TTP (time to PEAK) and RBV (regional blood volume) as valuable parameters to detect early flap failure

Abstract

Background: Free flap transplantation is used more and more frequently in order to cover extensive wound defects. The basic prerequisite for successful flap salvage after flap failure is a short time interval from failure until revision. For this reason many different flap monitoring systems have been tested over the last years. Objective: The aim of the experiment was to detect critical capillary perfusion using contrast enhanced ultrasound. Quantitative analysis should be performed by a special perfusion software (QONTRAST®; Bracco, Italy) appraising digital raw data of contrast enhanced ultrasound (CEUS). Additionally diverse risk factors for free flap transplantation were determined. Methods: Thirty-one patients were examined after free flap transplantation during the first 72 hours after operation. CEUS was performed with a linear transducer (6–9 MHz, LOGIQ E9/GE) and a bolus injection of 2.4 ml of contrast agent (SonoVue®, Bracco, Italy). Operation and examination were performed by either an experienced plastic surgeon or an experienced ultrasound examiner. Depth dependent capillary perfusion was analysed and quantitative perfusions analysis was performed using the perfusions software QONTRAST® (Bracco, Italy). Eleven revisions had to be performed: 7 due to haematoma and 4 due to superficial necrosis. Results: Reduced capillary perfusion was seen in all 11 complications using CEUS. Significant difference comparing the no complication and the complication group was observed using TTP (time to PEAK) and RBV (regional blood volume) quantitative analysis. Mean RBV was 922.1 ± 150.9 in the no complication and 303.0 ± 53.9 in the complication group (p = 0.001). Mean TTP was 37.6 ± 3.8 in the no complication and 21.3 ± 3.4 in the complication group (p = 0.006). Tendency to higher complication rate was seen in older male patients with vascular or malignant primary disease. Conclusion: In this clinical trial, capillary perfusion after free flap transplantation as well as detection of vascular complications was demonstrated using CEUS. Quantitative perfusions analysis could be performed and flap viability could be assessed easily.