Free flap monitoring using simultaneous non-invasive laser Doppler flowmetry and tissue spectrophotometry

Postoperative quantitative assessment of reconstructive tissue status in a cutaneous flap model using spatial frequency domain imaging

BACKGROUND

The purpose of this study was to investigate the capabilities of a novel optical wide-field imaging technology known as spatial frequency domain imaging to quantitatively assess reconstructive tissue status.

METHODS

Twenty-two cutaneous pedicle flaps were created on 11 rats based on the inferior epigastric vessels. After baseline measurement, all flaps underwent vascular ischemia, induced by clamping the supporting vessels for 2 hours (either arteriovenous or selective venous occlusions); normal saline was injected into the control flap and hypertonic-hyperoncotic saline solution was injected into the experimental flap. Flaps were monitored for 2 hours after reperfusion. The spatial frequency domain imaging system was used for quantitative assessment of flap status over the duration of the experiment.

RESULTS

All flaps demonstrated a significant decline in oxyhemoglobin and tissue oxygen saturation in response to occlusion. Total hemoglobin and deoxyhemoglobin were increased markedly in the selective venous occlusion group. After reperfusion and the administration of solutions, oxyhemoglobin and tissue oxygen saturation in those flaps that survived gradually returned to baseline levels. However, flaps for which oxyhemoglobin and tissue oxygen saturation did not show any signs of recovery appeared to be compromised and eventually became necrotic within 24 to 48 hours in both occlusion groups.

CONCLUSIONS

Spatial frequency domain imaging technology provides a quantitative, objective method of assessing tissue status. This study demonstrates the potential of this optical technology to assess tissue perfusion in a very precise and quantitative way, enabling wide-field visualization of physiologic parameters. The results of this study suggest that spatial frequency domain imaging may provide a means for prospectively identifying dysfunctional flaps well in advance of failure.

Early detection of complete vascular occlusion in a pedicle flap model using quantitative [corrected] spectral imaging

BACKGROUND

Vascular occlusion after tissue transfer is a devastating complication that can lead to complete flap loss. Spatial frequency domain imaging is a new, noncontact, noninvasive, wide-field imaging technology capable of quantifying oxygenated and deoxygenated hemoglobin levels, total hemoglobin, and tissue saturation.

METHODS

Pedicled fasciocutaneous flaps on Wistar rats (400 to 500 g) were created and underwent continuous imaging using spatial frequency domain imaging before and after selective vascular occlusion. Three flap groups (control, selective arterial occlusion, and selective venous occlusion) and a fourth group composed of native skin between the flaps were measured.

RESULTS

There were no statistically significant differences between the control flap group and the experimental flap groups before selective vascular occlusion: oxyhemoglobin (p=0.2017), deoxyhemoglobin (p=0.3145), total hemoglobin (p=0.2718), and tissue saturation, (p=0.0777). In the selective arterial occlusion flap group, percentage change in total hemoglobin was statistically different from that of the control flap group (p=0.0218). The remaining parameters were not statistically different from those of the control flap: percentage change in oxyhemoglobin (p=0.0888), percentage change in deoxyhemoglobin (p=0.5198), and percentage change in tissue saturation (p=0.4220). The selective venous occlusion flap group demonstrated changes statistically different compared with the control flap group: percentage change in oxyhemoglobin (p=0.0029) and deoxyhemoglobin, total hemoglobin, and tissue saturation (p<0.0001).

CONCLUSIONS

Spatial frequency domain imaging provides two-dimensional, spatially resolved maps of tissue oxyhemoglobin, deoxyhemoglobin, total hemoglobin, and tissue saturation. Results presented here indicate that this can be used to quantify and detect physiologic changes that occur after arterial and venous occlusion in a rodent tissue transfer flap model. This portable, noncontact, noninvasive device may have a high clinical applicability in monitoring postoperative patients.

Early experience with fluorescent angiography in free-tissue transfer reconstruction

BACKGROUND

Soft-tissue and bony reconstruction with free-tissue transfer is one of the most versatile tools available to the reconstructive surgeon. Determination of flap perfusion and early detection of vascular compromise with prompt correction remain critical in free-tissue transfer success. The aim of this report is to describe the utility of laser-assisted indocyanine green fluorescent dye angiography in free-tissue transfer reconstruction.

METHODS

From October of 2007 to March of 2008, 27 nonrandomized, nonconsecutive patients underwent surgical free flaps in conjunction with intraoperative Novadaq SPY fluorescent angiography.

RESULTS

Twenty-seven patients underwent 29 free-tissue transfers. There was one partial flap loss in this group requiring operative revision. No complications attributable to indocyanine green fluorescent dye administration were noted. Imaging procedures (including dye administration) added minimal additional time to the operative time and anesthesia, and assisted in intraoperative decision-making.

CONCLUSIONS

Novadaq's SPY fluorescent angiography system provides simple and efficient intraoperative real-time surface angiographic imaging. This technology places control of vascular anastomosis evaluation and flap perfusion in the hands of the surgeon intraoperatively in a visual manner that is easy to use and is helpful in surgical decision-making.

