Current Evidence for Postoperative Monitoring of Microvascular Free Flaps: A Systematic Review

Cook-Swartz Doppler Probe Surveillance for Free Flaps-Defining Pros and Cons

Introduction  The main postoperative complication of free flaps is perfusion compromise. Urgent intervention is critical to increase the chances of flap survival. Invasive flap perfusion monitoring with direct blood flow feedback through the Cook–Swartz Doppler probe could enable earlier detection of perfusion complications.

Materials and Methods  Between 2012 and 2016, 35 patients underwent breast reconstruction or defect coverage after trauma with a deep inferior epigastric perforator, anterolateral thigh, transverse musculocutaneous gracilis, gracilis, or latissimus dorsi flap in our department. All flaps were monitored with a Cook–Swartz probe for 10 days postoperatively. The 20 MHz probe was placed around the arterial–venous anastomosis. A flap monitoring protocol was established for standardized surveillance of postoperative perfusion. In the event of probe signal loss, immediate surgical revision was initiated.

Results  Signal loss was detected in 8 of the 35 cases. On return to the operating room, six were found to be true positives (relevant disruption of flap perfusion) and two were false positives (due to Doppler probe displacement). There were also two false negatives, resulting in a slowly progressive partial flap loss. Flap perfusion was restored in three of the six cases (50%) identified by the probe. Following surgical intervention, three of the six cases had persistent problems with perfusion, resulting in two total flap losses and one partial flap necrosis leading to an overall 5.7% total flap loss.

Conclusion  Postoperative flap perfusion surveillance is a complex matter. Surgical experience is often helpful but not always reliable. The costs, false-positive, and false-negative rates associated with invasive perfusion monitoring with Cook–Swartz probe make it most appropriate for buried flaps.

Level of Evidence  This is an original work.

Real-time optical vascular imaging: a method to assess the microvascular circulation of myofascial free flaps used in the head and neck region

Microvascular free flaps are considered the gold standard in head and neck reconstructive surgery. Myofascial flaps, in particular, are useful in certain oral and maxillofacial reconstruction cases, where mucosal regeneration over the transplanted tissue is planned. Despite high success rates, 1-6% of free flaps fail. A plethora of methods are available to assess transplanted tissue viability after reconstruction, including clinical observational monitoring, surface Doppler, implantable Doppler probe, colour Doppler sonography, laser Doppler flowmeter, surface temperature and indocyanine green angiography. However, no method has demonstrated adequate reliability or has proven to be cost-effective. The authors tested a technique called real-time optical vascular imaging to evaluate the microvascular circulation of myofascial free flaps. This technique was develop at Guy's Hospital, London to observe the microvascular anatomy of the oral cavity in vivo, non-invasively and without the need for patient preparation, with the aim of detecting and monitoring oral diseases. This technology detects the red blood cells flowing inside the microvasculature at a depth of approximately 2mm, allowing the microvascular architecture and blood flow to be determined. This study showed that RTOVI may prove to be beneficial for the early detection of vascular compromise due to its immediacy and the feasibility of assessing multiple graft tissue regions.

Retrospective evaluation of diagnostic accuracy of free flap monitoring with the Cook-Swartz-Doppler probe in head and neck reconstruction

The Cook-Swartz-Doppler probe is an easy to handle and reliable tool for free flap monitoring. In the head and neck region different confounders can affect the read out. We therefore analyzed the use of the Doppler probe regarding these potential difficulties and to compare the diagnostic accuracy in arterial or venous monitoring of free flaps in the head and neck region. A retrospective study was performed in which all patients were included who underwent free flap surgery in the head and neck region in the Department of Plastic Surgery and the Department of Maxillofacial Surgery of our institution between 2010 and 2018 and were monitored with an implanted Doppler probe. 147 free tissue transfers were included. No significance was found for arterial and venous placement of the Doppler probe for sensitivity (artery 83.3%; vein 84.6%; p = 0.87), specificity (artery 89.2%; vein 96.1%; p = 0.17) and negative predictive value (artery 96.7%; vein 94.2%; p = 0.55). A better positive predictive value for placing the Doppler probe around the artery (82.7%) than the vein (61.1%) was found in our study (p = 0.056). The better positive predictive value in arterial monitoring suggests that this is the more reliable measuring method to assess flap perfusion in the head and neck region.

