The primary aim of this study is to investigate fluid loss from the blood stream (''endothelial leakage'') and the damage on the vessel wall (''endothelial function'') during surgery.

Cardiovascular complications during surgery are said to have different causes, e.g. lack of fluid in the blood stream (''hypovolemia'') and decreased vascular tone. Hypovolemia can have different causes, one being damage to the endothelial function. During trauma and infection, it has been previously shown, that damage to the endothelial function causes fluid loss from the blood stream. Nevertheless, this has never been demonstrated during surgery.

Secondary this study will measure the blood flow using a thermo-camera during surgery. This will together with selected blood tests provide information on various possible causes to hypovolemia.

The purpose of this study is to describe and quantify endothelial damage (assessed by selected endothelial biomarkers) and albumin escape rate as a proxy for endothelial leakage (assessed by measuring radioactive 125-I labeled HSA injected postoperatively), combined with assessment of MTS (assessed by Laser Speckle Contrast Imaging (LSCI) and digital thermography). This will allow a detailed description of the surgery's impact on the endothelial integrity and contribute to a better understanding of the physiological changes that occur postoperatively.

The study will investigate patients undergoing pancreaticoduodenectomy (Whipple) and total pancreatectomy. These patients have a vast clinical need, being one of the most extensive abdominal surgical procedures with great stress response.

The study is a prospective exploratory cohort study and methods include blood sampling pre- and post-operatively, 125-I labeled humane serum albumin postoperatively (and preoperatively if logistically possible) and thermography.

The hypothesis of this study is that the extent of endothelial damage measured by selected biomarkers is associated with the level of albumin escape rate after major abdominal surgery. Secondly, inflammation increases albumin escape rate after major abdominal surgery.

Inclusion Criteria:

• Age ≥ 18 years
• Patients are scheduled for Whipple or total pancreatectomy

Exclusion Criteria:

• Patient having received immunomodulating treatments less than four weeks prior to surgery
• Patient having other major surgery performed less than four weeks prior to surgery. Thus, minor surgery allowed, for instance minor skin incisions
• Patient having endoscopic retrograde cholangiopancreatography (ERCP) or Percutaneous transhepatic cholangiography (PTC) performed less than two weeks prior to surgery
• Patients scheduled for major vascular surgery during Whipple or total pancreatectomy
• Patient is diagnosed with chronic kidney failure or is in diuretics treatment

Major abdominal surgery patients will be included. Patients are screened prior to surgery from electronic medical charts. Patients can be co-enrolled in other non-intervention trials. An outline of scheduled study activities is shown in figure one.

The data for all included patients will be available for other selected research colleagues

Up to 5 years after data collected