Evaluation of near infrared spectroscopy in monitoring postoperative regional tissue oxygen saturation for fibular flaps

Experimental study of contrast-enhanced ultrasound in the evaluation of random-pattern flap blood supply in the early postoperative stage in rats

PURPOSE

This study aims to investigate whether contrast-enhanced ultrasound (CEUS) could be used to reveal the status of blood supply of the superficial flap of rat model in the early postoperative stage.

METHODS

One viable and one ischemic random-pattern flap were prepared on the left and right back of the same rat respectively with a number of 40. CEUS examinations were applied within 12 h and 7 days postoperatively, and the quantitative measurements of microvascular blood volume (BV) of the base and the end of both flaps were expressed using acoustic intensity as a ratio to that of the healthy skin.

RESULTS

Within 12 h post operation, there was a smaller BV value of the ischemic ends than that of both the ischemic bases and viable ends (p < 0.001), while no difference was indicated between ischemic bases and viable bases or between viable bases and viable ends. The same result was provided 7 days post operation.

CONCLUSION

Microcirculation of superficial tissues such as random-pattern flaps in this rat model can be assessed quantitatively by CEUS. It could sensitively and accurately reveal the objective status of tissue perfusion in the early postoperative stage.

Continuous Monitoring of Buried Free Bone Flap Microcirculation Using a Near-Infrared Spectroscopy System

SUMMARY

Postoperative evaluation of free flaps remains a challenging task. The current accepted standard for diagnosis of vascular compromise remains clinical observation. In recent years, near-infrared spectroscopy (NIRS) has been widely used as a noninvasive objective monitoring tool for postoperative evaluation of soft-tissue flaps. However, methods for monitoring bone flaps remain inadequate. In this study, NIRS was applied for the first time to monitor free buried bone flaps that were used for mandibular reconstruction. The penetrating property of NIRS was used to measure the tissue oxygenation index (TOI) of deep tissues, which reflected the microcirculatory status of the tissues. Changes in TOI values were monitored continuously in 59 cases of free bone flaps up to 72 hours after surgery. Five cases of vascular compromise were noted by clinical observation. Two fibula flaps were total failures, one of which showed a sharp decrease in TOI value to 45% in a short period of time; the other showed a continual gradual decrease to 55%. The observed sudden (<50%) and continuous (>10%) decreases in TOI values suggest that more attention should be paid to revision surgical procedures. The authors conclude that NIRS holds promise as an objective and valid method for clinical evaluation of buried bone flaps.

Adjunctive technologies in postoperative free-flap monitoring: a systematic review

Patent microvascular anastomoses are essential for successful free tissue transfer. Early accurate detection of microvascular compromise is required for flap salvage. Adjunctive monitoring techniques, in addition to clinical examination, are increasingly used to detect flap compromise. This systematic review synthesized and appraised the literature to determine the efficacy of different postoperative monitoring technologies. Rates of flap takeback, salvage, failure, and mean time to detection of microvascular compromise were extracted, synthesized, and reviewed. Twenty-two studies were included, comprising 6370 flaps. One thousand three hundred and ninety-five flaps were monitored with Cook Swartz Doppler (21.83%), 1417 flaps with tissue oximetry (22.24%), 291 with laser Doppler (4.56%), 175 with duplex echography (2.74%), 210 with indocyanine green (ICG) fluorescence (3.30%), 196 with Synovis flow coupler (3.07%), and 81 (1.27%) with light spectroscopy. The overall true positive rate for microvascular compromise in taken back flaps was 70.18%. Cook Swartz Doppler (n = 1391) had a true positive rate of 80.17% and 83.63% salvage rate and was associated with an overall 2.60% rate of flap failure. Tissue oximetry (n = 1417) had a true positive rate of 74.76% and a salvage rate of 88.62%. Laser Doppler, duplex echography, light spectroscopy, and Synovis flow coupler demonstrated true positive rates between 69.4% and 100% with salvage rates between 64% and 100%. Cook Swartz Doppler and tissue oximetry are associated with prompt identification of microvascular compromise and return to theatre. Alternative modalities, including near-infrared spectroscopy, laser Doppler, and duplex echography, show promise. Further well-designed randomised controlled trials (RCTs) appraising head-to-head efficacy are required to comparatively assess adjunctive technologies.

Near-Infrared Spectroscopy for Continuous Noninvasive Monitoring of Free Flap in Head and Neck Reconstruction: Systematic Review of the Literature and Personal Experience

BACKGROUND

Buried free flaps represent a reconstructive challenge concerning monitoring of vitality, which is fundamental for an early detection of flap failure and prompt surgical salvage. Many flap monitoring techniques have been developed over time, and there is still no consensus concerning the best monitoring technique for buried reconstructions.

METHODS

We performed a systematic review of the literature on NIRS monitoring for head and neck free flaps. Moreover, we presented a case of orbital reconstruction through a buried free myo-fascial anterolateral tight flap (ALTF) in which postoperative monitoring was performed by means of NIRS.

RESULTS

Four studies were included with a total of 200 monitored head and neck free flap reconstructions. Flap survival was reported in 96.5% of studies (n = 193/200) with a 3.5% of total flap failure rate (n = 7/200). We monitored the buried myo-fascial ALTF for 7 post-operative days measuring a regional oxygen saturation (rSO2) ranging from 55% to 72% (mean = 66%).

CONCLUSIONS

This device appeared to be an efficient choice for monitoring buried flaps, thanks to its ability to measure tissue perfusion deep under the skin, to the continuous availability of recorded data on the monitor, and to its low impact on the patient. Further prospective studies are advised in order to standardize this monitoring technique and define warning values.

