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

Abstract

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. 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. 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). 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.