Prevention of thrombosis after microvascular tissue transfer in the head and neck. A review of the literature and the state of affairs in Dutch Head and Neck Cancer Centers

Acetylsalicylic Acid is Not Associated With Improved Clinical Outcomes After Microsurgical Breast Reconstruction

INTRODUCTION

Microvascular thrombosis with resultant flap loss remains a devastating complication in autologous breast reconstruction. While acetylsalicylic acid (ASA) for prevention of microvascular thrombosis is commonly administered postoperatively, clinical evidence supporting this practice remains insufficient. Here, we investigate the association of postoperative ASA administration with differences in clinical outcomes following microsurgical breast reconstruction.

METHODS

A prospectively maintained database was queried to identify patients who had undergone microsurgical breast reconstruction. Patients were categorized based on whether they had received postoperative ASA for 30 d (Group 1) or had not received ASA (Group 2). Patient demographics, reconstructive outcomes, complications, and transfusion requirements were retrieved.

RESULTS

One hundred thirty six patients with a mean age of 49.5 y and a mean body mass index of 28.5 kg/m² who had undergone a total of 216 microsurgical breast reconstructions were included. No significant differences were noted with regard to patient demographics with the exceptions of increased rates of neoadjuvant chemotherapy and delayed reconstruction in Group 1. There were no significant differences in the rates of postoperative complications including breast hematoma, mastectomy skin flap necrosis, partial flap necrosis, seroma, and deep venous thrombosis between patients who did or did not receive ASA postoperatively. Similarly, no difference was noted regarding postoperative blood transfusion rates (Group 1: 9.9% versus Group 2: 9.1%; P = 0.78). Finally, patients in Group 1 had significantly longer hospital stays (Q1 = 4, median = 4.5, Q3 = 5).

CONCLUSIONS

Postoperative ASA administration is not associated with improved postoperative clinical outcomes. The use of ASA routinely after autologous breast reconstruction does not appear to be a necessity in practice.

Analysis of intraoral microvascular anastomosis in maxillofacial defects reconstruction

This review summarizes the research progress in the field of intraoral microvascular anastomosis techniques (IAT) and attempts to investigate the indications for procedures in which IAT can be applied, the surgical procedure and the difficulties involved, technical assessments, result evaluation and the perspective. Currently, microvascular anastomosis technique is widely used in maxillofacial defects reconstruction from various causes including cutaneous injury or congenital deformity which usually required extensive flap reconstruction and therefore a vascular free flap is routinely used. Conventional microvascular anastomosis reconstruction techniques cannot avoid new incisions, which will affect the postoperative aesthetic situation. Surgeons have therefore attempted to improve this technique to effectively eliminate scars caused by surgery: some patients can be chosen to undergo microvascular anastomosis of the free flap intraorally, thus reducing the extraoral incision caused by the anastomosis located in neck or maxillofacial improving the postoperative appearance of the patients. In addition to preserving the external appearance, intraoral anastomosis technique (IAT) can also solve some other problems of maxillofacial vascular anastomosis, such as insufficient vessel pedicle length and high risk of facial nerve injury.

Standardized Perioperative Protocol and Routine Ketorolac Use for Head and Neck Free Flap Reconstruction

No consensus exists on ideal perioperative management or anticoagulation regimen for free flap reconstruction of the head and neck. Perceived benefits from antiplatelet therapy need to be balanced against potential complications. Ketorolac, a platelet aggregation inhibitor and a parenteral analgesic, was introduced as part of a standardized perioperative protocol at our institution. In this study, we aimed to examine the impact of implementation of this protocol as well as complications associated with the routine use of perioperative ketorolac in a diverse group of patients who underwent head and neck free flap reconstruction.

Pain management with popliteal block for fibular graft harvesting in head and neck reconstruction; a randomised double-blind placebo-controlled study

BACKGROUND AND OBJECTIVES

Curative treatment for locally advanced head and neck tumours often includes reconstructive surgery using a microvascular free flap. Effective recuperation is essential but may be impeded by postoperative donor site pain. The aim of this study was to evaluate the effects of a continuous popliteal block on postoperative pain after fibular graft harvesting.

