Biomarkers, Blood Pressure, BIS: Risk Stratification/Management of Patients at Cardiac Risk in Major Noncardiac Surgery

Major adverse cardiovascular events (MACE) are a leading cause of serious complications and death following major noncardiac surgery. The heart biomarkers brain-type natriuretic peptide (BNP) and high-sensitivity troponin I/T (hs-TnI/T), may aid in estimating the risk of surgery - low values may permit identifying patients at a very low risk of postoperative complications, potentially helping to avoid unnecessary tests and delays prior to surgery. Recent studies suggest that the manner in which an anesthetic is conducted may have an important impact on postoperative outcomes. The combination of low blood pressure (BP) and a deep level of anesthesia despite a low dose of anesthetic - also known as a "triple low" - has been linked to increased complications and death following surgery. However, it is unclear whether triple lows actually cause postoperative complications or whether they are merely an indicator of a sick patient, who is in general more likely to suffer from cardiovascular events in the near future. To answer this question, in this study patients will be randomly assigned to groups with lower and higher blood pressures, and the postoperative rates of major adverse cardiovascular events and of relevant increases in hs-TnI (a marker of cardiac injury) compared. Another important question is that of the optimal blood pressure target during surgery. Currently there are no established methods of tailoring blood pressure management to the individual patient. In the study the investigators will perform ambulatory 24h BP measurements prior to surgery to measure the patients' average BP during sleep. In the analysis of the study data, the investigators will try to determine the relationship of preoperative biomarker levels, intraoperative BP (both in relation to fixed targets and to the patient's own night-time BP) and of anesthetic depth with the occurrence of major adverse cardiovascular events after surgery.