Background: Early detection of vascular impairments after free tissue transfers are essential to prevent flap failure. Near-infrared spectroscopy showed good promise to monitor flaps at deep levels successfully without being invasive. The purpose of this study was to test whether the INVOS 3100 cerebral oxymeter is capable of detecting circulatory impairments.
Methods: In 10 healthy adults, near-infrared spectroscopy was used to measure regional saturation values during tourniquet ischemia and venous outflow restriction, in two test cycles. The probe, containing an infrared-light-emitting source and two infrared-light sensors, was placed below the elbow above the brachioradialis muscle. Statistical comparison of the data was performed using the Friedman test and the Wilcoxon-Wilcox test.
Results: Venous and arterial occlusions were characterized by an instantaneous fall of the regional saturation. Arterial occlusion showed a mean decrease of the saturation values down to 28+/-9%, whereas venous occlusion showed a mean fall of saturation values down to 51+/-12%. These falls were significant after 3 minutes of occlusion compared with baseline values (74+/-6%). The differences between arterial and venous occlusions were statistically significant.
Conclusion: This study, designed to test less-expensive equipment, was able to measure absolute values, and was not prone to interference caused by probe movement, providing information on the oxygenation profile accurately and noninvasively, and distinguishing between arterial and venous occlusion.