Analysis of an implantable venous anastomotic flow coupler: experience in head and neck free flap reconstruction

Abstract

Monitoring microvascular free flaps can present a difficult challenge. This is especially true in cases of buried or intra-oral free flaps. The authors conducted a retrospective review of 19 consecutive free flaps for head and neck reconstruction using a novel monitoring device, which combines a venous anastomotic coupler and an implantable microdoppler (Synovis Micro Companies Alliance Inc., Birmingham, AL, USA). 20 venous anastomoses were performed and monitored with the venous flow coupler device. Monitoring ranged from intra-operatively to postoperative day 7 (mean 4.2 days). Accurate flow signal interpretation was correct in 18 of 20 anastomoses (90%) but only 14 of the 20 coupled anastomoses (70%) were monitored for the complete period of time as desired by the surgeons. All 19 flaps survived. The venous anastomotic flow coupler appears to be a reliable adjunct to free flap monitoring and may help to improve it, with early detection of flap compromise and salvage.

Microvascular tissue transfer has become an integral part of the reconstruction of patients with defects of the head and neck. Although success rates greater than 90% have been reported, the consequences of a failed flap reconstruction can be devastating for the patient. To help prevent these failures and allow for early and successful salvage, various methods of monitoring have been utilized. A novel device has been developed which combines the use of an implantable microvascular venous anastomotic coupler and an internal flow Doppler (Synovis Micro Companies Alliance Inc., Birmingham, AL, USA). The authors present their experience with this novel technology and its application in maxillofacial reconstruction.

Materials and methods

A retrospective review was undertaken of 19 consecutive free flaps for maxillofacial reconstruction using an implantable venous flow coupler from April 2010 through March 2011. This review was approved by the Institutional Review Boards for ethical human research at the University of Maryland and Legacy Emanuel Hospital and Health Center. All flap surgeries were performed by the senior authors (JEL, JFC), at either the University of Maryland Medical Center, Baltimore, MD, USA, or at Legacy Emanuel Hospital and Health Center, Portland, OR, USA. 20 flow couplers were used ranging in sizes from 2 to 3 mm in diameter. The diameter of the flow coupler selected for anastomosis was based on manufacturer availability (2, 2.5 and 3 mm) and correct vessel diameter match. Interpretation of the Doppler sound was evaluated by the senior surgeon and the surgical fellows, residents and nursing staff. The Doppler sound was categorized as good, poor or absent. The venous flap signal was evaluated after completion of the anastomosis intra-operatively and the sound heard was considered the baseline sound for comparison. The sound was verified by occluding the vessel distal to the anastomosis with a microforceps and noting an absence of sound, which returned to baseline when the forceps was released. Accurate venous flow was confirmed using both a manual backflow venous pinch test and a comparison external microdoppler probe. If the signal through the venous flow coupler was deemed to be poor, or a change in sound was noted then clinical assessment of the external skin or muscle monitor was available for further evaluation of flap viability in all but two patients with buried vascularized iliac crest osteomuscular flaps. The arterial Doppler signal was monitored in a standard fashion with audible Doppler signals on the skin paddle or an implantable Doppler probe (Cook-Swartz Doppler, Cook Vascular Inc., Vandergrift, PA, USA) placed around the artery. Flap monitoring was performed using a standard routine and included Doppler signal and clinical assessment every hour for the first 24 h and every 2 h for the next 48 h. The implantable Doppler wire lead was secured to the skin with suture and was removed with gentle pulling or cutting of the wire usually on postoperative day 5 or 6. Follow-up time ranged from 2 to 8 months ( Figs. 1–3 ).

Fig. 1
Flow coupler venous anastomosis: thoracodorsal vein to superficial temporal vein.

Fig. 2
Flow coupler venous anastomosis with monitoring lead secured to the skin.

Fig. 3
Flow coupler monitoring console. Two veins can be monitored through an A and B channel.

Results

20 implantable venous flow couplers were used in 19 consecutive free flaps. There were 11 female and 7 male patients (aged 20–76 years). One patient required two free flaps for the treatment of submucous fibrosis. Another patient required an interpositional vein graft, which involved the placement of two venous flow couplers at both ends of the venous anastomoses. The most common recipient veins used for venous coupler anastomosis were the facial vein (9 flaps) and the external jugular vein (6 flaps). Monitoring of the free flaps ranged from intra-operatively to postoperative day 7. The most common time frame for removal of the coupler lead was between postoperative days 5 and 6 (12 flaps). Four flow coupler leads were removed intra-operatively. Two of the flow couplers had their leads inadvertently pulled at the end of the operation during closure of the wounds. Signal quality was good in these anastomoses until that point in the operation. The other two coupler leads removed intra-operatively were due to vessel kinking which disrupted flow. This was confirmed with the poor to absent flow signal noted following vessel anastomosis. One case involved a technical error involving too much venous length causing the vessel to kink and occlude. The anastomosis was revised using a standard 3 mm vein coupler. The second case was caused by the weight of the wire causing twisting of the venous anastomosis. This was corrected with removal of the lead.

Two other flaps had their wire leads removed early (postoperative days 2 and 3, respectively). Both of these flaps had signal loss due to faulty Doppler equipment failure. The flaps were noted to have excellent perforator external Doppler signals and healthy capillary bleeding on surface scratch test evaluation. The remaining 14 venous flow couplers continued to have correct sound quality up to the time of elective lead removal on postoperative days 5–7. Sound quality through the coupler remained consistent regardless of the diameter size selected. All 19 flaps survived in this study ( Table 1 ).

Table 1
Consecutive free flap reconstruction using an implantable anastomotic venous flow coupler device.
Patient # Diagnosis Flap Coupler diameter Recipient vein
1 Scalp deformity Latissimus 2 mm, 3 mm Cephalic, EJ
2 Osteosarcoma Fibula 2.5 mm EJ
3 Esophageal stricture Radial forearm 2 mm Facial
4 Osteomyelitis Fibula 3 mm EJ
5 Metastatic neck carcinoma Anterolateral thigh 3 mm Facial
6 Ameloblastoma Fibula 2.5 mm EJ
7 Osteoradionecrosis DCIA 2.5 mm EJ
8 SCC tonsil Anterolateral thigh 2 mm IJ
9 BRONJ Scapula 3 mm EJ
10 SCC tongue Anterolateral thigh 2.5 mm Facial
11 Ameloblastoma Fibula 3 mm Retromandibular
12 Ameloblastoma DCIA 2.5 mm AJ
13 SCC retromolar trigone Fibula 3 mm Facial
14 Ameloblastoma Fibula 2.5 mm Facial
15 SCC maxillary gingiva Anterolateral thigh 2 mm Facial
16 Submucous fibrosis Radial forearm 3 mm Facial
Lateral arm 2 mm Facial
17 BCC scalp deformity Latissimus 2.5 mm Superficial temporal
18 Osteomyelitis Fibula 3 mm Facial
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Jan 26, 2018 | Posted by in Oral and Maxillofacial Surgery | Comments Off on Analysis of an implantable venous anastomotic flow coupler: experience in head and neck free flap reconstruction
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