Use of infrared thermography for the assessment of free flap perforators in autologous breast reconstruction: A systematic review

Perforator-based flaps have in recent years become the mainstay of autologous breast reconstruction practice. Imaging modalities ranging from Doppler ultrasound to CT angiography demonstrate varying utility in the preoperative identification and localisation of perforators. Despite these available radiological investigations, finding and quantitatively assessing perforators remain a time-consuming and tedious process that is often complicated by a number of factors including variable anatomy prior surgery and body habitus. Thermographic imaging shows promise as a novel modality for preoperative localisation of perforator vessels. This review summarises the currently available evidence for its application in perforator mapping for abdominal-based autologous breast reconstruction. We discuss the development of the technology over the years, its current use, its advantages and how it may impact on reconstructive breast surgery.

Intraosseous microdialysis for bone free flap monitoring in head and neck reconstructive surgery: A prospective pilot study

BACKGROUND

Although some researchers have positioned microdialysis catheters in the soft tissue surrounding bone, the results did not accurately reflect bone metabolism. The present study's objective was to establish the feasibility of microdialysis with a catheter positioned directly in bone.

METHODS

Thirty-four patients (19 males, 15 females; median age: 59) were included in a prospective, nonrandomized clinical trial in the Department of Maxillofacial Surgery at Amiens-Picardie University Hospital (Amiens, France). Fibula or iliac crest free flaps were used in reconstructive head and neck surgery (for cancer, osteoradionecrosis, trauma, or ameloblastoma) and monitored with microdialysis catheters positioned in a hole drilled into the bone. Glucose, lactate, pyruvate, and glycerol concentrations were analyzed for 5 days.

RESULTS

All catheters were positioned successfully, and thrombosis did not occur during the monitoring. In two patients, an increase in the lactate concentration and a glucose level close to 0 were associated with signs of flap necrosis, with removal on Days 9 and 50. In viable flaps, the mean glucose level was 2.02 mmol/L, the mean lactate level was 8.36 mmol/L, and the mean lactate/pyruvate ratio was 53. Forty percent of the glucose values were below 1 mmol/L, and 50% of the lactate/pyruvate ratio values were above 50-suggesting a specific metabolic pattern because these values would be considered as alert values in soft tissue.

CONCLUSION

Monitoring bone free flaps with intraosseous microdialysis is feasible. This technique specifically assesses bone viability, and further studies are now necessary to define the alert values in bone.

Relative Tissue Oxygenation and Temperature Changes for Detecting Early Upper Extremity Skin Ischemia

The authors' purpose was to determine whether there are reliable noninvasive methods of assessing upper extremity ischemia regardless of skin pigmentation. The authors conducted a study of healthy subjects classified based on skin pigmentation using the Fitzpatrick scale, the von Luschan color scale, and self-described race (two Hispanics, three Caucasians, and four African Americans). A surface temperature probe and a near-infrared spectroscopy monitor were placed on the posterior interosseous artery skin territory. Temporary upper limb ischemia was induced by tourniquet insufflation. Readings from both devices were taken at baseline and every 15 seconds for a total of 10 minutes of ischemia. During tourniquet insufflation, the authors found a reliable decrease in tissue oxygenation measured by near-infrared spectroscopy in all subjects and no significant change in temperature readings for any subjects. There was an average decrease of 19 percent in tissue oxygenation using near-infrared spectroscopy, with measurements on average starting at 77 percent and ending at 57 percent. There was no significant difference in the change in near-infrared spectroscopy oxygenation between participants with Fitzpatrick skin types 3, 4, and 5 or when participants were grouped into Fitzpatrick skin type less than or equal to 3 versus greater than 3, or when grouped into Fitzpatrick skin type less than or equal to 4 versus greater than 4. There was also no significant difference in participants grouped into von Luschan scores less than or equal to 20 versus greater than 20. In this healthy subjects study, near-infrared spectroscopy rapidly identified ischemia in all cases, whereas skin surface temperature did not. Near-infrared spectroscopy may be a reliable way of noninvasively monitoring for ischemia regardless of skin pigmentation degree. CLINICAL QUESTION/LEVEL OF EVIDENCE:: Diagnostic, IV.

