The study will investigate if non-invasive continuous transcutaneous blood gas monitoring can detect tissue perfusion and hypoxemia and the relation to other circulatory parameters such as pulse, blood pressure, cardiac output and arterial saturation.

Macro circulatory parameters such as cardiac output, mean arterial pressure and arterial oxygen saturation are used to monitor the hemodynamic function and tissue perfusion in surgical patients. Though none of the methods are directly monitoring changes in the metabolism of the tissue. Arterial blood gas analysis is used as the golden standard for the detection of metabolic disturbances before, during and after surgery. Disadvantages of the method are 1) the fact that the technique is invasive to the patient, 2) that the method measures the "total gas" (each tissue's contribution to the blood gas in the total circulating blood) and 3) that the methods only provide a snapshot of the patient's blood gas status. Transcutaneous monitoring can be used as a continuous monitoring of the underlying tissue's carbon dioxide and oxygen levels in patients. The method is already used in neonates as a surrogate for the arterial blood gas analysis. Reduced tissue oxygenation due to inadequate perfusion, will initiate an anaerobic tissue metabolism resulting in low oxygen levels and high carbon dioxide levels. The transcutaneous monitoring can therefore potentially be used to detect tissue hypoxia and become a direct measurement of the underlying tissue metabolism.

Inclusion Criteria:

• patients undergoing surgery for abdominal cancer
• patients undergoing femoral endarterectomy

Exclusion Criteria:

• patients not able to give a informed consent

Patients admitted to Rigshospitalet due to surgery for abdominal cancer (Whipple procedure) and vascular surgery (femoral endarterectomy)