MATERIAL AND METHODS

In this randomized double-blind placebo-controlled study adult patients scheduled for reconstructive head and neck surgery with a microvascular free fibular graft received an indwelling popliteal nerve block catheter and were randomized to receive continuous levobupivacaine/ropivacaine or placebo during the first postoperative week. Primary outcome was postoperative extremity pain assessed using the numerated rating scale (NRS). Secondary outcomes included opioid consumption.

RESULTS

In total 24 patients were included. The median (median, IQR [range]) postoperative extremity NRS scores was lower in the local anaesthetic (LA) group (2, 0-3 [0-10]) compared to the placebo group (2, 1-4 [0-10]), p = 0.008. The LA group also experienced fewer episodes of breakthrough pain, defined as NRS ≥ 4 (17% vs 33% of observations), p = 0.009. Furthermore, median (median, IQR [range]) opioid consumption the first postoperative week was lower in the LA group (109 mg, 74-134 [19-611]) compared to the placebo group (202 mg, 135-241 [78-749]), p = 0.010. No complications attributed to the blocks were observed.

CONCLUSION

Continuous popliteal block significantly reduced postoperative extremity pain and opioid consumption in patients undergoing fibular graft harvesting for head and neck reconstructive surgery.

Infrared Thermography in Wound Care, Surgery, and Sports Medicine: A Review

For many years, the role of thermometry was limited to systemic (core body temperature) measurements (e.g., pulmonary catheter) or its approximation using skin/mucosa (e.g., axillary, oral, or rectal) temperature measurements. With recent advances in material science and technology, thermal measurements went beyond core body temperature measurements and found their way in many medical specialties. The article consists of two primary parts. In the first part we overviewed current clinical thermal measurement technologies across two dimensions: (a) direct vs. indirect and (b) single-point vs. multiple-point temperature measurements. In the second part, we focus primarily on clinical applications in wound care, surgery, and sports medicine. The primary focus here is the thermographic imaging modality. However, other thermal modalities are included where relevant for these clinical applications. The literature review identified two primary use scenarios for thermographic imaging: inflammation-based and perfusion-based. These scenarios rely on local (topical) temperature measurements, which are different from systemic (core body temperature) measurements. Quantifying these types of diseases benefits from thermographic imaging of an area in contrast to single-point measurements. The wide adoption of the technology would be accelerated by larger studies supporting the clinical utility of thermography.

Multidisciplinary Practice Variations of Anti-Thrombotic Strategies for Free Tissue Transfers

Background: Venous thrombosis, the leading cause of free flap failure, may have devastating consequences. Many anti-thrombotic agents and protocols have been described for prophylaxis and treatment of venous thrombosis in free flaps. Methods: National surveys were distributed to microsurgeons (of both Plastics and ENT training) and hematology and thrombosis specialists. Data were collected on routine screening practices, perceived risk factors for flap failure, and pre-, intra-, and post-operative anti-thrombotic strategies. Results: There were 722 surveys distributed with 132 (18%) respondents, consisting of 102 surgeons and 30 hematologists. Sixty-five surgeons and 9 hematologists routinely performed or managed patients with free flaps. The top 3 perceived risk factors for flap failure according to surgeons were medical co-morbidities, past arterial thrombosis, and thrombophilia. Hematologists, however, reported diabetes, smoking, and medical co-morbidities as the most important risk factors. Fifty-four percent of physicians routinely used unfractionated heparin (UFH) or low-molecular-weight heparin (LMWH) as a preoperative agent. Surgeons routinely flushed the flap with heparin (37%), used UFH IV (6%), or both (8%) intra-operatively. Surgeons used a range of post-operative agents such as UFH, LMWH, aspirin, and dextran while hematologists preferred LMWH. There was variation of management strategies if flap thrombosis occurred. Different strategies consisted of changing recipient vessels, UFH IV, flushing the flap, adding post-operative agents, or a combination of strategies. Conclusions: There are diverse practice variations in anti-thrombotic strategies for free tissue transfers and a difference in perceived risk factors for flap failure that may affect patient management.