Evaluation of the Intraoperative Blood Flow of Pedicled Perforator Flaps Using Indocyanine Green-fluorescence Angiography

Although indocyanine-green fluorescence angiography (ICG-FA) has been established as a useful tool to assess perfusion in free tissue transfer, only few studies have applied this modality to pedicled perforator flaps. As both volume and reach of pedicled perforator flaps are limited and tip necrosis often equals complete flap failure, ICG-FA may help to detect hypoperfusion in pedicled flaps.

Methods

In 5 patients, soft tissue reconstruction was achieved with pedicled perforator flaps. ICG-FA was utilized intraoperatively to visualize flap perfusion.

Results

Three pedicled anterolateral thigh flap flaps and 2 propeller flaps were transferred. ICG-FA detected hypoperfusion in 2 flaps. No flap loss occurred; in 2 cases, prolonged wound healing was encountered.

Conclusions

ICG-FA confirmed clinical findings and reliably detected tissue areas with hypoperfusion. A clear cut-off point between nonvital tissue and such that stabilized in the following clinical course could not be found. ICG-FA is a promising technology which could also be used in pedicled perforator flaps.

Anesthesia and Enhanced Recovery After Head and Neck Surgery

Enhanced recovery protocols have been developed from gastrointestinal, colorectal, and thoracic surgery populations. The basic tenets of head and neck enhanced recovery are: a multidisciplinary team working around the patient, preoperative carbohydrate loading, multimodal analgesia, early mobilization and oral feeding, and frequent reassessment and auditing of protocols to improve patient outcomes. The implementation of enhanced recovery protocols across surgical populations appear to decrease length of stay, reduce cost, and improve patient satisfaction without sacrificing patient quality of care or changing readmission rates. This article examines evidence-based enhanced recovery interventions and tailors them to a major head and neck surgery population.

Externalized Mesentery Monitoring of Vascularized Jejunum Transfers

PURPOSE

The use of externalized jejunal monitoring flaps for jejunum transfers could be facilitative for the direct clinical assessment. Although this monitoring method would seem to be highly reliable, we modified this method and used mesentery only as a monitor to make it easy to manage the monitor more.

METHODS

Between 2013 and 2018, 43 patients underwent vascularized jejunum transfer for reconstruction of laryngopharyngectomy using the externalized mesentery monitor. There were 39 men and 4 women, and patient ages ranged from 40 to 80 years (average, 66.6 years). The nursing staff monitored the externalized mesentery by using handheld Doppler ultrasonography every 2 hours for 7 days after surgery.

RESULTS

Three patients had rather weak signal of handheld Doppler ultrasonography on the externalized mesentery monitors during operation, and handheld Doppler ultrasonography could not be applied. Of the remaining 40 patients using the externalized mesentery monitor with handheld Doppler ultrasonography, 39 had an uncomplicated postoperative period. In 1 patient, no signal of Doppler ultrasonography and lack of bleeding by pin prick from the monitor segment were noted in the immediate postoperative period, and revision of the vascular anastomosis was performed. Finally, the graft was salvaged. There was no case of infection in the monitoring flap or hypertrophic scar at the resected part of the flap.

CONCLUSIONS

Using the externalized mesentery monitoring flaps, clinical monitoring by examining the exteriorized monitoring flap is possible, and only mesentery monitors were managed easily compared with jejunum monitoring flaps.

Measuring Flap Oxygen Using Electron Paramagnetic Resonance Oximetry

OBJECTIVES/HYPOTHESIS

To determine if electron paramagnetic resonance (EPR) oximetry is a viable technology to aid in flap monitoring.

STUDY DESIGN

Prospective cohort.

METHODS

This was a cohort study assessing accuracy and speed of EPR oximetry in detecting ischemia of a saphenous artery-based flap in a rat model, using transcutaneous oximetry as a control. Measurements were obtained under both resting and ischemic conditions for nine Sprague Dawley rats (18 flaps), for 3 postoperative days following flap elevation.

