Multiple adjuncts to clinical free flap monitoring have been presented in the literature. They can be summarized as either 1) invasive (e.g. implantable Doppler); 2) minimally invasive (e.g. microdialysis); or 3) non-invasive techniques (e.g. Doppler, near-infrared spectroscopy), that may be contrast enhanced (e.g. contrast enhanced ultrasound, fluorescein angiography). All should be used in combination with regular clinical assessment, but early deterioration in blood flow and flap physiology may be detectable by these techniques before clinically apparent.1 End-capillary blood flow is vital for flap survival. Although some of the current methods for monitoring that are available can give an indirect measure of capillary flow via the presence of oxygenated hemoglobin, such as photophlethysmography or near-infrared spectroscopy, but there is no real-time visualization of the pattern of flow. The Doppler effect is commonly utilized in free flap monitoring provide acoustic or visual evidence of blood flow in the macrocirculation,2 but it lacks the resolution at the microcirculatory level. Disturbance in the end-capillary circulation may indicate a correctable deficit in the source vessels, or a localized microcirculatory problem, such as excessive wound tension.
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