Factors impacting successful salvage of the failing free flap

BACKGROUND

Understanding factors impacting successful salvage of a compromised free flap.

METHODS

Multi-institutional review of free flap reconstructions for head and neck defects (n = 1764).

RESULTS

Free flap compromise rate: 9% (n = 162); 46% salvaged (n = 74). Higher salvage rates in initial 48 hours (64%) vs after (30%; P < .001). Greater compromise (14%) and failure (8%) if inset challenging vs straightforward (6% compromise, 4% failure; P = .035). Greater compromise (23%) and failure (17%) following intraoperative anastomosis revision vs no revision (7% compromise, 4% failure; P < .0001). Success following arterial insufficiency was lower (60% failed, 40% salvaged) vs venous congestion (23% failed, 77% salvaged) (P < .0001). Greater flap salvage following thrombectomy (66%) vs no thrombectomy (34%; P < .0001). Greater flap salvage if operative duration ≤8 hours (57%), vs >8 hours (40%) (P = .04).

CONCLUSIONS

There were higher rates of free flap salvage if the vascular compromise occurred within 48 hours, if due to venous congestion, if operative duration ≤8 hours, and if the anastomosis did not require intraoperative revision.

Thromboelastometry for Assessing Risks of Free Flap Thrombosis in Patients Undergoing Microvascular Surgery

Introduction: Coagulation assessment is often missing in microvascular surgery. We aimed at evaluating the predictive value of thromboelastometry for free flap thrombosis in microvascular surgery patients. Materials and Methods: We enrolled 103 adult patients with traumatic injuries scheduled for microvascular free flap surgery into a prospective observational study. Thirty-six patients with recent trauma underwent surgery within 30 days (ES group), and were compared with 67 trauma patients who underwent surgery later than 30 days (late surgery, LS group) after the injury. Rotational thromboelastometry (RTE) was performed before surgery. Functional fibrinogen to platelet ratio (FPR) ≥ 42 was selected as the main hypercoagulability index. Free flap thrombosis was set as primary outcome. Thrombotic risk factors and duration of surgery related to free flap thrombosis were secondary outcomes. Statistical significance p < 0.05; not significant NS. Results: Six patients (16.7%) in the ES group and 10 (14.9%) in the LS group had free flap thrombosis (NS). In the entire cohort, free flap thrombosis rate increased in the presence of thrombogenic comorbidities (OR 4.059, CI 1.33-12.37; p = 0.014) and prolonged surgery times (OR 1.007, CI 1 - 1.012; p = 0.05). Although hypercoagulability occurred more frequently in the ES group (44.4%) than in the LS group (11.9%; p < 0.001), it was not associated with higher free flap thrombosis rate. In ES group patients with surgery times > 240 min, the risk of free flap thrombosis increased (OR 3.5, CI 1.16-10.6; p = 0.026) with 93.3% sensitivity and 86.7% specificity (AUC 0.85; p = 0.007). In contrast, in LS patients hypercoagulability increased the odds of free flap thrombosis (OR 8.83, CI 1.74-44.76; p = 0.009). Moreover, a positive correlation was found between FPR ≥ 42 and free flap thrombosis rate (r = 0.362; p = 0.003). In the LS group, the presence of thrombogenic comorbidities correlated with free flap thrombosis rate (OR 7, CI 1.591-30.8; p = 0.01). Conclusions: In LS patients with thrombogenic comorbidities, thromboelastometry supports the detection of hypercoagulability and predicts free flap thrombosis risk. In ES patients, postoperative hypercoagulability did not predict free flap thrombosis. Prolonged surgery time should be considered as a risk factor.

Tourniquet use and factors associated with hematoma formation in free tissue transfer

PURPOSE

Our objective was to understand which variables are associated with hematoma formation at both the donor and recipient sites in head and neck free tissue transfer and if hematoma rates are affected by tourniquet use.

METHODS

Patients were identified who underwent free tissue transfer at three institutions, specifically either a radial forearm free flap (RFFF) or a fibula free flap (FFF), between 2007 and 2017. Variables including use of tourniquet, anticoagulation, treatment factors, demographics, and post-operative factors were examined to see if they influenced hematoma formation at either the free tissue donor or recipient site.

