Detection of Free Flap Pedicle Thrombosis By Infrared Surface Temperature Imaging

1. The concise purpose

•To clarify the relationship between the free flap surface temperature change and vascular pedicle thrombosis.

•To develop surface temperature parameter for free flap monitoring.

2. The methods and materials used

- Animal study

•Swine of 15-20 kg was anesthetized by IV pentobarbital

•Pedicle myocuaneous flap of Pectoralis Major, Rectus Abdominis, or Latissimus Dorsi was harvest

•The flap was monitored by IR imaging camera in 2-minute interval; room temperature, and swine core temperature were also recorded

•The flap was left undisturbed for 2 hours after harvesting

•Either the flap artery or vein was clamped for 2 hours then released

•Contralateral skin was recorded as control

- Human study

•Those patients who underwent free flap reconstruction surgery by PS doctor at VGHTPE from 2012/3/1 to 2013/2/28, and only non-buried flap was included.

•Upon arrival to the intensive care unit for postoperative management, free flap temperature (Ts) was monitored by IR imaging camera in 2-minute interval; room temperature (Tr), and human body core temperature (Tc) were also recorded for 24 hours. Simultaneous presence of Doppler signals were also recorded.

3. Experience including number of cases and follow-up

•Total patients of flap with external skin exposure were 21 cases (Male:19 Female:2)

•Average age was 51.9 years-old (19~69)

•20 flaps were for head and neck reconstruction; 1 flap for limb reconstruction. 

•2 of 21 cases suffered from venous thrombosis(9.5%). One flap was total failure (4.7%).

4. Summary of results

• In animal study: Predicted surface temperature with flap pedicle occlusion

   Stabilized flap surface temperature will be Ts = 0.66Tc + 0.40Tr;  R2 = 1.00.  delta T=Ts– predicted stabilized Ts

                                                                

• In the human study: Predicted surface temperature with flap pedicle occlusion

   Stabilized flap surface temperature will be Ts = 0.16Tc + 1.06Tr;  R2 = 0.456.  delta T=Ts– predicted stabilized Ts

5. Conclusions

•Based on our animal and human study, stabilized flap surface temperature after pedicle thrombosis  may be  predicted  simply by core and room temperature, and may be used to predict flap pedicle thrombosis.

•In human study, with patent vascular pedicle, the difference between the flap surface temperature (Ts) and the  predicted one (pred. Ts) had a high specificity to predict flap pedicle thrombosis . However, It needs further study for better interpretation.

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