Prediction of flap necrosis with laser induced indocyanine green fluorescence in a rat model

Preputial pedicle flap ICG blood flow assessment during proximal hypospadias repair: Development of a standardized protocol

INTRODUCTION

Blood supply to preputial flap drives outcomes of hypospadias repair. Unfortunately, we only have surgeon's subjective assessment to evaluate flap perfusion which may not be accurate. Indocyanine green (ICG) has been used in a multitude of surgeries for perfusion assessment, however, no standardized protocol has been described for use of ICG in hypospadias repairs. The aim of this study is to develop a standardized protocol of ICG use in proximal hypospadias and establish perfusion patterns of preputial flaps.

STUDY DESIGN

A pilot study was conducted using ICG in patients with proximal hypospadias undergoing first stage repair with a preputial flap. The Stryker SPY PHI system and novel quantification software, SPY-QP, were used for ICG imaging. An adaptive approach was taken to develop and implement a standardized protocol (Summary Figure). Per the protocol, ICG was administered at 3 time points which were felt to be critical for assessment of flap perfusion. Of the study patients who have undergone second stage repair, ICG was also used to reassess the flap prior to tubularization of the urethra.

RESULTS

A total of 14 patients underwent first stage hypospadias repair with preputial flaps and intraoperative use of ICG. Median ICG uptake of the prepuce after degloving (dose 1) was 58.5% (IQR 43-76). ICG uptake decreased after flap harvest and mobilization (dose 2) with a median ICG uptake of 34% (IQR 26-46). ICG uptake remained stable after securing the flap in place and closing the skin (dose 3) with a median ICG uptake of 34% (IQR 25-48). ICG was able to delineate subtle findings in the preputial flaps not visible to the naked eye and in one case impacted intraoperative decision making. To date, 5 patients have undergone second stage repair. Flap assessment prior to tubularization of the urethra showed hypervascularity with a median ICG uptake of 159%.

CONCLUSIONS

A standardized protocol for ICG use in proximal hypospadias was successfully developed and implemented. ICG uptake in the preputial flap decreased with increasing manipulation and mobilization of the flap. ICG was able to detect changes to flap perfusion which were not able to be seen with the naked eye. Reliance on surgeon's subjective assessment of flap perfusion may be inadequate and ICG could provide a useful tool for surgeons to improve preputial flap outcomes. ICG may also enhance the learning experience for trainees and early career urologists in these complex surgeries.

Perfusion Dynamics during Secondary Flap Debulking with Liposuction

BACKGROUND

 Lower extremity trauma often necessitates reconstruction with flap transfer. One of the reconstructive goals is a thin soft tissue coverage with appropriate contour. Therefore, a secondary debulking of the flap is usually performed.

METHODS

 Debulking through conventional lipectomy is compared with liposuction followed by excision of the defatted flap excess. Demographic data, surgical details, and postoperative outcomes are compared and analyzed. The perfusion dynamics of the flaps undergoing liposuction debulking are studied by means of perioperative indocyanine green fluorescence angiography, as well as postoperative laser Doppler imaging.

RESULTS

 Patients undergoing lipectomy (n = 69; 57.5%) or liposuction (n = 51; 42.5%) debulking had a similar rate of postoperative complications. Partial necrosis was observed in 7.2% (lipectomy) versus 7.8% (liposuction) of flaps. Fluorescence angiography showed a substantial decrease in flap perfusion following the infiltration with an epinephrine-containing tumescent solution (74.3% ± 8.2% prior to infiltration versus 16.8% ± 7.1% after infiltration; p < 0.001), resulting in a dark flap appearance. Laser Doppler imaging confirmed the hypoperfusion on postoperative day 1.

CONCLUSION

 Secondary debulking of a lower extremity flap can be safely and efficiently performed through liposuction combined with peripheral excision of the defatted flap in a single stage. Perfusion studies may show a misleading hypoperfusion of the defatted flap, which does not accurately predict subsequent necrosis or complications.

Current status of indocyanine green fluorescent angiography in assessing perfusion of gastric conduit and oesophago-gastric anastomosis

Anastomotic leak (AL) remains a significant complication after esophagectomy. Indocyanine green fluorescent angiography (ICG-FA) is a promising and safe technique for assessing gastric conduit (GC) perfusion intraoperatively. It provides detailed visualization of tissue perfusion and has demonstrated usefulness in oesophageal surgery. GC perfusion analysis by ICG-FA is crucial in constructing the conduit and selecting the anastomotic site and enables surgeons to make necessary adjustments during surgery to potentially reduce ALs. However, anastomotic integrity involves multiple factors, and ICG-FA must be combined with optimization of patient and procedural factors to decrease AL rates. This review summarizes ICG-FA's current applications in assessing esophago-gastric anastomosis perfusion, including qualitative and quantitative analysis and different imaging systems. It also explores how fluorescent imaging could decrease ALs and aid clinicians in utilizing ICG-FA to improve esophagectomy outcomes.

The Role of Fluorescent Angiography in Free Flap Reconstruction of the Head and Neck

OBJECTIVES

Highlight the use of fluorescent angiography in free flap reconstruction of the head and neck. Qualify how fluorescent angiography can be selectively added to management paradigms for head and neck free flap reconstruction.

METHODS

Retrospective chart review of 993 free flaps completed from the time the SPY Elite® system first became available at our institution between September 2013, until August 2020. Cases that used the SPY Elite® system were grouped into three broad categories: evaluation during initial flap harvest while still attached to the donor site, evaluation after anastomosis in the head and neck area, and evaluation post-operatively for questionable flap viability.

RESULTS

The SPY Elite® system was used in 64 cases. Forty flaps were evaluated intraoperatively during initial harvest and before anastomosis to the head and neck area. Of these, 20 had signs of poor perfusion of the entire skin paddle, 12 had large myogenous or skin flaps with questionable perfusion of the distal aspect, and 8 were evaluated for other reasons. In this group the use of SPY Elite® changed the management of the patient in 20 cases (50%). Ten flaps were evaluated intraoperatively after anastomosis to the head and neck to ascertain adequate flow to the entire flap. In this group management was changed in two (20%). Fourteen flaps were evaluated 3-5 days post operatively due to suspected failure of a component. In five cases (36%), the use of SPY Elite® determined management with either trimming or discarding the flap.

