Technique

The electrode is typically mounted on a silicone cuff, which is wrapped gently but snugly around the venous pedicle ( Fig. 1 ), and a thin wire connects the probe to the external monitor ( Fig. 2 ). The Doppler probe produces a pulsatile sound when attached to the artery and a venous hum when attached to the vein. The monitoring system is designed to be used for 5 to 10 days, after which the electrode is detached from the silicone cuff with minimal tension by pulling on the externalized wire.

The electrode is typically mounted on a silicone cuff, which is wrapped gently but snugly around the venous pedicle.

A thin wire connects the implantable Doppler probe to the external monitor.

Indications and settings for the implantable Doppler

The use of the implantable Doppler has been described by numerous investigators in a variety of settings, including reconstruction of the head and neck, breast, and extremities. Guillemaud and colleagues published one of the largest series on head and neck free flaps, mostly for oncologic defects, monitored via the implantable Doppler. In the retrospective series of 351 patients, the investigators found that a change in the Doppler signal increased the salvage rates from 61.5% to 92.0%, when compared with flaps in which no vascular complication was detected. The investigators attributed failures in detection to their choice of arterial monitoring.

A more recent retrospective review by Paydar and colleagues of 169 consecutive free flaps for head and neck reconstruction also found a high overall salvage rate of 94.7%. Of the 19 flaps (4 buried flaps) that had changes in Doppler signals, the only flap failure occurred in 1 of the buried flaps. In contrast with Guillemaud and colleagues, Paydar and colleagues used the implantable Doppler to monitor venous flow, with a sensitivity and specificity of 100% and 98.7%, respectively. None of the false-positive results required operative exploration after correlation with clinical examination, and there were no complications attributable to use of the implantable Doppler.

The implantable Doppler has also demonstrated applications in breast reconstruction. Rozen and colleagues recently published their experience with 527 consecutive patients who underwent breast reconstruction using free tissue transfer, including deep inferior epigastric perforator, superficial inferior epigastric artery, and superior gluteal artery perforator. The investigators compared the efficacy of clinical monitoring in the first 426 patients with that of monitoring using the implantable Doppler in the subsequent 121 patients, with salvage rates of 66% and 80%, respectively. Although this difference was not significant, the investigators’ meta-analysis of related literature showed a significant improvement in salvage rates associated with the use of this device. Smit and colleagues similarly reviewed 121 microvascular breast reconstructions retrospectively, all of which were monitored with implantable venous Doppler probes. A total of 14 flaps required salvage efforts, with an overall false-positive rate of 6.7% and a false-negative rate of 0%.

Whereas nonburied flaps can be monitored with a combination of clinical observation and implantable Doppler, buried flaps pose a particular challenge in postoperative care. In a retrospective review of 750 free flaps monitored only with conventional techniques, Disa and colleagues reported that buried flaps had a significantly lower salvage rate of 0% compared with 77% for nonburied flaps. This result was associated with a significantly higher failure rate in buried flaps, 6.5% when compared with 1.8% in nonburied flaps. Unsurprisingly, the implantable Doppler has been used to monitor buried free flaps for head and neck, as well as for breast reconstruction. Rozen and colleagues published a unique series of 8 patients who underwent microvascular breast reconstruction using completely buried flaps; the investigators suggested that the implantable venous Doppler allows for the expanded use of such techniques.

Indications and settings for the implantable Doppler

The use of the implantable Doppler has been described by numerous investigators in a variety of settings, including reconstruction of the head and neck, breast, and extremities. Guillemaud and colleagues published one of the largest series on head and neck free flaps, mostly for oncologic defects, monitored via the implantable Doppler. In the retrospective series of 351 patients, the investigators found that a change in the Doppler signal increased the salvage rates from 61.5% to 92.0%, when compared with flaps in which no vascular complication was detected. The investigators attributed failures in detection to their choice of arterial monitoring.

A more recent retrospective review by Paydar and colleagues of 169 consecutive free flaps for head and neck reconstruction also found a high overall salvage rate of 94.7%. Of the 19 flaps (4 buried flaps) that had changes in Doppler signals, the only flap failure occurred in 1 of the buried flaps. In contrast with Guillemaud and colleagues, Paydar and colleagues used the implantable Doppler to monitor venous flow, with a sensitivity and specificity of 100% and 98.7%, respectively. None of the false-positive results required operative exploration after correlation with clinical examination, and there were no complications attributable to use of the implantable Doppler.

The implantable Doppler has also demonstrated applications in breast reconstruction. Rozen and colleagues recently published their experience with 527 consecutive patients who underwent breast reconstruction using free tissue transfer, including deep inferior epigastric perforator, superficial inferior epigastric artery, and superior gluteal artery perforator. The investigators compared the efficacy of clinical monitoring in the first 426 patients with that of monitoring using the implantable Doppler in the subsequent 121 patients, with salvage rates of 66% and 80%, respectively. Although this difference was not significant, the investigators’ meta-analysis of related literature showed a significant improvement in salvage rates associated with the use of this device. Smit and colleagues similarly reviewed 121 microvascular breast reconstructions retrospectively, all of which were monitored with implantable venous Doppler probes. A total of 14 flaps required salvage efforts, with an overall false-positive rate of 6.7% and a false-negative rate of 0%.

Whereas nonburied flaps can be monitored with a combination of clinical observation and implantable Doppler, buried flaps pose a particular challenge in postoperative care. In a retrospective review of 750 free flaps monitored only with conventional techniques, Disa and colleagues reported that buried flaps had a significantly lower salvage rate of 0% compared with 77% for nonburied flaps. This result was associated with a significantly higher failure rate in buried flaps, 6.5% when compared with 1.8% in nonburied flaps. Unsurprisingly, the implantable Doppler has been used to monitor buried free flaps for head and neck, as well as for breast reconstruction. Rozen and colleagues published a unique series of 8 patients who underwent microvascular breast reconstruction using completely buried flaps; the investigators suggested that the implantable venous Doppler allows for the expanded use of such techniques.