RESULTS

The mean partial pressure of oxygen prior to tourniquet application was 66.9 ± 8.9 mm Hg with EPR oximetry and 64.7 ± 5.2 mm Hg with transcutaneous oximetry (P = .45). Mean partial pressures of oxygen during tourniquet application were 8.9 ± 3.2 mm Hg and 8.5 ± 2.9 mm Hg for EPR oximetry and transcutaneous oximetry, respectively (P = .48), and 67.2 ± 6.9 mm Hg and 65.3 ± 6.1 mm Hg after tourniquet release for EPR oximetry and transcutaneous oximetry, respectively (P = .44). The mean ischemia detection time of EPR oximetry was 49 ± 21 seconds.

CONCLUSIONS

Offering timely, accurate, and noninvasive tissue oxygen measurements, EPR oximetry is a promising adjunct in flap monitoring.

LEVEL OF EVIDENCE

NA Laryngoscope, 129:E415-E419, 2019.

Free Flap Reconstruction Monitoring Techniques and Frequency in the Era of Restricted Resident Work Hours

Importance

Free flap reconstruction of the head and neck is routinely performed with success rates around 94% to 99% at most institutions. Despite experience and meticulous technique, there is a small but recognized risk of partial or total flap loss in the postoperative setting. Historically, most microvascular surgeons involve resident house staff in flap monitoring protocols, and programs relied heavily on in-house resident physicians to assure timely intervention for compromised flaps. In 2003, the Accreditation Council for Graduate Medical Education mandated the reduction in the hours a resident could work within a given week. At many institutions this new era of restricted resident duty hours reshaped the protocols used for flap monitoring to adapt to a system with reduced resident labor.

Objectives

To characterize various techniques and frequencies of free flap monitoring by nurses and resident physicians; and to determine if adapted resident monitoring frequency is associated with flap compromise and outcome.

Design, Setting, and Participants

This multi-institutional retrospective review included patients undergoing free flap reconstruction to the head and/or neck between January 2005 and January 2015. Consecutive patients were included from different academic institutions or tertiary referral centers to reflect evolving practices.

Main Outcomes and Measures

Technique, frequency, and personnel for flap monitoring; flap complications; and flap success.

Results

Overall, 1085 patients (343 women [32%] and 742 men [78%]) from 9 institutions were included. Most patients were placed in the intensive care unit postoperatively (n = 790 [73%]), while the remaining were placed in intermediate care (n = 201 [19%]) or in the surgical ward (n = 94 [7%]). Nurses monitored flaps every hour (q1h) for all patients. Frequency of resident monitoring varied, with 635 patients monitored every 4 hours (q4h), 146 monitored every 8 hours (q8h), and 304 monitored every 12 hours (q12h). Monitoring techniques included physical examination (n = 949 [87%]), handheld external Doppler sonography (n = 739 [68%]), implanted Doppler sonography (n = 333 [31%]), and needle stick (n = 349 [32%]); 105 patients (10%) demonstrated flap compromise, prompting return to the operating room in 96 patients. Of these 96 patients, 46 had complete flap salvage, 22 had partial loss, and 37 had complete loss. The frequency of resident flap checks did not affect the total flap loss rate (q4h, 25 patients [4%]; q8h, 8 patients [6%]; and q12h, 8 patients [3%]). Flap salvage rates for compromised flaps were not statistically different.

Conclusions and Relevance

Academic centers rely primarily on q1h flap checks by intensive care unit nurses using physical examination and Doppler sonography. Reduced resident monitoring frequency did not alter flap salvage nor flap outcome. These findings suggest that institutions may successfully monitor free flaps with decreased resident burden.

Critical Ischemia Time, Perfusion, and Drainage Function of Vascularized Lymph Nodes

BACKGROUND

Vascularized lymph node transfer is a promising surgical treatment for lymphedema. This study investigated the effect of ischemia on the lymphatic drainage efficiency of vascularized lymph node flaps and the critical ischemia time of lymph nodes.

METHODS

Twenty-four lymph nodes containing groin flaps in 12 Sprague-Dawley rats were dissected. Clamping of the vascular pedicle was performed for 0, 1, 3, 5, 6, or 7 hours; then, each was allowed to reperfuse by means of the vascular pedicle for 1 hour. Perfusion and ischemic changes were assessed using indocyanine green lymphography; laser Doppler flowmetry; and histologic studies with associated lymphatic vessel endothelial hyaluronan receptor-1, CD68, 4',6-diamidino-2-phenylindole, terminal deoxynucleotidyl transferase-mediated dUTP nick end-labeling, and glutathione assay stains.