RESULTS

1410 patients at three institutions were included in the analysis. There were 692 (49.1%) RFFF and 718 (50.9%) FFF. Tourniquets were used in 764 (54.1%) cases. There were 121 (8.5%) hematomas. Heparin drips (p < .001) and DVT prophylaxis (p = .03) were significantly associated with hematoma formation (OR 95% CI 12.23 (4.98-30.07), 3.46 (1.15-10.44) respectively) on multivariable analysis.

CONCLUSIONS

Heparin Drips and DVT prophylaxis significantly increased hematoma rates in free flap patients while tourniquets did not affect rates of hematoma.

Utilization of microvascular couplers in salvage arterial anastomosis in head and neck free flap surgery: Case series and literature review

BACKGROUND

In microvascular reconstruction of ablative oncologic defects, coupler devices have traditionally been used for venous anastomosis, whereas the arterial anastomosis is hand-sewn. In the setting of repeated intraoperative arterial anastomotic thrombosis, a coupler device may be of use in reducing the risk of rethrombosis.

METHODS

Two patients were seen with advanced stage head and neck cancer and underwent oncologic resection. During microvascular reconstruction, a clot at the arterial anastomosis was encountered in both cases.

RESULTS

After starting therapeutic anticoagulation and attempting unsuccessful suture reanastomosis, coupler devices were used for arterial anastomosis, resulting in viable free-tissue transfer.

CONCLUSIONS

Although traditionally used for venous anastomosis, coupler devices may serve a purpose in the salvage setting when facing repeated intraoperative arterial thrombosis.

Clinical Factors Associated With Reoperation and Prolonged Length of Stay in Free Tissue Transfer to Oncologic Head and Neck Defects

Importance

Prolonged hospitalization and reoperation after free tissue transfer may be associated with certain clinical factors.

Objective

To determine patient and surgical factors associated with length of stay (LOS) and reoperation following surgical procedures for malignant neoplasm of the head and neck involving microvascular free tissue transfer reconstruction.

Design, Setting, and Participants

This was a retrospective review of American College of Surgeons National Surgical Quality Improvement Program data from 2012 to 2014 using International Classification of Diseases, Ninth Revision (ICD-9), codes for malignant neoplasms of the head and neck. Multivariable logistic regression modeling was used to examine correlation of patient and surgical variables with reoperation and LOS. The national retrospective database included outcomes from community and academic participant hospitals (517 member institutions in 2014). A total of 1115 cases of head and neck malignant neoplasm ablation with microvascular free tissue transfer flap were reviewed retrospectively.

Main Outcomes and Measures

Incidence of reoperation within 30 days of index operation and hospitalization equal to or longer than 13.0 days, which is equal to being in the top quartile for duration of stay.

Results

Of the 1115 patients, 370 (33.2) were female, and the mean (SD) age was 66.8 (3.9) years. Predictors of prolonged length of stay included return to the operating room (odds ratio [OR], 4.8; 95% CI, 3.3-6.9), smoking (OR, 2.1; 95% CI, 1.5-3.1), clean-contaminated wound (OR, 2.2; 95% CI, 1.3-4.0), bony flap (OR, 1.8; 95% CI, 1.2-2.8), age (OR, 1.5; 95% CI, 1.2-1.7), and operative time (OR, 1.2; 95% CI, 1.1-1.3). Reoperation occurred 298 times for 225 patients (20.2%). Mean (SD) time to reoperation was 8.0 (7.7) days, with 180 (80%) occurring before discharge from the primary operation. The most common indications for reoperation were neck exploration (37 [12.4%]) or incision and drainage of neck (35 [11.7%]).

Conclusions and Relevance

American College of Surgeons National Surgical Quality Improvement Program data allow for large database analysis of free flap transfer to the head and neck. The data herein provide information to help guide surgeons on which patients will require longer stay in hospital and the most common reasons for return to the operating room. Wound class of index operation, subsequent wound-related complications, and long duration of the index operation were the primary drivers of increased risk for reoperation and, therefore, prolonged hospitalization. These same factors were also associated with prolonged hospitalization without reoperation.