CONCLUSION

Assessment of flap perfusion via fluorescent angiography during initial flap harvest or when flap compromise is suspected post-operatively can guide decision making in free flap reconstruction of the head and neck and can be added to existing planning and management paradigms.

LEVEL OF EVIDENCE

4 Laryngoscope, 2022.

Combined treatment using cross-leg free flap and the Masquelet technique: a report of two cases

We introduce a treatment that combines the cross-leg free flap with the Masquelet technique and describe two cases using this method for bone and soft tissue reconstruction. Both patients were successfully treated and ambulatory. This novel method can be safely performed using the delay technique, indocyanine-green angiography and near-infrared spectroscopy.

Intra- and Early Postoperative Evaluation of Malperfused Areas in an Irradiated Random Pattern Skin Flap Model Using Indocyanine Green Angiography and Near-Infrared Reflectance-Based Imaging and Infrared Thermography

Background: Assessment of tissue perfusion after irradiation of random pattern flaps still remains a challenge. Methods: Twenty-five rats received harvesting of bilateral random pattern fasciocutaneous flaps. Group 1 served as nonirradiated control group. The right flaps of the groups 2–5 were irradiated with 20 Gy postoperatively (group 2), 3 × 12 Gy postoperatively (group 3), 20 Gy preoperatively (group 4) and 3 × 12 Gy preoperatively (group 5). Imaging with infrared thermography, indocyanine green angiography and near-infrared reflectance-based imaging were performed to detect necrotic areas of the flaps. Results: Analysis of the percentage of the necrotic area of the irradiated flaps showed a statistically significant increase from day 1 to 14 only in group 5 (p < 0.05). Indocyanine green angiography showed no differences (p > 0.05) of the percentage of the nonperfused area between all days in group 1 and 3, but a decrease in group 2 in both the left and the right flaps. Infrared thermography and near-infrared reflectance-based imaging did not show evaluable differences. Conclusion: Indocyanine green angiography is more precise in prediction of necrotic areas in random pattern skin flaps when compared to hyperspectral imaging, thermography or clinical impression. Preoperative fractional irradiation with a lower individual dose but a higher total dose has a more negative impact on flap perfusion compared to higher single stage irradiation.

Assessment of deep inferior epigastric perforator flap perfusion with near-infrared fluorescence: A pilot study and description of a standardized working protocol

Fat necrosis (FN) is a common complication after autologous breast reconstruction (ABR) using a free flap, which can influence reconstruction outcome and patient satisfaction. Intraoperative near-infrared fluorescence imaging using indocyanine green (ICG) permits the visualization of flap perfusion. The aim of this study was to assess the effect of near-infrared fluorescence on FN incidence in patients undergoing an ABR with a deep inferior epigastric perforator flap (DIEP) and to propose a standard working protocol for this technique. In this prospective study, patients undergoing one-sided ABR with a DIEP were included. The standard DIEP procedure was complemented with near-infrared fluorescence imaging using the fluorescent tracer ICG to evaluate flap perfusion. This cohort was compared to a retrospective cohort of DIEP procedures without near-infrared fluorescence imaging. Patients and surgery characteristics, as well as postoperative complications, were registered and compared. In both cohorts, 24 patients were included. No significant differences were present between patients and surgery characteristics, including no difference in duration of surgery. In the prospective and retrospective group, the incidence of FN was 4.2% and 33%, respectively (p-value = 0.023). Moreover, microsurgeons were positive about using near-infrared fluorescence as it either provided additional information about perfusion or confirmed the clinical assessment. Our pilot study showed a significant decrease of FN in patients undergoing an ABR with a DIEP when near-infrared fluorescence imaging was used to assess flap perfusion. This study provides a standardized working protocol for near-infrared fluorescence imaging. In the future, large multicenter studies should focus on the quantification of near-infrared fluorescence imaging.

Hyperbaric Oxygen Therapy in Management of Diabetic Foot Ulcers: Indocyanine Green Angiography May Be Used as a Biomarker to Analyze Perfusion and Predict Response to Treatment

SUMMARY

The authors present indocyanine green angiography to assess the effects of hyperbaric oxygen therapy and as a potential biomarker to predict healing of chronic wounds. They hypothesize that favorable initial response to hyperbaric oxygen therapy (improved perfusion) would be an early indicator of eventual response to the treatment (wound healing). Two groups were recruited: patients with chronic wounds and unwounded healthy controls. Inclusion criteria included adults with only one active wound of Wagner grade III diabetic foot ulcer or caused by soft-tissue radionecrosis. Patients with chronic wounds underwent 30 to 40 consecutive hyperbaric oxygen therapy sessions, once per day, 5 days per week; controls underwent two consecutive sessions. Indocyanine green angiography was performed before and after the sessions, and perfusion patterns were analyzed. Healing was determined clinically and defined as full skin epithelialization with no clinical evidence of wound drainage. Fourteen chronic-wound patients and 10 controls were enrolled. Unlike unwounded healthy volunteers, a significant increase in indocyanine green angiography perfusion was found in chronic-wound patients immediately after therapy (p < 0.03). Moreover, the authors found that 100 percent of the wounds that demonstrated improved perfusion from session 1 to session 2 went on to heal within 30 days of hyperbaric oxygen therapy completion, compared with none in the subgroup that did not demonstrate improved perfusion (p < 0.01). This study demonstrates a beneficial impact of hyperbaric oxygen therapy on perfusion in chronic wounds by ameliorating hypoxia and improving angiogenesis, and also proposes a potential role for indocyanine green angiography in early identification of those who would benefit the most from hyperbaric oxygen therapy.

CLINICAL QUESTION/LEVEL OF EVIDENCE

Therapeutic, IV.

Compromised Flap Salvage With Closed Incision Negative Pressure Therapy Under Real-Time Indocyanine Green Fluorescence Assessment

BACKGROUND

Skin flap transfer is a commonly used technique by surgeons; however, compromised blood flow may result in flap ischemia and necrosis. We describe the use of closed incision negative pressure therapy (ciNPT) to help manage skin flap reconstructions with indocyanine green fluorescence angiography (ICG-FA) to assess perfusion of the flaps before and after ciNPT.

