Monitoring free flaps with Cook-Swartz implantable Doppler probe in head-and-neck reconstruction.

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.

Free flaps to the lower limb have inherently high venous pressures, potentially impairing flap viability, which may lead to limb amputation if flap failure ensues. Adequate monitoring of flap perfusion is thus essential, with timely detection of flap compromise able to potentiate flap salvage. While clinical monitoring has been popularized, recent use of the implantable Doppler probe has been used with success in other free flap settings. A comparative study of 40 consecutive patients undergoing microvascular free flap reconstruction of lower limb defects was undertaken, with postoperative monitoring achieved with either clinical monitoring alone or the use of the Cook-Swartz implantable Doppler probe. The use of the implantable Doppler probe was associated with salvage of 2/2 compromised flaps compared to salvage of 2/5 compromised flaps in the group undergoing clinical monitoring alone (salvage rate 100% vs. 40%, P = 0.28). While not statistically significant, this was a strong trend toward an improved flap salvage rate with the use of the implantable Doppler probe. There were no false positives or negatives in either group. One flap loss in the clinically monitored group resulted in limb amputation (the only amputation in the cohort). A trend toward early detection and salvage of flaps with anastomotic insufficiency was seen with the use of the Cook-Swartz implantable Doppler probe. These findings suggest a possible benefit of this technique as a stand-alone or adjunctive tool in the clinical monitoring of free flaps, with further investigation warranted into the broader application of these devices.

Recent advances in postoperative free microvascular flap monitoring

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.

Postoperative monitoring of free flaps is important to minimize the risk of flap failure, but monitoring buried free flaps is difficult because the standard methods of clinical examination and surface Doppler monitoring are not possible. Buried free flaps are often monitored using an implantable 20-MHz ultrasonic Doppler probe. The authors conducted a retrospective clinical study of buried free flaps to assess the reliability of the implantable Doppler probe in postoperative monitoring of free flaps. During the 38-month study period, 956 free flap operations were performed at the authors' institution. Twenty (2.1 percent) of these cases involved completely buried free flaps in which an implantable Doppler probe was used for flap monitoring. Implantable Doppler probe monitoring had a 100 percent sensitivity rate in detecting loss of flap perfusion, making it a good screening test for free flap viability. However, it suffered from a high false-positive rate of 88 percent, which resulted in a high proportion of subsequent negative surgical explorations. In one case, color duplex sonography, a rapid and noninvasive test, revealed that the loss of signal from the implantable Doppler probe was a false-positive result. The implantable Doppler probe is a sensitive method for postoperative monitoring of free flaps but is prone to false-positive signals. The use of color duplex sonography to confirm implantable Doppler probe findings may avert unnecessary surgical exploration, thereby improving postoperative monitoring of free flaps.

Free flap failure or vascular compromise remains a dreadful complication of microvascular free tissue transfer. Near-infrared spectroscopy (NIRS) is a novel technique for free flap monitoring that has the propensity for early detection of vascular compromise when compared to the current gold standard, clinical monitoring (CM). The objective of this review is to evaluate the efficacy of a NIRS system in the postoperative monitoring of free flaps and its effect on flap salvage. A comprehensive literature review was performed including English-language articles evaluating the use of NIRS in free flap monitoring. MEDLINE, Embase, Cochrane Central Register of Controlled Trials (CENTRAL), OVID, and Web of Science were searched upto December 2017. A total of 590 articles were identified, and 10 articles were included for analysis. Overall, flaps with vascular compromise monitored with NIRS had a significantly higher salvage rate of 89% compared with a salvage rate of 50% in the flaps monitored by CM alone (p < .01). Partial loss occurred in 15% of the successful salvages in the NIRS group versus 80% with CM alone (p < .01). Detection of vascular compromise by NIRS preceded clinical signs on average by 82 ± 49 min. NIRS was accurate in detecting compromised flaps with a low false-positive and false-negative rate. Despite lack of robust data, NIRS has the potential to be an objective, accurate, and continuous postoperative free flap monitoring technique with a greater flap salvage rate than CM alone.

