Postoperative Monitoring Of Free Flaps Research Articles

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.

222 Pediatric Pulse Oximetry to Monitor the Post-Operative Integrity of Free Flaps

Abstract Introduction The post-operative monitoring of free-flaps can be a challenge, particularly for junior staff on-call and in patients with darker or mottled skin. We present a case employing paediatric pulse oximetry to monitor a free flap where clinical assessment was challenging, illustrating its value as an adjunct to existing techniques such as doppler. Case A 23-year-old patient underwent tenolysis to his anterior right leg compartment due to a painful, tethered scar following injury. He subsequently had a superficial circumflex iliac perforator (SCIP) flap anastomosed end-to-side to his posterior tibial artery. The operation was technically challenging, but the flap had a strong doppler and remained clinically well until day 4 post-op, where it became mottled but remained warm and soft. Clinical assessment was equivocal, and a paediatric pulse oximeter was taped to the flap, consistently showing saturations >95%, providing reassurance out-of-hours and facilitating the decision to delay haematoma evacuation for the following day. The flap survived and the patient did well. Conclusions The use of paediatric pulse oximetry to assess free flaps is a useful technique for clinically ambiguous cases where re-exploration could compromise survival. It is cheap, widely accessible and can be easily employed by junior clinicians and nurses who may be relatively inexperienced in their assessment of flaps’ clinical condition.

Postoperative free flap monitoring in reconstructive surgery-man or machine?

Free tissue transfer is widely used for the reconstruction of complex tissue defects. The survival of free flaps depends on the patency and integrity of the microvascular anastomosis. Accordingly, the early detection of vascular comprise and prompt intervention are indispensable to increase flap survival rates. Such monitoring strategies are commonly integrated into the perioperative algorithm, with clinical examination still being considered the gold standard for routine free flap monitoring. Despite its widespread acceptance as state of the art, the clinical examination also has its pitfalls, such as the limited applicability in buried flaps and the risk of poor interrater agreement due to inconsistent flap (failure) appearances. To compensate for these shortcomings, a plethora of alternative monitoring tools have been proposed in recent years, each of them with inherent strengths and limitations. Given the ongoing demographic change, the number of older patients requiring free flap reconstruction, e.g., after cancer resection, is rising. Yet, age-related morphologic changes may complicate the free flap evaluation in elderly patients and delay the prompt detection of clinical signs of flap compromise. In this review, we provide an overview of currently available and employed methods for free flap monitoring, with a special focus on elderly patients and how senescence may impact standard free flap monitoring strategies.

Reliability of Postoperative Free Flap Monitoring with a Novel Prediction Model Based on Supervised Machine Learning.

Postoperative free flap monitoring is a critical part of reconstructive microsurgery. Postoperative clinical assessments rely heavily on specialty-trained staff. Therefore, in regions with limited specialist availability, the feasibility of performing microsurgery is restricted. This study aimed to apply artificial intelligence in postoperative free flap monitoring and validate the ability of machine learning in predicting and differentiating types of postoperative free flap circulation. Postoperative data from 176 patients who received free flap surgery were prospectively collected, including free flap photographs and clinical evaluation measures. Flap circulation outcome variables included normal, arterial insufficiency, and venous insufficiency. The Synthetic Minority Oversampling Technique plus Tomek Links (SMOTE-Tomek) was applied for data balance. Data were divided into 80%:20% for model training and validation. Shapley Additive Explanations were used for prediction interpretations of the model. Of 805 total included flaps, 555 (69%) were normal, 97 (12%) had arterial insufficiency, and 153 (19%) had venous insufficiency. The most effective prediction model was developed based on random forest, with an accuracy of 98.4%. Temperature and color differences between the flap and the surrounding skin were the most significant contributing factors to predict a vascular compromised flap. This study demonstrated the reliability of a machine-learning model in differentiating various types of postoperative flap circulation. This novel technique may reduce the burden of free flap monitoring and encourage the broader use of reconstructive microsurgery in regions with a limited number of staff specialists.