METHODS

Three female and 5 male patients underwent various skin flap reconstructions, including local flaps, pedicled flaps, and propeller flaps, for wound defects related to trauma, infection, or cancer. After flap setting and suturing, ciNPT (-125 mm Hg) was applied to the closed incision for 7 days. Perfusion was assessed using ICG-FA before applying ciNPT and again at 24 hours later. The Shapiro-Wilk test and Wilcoxon signed rank test were used in statistical analysis.

RESULTS

Initial postoperative survival was observed for all skin flaps; however, 1 flap failed after 2 weeks due to uncontrolled infection. The remaining 7 flaps healed well without any surgical revision. All patients were initially determined to have impaired flap perfusion; however, skin flap perfusion was significantly higher after ciNPT than before ciNPT in each case (P = 0.012).

CONCLUSIONS

This study showed good healing outcomes for skin flap reconstructions without complications, despite the fact that each flap had compromised flap perfusion to some extent during the surgery. This case series is novel in that it used laser-assisted ICG-FA to provide a real-time assessment of skin flap perfusion before and after ciNPT.

The Use of Indocyanine Green Angiography for Cosmetic and Reconstructive Assessment in the Head and Neck

Reconstructive procedures in the head and neck can be a surgical challenge owing to the complex anatomical and physiological structure. Different locoregional and microvascular flaps are used for various defects to improve both function and cosmesis. Subjective clinical findings have been the mainstay for perfusion monitoring; however, areas of borderline perfusion are much more difficult to assess clinically. Multiple technologies that offer objective perfusion assessment have been developed to improve surgical outcomes. Indocyanine green (ICG) angiography has gained popularity owing to its minimal invasiveness and increased sensitivity and specificity in assessing flap perfusion particularly in the head and neck. It has been extensively used in free flaps, pedicled flaps (including nasal reconstruction), facelift procedures, random flaps, skull base reconstruction, and pharyngocutaneous fistula prediction. Its perioperative use has provided valuable qualitative and quantitative data that aid our understanding of flap hemodynamics. Clinically, this impacted decision-making in flap design, harvest, inset, and precocious salvage interventions. Though increased cost and intraoperative time could be limitations, cost-effectiveness studies have supported its use, particularly in high-risk individuals. Limitations include the lack of standardized dosing and consistent methodology agreement for data analysis. Future studies should involve larger cohorts and multi-institute studies to overcome such limitations.

A comparative analysis using flowmeter, laser-Doppler |spectrophotometry, and indocyanine green-videoangiography for detection of vascular stenosis in free flaps

The effects of gradual vascular occlusion on the blood supply of perfused areas are poorly described. Information relating to the comparison of flap monitoring techniques is lacking. Varying stenotic conditions (0%, 25%, 50%, 75% and 100%) were generated on purpose at the A. and V. femoralis in the rat model. Analyses included flowmeter, simultaneous laser-Doppler flowmetry and tissue spectrophotometry (O2C) and indocyanine green- (ICG-) videoangiography with integrated FLOW 800 tool. A Random Forests prediction model was used to analyse the importance of each method to diagnose the stenotic conditions. The ability to discriminate and to accurately estimate the probability of stenosis was assessed by Receiver Operating Characteristic (ROC) curves and calibration plots. Blood flow changes for all modalities were described in detail. Flowmeter displayed earliest a linear decrease as a result of increasing stenosis. A stenosis of 50% degrees was most difficult to detect correctly. The combination of flowmeter and ICG-videoangiography showed high diagnostic power for each stenotic situation (area under the ROC > 0.79). Flowmeter and ICG-videoangiography showed to be most relevant in detection of varying stenotic conditions and may change the clinical outcome. The O2C showed less effect on varying stenotic situations as the only surface monitoring device.

[Defect coverage after severe soft tissue infections: when and how?]

Severe infections frequently cause large soft tissue defects which require early defect coverage by plastic surgeons. A number of reconstructive treatment options are available, ranging from local flaps to microvascular free flap reconstructions. In this respect it is important that the selection of the optimal reconstructive technique is made based on individual patient characteristics and in a timely manner. Weeks of inpatient treatment with vacuum dressings often delay defect coverage and should be avoided as they burden both the patient and the healthcare system. Therefore, it is in the best interest of patients to receive early treatment by plastic surgeons. This manuscript presents the essential reconstructive treatment approaches based on highly informative case reports of patients from the plastic surgical practice at a university hospital.

Assessment of DIEP Flap Perfusion with Intraoperative Indocyanine Green Fluorescence Imaging in Vasopressor-Dominated Hemodynamic Support Versus Liberal Fluid Administration: A Randomized Controlled Trial With Breast Cancer Patients

BACKGROUND

Dogmatic denial of vasopressor agents for blood pressure regulation during free-flap surgery is associated with concomitant large-volume intraoperative fluid administration. Yet, the doctrinal banning of vasopressors during microvascular breast reconstruction still is a subject of controversy. Several retrospective observations have recently drawn attention to serious iatrogenic consequences of intravenous crystalloid overload in microsurgery such as thrombus formation and increased flap failure rates.

METHODS

This prospective randomized controlled trial investigated the potential effects of fluid-restrictive vasopressor-dominated hemodynamic support (FRV) compared with vasopressor-restrictive liberal fluid administration (LFA) on clinically relevant perfusion of the deep inferior epigastric perforator (DIEP) flap via intraoperative indocyanine green (ICG) fluorescence imaging. The primary end point of the study was quantitative assessment of the percentage of insufficiently perfused tissue (NP) on the overall flap. Major complications were assessed as secondary end points.

RESULTS

In 44 DIEP flap breast reconstructions after mastectomy, FRV circulatory support resulted in no statistically significant difference in total flap perfusion as detected via ICG fluorescence imaging in direct comparison with a traditional LFA strategy (NP_FRV, 31.8% ± 12.2% vs NP_LFA, 29.5% ± 13.3%; p = 0.559). One flap failure was registered with LFA, whereas no major complication occurred in the FRV cohort.

