Flap Monitoring by Transcutaneous PO₂ and PCO₂: Importance of Transcutaneous PCO₂ in Determining Follow-up Treatment for Compromised Free Flaps

ABSTRACT

The authors conducted a two-part study to determine whether transcutaneous oxygen pressure (TcPO₂) and transcutaneous carbon dioxide pressure (TcPCO₂) can be used to monitor flap viability after transplantation. The first part was an animal study in which TcPO₂ and TcPCO₂ were measured in 10 epigastric island flaps subjected to arterial or venous ischemia. The second part was a clinical study in which both were measured in 27 free skin flaps. In the experimental study, TcPO₂ decreased to nearly 0 mmHg after 10 minutes of arterial and venous ischemia. TcPCO₂ increased to 100 mmHg after 60 minutes of either type of ischemia. In the clinical study, congestion was suspected in six flaps on the basis of clinical signs alone. Three congested flaps with TcPCO₂ more than 90 mmHg were selected for intervention. The remaining three congested flaps, with TcPCO₂ 80 mmHg or less, survived completely without further treatment. The TcPO₂ of all treated flaps and of the six flaps not requiring further treatment was 0 mmHg. Results of experimental study indicate that TcPO₂ is more sensitive than TcPCO₂ to flap ischemia. However, results of clinical study suggest that it is very hard to distinguish congested flaps from healthy flaps by TcPO₂ alone. The authors believe that a congested flap with a TcPCO₂ more than 90 mmHg requires further treatment.

KEYWORDS

Free flap monitoring - TcPO₂ and TcPCO₂ measurement - flap necrosis

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