RESULTS

The mean latency period of the groin lymph node flaps was 247 ± 67, 83 ± 15, 72 ± 42, 30 ± 18, and 245 ± 85 seconds in the 0-, 1-, 3-, 5-, and 6-hour groups, respectively. Perfusion detected by laser Doppler was 85.2 ± 14.5, 87.2 ± 36.7, 129.8 ± 33.7, 140.4 ± 148.5, 156.1 ± 91.4, and 41.2 ± 34.8 perfusion units at ischemia times of 0, 1, 3, 5, 6, and 7 hours, respectively. Cell damage measured by glutathione was 46.8 ± 10.2, 67.7 ± 14.2, 62.8 ± 15.4, 126.6 ± 5.9, 259.0 ± 70.3, and 109.1 ± 27.5 at ischemia times of 0, 1, 3, 5, 6, and 7 hours, respectively. Histologically, as ischemia time increased, hemorrhage and congestion became more severe.

CONCLUSIONS

The critical ischemia time of vascularized lymph nodes is 5 hours in the rodent animal model, verified by indocyanine green lymphatic fluid uptake, laser Doppler perfusion, and histologic assessments. Interestingly, lymphatic drainage and perfusion of vascularized lymph nodes were improved with an increased ischemia time before the critical 5 hours was reached.

Modern postoperative monitoring of free flaps

PURPOSE OF REVIEW

Flap failure in microvascular reconstruction is a costly complication with total flap loss being the worst-case scenario. With the aim to rapidly identify a postoperative circulatory problem, some susceptible flaps can be saved by careful clinical monitoring or by various technical monitoring methods. In head and neck surgery, where the flaps are often buried and difficult to monitor clinically, a reliable technical monitoring method would be useful. A broad range of different techniques are in use varying according to practical and personal preferences among clinics and surgeons. However, no evidence for any particular technique being superb has emerged. We review reports of some frequently used and modern free flap monitoring techniques.

RECENT FINDINGS

Clinical monitoring is still the gold standard to which other techniques are compared to. Laser Doppler flowmetry and near-infrared spectroscopy have been reported to identify early circulatory problems, but both techniques are not well suited for buried flaps. Implantable Doppler, flow coupler, partial tissue oxygen pressure and microdialysis are invasive monitoring methods suitable for buried flaps.

SUMMARY

More research with practical and clinically relevant parameters, that is flap salvage rate, false positive rate and cost-efficiency are needed before objective comparisons between different monitoring techniques can be made.

Effectiveness of small monitoring skin paddle in free muscle flap for scalp reconstruction

BACKGROUND

Monitoring free muscle flaps with skin grafts is difficult. To intensify the monitoring process for this type of flap, a small skin paddle was included in the flap and analyzed its effects.

METHODS

A retrospective analysis of all patients who underwent scalp reconstruction with a free latissimus dorsi flap and skin graft between 1994 and 2016 was conducted. Flap monitoring was proceeded using a combination of clinical examination and handheld Doppler for both types of flaps.

RESULTS

A total of 71 patients were included in this study and were divided into a study group (skin paddle included; n = 30) and a control group (conventional method; n = 41). The time between initial surgery to pedicle exploration was significantly shorter in the study group (11.3 ± 2.5 vs 79.8 ± 42.6 hours; P = .024). The flap salvage rate was significantly higher in the study group (100% vs 16.7%; P = .048).

CONCLUSION

The efficacy of flap monitoring and flap salvage outcomes were improved by including a small monitoring skin flap.

Face Transplant: Status of Current Supporting Technology to Plan and Perform the Operation and Monitor the Graft in the Postoperative Period

Face transplant has rapidly advanced since the first operation in 2005, and to date, 40 partial or full-face transplants have been performed. The safety and efficacy of this operation are aided at all phases by supporting technologies. These include advanced imaging techniques to plan the operation, devices to monitor the flap in the immediate perioperative period, and noninvasive imaging and serum markers to monitor for acute and chronic rejection. Some of the technologies, such as those used in the immediate perioperative period, have extensive evidence supporting their use, whereas those to detect acute or chronic rejection remain investigational. The technologies of today will continue to evolve and make the operation safer with improved outcomes; however, the most significant barrier for face transplant continues to be immunologic rejection.

