Noninvasive Microcirculatory Flap Monitoring or Implantable Doppler Probes: only an Adjunct to Clinical Assessment for Reconstructive Microsurgery?

I read with great interest the recent work by Drs. Kind and Oliva, who mentioned the cautious interpretation of Doppler signals from implantable Doppler probes on the internal mammary artery.[1] The authors have a thorough expertise with the implantable Doppler probes. However, they observed false-negative Doppler signals with the use of the Doppler probe on the internal mammary vein. This is based on two cases, a 47-year-old woman and a 53-year-old woman who underwent reconstructive microsurgery for breast augmentation. Both patients were taken to the operating room based on a pale skin paddle in one case and a congested skin paddle in the other. Intraoperatively, an arterial thrombosis was found requiring thrombectomy followed by an interpositioned vein graft in one case and a venous thrombosis requiring thrombectomy and a vein graft in the other. The authors speculate that the thoracic cavity has influenced the false-negative result.

Given these observations, the authors based their decision for re-exploration on the clinical appearance of the skin paddle. Therefore, the need for the clinical inspection and palpation of the transferred free flap is mandatory and strengthened. A recent analysis among 1142 free-flap procedures performed from January 2002 to June 2003 with 113 flaps (9.9%) receiving reexploration mentioned their algorithm for flap monitoring.[2] All patients were cared for in the microsurgical intensive care unit for 5 days. Flap monitoring is performed in the clinic just cited by a team of specially trained nurses who perform hourly checks of flap color, capillary refill, turgor, and temperature. Pinprick testing and evaluation of vascular flow by handheld Doppler ultrasonography devices are performed when a flap is clinically suspected of compromise. The protocol for assessment of free flaps and indications for operative exploration were initiated and have been in use for > 17 years. Each patient who presents with clinically suspected flap compromise is evaluated by a senior resident, who in consultation with an attending physician makes the decision to take the patient to the operating room for reexploration.

A large retrospective analysis of more than 956 free-flap operations in 38 months found the implantable Doppler probe with a 100% sensitivity rate but with a high (88%) false-positive rate.[3] The authors suggested confirming the implantable Doppler findings with color duplex sonography. Furthermore, noninvasive microcirculatory monitoring of free flaps might be appropriate as an adjunct to clinical monitoring of the flap. Several distinct techniques have been published. As such, use of near-infrared spectroscopy has been reported for 30 patients undergoing autologous tissue perforator free-flap breast reconstruction with continuous monitoring of the flap.[4] Tissue oxygenation was determined in this study. Combinations of near-infrared spectroscopy and color-coded duplex sonography have been reported for pedicled traverse rectus abdominus musculocutaneous (TRAM) flaps.[5] In contrast, laser Doppler flowmetry has been reported for flap monitoring, such as for free-TRAM transfer, recently[6] as well as 15 years ago.[7]

The combination of both laser Doppler assessing capillary blood flow and spectroscopy assessing tissue oxygenation and postcapillary venous filling pressures have been applied for flap monitoring in free radial forearm flaps for facial reconstruction[8] as well as for buried flap monitoring following periorbital augmentation.[9]

In my view, however, these measures are currently only an adjunct to the clinical assessment of a free flap to guide the reconstructive microsurgeon. Prospective randomized controlled trials are key to elucidate whether these adjunct measures of flap monitoring, albeit encouraging, really change the surgical outcome when added to the clinical assessment of the flaps.

REFERENCES

• 1 Kind G B, Oliva A. Caution with regard to use of implantable Doppler probe on the internal mammary vein.  J Reconstr Microsurg. 2008;  24 71-72
• 2 Chen K T, Mardini S, Chuang D C et al.. Timing and presentation of the first signs of vascular compromise dictates the salvage outcome of free flap transfers.  Plast Reconstr Surg. 2007;  120 187-195
• 3 Rosenberg J J, Fornage B D, Chevray P M. Monitoring buried free flaps: limitations of the implantable Doppler and use of color duplex sonography as a confirmatory test.  Plast Reconstr Surg. 2006;  118 109-113
• 4 Keller A. Noninvasive tissue oximetry for flap monitoring: an initial study.  J Reconstr Microsurg. 2007;  23 189-197
• 5 Scheufler O, Exner K, Andresen R. Investigation of TRAM flap oxygenation and perfusion by near-infrared reflection spectroscopy and color-coded duplex sonography.  Plast Reconstr Surg. 2004;  113 141-152
• 6 Booi D I, Debats I B, Boeckx W D, van der Hulst R R. A study of perfusion of the distal free-TRAM flap using laser Doppler flowmetry.  J Plast Reconstr Aesthet Surg. 2008;  61 282-288
• 7 Tuominen H P, Asko-Seljavaara S, Svartling N E. Cutaneous blood flow in the free TRAM flap.  Br J Plast Surg. 1993;  46 665-669
• 8 Hölzle F, Loeffelbein D J, Nolte D, Wolff K D. Free flap monitoring using simultaneous non-invasive laser Doppler flowmetry and tissue spectrophotometry.  J Craniomaxillofac Surg. 2006;  34 25-33
• 9 Knobloch K, Gohritz A, Vogt P M. Noninvasive monitoring of microcirculatory perfusion and oxygenation in subcutaneous microsurgical flaps.  J Reconstr Microsurg. 2008;  , Epub ahead of print