Level of Evidence

NA.

Shift in the timing of microvascular free tissue transfer failures in head and neck reconstruction

OBJECTIVE

Analyze the cause and significance of a shift in the timing of free flap failures in head and neck reconstruction.

STUDY DESIGN

Retrospective multi-institutional review of prospectively collected databases at tertiary care centers.

METHODS

Included consecutive patients undergoing free flap reconstructions of head and neck defects between 2007 and 2017. Selected variables: demographics, defect location, donor site, free flap failure cause, social and radiation therapy history.

RESULTS

Overall free flap failure rate was 4.6% (n = 133). Distribution of donor tissue by flap failure: radial forearm (32%, n = 43), osteocutaneous radial forearm (6%, n = 8), anterior lateral thigh (23%, n = 31), fibula (23%, n = 30), rectus abdominis (4%, n = 5), latissimus (11%, n = 14), scapula (1.5%, n = 2). Forty percent of flap failures occurred in the initial 72 hours following reconstruction (n = 53). The mean postoperative day for flap failure attributed to venous congestion was 4.7 days (95% confidence interval [CI], 2.6-6.7) versus 6.8 days (CI 5.3-8.3) for arterial insufficiency and 16.6 days (CI 11.7-21.5) for infection (P < .001). The majority of flap failures were attributed to compromise of the arterial or venous system (84%, n = 112). Factors found to affect the timing of free flap failure included surgical indication (P = .032), defect location (P = .006), cause of the flap failure (P < .001), and use of an osteocutaneous flap (P = .002).

CONCLUSION

This study is the largest to date on late free flap failures with findings suggesting a paradigm shift in the timing of flap failures. Surgical indication, defect site, cause of flap failure, and use of osteocutaneous free flap were found to impact timing of free flap failures.

LEVEL OF EVIDENCE

4 Laryngoscope, 130:347-353, 2020.

Perioperative Care of Free Flap Patients

Microvascular free tissue transfer is an indispensable reconstructive option in head and neck reconstruction. Flap failure is relatively rare, but it is nonetheless very morbid and psychologically devastating to patients when it does occur. Further, complications after free tissue transfer to the head and neck remain common. There are numerous ongoing debates about various facets of preoperative, intraoperative, and postoperative care of patients undergoing free flap reconstruction of the head and neck, all ultimately searching for the optimal treatment algorithm to further improve flap success, minimize complications, and maximize patient outcomes. Herein, the authors review current literature surrounding optimal preoperative nutritional support, intraoperative vasopressor use, perioperative fluid management, use of antithrombotic agents, antibiotic use, and other facets of the care of head and neck free flap patients to provide a guide to surgeons.

The use of tranexamic acid in microsurgery-is it safe?

Background

An appropriate and adequate blood flow and oxygen delivery is paramount to free flap viability and success. The perioperative use of tranexamic acid (TXA) is associated with less risk for blood loss and blood transfusion in trauma, gynaecology, ear nose and throat (ENT) and orthopaedic surgery. As an antifibrinolytic drug, TXA has generally been avoided in microsurgery. The aim of this study is to evaluate the safety and benefit of using TXA in microsurgery.

Methods

We performed a retrospective single centre cohort study at the Pyramid Clinic, Zurich, Switzerland, including 98 free tissue transfers for breast reconstruction from 2011 to 2013. According to the estimated blood loss, up to 3 g TXA were administered intravenously in 63 free flaps perioperatively.

Results

No thrombosis (0%) of micro-anastomosis and 5 haematomas (10.0%) occurred after administration of TXA. In the control group, 1 thrombosis (3.0%) of a flap-vein and 6 haematomas (18.2%) occurred. Blood loss was significant lower (P<0.001) after administration of TXA.

Conclusions

In this study, administration of TXA did not increase thrombosis in free tissue transfer and showed a reduced haematoma rate and significant reduction of blood loss. TXA is supposed to be safe and a reasonable adjunct for patients with anaemia and a higher intraoperative or postoperative blood loss.