Difference between Capillary Blood Glucose of Free Flap and the Patient: A Novel Objective Marker of Free Flap Vascular Compromise during Postoperative Monitoring.

Background Defining cut-off values of flap glucose levels in diagnosing free flap vascular compromise, without taking patients' glucose levels into account, does not hold good in all circumstances, especially in cases of high fluctuations in patients' capillary blood glucose and in diabetic patients. The aim of our study was to establish the role of capillary blood glucose measurements of the flap in relation to patients' fingertip, as an objective tool for postoperative free flap monitoring. Methods A total of 76 free flaps underwent postoperative monitoring with reference test (clinical parameters) and simultaneously with our index test (difference between capillary blood glucose of free flap and the patient), in non-diabetic and diabetic patients. Patients' demography and flap characteristics were also recorded. An ROC curve was plotted to determine diagnostic accuracy and cut-offs of the index test in diagnosing free flap vascular compromise. Results Our Index test has a cut-off value of 24.5 mg/dL with 68.75% sensitivity and 93% specificity, with an accuracy of 91.54%. Conclusion The difference between capillary blood glucose of free flap and the patient is simple, feasible, and inexpensive, and can be done by any health care professional and does not require any specialized facilities or training. It has an excellent diagnostic accuracy to detect impending free flap vascular compromise, especially in non-diabetics. Although in diabetics, this test becomes less accurate. Being an observer-independent objective test, the difference in capillary blood glucose of patient and flap measurement can be used as a highly reliable tool for postoperative free flap monitoring.

An Analysis of the Implantable Doppler Probe for Postoperative Free-Flap Monitoring and Risk Factor Analysis for Revision Surgery in Facial Reanimation Surgery.

Background: Postoperative monitoring after free functional gracilis transfer for smile reconstruction in long-standing facial paralysis is challenging as clinical assessments are limited. Objective: In patients receiving free gracilis transfer for smile reconstruction, we compared the implantable Doppler probe with a handheld Doppler/intraoperative blood flow regarding the reliability in detecting perfusion compromised free flaps. Methods: In a retrospective cohort study we analyzed facial paralysis patients who, after free functional smile reconstruction, were postoperatively monitored using the implantable Doppler probe. Furthermore, we conducted a multiple logistic regression analysis on risk factors for vascular complications. Results: We included 119 patients who received 125 free functional gracilis transfers. The sensitivity of the implanted Doppler probe was 1.0 and the specificity 0.88. There were no false-negative results (negative predictive value = 1.0). The calculated positive predictive value was 0.41. We used a handheld Doppler device to verify signal changes. The combined positive predictive value of both tests was 0.91. Previous surgery in the surgical field was a risk factor for impaired blood flow. Conclusions: The implantable Doppler probe proved to be a reliable tool for postoperative monitoring of free functional gracilis transfer in facial reanimation surgery. Special care should be taken in preoperated patients.

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.

Postoperative Monitoring of Free Flaps Using Smartphone Thermal Imaging May Lead to Ambiguous Results: Three Case Reports

Postoperative Monitoring of Free Flaps Using Smartphone Thermal Imaging May Lead to Ambiguous Results: Three Case Reports

Utilizing Mask RCNN for Monitoring Postoperative Free Flap: Circulatory Compromise Detection Based on Visible-Light and Infrared Images

The new postoperative free flap monitoring system combines visible-light and infrared techniques to overcome the limitations of our previous study, such as resistance to illumination change, patients with large movements, and the infrared images being too blurry to identify the boundary. In the visible-light system, the Mask region-based convolutional neural networks (RCNN) was adopted to segment the region of the free flap, and these time-course visible images were aligned using our proposed image registration method. Then, the registered visible images were projected onto the infrared image by the coordinate transformation. The analysis method adopted the residual factor analysis to extract the more unvarnished specific factors. The experiments were divided into two parts. In image processing, the accuracy of the coordinate transformation has a mean error of 1.78 pixels and a standard deviation of 0.98 pixels. The segmentation results showed excellent performance in the most severe case with apparent motion and rotation, covered by gauze and the ventilator, as well as illumination variation. The dice coefficient is 0.9551 ± 0.0158, and the Hausdorff distance is 2.3943 ± 0.3921 pixels. The image registration results also reveal that the Canny edge of the deformed image was superimposed onto the reference image well. In circulatory compromise detection, the vascular congestion was detected much earlier than manual observation, and the classified type of occlusion was the same as the clinical reports. Therefore, the dual-camera monitoring system provides a reliable tool for the surgeon to hold onto the chance of repairing the free flap with vascular obstruction.