CONCLUSIONS

According to the results of this study, neither a norepinephrine concentration of 0.065 ± 0.020 μg/kg/min (FRV) nor fluid administration of 5.1 ± 2.2 ml/kg/h (LFA) has a clinically significant impact on microperfusion in a standard DIEP flap procedure for breast reconstruction. Consistent with the current literature reporting a rise in complications with intraoperative fluid over-resuscitation, one flap failure occurred in the LFA cohort.

Flap warming improves intraoperative indocyanine green angiography (ICGA) assessment of perfusion. An experimental study

BACKGROUND

Indocyanine green angiography (ICGA) is slowly replacing conventional methods of evaluating perfusion during flap surgery. Microcirculatory changes during flap elevation create a marked state of hypoperfusion intraoperatively leading to ICGA underestimation of tissue viability and consequent resection of viable tissue. We propose a novel method of flap warming to induce maximum vasodilation before performing ICGA to increase accuracy in assessing perfusion.

METHODS

Submental flaps harvested on a single perforator were created in 8 pigs. ICG angiography was performed in the intraoperative phase (ICGA-C), after inducing maximum vasodilatation by warming the flap at 42 °C (ICGA-W) and at 24H postoperative (ICGA-24). By setting a fluorescence threshold of 33% as indicative of necrosis, the flap surface deemed viable by ICGA was measured for ICGAC, ICGAW and ICGA24. The results were then compared to the actual flap survival observed clinically at 7 days.

RESULTS

The mean of ICG-C predicted flap survival (FS-C = 49.17%) is 12.97% lower than the mean of actual flap survival on postoperative day 7 (FS = 62.14%). The mean difference between ICG-W and ICG-24 predicted flap survival (FS-W and FS-24) and actual flap survival in the postoperative day 7 (FS) is lower, 3.13% and 2.15%, respectively. Average perfusion recovery over 24 h was 10.83% (FS-24-FS-C).

CONCLUSIONS

Conventional intraoperative ICGA underestimated perfusion in all cases. Warming the flap intraoperatively and achieving maximum vasodilation mitigates the effects of vasoconstriction and mimics the microcirculatory environment encountered at 24 h. Performing angiography after induced vasodilation improves ICGA assessment of flap perfusion.

Amputation stump perfusion is predictive of post-operative necrotic eschar formation

Background

A large proportion of patients develop poor amputation stump healing. We hypothesize that Laser-Assisted Fluorescent Angiography (LAFA) can predict inadequate tissue perfusion and healing.

Methods

Over an 8-month period we reviewed all patients who underwent lower extremity amputation and LAFA. We evaluated intra-operative LAFA global and segmental stump perfusion, and post-operative modified Bates-Jensen (mBJS) wound healing scores.

Results

In 15 patients, amputation stumps with lower global perfusion demonstrated higher mBJS (P = 0.01). Lower suture-line perfusion also correlated with more eschar formation (P < 0.001). Diabetic patients had higher mBJS (P = 0.009), lower stump perfusion (P = 0.02), and increased eschar volume (P < 0.001).

Conclusion

LAFA is a useful adjunct for intra-operative stump perfusion assessment and can predict areas of poor stump healing and eschar formation. Diabetic patients seem to be at higher risk of stump eschar formation.

Fluorescence-Guided Surgery

Surgical resection of cancer remains an important treatment modality. Despite advances in preoperative imaging, surgery itself is primarily guided by the surgeon’s ability to locate pathology with conventional white light imaging. Fluorescence-guided surgery (FGS) can be used to define tumor location and margins during the procedure. Intraoperative visualization of tumors may not only allow more complete resections but also improve safety by avoiding unnecessary damage to normal tissue which can also reduce operative time and decrease the need for second-look surgeries. A number of new FGS imaging probes have recently been developed, complementing a small but useful number of existing probes. In this review, we describe current and new fluorescent probes that may assist FGS.

Accurate Prediction of Tissue Viability at Postoperative Day 7 Using Only Two Intraoperative Subsecond Near-Infrared Fluorescence Images

BACKGROUND

The ability to predict the future viability of tissue while still in the operating room and able to intervene would have a major impact on patient outcome. Although several objective methods to evaluate tissue perfusion have been reported, none to date has sufficient accuracy.

METHODS

In eight Sprague-Dawley rats, reverse McFarlane dorsal skin flaps were created. Continuous near-infrared fluorescence angiography using indocyanine green was performed immediately after surgery, for a total of 30 minutes. These dynamic measurements were used to quantify indocyanine green biodistribution and clearance, and to develop a simple metric that accurately predicted tissue viability at postoperative day 7. The new metric was compared to previously described metrics.

RESULTS

Reproducible patterns of indocyanine green biodistribution and clearance from the flap permitted quantitative metrics to be developed for predicting flap viability at postoperative day 7. Previously described metrics, which set the boundary between healthy and necrotic tissue as either 17 or 25 percent of peak near-infrared fluorescence at 2 minutes after indocyanine green injection, underestimated the area of necrosis by 75 and 48 percent, respectively. Our data suggest that both the shape and area of clinical necrosis occurring at postoperative day 7 can be predicted intraoperatively, with the boundary defined as near-infrared fluorescence intensities of 40 to 55 percent of peak fluorescence measured at 5 minutes.

CONCLUSION

Two 750-msec intraoperative near-infrared fluorescence images obtained at time 0 and at 5 minutes after injection of indocyanine green accurately predicted skin flap viability 7 days after surgery.

Transepidermal oxygen flux during arterial occlusion using ratiometric luminescence imaging

BACKGROUND

A physiological oxygen transport through a circulatory and microcirculatory system is essential for execution of cellular functions. Several pathological conditions e.g. infections, ischemia, cancer, diabetes, hypertension or chronic wounds show a change of oxygen distribution and oxygen tension in cellular microenvironment. Additionally complex operative procedures in order to reconstruct tissue defects require a reliable monitoring of microcirculation.

OBJECTIVE

Target of this study was to evaluate skin oxygenation during an ischemia-reperfusion experiment using transepidermal oxygen flux imaging.

METHODS

Twelve patients at the Department of Plastic and Reconstructive surgery of the University hospital of Regensburg underwent to elective hand operations. During the operation a tourniquet is standardly set on the upper arm to create ischemia in order to facilitate the operative procedure. Measurements were performed at the different time intervals: in rest, under ischemia and after reperfusion.