Endoscopic measurements of free-flap perfusion in the head and neck region using red-excited Indocyanine Green: preliminary results

BACKGROUND

Free-tissue transfer has become a standard procedure for reconstructive surgery in the head and neck area. Flap failures are relatively rare (<or=5%), and a high percentage can be salvaged if detected early. Indocyanine Green (ICG) angiography might be able to improve the detection of flap malperfusion at an early stage.

METHODS

So far, 11 patients with free-flap reconstructions of the upper aerodigestive tract (UADT) have participated in this study. Each participant underwent three endoscopic ICG angiographies (24h intra-operatively and 72h postoperatively). The data obtained were evaluated online as well as offline on a personal computer (PC), and the results compared to the clinical outcome.

RESULTS

There were no partial or complete flap losses. One flap was successfully salvaged following initial arterial kinking with impeded perfusion. The ICG fluorescence angiography was tolerated well in all patients. The free flaps showed a delayed yet equal ICG fluorescence as compared to the surrounding tissue. The timing and slope of fluorescence build-up were dependent on circulatory factors. The relative fluorescence maxima of flap versus surrounding were 33% in the initially failing flap and >or=64% for all other examinations.

CONCLUSIONS

It was possible to prove the feasibility of endoscopic ICG fluorescence angiography in patients undergoing free-flap transfer to the UADT. The method provides instant information about the perfusion state of the tissue and is easily performed without greater patient discomfort or risk of side effects. Due to the endoscopic approach, the method seems highly promising for this indication and merits further evaluation.

Capillary blood gas: a novel means of assessing free flap perfusion in an animal model

OBJECTIVE

To demonstrate that in comparison to implantable O(2) microelectrodes, capillary blood gas measurements represent a reliable, accessible, and easy method of identifying failing free flaps.

STUDY DESIGN

Groin fasciocutaneous flaps were elevated in 10 rats and following venous occlusion, O(2) microelectrode measurements (pO(2) and flow), and capillary blood gas measurements (pO(2), pCO(2), pH, HCO(3)) were obtained at 10-minute intervals.

RESULTS

Measurements with capillary blood gas paralleled measurements with O(2) microelectrodes. Average capillary blood gas pO(2) fell from 42.71 to 31.57 mm Hg at 10 minutes and then to 28.67 mm Hg at 20 minutes. Average pH fell from 7.38 to 7.33 at 10 minutes and to 7.30 at 20 minutes. Results were statistically significant with both the paired Student's t test and the Wilcoxon signed rank test.

CONCLUSION

While providing users an ability to simultaneously monitor accepted modalities of flap surveillance, pH and pO(2), capillary blood gas is a reliable, accessible, and reproducible marker of flap health.

Early reintervention of compromised free flaps improves success rate

INTRODUCTION AND AIM

To develop a protocolized monitor schedule in microvascular free flap reconstruction, we investigated a possible correlation between the outcome and the interval between clamp release and start of revision.

MATERIALS AND METHODS

All the charts of patients treated between 2000 and 2006 with a free flap were evaluated. The patients who underwent a flap revision were further analyzed.

RESULTS

A total of 608 free flaps were evaluated; 69 of these flaps were revised. Most vascular complications took place within the first 24 h; the latest complication was observed 8 days after surgery. After 6 days post surgery, the number of revisions decreased considerably. With regard to the salvaged flaps the mean time to start the revision was 46.5 h (SD 39). With regard to the failed revisions, the mean time to start the revision was 82.0 h (SD 47). This difference proved significant (P = 0.006).

CONCLUSION

Our data shows that the majority of anastomotic failures occur within the first 24 h. Thereafter, the frequency of failures decreases. We also found that the time between initial reconstruction and start of the salvage procedure influences the outcome of the revision negatively.

Continuous postoperative monitoring of cutaneous free flaps using near infrared spectroscopy

Reliable detection of circulatory compromise threatening free-flap viability is essential for prompt surgical intervention and flap salvage. Numerous techniques have been developed to address the issue of postoperative flap monitoring but none have achieved universal acceptance. Near infrared spectroscopy (NIRS) is a noninvasive technique that allows continuous monitoring of tissue oxygenation and perfusion. It is increasingly recognised to be a reliable method for flap viability assessment. This study was designed to investigate the ability of NIRS to detect and identify microvascular thrombosis endangering flap survival. To our knowledge, this is the first clinical evaluation of NIRS used for continuous monitoring of free flaps.

METHODS

Fifty flaps used for autologous breast reconstruction in 48 patients were included in this prospective clinical study. NIRS was employed for 72-h continuous postoperative monitoring. The data were compared to findings of clinical assessments.

RESULTS

Ten flaps (20%) developed 13 anastomosis thromboses (two arterial and 11 venous). NIRS detected all cases of flow failure prior to clinical observation with no false positives or negatives. Based on consistent patterns of NIRS parameter changes, it was possible to differentiate between changes caused by arterial and venous thrombosis with accuracy before surgical re-exploration. The salvage rate was 70%. Overall flap viability was 94%.

