THE USE OF NEAR-INFRARED SPECTROSCOPY FOR ASSESSING FLAP VIABILITY DURING RECONSTRUCTIVE SURGERY

The ability to assess viability of tissues by monitoring changes in ox ygenation and perfusion during harvesting and following transfer of fr ee and pedicled flaps is potentially important in reconstructive surge ry. Rapid detection of a critical change in tissue oxygenation could e nable earlier and more successful surgical intervention when such prob lems arise. In this study near infra-red spectroscopy (NIRS) was used to assess changes in tissue oxygenation, haemoglobin oxygenation and b lood volume in a porcine prefabricated myocutaneous flap model in resp onse to pedicle manipulations. As far as we are aware this is the firs t usage of a NIRS instrument to assess changes in oxygenation in a fla p model which closely simulates the clinical situation. A myocutaneous flap was raised (n=9 pigs), tubed and the flap circulation allowed to readjust for periods between 7 and 9 days. The pedicle vessels were t hen subjected to arterial (n=9), venous (n=12) and total occlusion (n= 6). Repeatable and reproducible patterns of change were measured in ea ch case. Comparison of mean values indicated that the differences betw een arterial and venous, and venous and total occlusions were signific ant for all NIRS parameters. The monitor was easily able to detect two additional features: (i) the presence of venous congestion indicated by raised levels of deoxygenated haemoglobin and an increase in blood volume; and (ii) the presence and magnitude of reactive hyperaemia. In tno flaps release of arterial or total occlusion did not result in th e expected reactive hyperaemia associated with an increase in blood vo lume (oxygenated haemoglobin) suggestive of possible damage to the vas cular bed. NIRS proved able to detect and distinguish between microcir culatory changes occurring as a result of arterial, venous or total va scular occlusion, We believe that NIRS provides a sensitive and reliab le postoperative monitor of tissue viability following transfer of fre e and pedicled flaps. It can accurately identify different types of pr oblems with the pedicle vessels. In addition its predictive capabiliti es would allow assessment of flaps buried deep to the skin. This monit or is excellent for surgical and intensive care unit monitoring since it is unaffected by light, portable and is extremely easy to use.