An Updated Systematic Review and Meta-Analysis of Tissue Oximetry Versus Conventional Methods for Postoperative Monitoring of Autologous Breast Reconstruction

BACKGROUND

Tissue oximetry monitoring has shown superior outcomes to conventional monitoring methods for autologous breast reconstruction in retrospective studies with consecutive cohorts. A recent study used consecutive cohorts with tissue oximetry as the earlier cohort and found that tissue oximetry was nonsuperior. We hypothesize that improvement in microsurgical outcomes with institutional experience confounds the superiority of tissue oximetry demonstrated in prior studies. This study aimed to perform a systematic review and meta-analysis of the outcomes of tissue oximetry monitoring compared with conventional monitoring.

METHODS

Relevant studies were found using PubMed, Embase, and Web of Science searches for keywords such as near-infrared spectroscopy or tissue oximetry and microsurgery. Studies included compared tissue oximetry and conventional monitoring in autologous breast reconstruction patients. Studies were excluded if they did not contain a comparison group. Random-effective models were used to analyze early returns to the operating room, the total number of partial or complete flap loss, and late fat necrosis.

RESULTS

Six hundred sixty-nine studies were identified; 3 retrospective cohort studies met the inclusion criteria. A total of 1644 flaps were in the tissue oximetry cohort, and 1387 flaps were in the control cohort. One study contained tissue oximetry as the former cohort; 2 had tissue oximetry as the latter. Neither technique was superior for any measured outcomes. The estimated mean differences between tissue oximetry and conventional monitoring method were early returns, -0.06 (95% confidence interval [CI], -0.52 to 0.410; P = 0.82); partial flap loss, -0.04 (95% CI, -0.86 to 0.79; P = 0.93); complete flap loss, -1.29 (95% CI, -3.45 to 0.87; P = 0.24); and late fat necrosis -0.02 (95% CI, -0.42 to, 0.39; P = 0.94).

CONCLUSIONS

In a systematic review and meta-analysis of mixed timeline retrospective cohort studies, tissue oximetry does not provide superior patient outcomes and shifts our current understanding of postoperative breast reconstruction monitoring. Prospective studies and randomized trials comparing monitoring methods need to be included in the existing literature.

Tissue Oximetry as a Potential Alternative to Indocyanine Green (ICG) Perfusion Assessment in Colorectal Anastomotic Cases

INTRODUCTION

Anastomotic margin tissue perfusion is recognized as critical to successful colorectal anastomosis creation. Near-infrared (NIR) fluorescence imaging with indocyanine green (ICG) is the most common modality used by surgeons as an adjunct to clinical assessment in confirming the adequacy of tissue perfusion. Tissue oxygenation as a surrogate for tissue perfusion has been described in a variety of surgical specialties but its use in colorectal surgery has been limited. Here, we report our experience using a handheld tissue-oxygen meter, IntraOx, for the evaluation of colorectal tissue bed oxygen saturation (StO 2 ) and compared its utility with NIR-ICG in identifying the viability of colonic tissue before anastomosis in a range of colorectal procedures.

MATERIALS AND METHODS

This was an institutional review board-approved multicenter trial consisting of 100 patients undergoing elective colon resections. After specimen mobilization, a clinical margin was chosen based on the oncologic, anatomic, and clinical assessment as per the clinicians' standard technique. The IntraOx device was then used to take a baseline reading of colonic tissue oxygenation on a normal segment of perfused colon. Following this, measurements were taken circumferentially at 5 cm intervals along the bowel proximally and distally to the clinical margin. A StO 2 margin was then determined based on the point at which the StO 2 dropped off by ≥10 percentage points. This was then compared with the NIR-ICG margin using the Spy-Phi system.

RESULTS

StO 2 was found to have a sensitivity and specificity of 94.8% and 93.1%, respectively, and a positive predictive value and negative predictive value of 93.5% and 94.5%, respectively when compared with NIR-ICG. At the 4-week follow-up, no significant complications or leaks were reported.

CONCLUSIONS

The IntraOx handheld device was found to be similar to NIR-ICG in identifying a well-perfused margin of colonic tissue while having the added benefits of high portability and reduced costs. Further studies looking at the effect of the IntraOx on preventing colonic anastomotic complications such as leak and stricture are warranted.

Comparing tissue oximetry to doppler monitoring in 1367 consecutive breast free flaps

BACKGROUND

Retrospective studies evaluating tissue oximetry in a more recent cohort have shown superiority in flap outcomes. This study compares the use of tissue oximetry in a historical cohort to clinical observation and handheld doppler in a more recent cohort. We hypothesize that there is no benefit to using tissue oximetry.

METHODS

A retrospective review was performed on patients who underwent abdominal-based autologous breast reconstruction by five microsurgeons at an academic institution from 2009 to 2020. Method of postoperative flap monitoring was determined then operative details and complications were analyzed.

RESULTS

1367 flaps were reviewed; 740 flaps in 460 patients were monitored with clinical observation and tissue oximetry, and 627 flaps in 391 patients were monitored with clinical observation and handheld doppler. There were no statistical differences in ischemic (p = .59) or congestive complications (p = .41), flap salvage rates when exploring for venous or arterial compromise (p = .52), or early flap loss (p = .56). Although not significant, acute flap-related return to the operating room was lower in the doppler group (4.6%) compared to the oximetry group (6.1%; p = .22). Flaps monitored with tissue oximetry had a statistical increase in length of stay (4.8 ± 1.4 days vs. 3.8 ± 1.6 days; p ≤ .001). The rates of late partial flap loss and fat necrosis were significantly higher in the oximetry group (2.6%, 19/740 vs. 0.3%, 2/740; p = .04) and (18.2%, 135/740 vs. 13.6%, 85/627; p = .02), respectively.