RESULTS

The transepidermal oxygen flux increased during the ischemic condition compared to normal condition and decreased to a lower value during reperfusion (rest: 0.043±0.007, ischemia: 0.063±0.014, reperfusion: 0.030±0.028).

CONCULSION

Transepidermal oxygen flux imaging by ratiometric luminescence imaging seems to be a reliable tool to assess skin oxygenation. However dynamic changes seem to be more informative than absolute thresholds. Further investigations are necessary to prove these promising results.

Factors Affecting Blood Flow at the Tip of the Reconstructed Gastric Tube During Esophagectomy: A Study Using Indocyanine Green Fluorescence Angiography

The objective of this study was to clarify the factors affecting blood flow at the tip of the gastric tube during esophagectomy using indocyanine green (ICG) fluorescence angiography. The time until enhancement of the gastric tube tip determined using ICG fluorescence imaging is a useful indicator of blood flow, and has been shown not to differ significantly according to the connection status of the right or left gastroepiploic artery. Using ICG fluorescence imaging, the time until enhancement of the gastric tube tip was measured in 50 patients undergoing esophagectomy. Blood flow at the gastric tube tip was compared between 2 groups of patients: those in whom a connecting vessel from the left gastro-epiploic artery to the short gastric artery (l-s GA) was present and those in whom it was absent. The factors affecting blood flow to the gastric tube tip were also investigated using univariate and multivariate logistic regression analysis. The median time taken for the gastric tube tip to show enhancement with ICG was significantly shorter in the group with an l-s GA connection (P = 0.02). Multivariate analysis showed that the absence of an l-s GA connection (P = 0.04) and presence of arteriosclerosis-related disease (P = 0.02) were significant independent factors that delayed blood flow to the gastric tube. It is essential to preserve the whole vessel arcade of the greater curvature to achieve good perfusion of the gastric tube with blood. The presence of arteriosclerosis-related disease is a major factor affecting the safety of anastomosis during gastric tube reconstruction.

Indocyanine green videoangiography-assisted prediction of flap necrosis in the rat epigastric flap using the flow® 800 tool

BACKGROUND

The decision to re-operate on a potentially ischemic free flap remains challenging. Indocyanine green videoangiography (ICG) with the FLOW^® 800 tool is a method which allows an immediate qualitative conclusion about the patency of an anastomosis. Is it also able to predict the outcome of potentially compromised vascular free flaps?

MATERIALS AND METHODS

An epigastric flap was raised and repositioned in 79 rats. Intraoperative fluorescence angiography was performed using ICG videoangiography and the FLOW^® 800 tool was applied. Six regions of interest were positioned systematically over the flap, changes of the ICG fluorescence were color coded with respect to time and 474 measurements were performed. The flap was clinically monitored for one week and the resulting necrotic areas were correlated with the ICG/FLOW^® 800 results.

RESULTS

Mean intensity of clinically vital areas was 83.39 ± 50.96 arbitrary units (AU) and 37.33 ± 15.14 AU in necrotic areas. The receiver operating characteristic curve and Youden-Index analysis revealed that the optimal cutoff for the maximal intensity of ICG after FLOW^® 800 analysis was ≤ 61.733 for the prediction of flap necrosis and > 61.733 for the prediction of flap survival (P < 0.0001; 95% CI = 0.85-0.91; Youden-Index: 0.67). The maximal intensity of ICG angiography had a specificity of 96.1% and sensitivity of 71.4%. The positive predictive value was 97.46% and the corresponding negative predictive value was 61.34%.

CONCLUSION

This demonstrates the potential additional value of ICG videoangiography including FLOW^® 800 analyses in the postoperative monitoring of transplanted flaps. © 2016 Wiley Periodicals, Inc. Microsurgery 37:235-242, 2017.

Evaluation of intraoperative fluorescence imaging-guided surgery in cancer-bearing dogs: a prospective proof-of-concept phase II study in 9 cases

The objective was to prospectively evaluate the application of intraoperative fluorescence imaging (IOFI) in the surgical excision of malignant masses in dogs, using a novel lipid nanoparticle contrast agent. Dogs presenting with spontaneous soft-tissue sarcoma or subcutaneous tumors were prospectively enrolled. Clinical staging and whole-body computed tomography (CT) were performed. All the dogs received an intravenous injection of dye-loaded lipid nanoparticles, LipImage 815. Wide or radical resection was realized after CT examination. Real-time IOFI was performed before skin incision and after tumor excision. In cases of radical resection, the lymph nodes (LNs) were imaged. The margin/healthy tissues fluorescence ratio or LN/healthy tissues fluorescence ratio was measured and compared with the histologic margins or LN status. Nine dogs were included. Limb amputation was performed in 3 dogs, and wide resection in 6. No adverse effect was noted. Fluorescence was observed in all 9 of the tumors. The margins were clean in 5 of 6 dogs after wide surgical resection, and the margin/healthy tissues fluorescence ratio was close to 1.0 in all these dogs. Infiltrated margins were observed in 1 case, with a margin/healthy tissues fluorescence ratio of 3.2. Metastasis was confirmed in 2 of 3 LNs, associated with LN/healthy tissues fluorescence ratios of 2.1 and 4.2, whereas nonmetastatic LN was associated with a ratio of 1.0. LipImage 815 used as a contrast agent during IOFI seemed to allow for good discrimination between tumoral and healthy tissues. Future studies are scheduled to evaluate the sensitivity and specificity of IOFI using LipImage 815 as a tracer.

Use of laser-assisted indocyanine green angiography for early division of the forehead flap pedicle

IMPORTANCE

The paramedian forehead flap is used to reconstruct medium to large nasal defects. The staged nature, with its vascular pedicle bridging the medial eyebrow to the nose, results in significant facial deformity. Earlier division lessens this morbidity.

OBJECTIVES

To quantify flap neovascularization 2 weeks after the initial flap transfer and to describe an algorithm for earlier division of the flap pedicle in select patient populations.