Early and late complications in the reconstructed mandible with free fibula flaps

Background and Objectives

Evaluation of mandibular reconstructions with free fibula flaps. Identification of factors associated with major recipient site complications, that is, necessitating surgical intervention under general anaesthesia.

Methods

Seventy‐nine reconstructions were included. The following factors were analyzed: fixation type, number of osteotomies, site of defect (bilateral/unilateral), surgeon, sex, ASA classification, continuous smoking, pathological N‐stage, age, defect size, flap ischemic time, and postoperative radiotherapy. Proportional hazards regression was used to test the effect on the time between reconstruction and intervention.

Results

Sixty‐nine (87%) of the 79 fibula flaps were successful at the last follow‐up. Forty‐eight major recipient site complications occurred in 41 reconstructions. Nineteen complications required surgical intervention within six weeks and were mostly vascular problems, necessitating immediate intervention. These early complications were associated with defects crossing the midline, with an estimated relative risk of 5.3 (CI 1.1‐20, P = 0.01). Twenty‐nine complications required surgical intervention more than 6 weeks after the reconstruction. These late complications generally occurred after months or years, and were associated with smoking, with an estimated relative risk of 2.8 (CI 1.0‐8.3, P = 0.05).

Conclusions

Fibula flaps crossing the midline have a higher risk of early major recipient site complications than unilateral reconstructions. Smoking increases the risk of late complications.

Does Low-Dose Heparin Have a Significant Role in Free Flap Surgery?

Background

It is controversial issue that heparin decreases thrombosis for microsurgical anastomosis, and its effective role is under discussion. This study is for proving whether low-dose heparin is preventing thrombosis in free flap reconstruction.

Methods

Through chart reviews of 134 patients, using low-dose heparin for free tissue transfer from 2011 to 2016, retrospective analysis was performed. 33 patients received low-dose heparin therapy after surgery. And 101 patients received no-heparin therapy. Complications included flap necrosis, hematoma formation, dehiscence and infection.

Results

In no-heparin therapy group, comparing the flap necrosis revealed 16 cases (15.84%). And, flap necrosis was 6 cases (18.18%) in low-dose heparin therapy group. The statistical analysis of flap necrosis rate showed no significant difference (p=0.75). The results showed that there was no significant difference of flap necrosis rate between two groups.

Conclusion

In this study, patients in the low-dose heparin group had no significantly lower rates of flap failure compared with no-heparin group. This suggests that low-dose heparin may not prevent thrombosis and subsequent flap failure to a significant extent.

[Prophylaxis of venous thromboembolic events in head and neck surgery]

BACKGROUND

Application of perioperative thrombosis prophylaxis in head and neck surgery lacks consistent standards in Germany. Due to sparse data, the latest German S3 guideline concerning prophylaxis of thromboembolic events recommends a restrictive handling of anticoagulants in head and neck surgery, with few specific recommendations.

OBJECTIVE

The aim of this paper is to provide concrete clinical recommendations based on a systematic literature review and the S3 guidelines.

MATERIALS AND METHODS

A keyword-based literature search was performed and the German S3 guideline "Prophylaxis of Venous Thromboembolic Events" was used to state the current level of evidence and provide a clinical algorithm.

RESULTS

Eight additional cohort studies dealing with the incidence of thromboembolic events in head and neck surgery were identified. There were no randomized controlled trials. In the proposed algorithm, a classification of dispositional (patient history) and expositional (operation time) risk into three groups enables preoperative risk evaluation indicating the individual demand for prophylaxis. In short operations without major tissue traumatization, routine drug-based thrombosis prophylaxis is not necessary, provided no third-grade risk factors (earlier thromboembolic event, coagulopathy, or malignant disease) are present. Low molecular weight heparins should be used as anticoagulants for drug-based prophylaxis.

CONCLUSION

Prophylaxis of thromboembolic events in head and neck surgery is of high clinical relevance but there is currently limited evidence regarding its implementation. This paper is based on a systematic literature review and provides a clinical algorithm for head and neck surgeons.