Multimodal analysis using flowmeter analysis, laser-Doppler spectrophotometry, and indocyanine green videoangiography for the detection of venous compromise in flaps in rats

Venous congestion results in tissue damage and remains the most common failure of free microvascular transfer if it is not recognized early. The purpose of this experimental study was to evaluate venous congestion and describe the findings with two different monitoring tools. A standardized epigastric flap was raised, and total occlusion of the draining vein was temporarily applied for 4, 5, 6, or 7 h. Blood flow measurements, including laser-Doppler flowmetry, and tissue spectrophotometry (O2C) and indocyanine green (ICG) videoangiography using the FLOW^® 800 tool, were performed systematically after each surgical step, an interval of venous occlusion, and 1 week of clinical observation. Both monitoring tools were capable of detecting acute venous occlusion. ICG videoangiography data showed a significant decrease in the first and second maximum, and the area under the curve, during venous occlusion, whereas hemoglobin levels in the O2C analysis remained stable. Changes in fluorescence values in border areas of the flap correlated significantly with the incidence of necrosis. O2C data later showed significant correlation with the area of necrosis, and more individual changes during flap monitoring. ICG videoangiography might therefore be useful in the prediction of flap necrosis in critical areas of perfusion.

The Effect of Skin Pigmentation on Determination of Limb Ischemia

PURPOSE

Timely identification of tissue ischemia is critical, both in the traumatized limb and following free tissue transfer. The purpose of this study was to determine if skin pigmentation affects the ability to detect limb ischemia.

METHODS

We conducted a study of healthy controls exposed to limb ischemia. The subjects were classified based on skin pigmentation using a defined skin type assessment tool, a visual color scale, and self-description of race. Participants were randomized by limb and tourniquet status; surgeons were blinded to both. Ischemia was induced by tourniquet insufflations, and board-certified orthopedic and plastic surgeons who had completed an accredited hand surgery fellowship conducted physical examinations. The surgeons monitored the forearms at 2, 6, and 10 minutes based on appearance of ischemia, capillary refill, and color in 3 locations on the limbs (posterior interosseous artery flap skin territory, radial forearm flap skin territory, and the digits).

RESULTS

We found a significant decrease in the ability to detect ischemia in participants with increased skin pigmentation, as documented by all metrics, when evaluating the posterior interosseous artery and radial forearm flap skin territories at all time points. For example, when monitoring the posterior interosseous artery flap with the tourniquet insufflated at time 10 minutes, 92.9% of Caucasians were correctly identified as being ischemic whereas only 23.3% of African Americans were correctly identified.

CONCLUSIONS

Skin pigmentation significantly affects the identification of an ischemic limb/skin flaps on physical examination. Whereas the standard treatment for monitoring of free tissue transfer is clinical examination, that may not be sufficient for patients with increased skin pigmentation. Surgeons should exercise particular vigilance during physical examination of a potentially ischemic limb/skin flaps with greater skin pigmentation.

TYPE OF STUDY/LEVEL OF EVIDENCE

Diagnostic II.

Hyperspectral imaging for monitoring of perfusion failure upon microvascular anastomosis in the rat hind limb

BACKGROUND/PURPOSE

Objective, reliable and easy monitoring of microvascular tissue perfusion is a goal that was achieved for many years with limited success. Therefore, a new non-invasive hyperspectral camera system (TIVITA™) was tested for this purpose in an in vivo animal model.

METHODS

Evaluation of tissue oxygenation during ischemia and upon reperfusion was performed in left hind limb in a rat model (n=20). Ischemia was induced by clamping and dissection of the superficial femoral artery. Reperfusion of the limb was achieved by microsurgical anastomosis of the dissected artery. Oxygenation parameters of the hind limb were assessed via TIVITA™ before and immediately after clamping and dissection of the artery, 3 and 30min after reperfusion as well as on postoperative days 1 and 2. Thereby, the non-operated hind limb served as control. As clinical parameters, the refill of the anastomosis as well as the progress of the affected leg were assessed.

RESULTS

In 12 from 20 cases, TIVITA™ recorded a sufficient reperfusion with oxygenation parameters comparable to baseline or control condition. However, in 8 from 20 cases oxygenation was found impaired after reperfusion causing a re-assessment of the microvascular anastomosis. Thereby, technical problems like stenosis or local thrombosis were found in all cases and were surgically treated leading to an increased tissue oxygenation.