DESIGN, SETTING, AND PARTICIPANTS

We performed a prospective and retrospective study at the Ambulatory Surgery Center, Stanford University, Palo Alto, California, from October 14, 2014, through January 21, 2015. Patients with defects appropriate for paramedian forehead flap reconstruction had partial-thickness defects, vascularized tissue in more than 50% of the recipient bed, and no nicotine use. The patients underwent reconstructive surgery by a single surgeon from August 24, 2012, through September 12, 2014. Laser-assisted indocyanine green angiography was used for imaging before and immediately after the initial flap transfer, before pedicle division with the pedicle atraumatically clamped, and immediately after pedicle division and flap inset. Analysis of data and calculation of relative perfusion were performed using a postprocessing analysis toolkit.

MAIN OUTCOMES AND MEASURES

Perfusion was calculated using the analysis toolkit as the percentage of the area of interest relative to a predetermined reference point in normal peripheral tissue.

RESULTS

We enrolled a total of 10 patients. The mean (SD) relative perfusion of the forehead donor site before flap transfer was 61.2% (3.4%); at initial flap transfer, 81.4% (50.2% [range, 31%-214%]) (P = .70 compared with measurement before flap transfer). The mean (SD) relative perfusion of the forehead donor site was 57.5% (21.2% [range, 32%-89%]) at the time of atraumatic pedicle clamping and 58.6% (32.4% [range, 16%-127%]) after pedicle division and flap inset (P = .85 compared with measurement before flap transfer). No flap failures or other complications were observed.

CONCLUSIONS AND RELEVANCE

In select patients (those meeting the inclusion criteria), division of the pedicle at 2 weeks after the initial flap transfer is safe. Earlier pedicle division and flap transfer reduces the duration of facial deformity for the patient.

LEVEL OF EVIDENCE

3.

Indocyanine Green Fluorescence for Free-Flap Perfusion Imaging Revisited: Advanced Decision Making by Virtual Perfusion Reality in Visionsense Fusion Imaging Angiography

BACKGROUND

Near-infrared indocyanine green video angiography (ICG-NIR-VA) has been introduced for free-flap surgery and may provide intraoperative flap designing as well as postoperative monitoring. Nevertheless, the technique has not been established in clinical routine because of controversy over benefits. Improved technical features of the novel Visionsense ICG-NIR-VA surgery system are promising to revisit the field of application. It features a unique real-time fusion image of simultaneous NIR and white light visualization, with highlighted perfusion, including a color-coded perfusion flow scale for optimized anatomical understanding.

METHODS

In a feasibility study, the Visionsense ICG-NIR-VA system was applied during 10 free-flap surgeries in 8 patients at our center. Indications included anterior lateral thigh (ALT) flap (n = 4), latissimus dorsi muscle flap (n = 1), tensor fascia latae flap (n = 1), and two bilateral deep inferior epigastric artery perforator flaps (n = 4). The system was used intraoperatively and postoperatively to investigate its impact on surgical decision making and to observe perfusion patterns correlated to clinical monitoring.

RESULTS

Visionsense ICG-NIR-VA aided assessing free-flap design and perfusion patterns in all cases and correlated with clinical observations. Additional interventions were performed in 2 cases (22%). One venous anastomosis was revised, and 1 flap was redesigned. Indicated by ICG-NIR-VA, 1 ALT flap developed partial flap necrosis (11%).

CONCLUSIONS

The Visionsense ICG-NIR-VA system allowed a virtual view of flap perfusion anatomy by fusion imaging in real-time. The system improved decision making for flap design and surgical decisions. Clinical and ICG-NIR-VA parameters correlated. Its future implementation may aid in improving outcomes for free-flap surgery, but additional experience is needed to define its final role.

Diverse applications for near infra-red intraoperative imaging

BACKGROUND

Near infra-red angiography using Indocyanine Green (ICG) has increasingly used as a tool for intraoperative diagnostics.

AIMS

The aim of this review is to explore the applications of ICG fluorescence angiography with particular emphasis on general surgical applications.

MATERIALS AND METHODS

A literature review was conducted to identify and summarise the diverse range of applications of ICG fluorescence.

RESULTS

ICG fluorescence angiography is increasingly used in a number of general surgical applications, including identification of colorectal liver metastases, assessment of skin flap perfusion, diagnosis of peritoneal endometriosis, ureteric identification, and localisation of colonic pathology.

DISCUSSION

ICG fluorescence angiography has clinical application in many areas as a tool for guiding surgical resection.

CONCLUSION

With the technological developments in near infra-red imaging it is likely that ICG fluorescence will play an increasing role in many routine surgical procedures.

Indocyanine Green: Historical Context, Current Applications, and Future Considerations

BACKGROUND

Indocyanine green (ICG) is a dye used in medicine since the mid-1950s for a variety of applications in in cardiology, ophthalmology, and neurosurgery; however, its fluorescent properties have only recently been used in the intraoperative evaluation of tissue perfusion.

METHOD

A literature review was conducted on the characterization and employment of ICG within the medical field. Historical and current context of ICG was examined while also considering implications for its future use.

RESULTS

ICG is a relatively nontoxic, unstable compound bound by albumin in the intravascular space until rapid clearance by the liver. It has widespread uses in hepatic, cardiac, and ophthalmologic studies, and its use in analyzing tissue perfusion and identifying sentinel lymph nodes in cancer staging is gaining popularity.

CONCLUSIONS

ICG has myriad applications and poses low risk to the patient. Its historical uses have contributed to medical knowledge, and it is now undergoing investigation for quantifying tissue perfusion, providing targeted therapies, and intraoperative identification of neurovascular anatomy, ophthalmic structures, and sentinel lymph nodes. New applications of ICG may lead to reduction in postoperative wound-related complications, more effective ophthalmologic procedures, and better detection and treatment of cancer cells.

Intraoperative indocyanine green fluorescence angiography to predict wound complications in complex ventral hernia repair

INTRODUCTION

Complex ventral hernia repair (VHR) is associated with a greater than 30% wound complication rate. Perfusion mapping using indocyanine green fluorescence angiography (ICG-FA) has been demonstrated to predict skin and soft tissue necrosis in many reconstructive procedures; however, it has yet to be evaluated in VHR.

