Post Anaesthesia Care Hypotension Prevention (PACH-1)

The goal of this clinical trial is to investigate if the use of the hypotension prediction index during the perioperative period leads to a decrease in hypotension both during and after surgery (24 hrs) in adults undergoing major abdominal surgery. The main question this trial aims to answer is: • Does the use of the hypertension prediction index (HPI) decrease hypotension during surgery and in the post-operative period? During and after their surgery, participants in the intervention group will be treated according to the HPI-algorithm. Participants in the control group will be treated following the standard of care.

Rationale: Hypotension during and after surgery is associated with serious complications. Using a machine learning algorithm, hypotension can be accurately predicted. Edwards Lifesciences developed this algorithm, called "Hypotension Prediction Index" and integrated this in their hemodynamical monitors. Recent studies have shown a decrease in intraoperative hypotension when using the hypotension prediction index. Objective: To investigate if the use of the hypotension prediction index during the perioperative period leads to a decrease in hypotension (time weighted average) both during and after surgery (24 hrs). Intervention: Patients in the intervention group will be treated using the hypotension prediction index algorithm to prevent hypotension. In case of actual hypotension the treatment thereof is at the discretion of the anaesthesiologist. Main study parameters/endpoints: The decrease in time weighted average of hypotension in the peri- and post-operative period.

In the intervention group the HemoSphere screen is visible and the anesthesiologist and PACU personal are instructed to follow the algorithm (chapter 4) in case of a HPI >85%. The purpose of the alarm at 85% and the presented algorithm is to prevent hypotension. If hypotension occurs, it should be treated as according to the standard of care.

Patients in the control group are connected to the HemoSphere monitor to evaluate the TWA of hypotension in this group. The screen is not visible to the anesthesiologist or PACU personal and the alarm is set silent. It will be explained to the anesthesiologist and PACU personal that the patients are included to this study and that a blood pressure with a MAP of 65 mmHg should be monitored.

Treatment of hypotension guided by the hypotension prediction index. Patients will receive treatment following the predetermined HPI-algorithm when the HPI exceeds 85%.

Patients receive standard of care treatment for hypotension, with a goal-mean arterial pressure (MAP) of 65mmHg.

Time Weighted Average (TWA) is measured as (depth of hypotension in mmHg below a MAP op 65mmHg x time in minutes spent below a MAP of 65mmHg) ÷ total duration of surgery/PACU admission in minutes)

Inclusion Criteria: Patients > 18 years old Patients planned to undergo laparotomy surgery Patients that will receive an invasive arterial catheter as part of their procedure Patients that are planned to go to the post anaesthetic care unit (PACU) post-operatively Exclusion Criteria: Patients with known arrythmias Patients with known severe heart valve disease Patients with the need for dialysis Clamping of the aorta or Pringle's manoeuvre during surgery Emergency procedures