Reliable detection of circulatory compromise threatening free-flap viability is essential for prompt surgical intervention and flap salvage. Numerous techniques have been developed to address the issue of postoperative flap monitoring but none have achieved universal acceptance. Near infrared spectroscopy (NIRS) is a noninvasive technique that allows continuous monitoring of tissue oxygenation and perfusion. It is increasingly recognised to be a reliable method for flap viability assessment. This study was designed to investigate the ability of NIRS to detect and identify microvascular thrombosis endangering flap survival. To our knowledge, this is the first clinical evaluation of NIRS used for continuous monitoring of free flaps.
Methods: Fifty flaps used for autologous breast reconstruction in 48 patients were included in this prospective clinical study. NIRS was employed for 72-h continuous postoperative monitoring. The data were compared to findings of clinical assessments.
Results: Ten flaps (20%) developed 13 anastomosis thromboses (two arterial and 11 venous). NIRS detected all cases of flow failure prior to clinical observation with no false positives or negatives. Based on consistent patterns of NIRS parameter changes, it was possible to differentiate between changes caused by arterial and venous thrombosis with accuracy before surgical re-exploration. The salvage rate was 70%. Overall flap viability was 94%.
Conclusions: Continuous NIRS monitoring can reliably detect and identify early stages of arterial and venous thrombosis, and is a credible method for noninvasive postoperative flap surveillance. Based on these findings, we advocate its use for monitoring of flaps with a cutaneous component.