Distinction between arterial and venous occlusion with tissue oxygen pressure in a porcine fascio-cutaneous flap model.

BACKGROUND In recent years, many devices have been developed to monitor free flaps. The Licox probe, which measures tissue oxygen pressure (PtO2 ), is one of the available devices. Our aim was to demonstrate that PtO2 could distinguish arterial from venous occlusion in a porcine fascio-cutaneous flap model. MATERIALS AND METHODS Twenty pigs (Sus scrofa domestica, Youna strain, males) were included in this study. The median weight was 87.6 kg (84.6-90.8). Bilateral fascio-cutaneous flaps based on the superficial inferior epigastric pedicle were harvested from each pig. Thirty-eight flaps were analyzed in this study and were monitored by a Licox system during vascular occlusion. The flaps were randomized into two groups according to the clamped vessel: the arterial group (n = 19) and the venous group (n = 19). After a stabilization period of almost 40 min, vascular clamping (arterial or venous) was performed using a microvascular clamp for almost 20 min. The curve profiles were compared between arterial and venous occlusion. RESULTS The inflection point was reached significantly faster in the arterial group: 11 min (9-16) for arterial clamping and 17 min (13-23) for venous clamping (p = .001). A total of 18/19 (95%) pigs in the arterial group and 13/19 (68%) in the venous group (p = .09) reached a level lower than 10 mmHg. The median duration for pressure to drop below 10 mmHg was 9 min (6-12) for arterial clamping and 10 min (9-16) for venous clamping (p = .06). CONCLUSION We showed that PtO2 decreased faster in cases of arterial occlusion than in cases of venous occlusion in a pig model. Based on this observation, it may be possible to distinguish arterial from venous occlusion.