Prospective Interventional Study Investigating a Goal-directed Therapy Based on Non-invasive Measurement of the Hypotension Prediction Index for the Reduction of Hypotension in Patients Undergoing Major Orthopedic and Trauma Surgery

Complications related to intraoperative hypotension (IOH) can be detected in most organ systems of which renal failure poses a relevant complication in the perioperative phase. Acute kidney injury (AKI) affects up to 25 % of patients attending the intensive care unit (ICU). Currently, serum creatinine and urea display the most common parameters used to detect AKI, but it may take a day or more for serum creatinine levels to accumulate in the blood of a patient with an AKI. For this reason, it may not reflect real time kidney damage or loss of function. To overcome this limitation, the cell cycle arrest biomarkers TIMP-2- and IGFBP7-quantification (Nephrocheck) has been successfully evaluated for the detection of AKI. The main advantage of both parameters is the opportunity of early detection of AKI and its point-of-care design, which makes them especially for the use on the ICU valuable.

Myocardial injury after non-cardiac surgery (MINS) displays another adverse outcome associated to IOH and endangers particularly patients with an age of 45 years and older and approximately 1% of all patients suffering of MINS die within 30 days after non-cardiac surgery.

In order to reduce the incidence of IOH, various goal-directed therapy (GDT) protocols have already been introduced with success regarding the reduction of postoperative AKI and MINS. However, these studies used an invasive hemodynamic monitoring which offered a continuous surveillance of the blood pressure. In contrast, standard non-invasive blood pressure monitoring results in a blind gap between two measurements (mostly three or five minutes). In order to address this limitation, different continuous non-invasive blood pressure monitoring devices have been introduced. The next evolutional step of non-invasive cardiac output monitoring was to prevent IOH before their onset by using the Hypotension Prediction Index (HPI). Based on the Edward ́s monitoring platform, HPI is a monitoring tool which aims to predict IOH (defined as MAP<65 mmHg for at least one minute) up to 15 min before its onset. Until today the arterial waveform analysis was dependent on invasive arterial measurement but since Edwards Lifesciences already promoted the start of the HPI on the ClearSight platform a non-invasive measurement will soon be possible.

Further, until now it has not yet been proven that the perioperative use of a continuous non-invasive blood pressure monitoring has a beneficial effect on the patient´s outcome. Especially, a GDT based on non-invasive blood pressure monitoring might not only be able to reduce the incidence of IOH but also of the occurrence of postoperative renal failure.

2.1 Study hypothesis 2.1.1 Primary study hypothesis The perioperative use of non-invasive HPI-guided GDT reduces the incidence of IOH in patients undergoing major trauma and orthopedic surgery.