CONCLUSIONS

There is no statistical benefit to the use of tissue oximetry compared to handheld doppler in flap monitoring with regards to flap outcomes.

Simple and Easily Interpretable Flap Monitoring Method Using a Commercial Pulse Oximeter and a Widely Used Bedside Patient Monitor

Background  Various methods for monitoring after free flap surgery have been reported in the literature. Among them, pulse oximetry shows a sensitive reaction to vascular issues, and it is easy to interpret visually. However, previous reports used special equipment that was less commonly used and difficult to generalize. In this study, we used a commercial pulse oximeter and a widely used bedside patient monitor to monitor transplanted free tissue and lower extremities of healthy subjects with impaired circulation. Methods  A reflectance pulse oximeter sensor was attached on the flap after free tissue transplantation. The sensor was connected to a bedside patient monitor, and the flap oxygen saturation (SpO₂) levels and arterial waveforms were continuously monitored. Additionally, blood circulation disorder was induced in the lower limbs of healthy volunteers using pressure cuff inflation on the thigh, and the waveform and SpO₂ levels on the pulse oximeter attached to the lower leg were monitored. Results  Twenty-two patients were included in this study. No postoperative vascular issues were observed in any case. Pulse oximeters showed normal rhythmic wavelengths, and the flap SpO₂ level ranged approximately >90%. The pulse oximeter waveform rapidly disappeared during arterial occlusion in the thigh pressure cuff inflation test, and the waveform flattened and the SpO₂ level decreased slightly during venous congestion. Conclusion  Flap monitoring using a commercially available pulse oximeter and a bedside patient monitor is a versatile, easy-to-interpret, and useful method. Changes in waveform and SpO₂ levels appear during arterial and venous circulation disorders, and these changes can be differentiated.

Comparing the Time-Dependent Evolution of Microcirculation in Gracilis vs. ALT Flaps Using Laser-Doppler Flowmetry and Tissue-Spectrometry

Postoperative free flap monitoring is considered a key component of care after microsurgical reconstruction. To achieve successful flap salvage after surgical revision, early recognition of vascular compromise is required. The aim of this study was to assess and compare the time-dependent evolution of microcirculation in gracilis muscle (GM) and anterolateral thigh (ALT) flaps. This study included continuous measurements of blood flow (flow), hemoglobin oxygenation (SO2) and the relative amount of hemoglobin (rHb) using laser-doppler flowmetry and tissue-spectrometry (O2C, LEA Medizintechnik, Gießen, Germany) over a time-period of 72 h. Microcirculation was assessed in a total of 66 viable free flaps (GM n = 40; ALT n = 26). A statistically significant positive correlation between time post-anastomosis and microvascular flow was found for both GM and ALT flaps with rs = 0.384 (p < 0.001) and rs = 0.178 (p = 0.015), respectively. No significant positive or negative correlations between time post-anastomosis and SO2 were found for both GM and ALT flaps with rs = 0.052 (p = 0.387) and rs = −0.018 (p = 0.805), respectively. Overall, a significant negative correlation between time post-anastomosis and rHb was found for GM flaps with rs = −0.140 (p = 0.019). For ALT flaps, no significant positive or negative correlation was found with rs = −0.011 (p = 0.887). Microcirculation differs in different flap entities, and surgeons should be aware of these differences in order to correctly evaluate and classify the values of flow, SO2 and rHb obtained when using the O2C device for postoperative monitoring.

The 72-Hour Microcirculation Dynamics in Viable Free Flap Reconstructions

BACKGROUND

 The risk for vascular complications is the highest within the first 24 hours after free flap transfer. Clinical signs of critical perfusion are often recognized with time delay, impeding flap salvage. To detect failing flaps as soon as possible and to prevent persisting microvascular impairments, knowledge of physiological perfusion dynamics in free flaps is needed. Aim of this study was to investigate the physiological perfusion dynamics of viable free flaps using the Oxygen to See (O2C) device for continuous monitoring.

METHODS

 Microcirculation was continuously monitored in 85 viable free flaps over a period of up to 72 hours following microvascular anastomosis using tissue spectrophotometry and laser Doppler flowmetry (O2C, LEA Medizintechnik, Gießen, Germany). The parameters investigated included capillary-venous blood flow (flow), oxygen saturation (SO₂), and relative amount of hemoglobin (rHB).

RESULTS

 Microcirculatory blood flow increased significantly overall, especially within the first 18 hours after microsurgical anastomosis, after which peak formation was occurred. Mean values of SO₂ showed a decreasing trend and the steepest decrease of SO₂ (slope: 1.0) occurred during the steepest increase of flow between 3 and 6 hours (slope: 4.7) postanastomosis. The rHB values remained fairly constant throughout the study period.

CONCLUSION

 Hyperemia after free flap transfer accounts for a significant increase of microvascular flow. Tissue oxygenation is reduced, likely due to an increase of oxygen consumption after anastomosis. A better understanding of physiological perfusion dynamics in free flaps can aid surgeons in recognizing compromised vasculature earlier and improve free flap salvage.

