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Statistical Measurement of Quantitative Fluorescence Performance: 4301 Readings. Negative Tests Signal the Surgeon to Sleep Soundly
Rudolf Buntic, MD, Darrell Brooks, MD, Bauback Safa, MD, Gregory Buncke, MD, Brian Parrett, MD.
The Buncke Clinic, San Francisco, CA, USA.
To precisely define the utility of quantitative fluorescence as a monitor in microsurgery using statistical measurements of performance.
All patients admitted to our microsurgical service from March 2010 to July 2010 were enrolled. Quantitative fluorescence readings were assessed by nurses at bedside with baseline, at 10 minutes after injection of fluorescein and at 60 minutes after injection of fluorescein. Adults were dosed with 1 ml of 10% fluorescein intravenously, pediatric patients with 1 mg/kg. Fluorescein perfusion measurements were made every 2 hours for the first 24-48 hours following admission after microsurgical replantation or flap coverage with a skin or fasciocutaneous flap. Reading were taken at both a control site, and the flap/replant site. After the first 24-48 hours, measurements were made every 4 hours. Measurements were discontinued before discharge or when the clinician felt there was little chance of circulatory compromise.
Binary classification of test results was performed and sensitivity, specificity, positive and negative predictive values were calculated.
A total of 4301 quantitative fluorometry readings were performed in 43 replants, 5 toe transplants, 2 radial forearm flaps, 1 venous flap and one revascularized ischemic finger.
In both arterial and venous phase testing, quantitative fluorescence showed a high sensitivity and specificity and 100% negative predictive value. The positive predictive value was 88%.
Walton described skin surface quantitative fluorescence (QF) as a predictor of flap viability in 1983. It has not gained wide spread acceptance to date. However, QF is able to predict perfusion disturbances in skin. It will predict adequate perfusion with near certainty (a rise and fall has a negative predictive value of 100%) and will flag potential cases of circulatory compromise. Of the flagged cases in the study 88% had clinical evidence for circulatory compromise, while 12% did not. This alerts the clinician to the need for potential intervention. This can include loosening of splints or dressings, patient repositioning in the hospital bed to remove mechanical vascular pedicle obstruction, or pharmacologic (leeching) or surgical management if indicated. The patients in whom a false monitor indication occurred did not suffer any complications, such as an unwarranted operative exploration or therapeutic maneuver.
These results demonstrate that QF is extremely sensitive, specific and has a high negative predictive value. In only 12% of patients, a positive test result was found to be false by secondary clinical evaluation. QF is indicated for use in monitoring patients during circulatory or perfusion examinations of skin or when there is a suspicion of compromised circulation. It is safe, effective and reliable. No other perfusion detection method has been found to be as sensitive, specific and with such a certain predictive value. If QF readings rise and fall, the surgeon can sleep soundly.
Statistical Measures of Quantitative Fluorometry
|Positive Predictive Value Arterial and Venous||88%|
|Negative Predictive Value||100%|
|Positive Predictive Value Arterial Insufficiency||92%|
|Positive Predictive Value Venous Insufficiency||85%|
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