METHODS

Patients undergoing complex VHR involving component separation and/or extensive subcutaneous advancement flaps were included in a prospective, blinded study. Patients with active infection were excluded. ICG-FA was performed prior to incision and prior to closure, but the surgeon was not allowed to view it. An additional blinded surgeon documented wound complications and evaluated postoperative photographs. The operative ICG-FA was reviewed blinded, and investigators were then unblinded to determine its ability to predict wound complications.

RESULTS

Fifteen consecutive patients were enrolled with mean age of 56.1 years and average BMI of 34.9, of which 60% were female. Most (73.3%) had prior hernia repairs (average of 1.8 prior repairs). Mean defect area was 210.4 cm2, mean OR time was 206 min, 66.6% of patients underwent concomitant panniculectomy, and 40% had component separation. Mean follow-up was 7 months. Two patients developed wound breakdown requiring reoperation, while 1 had significant fat necrosis and another a wound infection, requiring operative intervention. ICG-FA was objectively reviewed and predicted all 4 wound complications. Of the 12 patients without complications, 1 had an area of low perfusion on ICG-FA. This study found a sensitivity of 100% and specificity of 90.9% for predicting wound complications using ICG-FA.

CONCLUSION

In complex VHR patients, subcutaneous perfusion mapping with ICG-FA is very sensitive and has the potential to reduce cost and improve patient quality of life by reducing wound complications and reoperation.

Mass spectrometric characterization of limited proteolysis activity in human plasma samples under mild acidic conditions

We developed a limited proteolysis assay for estimating dynamics in plasma-borne protease activities using MALDI ToF MS analysis as readout. A highly specific limited proteolysis activity was elicited in human plasma by shifting the pH to 6. Mass spectrometry showed that two singly charged ion signals at m/z 2753.44 and m/z 2937.56 significantly increased in abundance under mild acidic conditions as a function of incubation time. For proving that a provoked proteolytic activity in mild acidic solution caused the appearance of the observed peptides, control measurements were performed (i) with pepstatin as protease inhibitor, (ii) with heat-denatured samples, (iii) at pH 1.7, and (iv) at pH 7.5. Mass spectrometric fragmentation analysis showed that the observed peptides encompass the amino acid sequences 1-24 and 1-26 from the N-terminus of human serum albumin. Investigations on peptidase specificities suggest that the two best candidates for the observed serum albumin cleavages are cathepsin D and E. Reproducibility, robustness, and sensitivity prove the potential of the developed limited proteolysis assay to become of clinical importance for estimating dynamics of plasma-borne proteases with respect to associated pathophysiological tissue conditions.

Hemodynamics of the reconstructed gastric tube during esophagectomy: assessment of outcomes with indocyanine green fluorescence

BACKGROUND

Construction of a gastric tube that is well perfused with blood during esophagectomy is the most important factor in avoiding anastomotic leakage. We clarified the hemodynamics of the reconstructed gastric tube with indocyanine green (ICG) fluorescence.

METHODS

In 20 patients undergoing gastric tube reconstruction during esophagectomy, we evaluated blood flow in the gastric tube with ICG fluorescence imaging. We divided the patients into two groups according to the quality of blood flow to the gastric tube-"good" (n = 9) and "sparse or absent" (n = 11)-based on visual assessment of the anastomosis of the right and left gastroepiploic vessels. We measured the time from initial enhancement of the root of the right gastroepiploic artery until enhancement of the most cranial branch of the left gastroepiploic artery and tip of the gastric tube.

RESULTS

The gastric tube was divisible into three zones according to the dominant arteries present in the greater curvature under ICG fluorescence. The left gastroepiploic artery was enhanced in a direction opposite that of physiological blood flow in all cases. The median period from initial enhancement of the root of the right gastroepiploic artery to the most cranial branch of the left gastroepiploic artery until perfusion up to the tip of the gastric tube did not differ significantly between the "good" and the "sparse or absent" groups (P = 0.24, 0.68) CONCLUSIONS: It is essential to preserve the whole vessel arcade of the greater curvature to achieve good blood perfusion in the gastric tube. The ICG fluorescence method has potential usefulness for evaluation of blood flow in the gastric tube.

Indocyanine green video angiography predicts outcome of extravasation injuries

BACKGROUND

Extravasation of cytotoxic drugs is a serious complication of systemic cancer treatment. Still, a reliable method for early assessment of tissue damage and outcome prediction is missing. Here, we demonstrate that the evaluation of blood flow by indocyanine green (ICG) angiography in the extravasation area predicts for the need of surgical intervention.

METHODS

Twenty-nine patients were evaluated by ICG angiography after extravasation of vesicant or highly irritant cytotoxic drugs administered by peripheral i.v. infusion. Tissue perfusion as assessed by this standardized method was correlated with clinical outcome.

RESULTS

The perfusion index at the site of extravasation differed significantly between patients with reversible tissue damage and thus healing under conservative management (N = 22) versus those who needed surgical intervention due to the development of necrosis (N = 7; P = 0.0001). Furthermore, in patients benefiting from conservative management, the perfusion index was significantly higher in the central extravasation area denoting hyperemia, when compared with the peripheral area (P = 0.0001).

CONCLUSIONS

In this patient cohort, ICG angiography as indicator of local perfusion within the extravasation area was of prognostic value for tissue damage. ICG angiography could thus be used for the early identification of patients at risk for irreversible tissue damage after extravasation of cytotoxic drugs.

Intraoperative prediction of postoperative flap outcome using the near-infrared fluorophore methylene blue

Methylene blue (MB) is a near-infrared fluorophore that provides a stable visual map of skin perfusion after intravenous injection. We explored the capability of MB to predict submental flap postoperative outcome using a single intraoperative measurement. Submental flaps were created in N = 15 pigs and imaged using the FLARE imaging system immediately after surgery and at 72 hours. Using the first 3 pigs, optimal MB dosing was found to be 2.0 mg/kg. Training and validation sets of 6 pigs each were then used for receiver operating characteristic analysis. In the training set, a contrast-to-background ratio (CBR) threshold of 1.24 provided the highest sensitivity and specificity to predict tissue necrosis at 72 hours. In the validation set, this threshold provided a prediction sensitivity of 95.3% and a specificity of 98.0%. We demonstrate that a single intraoperative near-infrared measurement can predict submental flap outcome at 72 hours.