Fingerstall-type Tissue Oximetry Reduced Anxiety of Nurses in Postoperative Nursing Monitoring of Free Flaps.

Background:Postoperative free flap monitoring is essential for immediately detecting obstruction of anastomosed vessels with successive recovery surgery for salvaging flaps. We performed postoperative nursing monitoring using handheld Doppler sonography, but nurses reported feeling anxious with this approach and demanded a clear-cut evaluation method. Therefore, we implemented monitoring with the fingerstall-type tissue oximeter Toccare, a noninvasive device that enables easy flap checking by simply touching the flap with a probe.Method:Handheld Doppler was used for nursing monitoring from April to October 2020, with anxiety associated with its use reported. We collected information via an anonymous questionnaire to determine the reason for the anxiety. Toccare was subsequently applied for postoperative free flap monitoring by nurses. The protocol involved measuring tissue oxygen saturation by touching the flap with a Toccare probe every 4 hours from 24 to 100 hours postoperatively. Seven months later, a second anonymous questionnaire was conducted, and results were compared.Result:Free deep inferior epigastric artery perforator flaps and anterolateral thigh flaps (n = 5 each) were included. The average tissue oxygen saturation values in the deep inferior epigastric artery perforator and anterolateral thigh flaps were 52.0% and 52.4%, respectively. According to the second questionnaire about Toccare, 7% felt anxious, 62% felt slightly anxious, and 31% did not feel anxious. Toccare was preferred by 89% of nurses who had used both methods.Conclusions:Flap monitoring using Toccare reduced nurses’ anxiety. A numerical evaluation method with easy handling and clear doctor call criteria is essential for low-anxiety nursing monitoring.

Postoperative Detection of Free Flap Congestion in a Fitzpatrick Skin Type VI Patient using the Flir Thermal Imaging Camera: A Case Report and Literature Review

BACKGROUND: Free flaps are routinely used in complex tissue reconstruction due to their functionality and reliability. Postoperative monitoring remains a challenge despite the current available modalities. Clinical examination remains the gold standard, with color being the most sensitive marker of flap compromise. Assessment of flap color is more challenging in Fitzpatrick V-VI skin types, masking visual signs of ischemia or congestion. A Forward-Looking Infrared (FLIR) ONE smartphone based thermal imaging camera can be used to detect differences in flap temperature from the surrounding native tissue and could be used to identify early flap compromise. This simple technology used with a smartphone may be a useful method to assess postoperative flap perfusion. METHODS: Institutional review board approval was obtained for postoperative flap monitoring using FLIR technology for patients undergoing complex reconstruction with a free anterolateral thigh (ALT) flap. The FLIR camera is a simple attachment that plugs into iPhone models 7–12 and takes thermal pictures with temperature readings by a spot pyrometer using their App. Preoperatively the FLIR camera spot pyrometer measured baseline temperature by ALT flap location. Temperature recordings of the flap and the surrounding native tissue were taken immediately postoperatively and then at regular intervals in addition to our standard free flap monitoring protocol. This protocol was utilized for one patient in this report who underwent a free ALT flap to scalp after sarcoma resection and Fitzpatrick skin type VI. RESULTS: FLIR thermography measured the preoperative central flap temperature at 32.6°C. Immediately postoperatively the flap temperature was 33.9°C, and the surrounding native skin was 35.8°C. Sixteen hours postoperatively the central portion of the flap was found to be 28.0°C, 8.4°C cooler than the surrounding native skin, suggesting flap ischemia. Clinical examination of the flap showed edema and return of dark blood on scratch test but no frank discoloration. Handheld Doppler signal showed arterial signal but no venous signal. The patient was taken immediately for operative exploration, which showed a 30 cm3 hematoma compressing the vascular pedicle. Following evacuation, the central flap’s temperature was 35.6°C. The patient was discharged on POD 7 and still has a complete reconstruction. CONCLUSIONS: FLIR ONE was helpful in detecting flap congestion and ultimately flap salvage. Prompt operative evacuation of the hematoma prevented flap loss and associated morbidity to the patient. This patient case highlights the inherent challenges in evaluating skin paddles of Fitzpatrick V–VI skin types and depicts the utility of a low-cost thermography camera that can aid in identifying a threatened flap. The user-friendly, non-contact nature of FLIR ONE adds a useful and objective datapoint in postoperative free flap monitoring that can improve patient outcomes when combined with conventional monitoring techniques in all patients, particularly those with difficult flaps to monitor. Our team hopes to continue studying thermal camera temperature differences in postoperative free flap monitoring to service our patients and provide insight into this technology’s utility for reconstructive plastic surgery.

