The Relationship Between Hypotension and Tissue O2 in Invasive Eadyn During Anesthesia Induction in Open Heart Surgery

Overview

Our aim is to identify patients who may experience hypotension during anesthesia induction. Intraoperative hemodynamic stability plays an important role in tissue oxygenation. Although the duration of hypotension can be kept short with the necessary interventions, it is important that hypotension is predictable in order to prevent intraoperative complications and postoperative organ damage. 40 patients scheduled for open heart surgery will be monitored from one minute before anesthesia is administered until ten minutes after. Patients will be divided into two groups based on the presence or absence of hypotension during the monitoring period. All patients will be monitored according to a standardized procedure. Demographic data, non-invasive and invasive hemodynamic parameters, primarily Eadyn, and cerebral and renal tissue saturation data will be collected. Moreover, vasopressor administration in response to hypotension will be recorded.

Introduction: Hypotension during and after the induction of anesthesia is a common occurrence. Several factors may contribute to post-induction hypotension, including prolonged fasting, underlying comorbidities, sympathetic blockade induced by anesthetic agents, vasodilation, decreased preload, and reduced cardiac contractility. Numerous studies have identified factors and predictors associated with post-induction hypotension; however, most of these predictors are non-modifiable. Previous research has shown that patients at risk for post-induction hypotension can be identified using variables such as the inferior vena cava collapsibility index, carotid intima-media thickness, pulse pressure variation (PPV), and stroke volume variation (SVV). Nevertheless, most of these studies have focused on assessing the cardiovascular system using preload- and fluid-responsiveness-related parameters, while the interaction between the arterial system and the ventricle has often been overlooked. Dynamic arterial elastance (Eadyn), defined as the ratio between pulse pressure variation (PPV) and stroke volume variation (SVV), integrates the flow generated by the heart and the opposing pressure from the arterial system during the respiratory cycle, and has been proposed as a functional measure of arterial load. Furthermore, recent studies suggest that post-induction hypotension is associated with arterial vasodilation rather than venous dilation or decreased myocardial contractility. In current anesthetic practice, interventions are typically applied only after hypotension has developed. We hypothesize that if patients at risk of developing hypotension during anesthesia induction can be identified in advance, prophylactic administration of fluids and vasopressors could reduce the duration and severity of hypotension, thereby preventing potential intraoperative complications and postoperative organ dysfunction. Material method: Patients scheduled for open heart surgery after October 17, 2025, are eligible for this study after ethical board approval. Inclusion criterions are (1) patients aged between 18-90 years with American Society of Anaesthesiologists (ASA) Physical Status classification I to III, (2)planned open heart surgery. Written informed consent will be obtained from all participants. Exclusion criteria are refusal to participate in the study, younger than 18 years of age; those with arrhythmias (including atrial fibrillation or frequent premature beats); severe valvular heart disease (aortic or mitral stenosis or insufficiency); severe heart failure (ejection fraction \< 40%); congenital heart disease; pre-existing severe pulmonary disease; chronic kidney disease requiring dialysis; severe peripheral vascular disease; morbid obesity; and patients undergoing emergency surgery. All patients received standard general anesthesia with monitoring that included Masimo SedLine -NIRS(noninvasive regional saturation), Mostcare invasive hemodynamic monitoring, and conventional standard monitors; Anesthesia induction was performed with midazolam (0.025 mg/kg), propofol (1.5-2.5 mg/kg), lidocaine (1 mg/kg), and rocuronium (1 mg/kg). Anesthetics and opioid administration was titrated according to hemodynamic parameters and Patient State Index (PSI) values between 25 and 50. For each patient, both the total cumulative dose of ephedrine administered and the number of times it was given were recorded.