Near-Infrared Spectroscopy (NIRS) versus Hyperspectral Imaging (HSI) to Detect Flap Failure in Reconstructive Surgery: A Systematic Review

Rapid identification of possible vascular compromise in free flap reconstruction to minimize time to reoperation improves achieving free flap salvage. Subjective clinical assessment, often complemented with handheld Doppler, is the golden standard for flap monitoring; but this lacks consistency and may be variable. Non-invasive optical methods such as near-infrared spectroscopy (NIRS) and hyperspectral imaging (HSI) could facilitate objective flap monitoring. A systematic review was conducted to compare NIRS with HSI in detecting vascular compromise in reconstructive flap surgery as compared to standard monitoring. A literature search was performed using PubMed and Embase scientific database in August 2021. Studies were selected by two independent reviewers. Sixteen NIRS and five HSI studies were included. In total, 3662 flap procedures were carried out in 1970 patients using NIRS. Simultaneously; 90 flaps were performed in 90 patients using HSI. HSI and NIRS flap survival were 92.5% (95% CI: 83.3–96.8) and 99.2% (95% CI: 97.8–99.7). Statistically significant differences were observed in flap survival (p = 0.02); flaps returned to OR (p = 0.04); salvage rate (p < 0.01) and partial flap loss rate (p < 0.01). However, no statistically significant difference was observed concerning flaps with vascular crisis (p = 0.39). NIRS and HSI have proven to be reliable; accurate and user-friendly monitoring methods. However, based on the currently available literature, no firm conclusions can be drawn concerning non-invasive monitoring technique superiority

Flap Monitoring Using Transcutaneous Oxygen or Carbon Dioxide Measurements

Free tissue transfer is a cornerstone of complex reconstruction. In many cases, it represents the last option available for a patient and their reconstruction. At high-volume centers, the risk of free flap failure is low but its occurrence can be devastating. Currently, the mainstay for flap monitoring is the clinical examination. Though reliable when performed by experienced clinicians, the flap exam is largely subjective, is performed discontinuously, and often results in significant time delay between detection of flap compromise and intervention. Among emerging flap monitoring technologies, the most promising appear to be those that rely on noninvasive transcutaneous oxygen and carbon dioxide measurements, which provide information regarding flap perfusion. In this article, we review and summarize the literature on various techniques but primarily emphasizing those technologies that rely on transcutaneous gas measurements. We also define characteristics for the ideal flap monitoring tool and discuss critical barriers, predominantly cost, preventing more widespread utilization of adjunct monitoring technologies, and their implications.

Prospective Trial of Near-Infrared Spectroscopy for Continuous Noninvasive Monitoring of Free Fibular Flaps

INTRODUCTION

Some free flaps develop postoperative vessel thrombosis, which influences the flap survival rate. Early discovery and identification of vascular crisis are critical to the success rate of flap salvage. The primary aims of this study were to determine the features of postoperative blood supply changes in fibular flaps with normal and abnormal blood flow, using near-infrared spectroscopy (NIRS), to monitor oxygenation and blood flow, and to characterize the probable risk factors for vascular crisis.

METHODS

Sixty-three consecutive patients undergoing reconstruction of unilateral mandibular defects with free fibular flaps at the Peking University School of Stomatology were included. Patients were divided into 2 groups, A (n = 38) and B (n = 25); fibular flaps in group A underwent continuous NIRS monitoring from immediately postoperatively until 7 days postoperatively (approximately 150 hours), whereas fibular flaps and opposite mandibles in group B underwent intermittent monitoring: once every 4 hours during the first 24 hours postoperatively and once every 12 hours from 24 to 168 hours postoperatively.

RESULTS

Six fibular flaps developed vascular thromboses: 4 were venous thromboses and 2 were arterial thromboses; 5 were rescued after exploration. Of 6 regional oxygen saturation (rSO2) values in the continuous monitoring group, 4 showed no significant differences at any time point compared with the intermittent monitoring group (P > 0.05). The rSO2 of the fibular flap was significantly different from that in the opposite mandible in the first 36 hours postoperatively (P < 0.05). This difference decreased over time. During the initial period of venous thrombosis, rSO2, deoxyhemoglobin, and oxygenated hemoglobin all rose slightly, then showed simultaneous rapid reduction. However, the magnitude of reduction was smaller for deoxyhemoglobin than for oxygenated hemoglobin.

CONCLUSIONS

Near-infrared spectroscopy can be used for noninvasive and reliable assessment of oxygenation and blood flow in free flaps through continuous, real-time monitoring. It is also portable, inexpensive, and simple to operate. In addition, the detection depth of NIRS is up to 2.0 cm, so it can be used to monitor buried flaps with depths <2.0 cm.

Investigating spectroscopic measurement of sublingual veins and tissue to estimate central venous oxygen saturation

BACKGROUND

Venous oxygen saturation reflects venous oxygenation status and can be used to assess treatment and prognosis in critically ill patients. A novel method that can measure central venous oxygen saturation (ScvO2) non-invasively may be beneficial and has the potential to change the management routine of critically ill patients.

OBJECTIVE

The study aims to evaluate the potential of sublingual venous oxygen saturation (SsvO2) to be used in the estimation of ScvO2.

METHODS

We have developed two different approaches to calculate SsvO2. In the first one, near-infrared spectroscopy (NIRS) measurements were performed directly on the sublingual veins. In the second approach, NIRS spectra were acquired from the sublingual tissue apart from the sublingual veins, and arterial oxygen saturation was measured using a pulse oximeter on the fingertip.

