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Overview :
The dye fluorescent index (DFI) can be used to determine if
a proposed amputation site is sufficiently perfused to heal adequately.
Fluorescent detection instrument (dermofluorometer)
• dual channel fiberoptic light guide
• one channel transmits a blue light capable of exciting a
fluorescein dye
• the second
channels transmits the fluorescent light generated back to a photomultiplier
tube for detection
Technique:
• background
readings are taken at the proposed amputation site and at a reference site on
the arm or upper torso before a fluorescent dye is injected
• readings are
taken at the same sites again after dye is injected
• multiple
readings are taken and an average reading used
Dose of fluorescein dye to inject:
• if Caucasian, dose is 4 mg/kg
• if of darker complexion, the dose is 6-8 mg/kg
• dose is diluted in 20 mL of normal saline and injected
intravenously slowly
fluorescent reading =
= (fluorescent reading after dye) - (background reading
before dye)
dye fluorescent index =
= (average fluorescent reading for proposed amputation site)
/ (average fluorescent reading at reference area) * 100
Interpretation:
• Areas with
better perfusion will have higher fluorescence than those that are poorly
perfused, with readings 10-20 times greater than background
• DFI > 42: high rate of amputation site healing
• DFI 38 - 42: borderline rate of healing
• DFI < 38: show poor healing
Limitations:
• Cellulitis or other skin disorders can interfere with the
fluorescent readings
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