507 Quantifying the Limitations of Clinical and Technology-Based Flap Monitoring Strategies Using A Systematic Recurrent Themes Analysis

Abstract Aim Multiple techniques exist to monitor free flap viability postoperatively, varying with practical and personal preference, yet the limitations of each technique remain unquantified. This systematic review aims to identify the most commonly reported limitations of these techniques in clinical practice. Method A systematic review was conducted according to PRISMA guidelines using MEDLINE, EMBASE and Web of Science with search criteria for postoperative free flap monitoring techniques. Search results were independently screened using defined criteria by two authors and a senior clinician. Limitations of the techniques found in the discussion section of eligible papers were recorded and categorised using recurrent theme analysis. Results A total of 4826 records were identified. 4643 articles met the eligibility criteria and were subsequently reviewed, with 195 papers included in the final analysis. The most frequently reported limitations of clinical monitoring were interpretation requiring expertise (25% of related papers), unsuitability for buried flaps (21%), and lack of quantitative/objective values (19%). For non-invasive technologies: lack of quantitative/objective values (21%), cost (16%) and interpretation requiring expertise (13%). For invasive technologies: application requiring expertise (25%), equipment design and malfunction (13%) and cost (13%). Conclusions This is the first systematic review to quantify the limitations of different flap monitoring techniques as reported in the literature. The limitations identified better inform clinicians to decide the best single or combined monitoring approach for their practice and aid development in new flap monitoring technologies.

Quantifying the Limitations of Clinical and Technology-based Flap Monitoring Strategies using a Systematic Thematic Analysis.

Background:Multiple techniques exist to monitor free flap viability postoperatively, varying with practical and personal preference, yet the limitations of each technique remain unquantified. This systematic review aims to identify the most commonly reported limitations of these techniques in clinical practice.Methods:A systematic review was conducted according to PRISMA guidelines using MEDLINE, EMBASE, and Web of Science with search criteria for postoperative free flap monitoring techniques. Search results were independently screened using defined criteria by two authors and a senior clinician. Limitations of the techniques found in the discussion section of eligible articles were recorded and categorized using thematic analysis.Results:A total of 4699 records were identified. In total, 2210 articles met the eligibility criteria and were subsequently reviewed, with 195 papers included in the final analysis. The most frequently reported limitations of clinical monitoring were interpretation requiring expertise (25% of related papers), unsuitability for buried flaps (21%), and lack of quantitative/objective values (19%). For noninvasive technologies, the limitations were lack of quantitative/objective values (21%), cost (16%), and interpretation requiring expertise (13%). For invasive technologies, the limitations were application requiring expertise (25%), equipment design and malfunction (13%), and cost (13%).Conclusions:This is the first systematic review to quantify the limitations of different flap monitoring techniques, as reported in the literature. This information may enhance the choice in monitoring strategy for a reconstructive service, and inform the development and refinement of new flap monitoring technologies.

