) (beats/min), central venous pressure (CVP, mmHg), systolic arterial blood pressure (SAB, mmHg), diastolic arterial blood pressure (DAB, mmHg), mean arterial pressure (MAP, mmHg), stroke volume index (SVI), cardiac index (CI), PPV, SVV, and carotid artery FTc, were assessed and recorded six times: T1:After induction is complete and preparations are made for the surgical procedure, before incision is started T2:Before starting sternotomy, 1 minute after LRM T3:After sternotomy within 5 minutes T4:After sternotomy, LRM is applied when hemodynamic stability is achieved. Measurement is made 1 minute after LRM. T5:Measurement is made 10 minutes after T4 when hemodynamic parameters are stable. T6:After the T5 measurement, the patient All measurements were taken at the beginning of surgery, terminated after 12 hours from the induction .

Measurements will be taken six times: T1.Before sternotomy T2.After LRM is performed before sternotomy T3.5 minutes After sternotomy T4.LRM was performed 10 minutes after sternotomy, the recording will be taken within 2 minutes after the LRM is finished T5.Before fluid loading (15 minutes after T4 if hemodynamics are stable) T6.After fluid loading (After the T5 measurement is taken, the fluid loading is done and after the fluid is finished, within 2 minutes T6 measurement is taken) We expect these measurements to be made during the first half of the surgery; if for any reason it takes longer than 12 hours, the patient will be removed from study