RESULTS

Twenty-six healthy subjects were included in the study. In the first and second approaches, average SsvO2 values were 75.0% ± 1.8 and 75.8% ± 2.1, respectively. The results of the two different approaches were close to each other and similar to ScvO2 of healthy persons (> 70%).

CONCLUSION

Oxygen saturation of sublingual veins has the potential to be used in intensive care units, non-invasively and in real-time, to estimate ScvO2.

Duplex echography as an adjuvant tool to clinical examination to detect early postoperative free flap vascular compromise

BACKGROUND

Clinical examination remains the cornerstone for postoperative monitoring of free flaps but is highly dependent on the surgeon's ability and experience. Duplex echography provides a noninvasive objective evaluation of tissue perfusion. The authors hypothesized that duplex echography may be a more sensitive and specific monitoring method for early detection of postoperative flap compromise compared to clinical examination alone. The goal was to evaluate any differences between combined duplex echography and clinical examination flap monitoring versus isolated clinical evaluation.

METHODS

A total of 730 free flaps in 700 patients were included in the study. We conducted an intra-subject prospective study of a cohort of patients who underwent free flap reconstruction in our unit to compare clinical examination with duplex echography for postoperative monitoring. An inter-subject study was also undertaken comparing the prospective cohort with a historical control group of patients in whom free flap monitoring was made using clinical examination alone. The patency flow and velocities through the artery and vein of the flap were measured at the donor and recipient vessels of every anastomosis by duplex scanning, by the same plastic surgeon every 4 hr, during the first 18 hr after surgery.

RESULTS

Duplex echography and clinical evaluation were used in 175 patients. The historical cohort included a total of 525 flaps. Every patient with suspicion of vascular compromise based on duplex echography was taken back for surgical re-exploration. There were no cases of overdiagnosis using duplex echography (Sensitivity 100%, Specificity 100%). Clinical evaluation detected issues with the vascularan astomoses in 23/175 flaps. However, it failed to detect 12/22 cases which presented with vascular complications and gave a false indication of possible complications in 13 flaps (Sensitivity 45%, Specificity 92%).

CONCLUSION

In our practice, duplex echography is considered a useful adjunct monitoring tool for early detection of postoperative flap compromise, which compliments clinical evaluation. It provides anatomic and hemodynamic information of the vascular status and may therefore increase survival of flaps by allowing earlier detection of vascular compromise, compared to clinical examination alone, in postoperative monitoring of free flaps.

Review of Flap Monitoring Technology in 2020

Advances in free flap reconstruction of complex head and neck defects have allowed for improved outcomes in the management of head and neck cancer. Technical refinements have decreased flap loss rate to less than 4%. However, the potential for flap failure exists at multiple levels, ranging from flap harvest and inset to pedicle lay and postoperative patient and positioning factors. While conventional methods of free flap monitoring (reliant on physical examination) remain the most frequently used, additional adjunctive methods have been developed. Herein we describe the various modalities of both invasive and noninvasive free flap monitoring available to date. Still, further prospective studies are needed to compare the various invasive and noninvasive technologies and to propel innovations to support the early recognition of vascular compromise with the goal of even greater rates of flap salvage.

Outpatient Microsurgical Breast Reconstruction

Background:

The extensive nature of perforator-based breast reconstructions, combined with the need for postoperative flap monitoring, often leads to long hospitalizations. We present an early report demonstrating the feasibility and advantages of a modified operative technique and recovery protocol, allowing us to perform outpatient breast reconstructions with the DIEP flap. This follow-up comprises the experience gained, which is expanded to other perforator-based flaps and not limited to DIEP breast reconstructions.

Methods:

We have implemented a general protocol in patients undergoing breast reconstruction with autologous flaps, promoting early mobilization and discharge by improving postoperative pain and decreasing opioid requirements. This protocol includes intraoperative local anesthesia, a microfascial incision for DIEP harvest with rib preservation, along with prophylactic anticoagulation.

Results:

Ninety-two consecutive patients underwent autologous tissue-based breast reconstruction with DIEP, IGAP, and PAP flaps. No intraoperative complications were reported. All patients were discharged within 23 hours, without evidence of flap compromise. One patient required operative takeback for evacuation of a hematoma on postoperative day 4. No partial or total flap losses were documented. The aim of any procedure should be to get to the patient back to the preoperative status as quickly as possible, as prolonged hospitalizations are associated with higher incidences of infection, deep venous thrombosis, overall dissatisfaction, and higher overall costs of care.

Conclusions:

By using a modified operative technique, multimodal pain control, and postoperative anticoagulant therapy, outpatient perforator-flap–based breast reconstructions can be performed with high success and low complication rates.

Use of Near-infrared Spectroscopy and Implantable Doppler for Postoperative Monitoring of Free Tissue Transfer for Breast Reconstruction: A Systematic Review and Meta-analysis

BACKGROUND

Failure to accurately assess the perfusion of free tissue transfer (FTT) in the early postoperative period may contribute to failure, which is a source of major patient morbidity and healthcare costs. This systematic review and meta-analysis aim to evaluate and appraise current evidence for the use of near-infrared spectroscopy (NIRS) and/or implantable Doppler (ID) devices compared with conventional clinical assessment (CCA) for postoperative monitoring of FTT in reconstructive breast surgery.

METHODS

A systematic literature search was performed in accordance with the preferred reporting items for systematic reviews guidelines. Studies in human subjects published within the last decade relevant to the review question were identified. Meta-analysis using random-effects models of FTT failure rate and STARD scoring was then performed on the retrieved publications.