Postoperative anticoagulation after free flap reconstruction for head and neck cancer: A systematic review

OBJECTIVE

Postoperative use of anticoagulation after free tissue transfer in head and neck ablative procedures is common practice, but a clear protocol has not been well established. The outcome measures including total flap failure, thrombosis, and hematoma formation for different anticoagulation regimens in free tissue transfer in the head and neck were reviewed.

DATA SOURCES

PubMed, Ovid, and Cochrane databases were examined for patients who underwent free tissue transfer following head and neck ablative procedures.

REVIEW METHODS

Preferred Reporting Items for Systematic Reviews and Meta-analyses guidelines were utilized to identify English-language studies reporting anticoagulation regimens following free tissue transfer in head and neck ablative procedures. Outcomes included total flap failure, thrombosis, and hematoma formation. Two independent reviewers assessed the quality of the articles by using the Methodological Index for Non-Randomized Studies.

RESULTS

A total of 368 articles were identified. An additional 36 articles were identified through screening of reference lists. Twenty-one of these studies met final inclusion criteria for qualitative analysis. Outcome data on total flap failure, thrombosis, and hematoma formation were extracted and analyzed for comparison against all anticoagulation regimens. Total flap failure, thrombosis, and hematoma formation rates were 4.4%, 4.5%, and 2.2%, respectively. Individual study rates ranged from 0.0% to 10.7%, 0.0% to 10.4%, and 0.6% to 7.2%, respectively.

CONCLUSIONS

There is not adequate evidence to develop a standardized anticoagulation protocol for head and neck free flap procedures. Comparable flap complications were reported between all the employed anticoagulation methods studied, though significant variability in study design among articles existed. Prospective, randomized studies are warranted to determine the optimal postoperative anticoagulation regimen following free tissue transfer of the head and neck. Laryngoscope, 128:412-421, 2018.

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.

The value of postoperative anticoagulants to improve flap survival in the free radial forearm flap: a systematic review and retrospective multicentre analysis

BACKGROUND

Free radial forearm flap (FRFF) reconstruction is a valuable technique in head and neck surgery, which allows closure of large defects while striving to maintain functionality. Anticoagulative drugs are often administered to improve flap survival, although evidence regarding effectiveness is lacking.

OBJECTIVE OF REVIEW

To investigate the effectiveness of postoperative anticoagulants to improve survival of the FRFF in head and neck reconstruction.

TYPE OF REVIEW

Systematic review and multicentre, individual patient data meta-analysis.

SEARCH STRATEGY

MEDLINE, EMBASE, Web of Science and CINAHL were searched for synonyms of 'anticoagulants' and 'free flap reconstruction'.

EVALUATION METHOD

Studies were critically appraised for directness of evidence and risk of bias. Authors of the highest quality publications were invited to submit their original data for meta-analysis.

RESULTS

Five studies were of adequate quality, and data from four studies (80%) were available for meta-analysis, describing 759 FRFF procedures. Anticoagulants used were as follows: aspirin (12%), low molecular weight dextran (18.3%), unfractioned heparin (28.1%), low molecular weight heparin (49%) and prostaglandin-E1 (2.1%). Thirty-one per cent did not receive anticoagulants. Flap failure occurred in 40 of 759 patients (5.3%) On univariate analysis, use of unfractioned heparin was associated with a higher rate of flap failure. However, these regimens were often administered to patients who had revision surgery of the anastomosis. In multivariate logistic regression analysis, anticoagulant use was not associated with improved flap survival or flap-related complications.

CONCLUSIONS

The studied anticoagulative drugs did not improve FRFF survival or lower the rate of flap-related complications. In addition, some anticoagulants may cause systemic complications.

Peroneal artery-vein index as a potential factor of thrombosis occurrence in free osteocutaneous fibula flap

BACKGROUND

Despite high popularity and great success rates of free osteocutaneous fibula flaps, the flap failure caused by vascular thrombosis is still a challenging problem. The authors present their evaluation of a potential thrombosis risk factor - a peroneal artery-vein index.