CONCLUSIONS

Continuous NIRS monitoring can reliably detect and identify early stages of arterial and venous thrombosis, and is a credible method for noninvasive postoperative flap surveillance. Based on these findings, we advocate its use for monitoring of flaps with a cutaneous component.

Palmar microcirculation does not deteriorate 2 years after radial artery harvesting—implications for reconstructive free forearm flap transfer

BACKGROUND

The functional consequences after radial artery-based forearm flaps for hand microcirculation remain unclear. We hypothesized that palmar microcirculation is compromised after radial artery removal in arteriosclerotic patients.

MATERIALS AND METHODS

A total number of 114 patients were included undergoing elective coronary revascularization using the radial artery of the nondominant forearm with non-pathological Allen's test. Palmar microcirculatory mapping with 1596 measurements was applied 2 years after removal of the radial artery regarding capillary flow, finger tip oxygenation, as well as postcapillary venous filling pressures throughout both hands using combined noninvasive real-time laser Doppler flowmetry and spectrophotometry.

RESULTS

Only 2/56 positions revealed a difference beyond a 5% threshold 25 +/- 5 months after radial artery removal. Superficial capillary blood flow decreased by 13% at the hypothenar eminence (242.0 +/- 153.6 vs 275.6 +/- 169.2, p = 0.009). Deep postcapillary venous filling pressure (8 mm) was significantly increased by 9% only at the fingertip of the fifth finger (112.4 +/- 49.7 vs 103.0 +/- 25.0, p = 0.033). No clinical signs of malperfusion were found after radial artery removal, and no patient was impaired in his daily palmar motor activity.

CONCLUSIONS

Pedicled removal of the radial artery does not compromise superficial or deep palmar capillary blood flow, finger tip oxygenation, or postcapillary venous filling pressures in a long-term perspective in arteriosclerotic patients. No clinical relevant signs of malperfusion or any deterioration of palmar motor function was encountered. The blood flow via the ulnar artery and the interosseal artery compensates palmar perfusion without microcirculatory deterioration even more than 2 years after removal of the radial artery.

Microvascular breast reconstruction pedicle thrombosis: How long can we wait?

Re-exploration plays a key role in salvaging vascularly compromised free flaps. A retrospective review of 290 free flaps in breast reconstruction was performed to determine whether the time delay between thrombosis detection and surgical re-exploration had any effect on flap salvage. Overall flap success was 97.6%. Postoperative thrombosis requiring re-exploration was documented in 6.2% cases. Fifty-five percent of take-back flaps were salvaged and 45% were lost. The median time between detection of flap compromise to surgical incision was 128 min in our saved flaps, and 228 min in the lost flap group. Our preliminary data suggests that re-exploration within 188 min may improve flap salvage.

Blood Perfusion of the Free Anterolateral Thigh Perforator Flap: Its Beneficial Effect in the Reconstruction of Infected Wounds in the Lower Extremity

BACKGROUND

In a prospective study, we evaluated the blood perfusion and the blood flow of anterolateral thigh (ALT) flap by both near-infrared spectroscopy and color Doppler ultrasonography. Moreover, we assessed the ability of the perforator flap to reconstruct infected wounds of the lower extremity in 11 patients.

METHODS

Near-infrared spectroscopy showed excellent oxygen saturation, and Doppler ultrasonography documented excellent blood flow and decreased vascular resistance in the ALT flap postoperatively.

RESULTS

All flaps were successful and all wounds healed uneventfully within 2 weeks without any signs of recurrences or persistent infection. All patients achieved acceptable gait function after rehabilitation.

CONCLUSIONS

Apart from the mandatory role of thorough debridement, our results indicate that the ALT flap offers rich blood supply to the recipient area, thus contributing to the sterilization and healing of an infected wound within a short time period.

Direct microvascular monitoring of a free autologous jejunal flap using microendoscopy: a case report

Background

Early identification of flap failure is an indispensable prerequisite for flap salvage. Although many technical developments of free flap monitoring have now reached clinical application, very few are considered to be reliable and non-invasive for early recognition of flap failure.

Case presentation

We used microendoscopic technique for microvascular monitoring of free autologous jejunal flap by the direct visualisation of the flow of erythrocytes through the capillary vasculature on both the mucosal and serosal surfaces.

Blood flow was seen to be pulsatile, with individual erythrocytes visible in the capillaries. The best view was obtained when the scope was focussed directly on the capillary rather than the graft surface. The view of the unstained mucosal surface was bland apart from the fine capillary loops which were seen to fill with each pulsatile event. The microendoscopic examination of the serosal surface revealed much larger calibre vessels with obvious blood flow.

Conclusion

The microendoscopic monitoring technique is simple and safe with direct visualisation of blood flow. The technique may also be useful for the monitoring of other free bowel transplants.