RESULTS

Nineteen studies met the inclusions criteria. For NIRS and ID, the mean sensitivity for the detection of FTT failure is 99.36% and 100% respectively, with average specificity of 99.36% and 97.63%, respectively. From studies with sufficient reported data, meta-analysis results demonstrated that both NIRS [OR = 0.09 (0.02-0.36); P < 0.001] and ID [OR = 0.39 (0.27-0.95); P = 0.04] were associated with significant reduction of FTT failure rates compared with CCA.

CONCLUSIONS

The use of ID and NIRS provided equivalent outcomes in detecting FTT failure and were superior to CCA. The ability to acquire continuous objective physiological data regarding tissue perfusion is a perceived advantage of these techniques. Reduced clinical staff workload and minimized hospital costs are also perceived as positive consequences of their use.

Use of near-infrared systems for investigations of hemodynamics in human in vivo bone tissue: A systematic review

A range of technologies using near infrared (NIR) light have shown promise at providing real time measurements of hemodynamic markers in bone tissue in vivo, an exciting prospect given existing difficulties in measuring hemodynamics in bone tissue. This systematic review aimed to evaluate the evidence for this potential use of NIR systems, establishing their potential as a research tool in this field. Major electronic databases including MEDLINE and EMBASE were searched using pre-planned search strategies with broad scope for any in vivo use of NIR technologies in human bone tissue. Following identification of studies by title and abstract screening, full text inclusion was determined by double blind assessment using predefined criteria. Full text studies for inclusion were data extracted using a predesigned proforma and quality assessed. Narrative synthesis was appropriate given the wide heterogeneity of included studies. Eighty-eight full text studies fulfilled the inclusion criteria, 57 addressing laser Doppler flowmetry (56 intra-operatively), 21 near infrared spectroscopy, and 10 photoplethysmography. The heterogeneity of the methodologies included differing hemodynamic markers, measurement protocols, anatomical locations, and research applications, making meaningful direct comparisons impossible. Further, studies were often limited by small sample sizes with potential selection biases, detection biases, and wide variability in results between participants. Despite promising potential in the use of NIR light to interrogate bone circulation, the application of NIR systems in bone requires rigorous assessment of the reproducibility of potential hemodynamic markers and further validation of these markers against alternative physiologically relevant reference standards. © 2018 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 36:2595-2603, 2018.

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.

Detection of free flap pedicle thrombosis by infrared surface temperature imaging

BACKGROUND

Reliable detection of any circulatory issue threatening flap viability after free flap surgery is essential for prompt flap salvage. Currently, the gold standard of flap monitoring is clinical monitoring. However, this method presents logistical challenges to insufficient trained personnel. Auxiliary methods are becoming increasingly vital.

MATERIALS AND METHODS

Twelve swine pedicle myocutaneous flaps were harvested and monitored using infrared cameras to investigate the developed monitoring parameters and vascular thrombosis in the free flap model.

RESULTS

The mean flap surface temperature after vein or artery occlusion decreased significantly, but the differences were relatively small. As a result, the difference between recorded (flap surface temperature [T_s]) and predicted (estimated surface temperature [T_es]) flap surface temperature (ΔT = T_s- T_es) was used as the parameter for pedicle thrombosis. A ΔT of <0.86°C was used as a vascular occlusion criterion; the sensitivity and specificity of this parameter were 90% and 81%, respectively. The standard deviation of the surface temperature (SD_T) was another indicator of vascular occlusion; the estimated sensitivity and specificity for vessel occlusion of SD_T < 0.48°C were 84% and 73%, respectively.

CONCLUSIONS

Infrared thermal imaging has the advantages of being noninvasive, contact-free, continuous, and able to detect the whole flap surface area. Two indicators, ΔT and SD_T, can be used with high sensitivity and specificity for early prediction of flap pedicle thrombosis. Further human studies are necessary to validate clinical application of infrared thermal imaging.

Current Techniques for Postoperative Monitoring of Microvascular Free Flaps

Free tissue transfer (FTT) is used in patients with complicated reconstructive needs; it can provide stable wound coverage, improved aesthetic appearance, and restore functional deficits. Despite the high success rates of free flaps, vascular occlusion is a significant risk leading to flap failure. Many studies have demonstrated that the salvage rate for flaps is inversely related to the time between onset of a vascular problem and its surgical correction. As a result, ongoing postoperative monitoring of free flaps for adequate perfusion is imperative to allow timely and accurate diagnosis of vascular compromise. Close monitoring and prompt notification of the physician if vascular compromise occurs are typically undertaken by first-line nurses. We conducted an integrative literature to identify and evaluate commonly used techniques for monitoring vascular free flaps during the postoperative period. We searched PubMed and Science Direct electronic databases, using the key words: "free-flap" and "monitoring." This article discusses commonly monitoring modalities, along with their advantages and limitations. Whereas large academic institutions may have an experienced nursing staff specifically trained in effective methods for monitoring free flap patients, this situation may not exist in all hospitals where free flap surgeries are performed. We describe techniques that allow easy and timely detection of flap compromise by nursing staff while reducing interuser variability.

Remote peripheral tissue oxygenation does not predict postoperative free flap complications in complex head and neck cancer surgery: A prospective cohort study

BACKGROUND

Patients undergoing free flap reconstruction after head and neck cancer may develop free flap complications. In the perioperative period, haemoglobin content and oxygen tissue saturation (StO₂) measured directly on the free flap reflect peripheral tissue oxygenation. However, in this type of surgery, StO₂ cannot always be applied directly or proximate to the free flap. The aim of this study was to assess the possible value of StO₂ measured at the thenar eminence and other 24hour perioperative factors on free flap complications.