METHODS

The authors evaluated the diameters of peroneal vessels and peroneal artery-vein indexes based on the computed tomography angiographies in 10 patients who underwent a mandible reconstruction with a free fibula flap and compared the results with clinical outcome.

RESULTS

In one case the flap was lost, because of thrombosis in the donor vein. This patient presented superficial varicose veins of both lower extremities. Peroneal vein diameters in this patient ranged from 5,05 mm to 6,68 mm and were higher than in patients without complications. The peroneal artery-vein index in the patient with thrombosis ranged from 0,37 to 0,50 with median 0,40 and was lower than in patients without complications.

CONCLUSIONS

High disproportion between peroneal artery and concomitant veins might be a potential risk factor of the occurrence of venal thrombosis. Detailed perioperative examination of peroneal veins in patients with varicosities should be considered.

Introduction of a microsurgical in-vivo embolization-model in rats: the aorta-filter model

Vascular thrombosis with subsequent distal embolization remains a critical event for patients. Prevention of this life-threatening event can be achieved pharmacologically or mechanically with intravascular filter systems. The ability to evaluate the risk of embolization of certain techniques and procedures in vascular and microvascular surgery, such as, tissue glue or fibrin based haemostatic agents lacks convincing models. We performed 64 microvascular anastomoses in 44 rats, including 44 micro-pore polyurethane filter-anastomoses and 20 non-filter anastomoses. The rats were re-anesthetized and the aorta was re-exposed and removed four hours, three, seven, fourteen, thirty-one days, and six months postoperatively. The specimens were examined macro- and microscopically with regard to the appearance of the vessel wall, condition of the filter and the amount of thrombembolic material. Typical postoperative histopathological changes in vessel architecture were observed. Media necrosis was the first significant change three days postoperatively. Localized intimal hyperplasia, media necrosis, increase of media fibromyocytes and adventitial hypercellularity were seen to a significant extent at day seven postoperatively. Significant neovascularization of adventitia adjacent to the filter was seen after 14 days. A significant amount of thrombotic material was seen after four hours, three and 14 days interval. Only three intravascular filters became completely occluded (6.82%). The aorta-filter-anastomosis model appeared to be a valid in-vivo model in situations at risk for thrombembolic events, for microsurgical research and allowed sensitive analysis of surgical procedures and protection of the vascularized tissue. It may be suitable for a wide range of in-vivo microvascular experiments particularly in the rat model.

Outcome of microvascular free flaps in a high-volume training centre

PURPOSE

Microvascular free tissue transfer allows major ablative defects following oncologic surgical and traumatic reasons to be reliably reconstructed in the head and neck region. A retrospective analysis of the microvascular flap procedures which were performed within one year in a high volume training centre was performed.

PATIENTS AND METHODS

The microvascular free flap procedures of the year 2011 were reviewed and followed up until the 31st December 2012. The type and indication of the reconstructive procedure, operation time, operating team, experience and level of training of the surgeons involved, postoperative IMC (intermediate care unit) and/or ICU (intensive care unit) time, inpatient time, flap revisions, further postoperative complications, preoperative and postoperative radiation of the patients, the placement of dental implants were studied.

RESULTS

From 1st of January 2011 to 31st of December, 2011, the data of 101 patients with 103 microvascular free flap procedures were analysed of which 72% (84 flaps) were harvested by residents. The patients ranged in age from 14 to 89 years (mean age 59 years, 71 males and 40 females). The mean operation time was 591 min with the longest operation times for scapular flaps (744 min) and the shortest operation times for ALT flaps (455 min). Mean inpatient time was 34.2 days with a minimal time for the fibular flaps of 27.2 days and a maximum of 45.7 days for the latissimus dorsi flaps. 24 flaps (23.3%) in total had to be revised with bleeding being the main cause of immediate revisions (41.7% of all revisions). 5 flaps (4.85% of all flaps) were lost despite a revision procedure meaning a successful revision rate in 79.2% of all revisions.

CONCLUSION

Microvascular reconstruction procedures are safe and should be considered as standard procedures for reconstruction of large defects especially in high volume training centres. Intensive flap monitoring and early revisions maximize the flap outcome.