CONCLUSIONS

The TIVITA™ camera system is a valid non-invasive tool to assess tissue perfusion after microvascular anastomosis. As it safely shows problems in oxygenation, it allows the clinician a determined revision of the site in time in order to prevent prolonged ischemia.

Perfusion control of a partial revascularized hand via application of Indocyanine green (ICG) and Near-infrared Fluorescence Imaging

BACKGROUND

Intra- and postoperative assessment of perfusion with near-infrared fluorescence imaging is commonly used among plastic surgeons to evaluate the quality of a microsurgical anastomosis in free flaps.

OBJECTIVE

As microsurgical anastomosis can be monitored with near-infrared fluorescence imaging there is potential concerning revascularized fingers and hands with soft tissue depths not exceeding 7 mm above anastomosis. In a case of a severe crush injury of the hand more information about the perfusion was necessary as clinical assessment suspected loss of perfusion.

METHODS

A 49-year old male suffered from a severe crush injury of his left hand with dissection of the ulnar superficial palmar arterial arch and a lesion of median nerve. After revascularization and reconstruction of the nerve, the patient developed postoperatively a loss of perfusion of thumb and index finger. An evaluation of the perfusion status was obtained by fluorescence imaging after intravenous application of ICG.

RESULTS

After intravenous application of ICG the near-infrared imaging showed a delayed but sufficient perfusion of the hand so that a salvage surgery was not indicated.

CONCLUSIONS

In scenarios of critical perfusion in revascularized fingers and hands, the perfusion control via application of ICG and near-infrared fluorescence imaging can be a helpful tool.

Evaluation of Sidestream Darkfield Microscopy for Real-Time Imaging Acellular Dermal Matrix Revascularization

BACKGROUND

Acellular dermal matrices (ADMs) serve as a regenerative framework for host cell integration and collagen deposition to augment the soft tissue envelope in ADM-assisted breast reconstruction-a process dependent on vascular ingrowth. To date noninvasive intra-operative imaging techniques have been inadequate to evaluate the revascularization of ADM.

METHODS

We investigated the safety, feasibility, and efficacy of sidestream darkfield (SDF) microscopy to assess the status of ADM microvascular architecture in 8 patients at the time of tissue expander to permanent implant exchange during 2-stage ADM-assisted breast reconstruction. The SDF microscopy is a handheld device, which can be used intraoperatively for the real-time assessment of ADM blood flow, vessel density, vessel size, and branching pattern. The SDF microscopy was used to assess the microvascular architecture in the center and border zone of the ADM and to compare the native, non-ADM-associated capsule in each patient as a within-subject control.

RESULTS

No incidences of periprosthetic infection, explantation, or adverse events were reported after SDF image acquisition. Native capsules demonstrate a complex, layered architecture with an average vessel area density of 14.9 mm/mm and total vessel length density of 12.3 mm/mm. In contrast to native periprosthetic capsules, ADM-associated capsules are not uniformly vascularized structures and demonstrate 2 zones of microvascular architecture. The ADM and native capsule border zone demonstrates palisading peripheral vascular arcades with continuous antegrade flow. The central zone of the ADM demonstrates punctate perforating vascular plexi with intermittent, sluggish flow, and intervening 2- to 3-cm watershed zones.

CONCLUSIONS

Sidestream darkfield microscopy allows for real-time intraoperative assessment of ADM revascularization and serves as a potential methodology to compare revascularization parameters among commercially available ADMs. Thr SDF microscopy demonstrates that the periprosthetic capsule in ADM-assisted implant-based breast reconstruction is not a uniformly vascularized structure.

Implantable Doppler monitoring of buried free flaps during vascularized lymph node transfer

BACKGROUND AND OBJECTIVES

Reliable flap monitoring is crucial to the success of free tissue transfer, including vascularized lymph node transfer (VLNT). However, no large-scale study has examined implantable Doppler monitoring in VLNT. We aimed to determine whether an implantable Doppler system can reliably monitor flap perfusion during VLNT and also to calculate the sensitivity and specificity of this system for detecting compromise in the monitored vessel.

