Perioperative anesthesiologists can benefit from easily obtainable hemodynamic variables detecting or quantifying the lack of an adequate compensatory capacity of the cardiovascular system in order to optimize patient management and improve patient outcomes. Parameters of the Pressure Recording Analytical Method (PRAM; Vygon, Padua, Italy) of the MostCare system, specifically cardiac cycle efficiency has been proposed as such variables. Yet, their value in anesthesia and especially in hypertensive patients is not studied. The goal of the PRAM-in-HYPO study is to prospectively evaluate the relationship between cardiac reserve and efficiency and cardiovascular risk factors in patients wo will undergo major surgical procedures using the state-of-the-art hemodynamic monitors. Also the investigators aim to build a predictive model to identify patients with decreased cardiac reserve due to hypertension and other cardiovascular risk factors, who are susceptible to post-induction hypotension. The investigators seek to include high-risk patients or patients presenting for major surgery, who are monitored with an advanced hemodynamic monitor to adequately evaluate the differences in cardiac reserve and cardiac efficiency.

Untreated hypertension decreases the cardiac reserve through several mechanisms, which are augmented by other cardiovascular risk factors such as diabetes mellitus and coronary artery disease. Perioperative stress on top of these overlapping diseases causes wide variations in the arterial blood pressure. From the anesthesiologist's point of view, this translates into a wide variation in response to surgical stress among patients with seemingly similar cardiovascular risk factors.

The cardiac reserve may be measured by cardiac catheterization or echocardiography, none of which are feasible during a surgery. Recently, some parameters of the Pressure Recording Analytical Method (PRAM) were shown to be affected by hypertension or intraoperative events such as pneumoperitoneum and position changes. This suggests that PRAM may be used to evaluate the risk of adverse hemodynamic events in newly diagnosed, untreated hypertensive patients.

The investigators hypothesized that there is a relationship between hypertension, diabetes mellitus and decreased cardiac reserve and efficiency and that PRAM parameters may identify this. Also, the static or dynamic PRAM parameters may predict pre-incision hypotension in patients wo will undergo major surgical procedures.

In order to test these hypothesis, a prospective cohort study was planned, as the outcome has a very short latency and the intent is to observe the outcome, not to prevent or treat it. The investigators aim to collect high quality hemodynamic data from normotensive, hypertensive, and untreated hypertensive patients. In order to obtain sufficient relevant data, only patients scheduled for major surgeries will be included. Patients who are planned to be monitored with the MostCare hemodynamic monitor, and who need a passive leg raising test will be included in the study.

Hypertension is the most prevalent of cardiovascular risk factors, namely diabetes mellitus, coronary artery disease, smoking, obesity, and dyslipidemia, which may present as either the mediator or cofounder of hypertension. Therefore a detailed medical history including information relevant to these conditions will be collected.

Inclusion Criteria:

• Age at least 18 years
• Undergoing major surgery under general anesthesia
• Expected surgery time >2 h
• Expected length of postoperative stay >2 d
• Invasive blood pressure (radial or femoral) and Mostcare monitoring
• Indication for a passive leg raising test: risk of hypovolemia (preoperative fasting, bowel preparation, loss of appetite, limited access to water) or expected major surgery, expected blood loss, cardiovascular comorbidity (hypertension, diabetes mellitus, coronary artery disease, peripheral artery disease, hyperlipidemia, morbidity, active smoking).
• Recruitment after booking for surgery with sufficient time to read, understand and question study patient information prior to attending for surgery.
• Ability and willingness to provide informed consent

Exclusion Criteria:

• Refuse to consent to the study
• Arterial wave form distortion
• Cardiac arrhythmia
• Inappropriate identification of the dicrotic notch for any reason
• Planned intraoperative mean arterial blood pressure < 65 mmHg
• Hemodynamic instability defined as mean arterial blood pressure < 65 mmHg
• Preoperative requirement of inotrope/vasopressor infusion
• Preoperatively receiving vasoactive drugs
• Patients fitted with an intra-aortic balloon pump
• Patients fitted with Extracorporeal Membrane Oxygenation
• Critically ill patients requiring preoperative intensive care unit
• Presence of intraabdominal hypertension
• New York Heart Association Class 3-4 heart failure
• Congestive heart failure with ejection fraction < 35%
• Glomerular filtration rate < 30 ml/min/1.73 m2
• Ongoing renal replacement therapy

Patients who are scheduled for any major surgery will be included. Major surgery includes a broad list of cardiac surgery, thoracic surgery, hepatic surgery, pancreatic surgery, colorectal surgery, major orthopedic surgeries, cancer surgeries, where blood loss or intravascular volume loss is expected due to factors related to the patient or surgery.

The Ethics Committee's approval is required to make individual participant data available to other researchers.