Monitoring Breast Reconstruction Flaps Using Near-Infrared Spectroscopy Tissue Oximetry.

Free flap reconstruction is a common procedure with success rates greater than 99%. However, vascular complications may occur, resulting in flap failure. For this reason, early detection of vascular compromise is crucial for flap salvage. Vascular complications may be detected early by monitoring tissue oximetry parameter changes using near-infrared spectroscopy (NIRS). This method of noninvasive monitoring can evaluate changes in flap oxygenation levels caused by arterial and venous thrombosis before surgical reexploration. The goal of this study was to assess the validity of using NIRS oximetry for monitoring free flaps. We conducted a prospective cohort observational study of 10 patients undergoing breast reconstruction. We used the INVOS 7100 cerebral oximetry monitoring system (Medtronic, Dublin, Ireland) to provide 24-hr continuous postoperative monitoring of flap perfusion and compared the data with clinical assessment findings. The median patient age was 57 years (range = 41-61 years). Patients underwent immediate breast reconstruction with deep inferior epigastric perforator (DIEP) flap surgery (n = 4), delayed reconstruction with DIEP flap surgery (n = 4), transverse upper gracilis flap surgery (n = 1), and latissimus dorsi flap with lipofilling (n = 1). We successfully monitored all 10 flaps for 24 hr postoperatively. The overall flap survival rate was 100%. Findings of clinical examination, Doppler studies, and surgical outcome were consistent with NIRS monitoring. In conclusion, NIRS tissue oximetry could potentially provide a noninvasive method for effective postoperative monitoring of free flaps.

Response to: “Commentary on: Postoperative monitoring of free flaps using a low-cost thermal camera: a pilot study by Hummelink S, Kruit AS, van Vlaenderen ARW, Schreinemachers MJM, Steenbergen W &amp; Ulrich DJO”

Response to: “Commentary on: Postoperative monitoring of free flaps using a low-cost thermal camera: a pilot study by Hummelink S, Kruit AS, van Vlaenderen ARW, Schreinemachers MJM, Steenbergen W &amp; Ulrich DJO”

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

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. 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. 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%). 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.

Random-pattern versus perforator-based adipocutaneous skin paddles for postoperative monitoring of free muscle flaps—a comparative retrospective cohort study

Free microvascular muscle flaps represent well-established reconstructive options for complex soft tissue defects. However, due to their lack of cutaneous capillary beds, they are difficult to monitor postoperatively. To this end, random and axial-pattern adipocutaneous skin paddles are often included. The objective of the study was to compare the impact of random-pattern versus perforator-based adipocutaneous skin paddles on operative efficacy and muscle flap safety. Between August 2014 and July 2016, a total of 120 free muscle flaps were included in this retrospective monocentric cohort study. Based on their skin-paddle type, they were either grouped into a 'perforator-based' (group Pb) or 'random-pattern' (group Rp) cohort. The electronic medical records and operative reports of all patients were subsequently reviewed and patient, defect, and flap characteristics of both groups were compared. The effect of the competing skin paddle types on the overall operative time, incidences of flap loss or microvascular complications, and total length of hospital stay were then assessed. Group Pb comprised 72 flaps, whereas 48 flaps constituted group Rp. Patient, defect, and flap characteristics were similar between both groups. Groups Pb and Rp were comparable regarding patient age (group Pb: 61 (10-90) vs. Rp: 59 (13-81), p = 0.556), ASA (American Society of Anesthesiologists) class (group Pb: 3 (1-4) vs. Rp 3 (1-3), p = 0.977), and comorbidities, summarized by the Charlson comorbidity index (CCI; group Pb: 1 (0-4 vs. Rp: 1 (0-5), p = 0.295). Both types of monitoring skin paddles were equally reliable. There was no significant difference in the mean operation time between both groups (group Pb: 373 ± 122 min vs. Rp: 342 ± 84 min, p = 0.124). In-patient treatment after flap surgery and total length of hospital stay were significantly shorter in group Pb (group Pb: 24 ± 10 days vs. Rp: 32 ± 17 days, p = 0.002 and group Pb: 39 ± 15 vs. Rp: 48 ± 24, p = 0.022). Perforator-based skin paddles are a reliable tool for postoperative perfusion monitoring of free muscle flaps and help avoid additional surgical interventions as opposed to their random-pattern counterparts. Thus, the overall and postoperative length of hospital stay is significantly reduced.