METHODS

Inclusion criteria corresponded to patients with head and neck cancer with free flap surgery in whom direct StO₂ could not be monitored on the flap nor in its peripheral area. Patient characteristics and intraoperative data, such as haemoglobin and fluid management, were prospectively collected. StO₂ was measured remotely on the thenar eminence. Data were collected for 24hours and free flap complications were recorded for up to 15days after surgery. Patients were thereafter classified into two groups: with or without free flap complications and the data were compared in consequence.

RESULTS

Forty consecutive patients were prospectively included. Ten patients had postoperative free flap complications and were compared to the 30 other patients without complications. The haemoglobin level at the reperfusion of the flap: (AUC 0.80 [0.65-0.91], threshold 9.9g/dL, P<0.001) and body mass index [BMI] (AUC 0.80 [0.64-0.72], threshold 24.5kg/m², P<0.01) were significantly related to complications.

CONCLUSION

In head and neck complex oncologic reconstructive surgery, haemoglobin and BMI were the most sensitive tools for predicting postoperative free flap complications, while thenar eminence StO₂ was not.

Free Flap Monitoring Using Near-Infrared Spectroscopy: A Systemic Review

BACKGROUND

Although free flaps have become a reliable technique, vascular occlusion remains a significant risk. Flap survival is closely linked to the time interval between the onset and surgical repair of a microvascular problem. The newly emerged near-infrared spectroscopy (NIRS) shows the characteristics of being noninvasive, continuous, easy to use, objective, and immediately reflective, possibly making it an ideal candidate for postoperative flap monitoring.

METHODS

A systemic review was conducted to determine the clinical value of NIRS in the early detection of vascular crisis associated with a free flap. A literature search was conducted using PubMed (MEDLINE), the Cochrane Library, and Web of Science from database inception through October 2013. Studies were selected strictly according to the inclusion/exclusion criteria by 2 independent reviews.

RESULTS

Eight studies were finally included in this review. A total of 710 free flap procedures were performed in 629 patients using NIRS for monitoring. At the same time, 433 free flaps performed in 430 patients without the use of NIRS were included as the control group. No significant differences in the rates of vascular crisis (P = 0.917) and re-exploration (P = 0.187). However, there were significant differences in the salvage rates (P < 0.001) and flap failure rates (P = 0.003). For the free flaps monitored by NIRS that were not associated with vascular crisis, no alarms were raised by NIRS, giving 100% sensitivity and specificity.

CONCLUSION

Near-infrared spectroscopy seems to be a highly suitable candidate for postoperative flap monitoring. Larger-scale, randomized, multicentric clinical trials are needed in the future.

Diffuse reflectance spectroscopy for the measurement of tissue oxygen saturation

Tissue oxygen saturation (StO2) is a useful parameter for medical applications. A spectroscopic method has been developed to detect pathologic tissues, due to a lack of normal blood circulation, by measuring StO2. In this study, human blood samples with different levels of oxygen saturation have been prepared and spectra were acquired using an optical fiber probe to investigate the correlation between the oxygen saturation levels and the spectra. A linear correlation between the oxygen saturation and ratio of the intensities (760 nm to 790 nm) of the spectra acquired from blood samples has been found. In a validation study, oxygen saturations of the blood samples were estimated from the spectroscopic measurements with an error of 2.9%. It has also been shown that the linear dependence between the ratio and the oxygen saturation of the blood samples was valid for the blood samples with different hematocrits. Spectra were acquired from the forearms of 30 healthy volunteers to estimate StO2 prior to, at the beginning of, after 2 min, and at the release of total vascular occlusion. The average StO2 of a forearm before and after the two minutes occlusion was significantly different. The results suggested that optical reflectance spectroscopy is a sensitive method to estimate the StO2 levels of human tissue. The technique developed to measure StO2 has potential to detect ischemia in real time.

Do adjunctive flap-monitoring technologies impact clinical decision making? An analysis of microsurgeon preferences and behavior by body region

BACKGROUND

Multiple perfusion assessment technologies exist to identify compromised microvascular free flaps. The effectiveness, operability, and cost of each technology vary. The authors investigated surgeon preference and clinical behavior with several perfusion assessment technologies.

METHODS

A questionnaire was sent to members of the American Society for Reconstructive Microsurgery concerning perceptions and frequency of use of several technologies in varied clinical situations. Demographic information was also collected. Adjusted odds ratios were calculated using multinomial logistic regression accounting for clustering of similar practices within institutions/regions.

RESULTS

The questionnaire was completed by 157 of 389 participants (40.4 percent response rate). Handheld Doppler was the most commonly preferred free flap-monitoring technology (56.1 percent), followed by implantable Doppler (22.9 percent) and cutaneous tissue oximetry (16.6 percent). Surgeons were significantly more likely to opt for immediate take-back to the operating room when presented with a concerning tissue oximetry readout compared with a concerning handheld Doppler signal (OR, 2.82; p < 0.01), whereas other technologies did not significantly alter postoperative management more than simple handheld Doppler. Clinical decision making did not significantly differ by demographics, training, or practice setup.

CONCLUSIONS

Although most surgeons still prefer to use standard handheld Doppler for free flap assessment, respondents were significantly more likely to opt for immediate return to the operating room for a concerning tissue oximetry reading than an abnormal Doppler signal. This suggests that tissue oximetry may have the greatest impact on clinical decision making in the postoperative period.

