Patients undergoing free flap reconstruction after head and neck cancer may develop free flap complications. In the perioperative period, haemoglobin content and oxygen tissue saturation (StO₂) measured directly on the free flap reflect peripheral tissue oxygenation. However, in this type of surgery, StO₂ cannot always be applied directly or proximate to the free flap. The aim of this study was to assess the possible value of StO₂ measured at the thenar eminence and other 24hour perioperative factors on free flap complications.

Inclusion criteria corresponded to patients with head and neck cancer with free flap surgery in whom direct StO₂ could not be monitored on the flap nor in its peripheral area. Patient characteristics and intraoperative data, such as haemoglobin and fluid management, were prospectively collected. StO₂ was measured remotely on the thenar eminence. Data were collected for 24hours and free flap complications were recorded for up to 15days after surgery. Patients were thereafter classified into two groups: with or without free flap complications and the data were compared in consequence.

Forty consecutive patients were prospectively included. Ten patients had postoperative free flap complications and were compared to the 30 other patients without complications. The haemoglobin level at the reperfusion of the flap: (AUC 0.80 [0.65–0.91], threshold 9.9g/dL, P<0.001) and body mass index [BMI] (AUC 0.80 [0.64–0.72], threshold 24.5kg/m², P<0.01) were significantly related to complications.

In head and neck complex oncologic reconstructive surgery, haemoglobin and BMI were the most sensitive tools for predicting postoperative free flap complications, while thenar eminence StO₂ was not.