Endoscopic assessment of free flap perfusion in the upper aerodigestive tract using indocyanine green: a pilot study

INTRODUCTION

Malfunction of microvascular anastomoses is the main reason for free-flap failures. The aim of this investigation was to prove the feasibility of endoscopic free-flap perfusion measurements in the upper aerodigestive tract (UADT) using indocyanine green (ICG).

METHODS

Twenty-five patients undergoing free-flap reconstruction of the UADT were included. At least three ICG angiographies (0 h, 24 h and 72 h) were performed per participant. The sequences were subjectively judged online. The data were subsequently analysed, the results compared to clinical outcome and a survey with clinical staff (n = 21) performed.

RESULTS

All 25 flaps survived. The ICG angiographies were tolerated well, showing a delayed fluorescence gain in transplanted tissue compared to surrounding but comparable final maximum fluorescence intensities. Four surgical revisions (two for a true and two for a false indication) could be additionally investigated. The two flaps with a real perfusion compromise showed fluorescence Indices (relative fluorescence maxima of transplant vs. surrounding) of 33% and 37%, whereas these values lay above 60% for all other examinations (including those two flaps that were revised for a false indication). The survey showed that ICG angiography leads to a better discrimination of well- and malperfused flaps compared with conventional inspection.

CONCLUSION

In this small level IIb study, it was possible to prove the feasibility of endoscopic ICG angiography in patients with free-tissue transfer to the UADT. In difficult situations, it seems a welcome adjunct to conventional screening and might aid in the decision whether to revise a clinically suspect flap.

Intraoperative laser angiography using the SPY system: review of the literature and recommendations for use

Inadequate tissue perfusion is a key contributor to early complications following reconstructive procedures. Accurate and reliable intraoperative evaluation of tissue perfusion is critical to reduce complications and improve clinical outcomes. Clinical judgment is the most commonly used method for evaluating blood supply, but when used alone, is not always completely reliable. A variety of other methodologies have been evaluated, including Doppler devices, tissue oximetry, and fluorescein, among others. However, none have achieved widespread acceptance. Recently, intraoperative laser angiography using indocyanine green was introduced to reconstructive surgery. This vascular imaging technology provides real-time assessment of tissue perfusion that correlates with clinical outcomes and can be used to guide surgical decision making. Although this technology has been used for decades in other areas, surgeons may not be aware of its utility for perfusion assessment in reconstructive surgery. A group of experts with extensive experience with intraoperative laser angiography convened to identify key issues in perfusion assessment, review available methodologies, and produce initial recommendations for the use of this technology in reconstructive procedures.

A review of indocyanine green fluorescent imaging in surgery

The purpose of this paper is to give an overview of the recent surgical intraoperational applications of indocyanine green fluorescence imaging methods, the basics of the technology, and instrumentation used. Well over 200 papers describing this technique in clinical setting are reviewed. In addition to the surgical applications, other recent medical applications of ICG are briefly examined.

Extracorporeal shock wave treatment protects skin flaps against ischemia-reperfusion injury

Advances in the treatment of ischemia-reperfusion injury have created an opportunity for plastic surgeons to apply these treatments to flaps and implanted tissues. Using an extended inferior epigastric artery skin flap as a flap ischemia-reperfusion injury (IRI) model, we examined the capability of extracorporeal shock wave treatment (ESWT) to protect tissue against IRI in a rat flap model. Twenty-four rats were used and randomly divided into three groups (n=8 for each group). Group I was the sham group and did not undergo ischemic insult; rather, the flap was raised and immediately sutured back (non-ischemic control group). Group II (ischemia control) and Group III (ESWT) underwent 3h of ischemic insult. During reperfusion Group III was treated with ESWT and Group II was left untreated. Histological evaluation was made to investigate treatment induced tissue alterations. Survival areas were assessed at 5d postoperatively. Skin flap survival and perfusion improved significantly in the ischemic animals following ESWT (p<0.001, respectively). The tissue protecting effect of ESWT resulted in flap survival areas and perfusion data equal to non-ischemic, sham operated flaps. In line with the observation of better flap perfusion, tissue from ESWT-treated animals (Group III) revealed a significantly increased frequency of CD31-positive vessels compared to both the ischemic (Group II; p=0.003) and the non-ischemic, sham operated control (Group I; p<0.005) and an enhanced expression of pro-angiogenic genes. This was accompanied by a mild suppression of pro-inflammatory genes. Our study suggests that ESWT improves flap survival in IRI by promoting angiogenesis and inhibiting tissue inflammation. The study identifies ESWT as a low-cost and easy to use technique for surgical techniques that aim at reducing ischemia-reperfusion-induced tissue injury.

Fluorescent angiography

Fluorescent angiography is a simple and effective real-time tool for measurement of tissue perfusion both in and out of the operating room. It has multiple uses including: (1) identifying perforating vessels during flap planning; (2) locating primary and secondary angiosomes within a prepared flap; (3) as an aid in decision making for tissue debridement and flap creation; (4) intraoperative evaluation of microanastomoses; (5) postoperative flap monitoring, and (6) documentation of perfusion. The technology is easy to use in the hands of the operating surgeon and is safe for the patient, as it requires no radiation exposure.

Current trends and emerging future of indocyanine green usage in surgery and oncology: a literature review

Ever since Kitai first performed fluorescent navigation of sentinel lymph nodes (SLNs) using indocyanine green (ICG) dye with a charge-couple device and light emitting diodes, the intraoperative use of near infrared fluorescence has served a critical role in increasing our understanding in various fields of surgical oncology. Here the authors review the emerging role of the ICG fluorophore in the development of our comprehension of the lymphatic system and its use in SLN mapping and biopsy in various cancers. In addition, they introduce the novel role of ICG-guided video angiography as a new intraoperative method of assessing microvascular circulation. The authors attempt to discuss the promising potential in addition to assessing several challenges and limitations in the context of specific surgical procedures and ICG as a whole. PubMed and Medline literature databases were searched for ICG use in clinical surgical settings. Despite ICG's significant impact in various fields of surgical oncology, ICG is still in its nascent stages, and more in-depth studies need to be carried out to fully evaluate its potential and limitations.