METHODS

An analysis of prospectively collected data of patients who underwent buried VLNT with implantable Doppler monitoring between 2014 and 2015 was performed.

RESULTS

A consecutive series of 100 patients underwent VLNT with implantable Doppler monitoring. Five cases required return to the operating room for flap exploration due to a change in Doppler signal quality. All compromised flaps were salvaged. The sensitivity of the implantable Doppler system for flap monitoring was 100%, the specificity was 97.9%, the positive predictive value was 60%, and the negative predictive value was 100%. The false-positive rate was 2%.

CONCLUSIONS

This is the largest reported series of implantable Doppler monitoring of free flap perfusion during VLNT. Our experience suggests that this is a safe and effective technique for postoperative monitoring of VLNT.

Implantable Doppler Probes for Postoperatively Monitoring Free Flaps: Efficacy. A Systematic Review and Meta-analysis

Background:

Although clinical assessment remains the gold standard for monitoring the circulation of free flaps, several adjunct techniques promote timely salvage by detecting circulation compromise early. The objective of this systematic review was to evaluate the efficacy of an implantable Doppler probe for postoperatively monitoring free flaps.

Materials and Methods:

English-language articles evaluating the efficacy of implantable Doppler probes compared with clinical assessment for postoperatively monitoring free flaps were analyzed. The outcome measures were total flap failure rates, salvage rates, sensitivity, false-positive rates, and positive likelihood ratios.

Results:

Of the 504 citations identified, 6 comparative studies were included for meta-analysis. An implantable Doppler probe significantly lowered the flap failure rate (risk ratio: 0.40; 95% confidence interval: 0.21–0.75) and raised the successful salvage rate (risk ratio: 1.73; 95% confidence interval: 1.16–2.59). Pooled sensitivity was higher (1.00 vs 0.98), the positive likelihood ratio was lower (72.16 vs 220.48), and the false-positive rate was higher (0.01 vs 0) in the implantable Doppler probe group than in the clinical assessment group.

Conclusion:

An implantable Doppler probe is significantly more efficacious than clinical assessment for postoperatively monitoring free flaps.

The medial femoral trochlea flap with a monitor skin island-Report of two cases

In this report, we present two cases of the bony reconstruction with the medial trochlea (MFT) flap including a skin island that was used to monitor the perfusion of flap in the postoperative period. Between March 2013 and April 2015, we performed surgery on two patients who suffered from scaphoid and talus non-union after trauma and initial treatment by osteosynthesis. A skin island (1 cm × 1 cm and 3 cm × 1 cm, respectively) was included with the osseous flap (1.6 cm × 1 cm × 1 cm and 2 cm × 3 cm × 2 cm, respectively) to assess the perfusion of the flap. The design of the skin island was based on either the saphenous artery perforator or a cutaneous perforator of the descending genicular artery. Both flaps remained viable throughout the postoperative period, and there were no donor site complications. After a follow-up of 36 and 11 months, bony union was observed in both patients with a high degree of satisfaction. Thus, a MFT flap with a skin island could be a tool to assess the perfusion of the flap in the early postoperative period. © 2016 Wiley Periodicals, Inc. Microsurgery 37:431-435, 2017.

What Are the Optimal Monitoring Techniques in Head and Neck Microvascular Reconstruction?

PURPOSE

We evaluated the outcomes for widely used systems in terms of accuracy, salvage rates, and added cost compared to conventional monitoring.

METHODS

We performed a narrative review of the literature (high-impact report).

RESULTS

The overall free flap success for head and neck reconstruction is at least 95% using any type of monitoring. Salvage rates in decreasing frequency of monitoring techniques are 85% with near-infrared spectroscopy (NIRS), 81% with implantable Doppler, and 61.5% with conventional monitoring. False-positive rates in increasing frequency are 0% for NIRS, 0.4% for conventional monitoring, and <10% for implantable Doppler. Current data show implantable Doppler to be potentially cost-effective for institutions with a failure rate of at least 6%. Buried flaps may be monitored with conventional monitoring using an exteriorized paddle, or using implantable Doppler.

CONCLUSIONS

The cost-effectiveness of advanced flap monitoring systems beyond conventional monitoring is related to the success rate of each institution. Cost-effectiveness studies are necessary to determine at what point NIRS becomes advantageous.