In order to estimate the effect of fluid management in regard to postoperative complications this observatory study will document every kind of fluid intervention peri- and intraoperatively.

The extend of mass transfusions is known to correlate with postoperative complications. However, also crystalloid and colloidal infusions are under suspicion to cause postoperative complications. This study will capture any kind of fluid intervention perioperatively as well as intraoperatively. Intraoperative fluid management will be documented and matched with the operation steps respectively. The extend of fluid therapy will be correlated with general postoperative complications and especially with the survival of microvascular transplants.

For this purpose, there will be four questionaires. After informed consent, the first questionaire will cover the patient's history, risk factors and previous operations. The second questionaire will cover intraoperative fluid management, documented with the actual operation step. Furthermore, it will also intraoperative complications, cardiovascular-active medication. For closer monitoring, data from Picco will also be included. The third questionaire will be complete in the ICU covering similar content as the second questionaire. The last questionaire will cover the patient's progress on the general ward. Fluid management and tube feeding, as well as general postoperative complication and flap specific complications will be noted.

This study aims for 50-80 patients.

Inclusion Criteria:

• 18 years old or older
• admitted for head and neck surgery with microvascular transplantation due to head and neck tumors

Exclusion Criteria:

• Pregnancy
• underage
• missing informed consent
• revisions and relapse operations
• non tumor-associated operations
• surgery without microvascular transplants

Full grown, able to consent patients admitted for major head and neck surgery with planned microvascular transplants for reconstruction due to tumors in the head and neck region.