Examination of tissue oxygen saturation (StO2) changes associated with vascular pedicle occlusion in a rat Island flap model using near-Infrared spectroscopy

PURPOSE

The purpose of this study was to perform continuous StO(2) monitoring of rat island flaps during pedicle vessel occlusion using near-infrared spectroscopy (NIRS) in order to collect experimental data for StO(2) flap monitoring under optimized conditions.

MATERIALS AND METHODS

Twenty rats were used in this study. The 3 × 3 cm(2) epigastric skin island flaps were elevated on either side. The animals were randomly assigned to two groups; an arterial occlusion group (n = 10) and a venous occlusion group (n = 10). The StO(2) values of the flaps were observed for over 30 min for the pedicle artery or venous occlusion, followed by an additional 30 min release.

RESULTS

The baseline StO(2) value was 78.4% ± 3.2% in the arterial occlusion group, compared to 78.5% ± 5.8% in the venous occlusion group, with no significant differences (P > 0.05). The StO(2) values decreased immediately after arterial occlusion, whereas a temporal StO(2) increase was initially observed after venous occlusion, followed by a StO(2) decrease. The StO(2) values decreased 27.3% ± 7.1% after arterial occlusion and 28.4% ± 19.1% after venous occlusion at 30 min after pedicle vessel clamping (P > 0.05). The StO(2) values were 0.4% ± 5.8% lower than baseline 30 min after arterial release (P > 0.05), while 18.9% ± 11.3% lower than baseline 30 min after venous release (P < 0.01).

CONCLUSION

NIRS can be used to indicate StO(2) changes in flaps with the pedicle vessel occlusion and differentiate between pedicle artery and vein occlusion. Further investigations are needed to obtain definitive evidence associated with predicting the degree of flap viability and determine the practical use of this technique.

Variables affecting postoperative tissue perfusion monitoring in free flap breast reconstruction

Postoperative flap monitoring is a key component for successful free tissue transfer. Tissue oxygen saturation measurement (TOx) with near-infrared spectrophotometry (NIRS) is a method used for this purpose. The aim of this study was to identify external variables that can affect TOx. Patients who had breast reconstruction with free flaps were monitored prospectively and intra-operative details were recorded. Flap TOx was recorded with NIRS pre-extubation, postextubation, and then every four hours for 36 hours. At each of these time points, blood oxygen saturation (SO2), amount of supplemental oxygen, and blood pressure were recorded. Thirty flaps were monitored. Initially, a significant trend over time was detected such that for every increase of 24 hours, TOx decreased on average by 2.1% (P = 0.025). However, when accounting for SO2 levels, this decrease was no longer significant (P = 0.19). An increase by 1% in SO2 produced an increase in TOx reading of 0.36 (P = 0.007). The amount of supplemental O2, systolic blood pressure, and diastolic blood pressure did not have a significant impact on TOx (P > 0.05). The TOx values were highest in the free TRAM flaps and were lower in decreasing order in the muscle-sparing TRAM, DIEP, and SIEA flaps (P > 0.05). The TOx values did not significantly correlate with vessel size, perforator number, or perforator row. Postoperative flap TOx was found to correlate with SO2 and was not significantly dependent on blood pressure, supplemental O2, or surgical variables. Careful interpretation of oximetry values is essential in decision making during postoperative flap monitoring.

Color Doppler ultrasound: effective monitoring of the buried free flap in facial reanimation

OBJECTIVE

The gracilis muscle free flap has become a reliable means for smile reanimation for patients with facial paralysis. Because it is a buried flap, it presents a postoperative monitoring challenge. We sought to evaluate our experience with color Doppler ultrasound in the monitoring of gracilis free flap viability in the immediate postoperative setting.

STUDY DESIGN

Case series with planned data collection.

SETTING

Tertiary medical center.

METHODS

Patients with facial paralysis treated with gracilis muscle free flap for smile reanimation performed between March 2009 and November 2010 were evaluated by color Doppler ultrasound and included in the study. Our experience with the use of the color Doppler ultrasound to monitor the gracilis muscle flap is presented.

RESULTS

Forty-six patients were identified. In all cases, color Doppler ultrasound was used postoperatively to assess flow through the vascular pedicle. Outcomes included an early flap survival rate of 100%, with no instances of equivocal or absent flow on either the arterial or venous side. Color Doppler ultrasound provided important objective information regarding muscle perfusion postoperatively in several instances of equivocal postoperative perfusion of the flap.

CONCLUSION

Color Doppler ultrasound is a safe, noninvasive method that can be performed serially to evaluate a buried free flap. We have had success in verifying normal arterial and venous flow through the pedicle using this method of monitoring of the gracilis muscle free flap during facial reanimation, and in 3 instances, it eliminated the need for wound exploration to verify appropriate muscle perfusion.

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

BACKGROUND

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

Outcome measures for evaluation of treatments for osteonecrosis

With the advent of cell-based therapies, biologics, and pharmaceuticals for the potential treatment of osteonecrosis, it is important to conduct evaluations using scientifically accepted outcomes measures. For the treatment of osteonecrosis, most studies have focused on pain relief, surgery, or the need for surgery, disease progression (advancing stage), and change in lesion size. Quantification of imaging techniques continue to gain in sophistication but have not yet been validated for use in clinical trials. Despite recent interest in using biomarkers or genetic markers in the diagnosis and analysis of disease progression, more research is needed to determine the sensitivity and specificity of these techniques with respect to osteonecrosis.