Post-operative monitoring of free flaps using a low-cost thermal camera: a pilot study

BackgroundCareful post-operative monitoring of free flaps is important in flap survival; immediate action increases flap salvage rate. Although various methods are available, room for improvement remains. Thermal cameras have proven their value in medicine and are nowadays readily available at low costs. The objective of this study was to evaluate the potential of an affordable infrared thermal camera and software in the detection of failing free flaps during post-operative monitoring.MethodsFree myocutaneous rectus abdominis flaps were harvested in 16 female landrace pigs and replanted after several hours of storage. All flaps were assessed with indocyanine green fluorescence angiography as well as hourly clinical assessment of skin colour, turgor and capillary refill. Furthermore, thermal photographs were taken simultaneously with the FLIR One thermal camera smartphone module. These photographs were processed in MATLAB and evaluated on their additional value as an indicator for flap failure.ResultsOut of 16 flaps, three flaps failed due to arterial failure and one flap developed venous congestion. The mean flap temperature compared to adjacent control skin proved to be most indicative for flap failure. All unsuccessful flaps showed lower temperatures after failure compared to the uncompromised free flaps.ConclusionsAn affordable thermal camera module can potentially contribute to post-operative free flap monitoring. Vascular compromise in free flaps can be distinguished by investigating relative temperature differences between the flap and reference skin. Until the FLIR One camera has been extensively investigated in a human population, it should be used in conjunction with conventional monitoring techniques.Level of evidence: Level IV, diagnostic study

Comparison of arterial and venous implantable Doppler postoperative monitoring of free flaps: Systematic review and meta‐analysis of diagnostic test accuracy

Early detection of vascular compromise following free flap microsurgical reconstruction is essential. This can lead to timely reoperations and flap salvage. Both arteries and veins are monitored postoperatively with implantable ultrasound Dopplers based on surgeon preference with no consensus as to which method is best. This systematic review and meta-analysis compared arterial to venous implantable Dopplers for postoperative monitoring of microsurgical free flap reconstruction. Five databases (MEDLINE via PubMed, EMBASE, Cochrane Library, Web of Science, and Scopus) were systematically and independently searched. PRISMA and Cochrane guidelines were strictly followed. Clinical characteristics, donor and recipient sites, specific arterial or venous vessels, diagnostic data, outcomes, and complications were recorded. The seven studies included in the meta-analysis were published from 1994 to 2018, with results from 38 of the possible 64 outcomes and complications queried. A total of 763 flaps with implantable Doppler probes on 527 arteries and 388 veins were included in the study. Compared to patients monitored with venous implantable Dopplers, arterial monitoring was associated with a risk of false-positives reduced by 74% (RR:0.26, 95% CI:0.12, 0.55, I2 = 40%, p = .0004) and risk of signal loss reduced by 63% (RR:0.37, 95% CI:0.24, 0.59, I2 = 26%, p < .0001). Patients being monitored with a venous implantable Doppler did not show significantly different sensitivities, specificities, true-positives, false-negatives, true-negatives, positive predictive values, negative predictive values, time to signal loss, take-backs, salvage rates, flap failures, flap failure rates, arterial, venous, vascular, and hematoma compromise compared to an arterial implantable Doppler. These findings suggest arteries may be the best vessels to monitor when using an implantable Doppler following free flap microsurgical reconstruction. Caution is advised when interpreting these findings for clinical significance due to no significant differences in take-backs, SR, flap failures, and FFR.

Postoperative Free Flap Monitoring in Lower Extremity Trauma

Postoperative Free Flap Monitoring in Lower Extremity Trauma