The primary objective of this observational study is to investigate the risk factors for intraoperative hypotension and identify the underlying pathomechanisms leading to it, both during the period after general anesthesia induction and throughout its course.

The main questions it aims to answer are:

• how frequent is intraoperative hypotension
• what are the underlying pathomechanism causing it The study is including patients who have been identified as having a high risk of perioperative complications (ASA3 or ASA4). Patients included in the study undergo advanced hemodynamic monitoring during the procedure. Anesthesia induction, maintenance, and termination are conducted by an anesthesiologist in accordance with current medical knowledge, and the planned experiment does not in any way influence the course of action.

Investigators will analyse medical documentation, including the patient's medical history, anesthesia records, and hemodynamic parameter data obtained from the hemodynamic monitor (an Excel file containing comprehensive data related to specific cardiovascular parameters) to describe the incidence of intraoperative hypotension and answer key questions in accordance with the designed study protocol.

Inclusion Criteria:

• Age >18 years old.
• Capability of providing informed consent by the patient.
• Planned surgeries.
• Surgeries other than thoracic, cardiac, or obstetric procedures.
• ASA (American Society of Anesthesiologists) physical status classification of 3 or 4, indicating high risk.
• Patients at high risk of postoperative complications.
• Preoperative qualification for advanced hemodynamic monitoring.
• Access to complete preoperative health status data.
• Access to complete data regarding the course of anesthesia and hemodynamic parameters obtained from the hemodynamic monitoring platform.
• Initiation of hemodynamic monitoring prior to general anesthesia induction.

Exclusion Criteria:

• Age <18 years old.
• Cardiac surgeries.
• Thoracic surgeries.
• Obstetric procedures.
• Inability of the patient to provide informed consent.
• ASA physical status classification of 1, 2, or 5, indicating low or moderate risk.
• Urgent and emergent surgeries.
• Lack of complete preoperative health status data.
• Lack of complete data regarding the course of anesthesia.
• Inability to initiate hemodynamic monitoring prior to general anesthesia induction.
• Interruption in hemodynamic monitoring lasting longer than 5 minutes (lack of parameter values in the obtained hemodynamic monitor file).

Age: > 18 years old. Gender: Women and men. Preoperative qualification for advanced hemodynamic monitoring based on the estimated high risk of postoperative complications.