To assess the accuracy and reliability of the flow coupler relative to the implantable arterial Doppler probe in postoperative monitoring of head and neck free flaps. Retrospective single-institution study, April 2015 to March 2017. Both the venous flow coupler and arterial Doppler were employed in 120 consecutive head and neck free flap cases. When Doppler signal loss occurred, flaps were evaluated by physical exam to determine whether signal loss was a true positive necessitating operating room takeback. Sensitivity, specificity, and false positive rate (FPR) were recorded for each device. Logistic regression was conducted to identify user trends over time. Eleven of 120 patients (9.2%) required takeback, 10 from venous thrombosis and one from arterial thrombosis. Permanent signal loss (PSL) occurred in the flow coupler in all takebacks; PSL occurred in the arterial Doppler only in the case of arterial thrombosis. Salvage rate was 9/11 (81.8%). For the flow coupler, sensitivity was 100%, specificity 86.4%, and FPR 13.6%. For the arterial probe, sensitivity was 9.1%, specificity 97.1%, and FPR 2.9%. A 4.1% decrease in false positives with each additional flow coupler use was observed. Monitoring the vein via flow coupler has high sensitivity in identifying vascular compromise compared to the arterial probe, especially for venous thrombosis. There is moderate FPR; this decreases with increased usage and, when supplemented with physical examination, does not result in unnecessary takebacks. The flow coupler can be a valuable tool in postoperative monitoring of head and neck free flaps. 4. Laryngoscope, 128:812-817, 2018.

Background:Measurement of transcutaneous oxygen pressure (TcPO2) and transcutaneous carbon dioxide pressure (TcPCO2) has been used for free flap monitoring. Because these values are obtained with sensor probes heated to 44°C, there is potential for low-temperature burns on skin flaps. We measured TcPO2 and TcPCO2 at 37°C in both animals and humans to determine the feasibility and safety of the procedure as a postoperative flap monitoring method.Methods:Twelve epigastric island flaps were elevated in rabbits, and TcPO2 and TcPCO2 were measured at 37°C before and after ligation of the pedicles. In addition, TcPO2 and TcPCO2 at 37°C were measured in healthy men. Subsequently, the method was applied to postoperative monitoring of free flaps in 49 clinical cases.Results:TcPO2 and TcPCO2 values were significantly affected by the experimental flap elevation. A rapid increase in TcPCO2 was observed with both arterial and venous occlusion. In the healthy men, TcPO2 and TcPCO2 were measurable at all skin surface sites. In the clinical cases of free flap transfer, TcPO2 values remained very low for at least 72 hours. TcPCO2 values ranged from 40 to 70 mm Hg for 72 hours in more than 80% of cases. In 2 cases, TcPCO2 values increased to more than 90 mm Hg, and exploration surgery was performed. These compromised flaps were saved by reanastomosis of the veins.Conclusions:Continuous monitoring of TcPCO2 at 37°C can provide objective information and alert doctors and nurses to the need for checking the free flap.

The aim of this study is to investigate static and dynamic infrared (IR) thermography for intra- and postoperative free-flap monitoring following oropharyngeal reconstruction. Sixteen patients with oropharyngeal reconstruction by free radial forearm flap were included in this prospective, clinical study (05/2013-08/2014). Prior ("intraop_pre") and following ("intraop_post") completion of the microvascular anastomoses, IR thermography was performed for intraoperative flap monitoring. Further IR images were acquired one day ("postop_1") and 10days ("postop_10") after surgery for postoperative flap monitoring. Of the 16, 15 transferred free radial forearm flaps did not show any perfusion failure. A significant decreasing mean temperature difference (∆T: temperature difference between the flap surface and the surrounding tissue in Kelvin) was measured at all investigation points in comparison with the temperature difference at "intraop_pre" (mean values on all patients: ∆T intraop_pre=-2.64K; ∆T intraop_post=-1.22K, p<0.0015; ∆T postop_1=-0.54K, p<0.0001; ∆T postop_10=-0.58K, p<0.0001). Intraoperative dynamic IR thermography showed typical pattern of non-pathological rewarming due to re-established flap perfusion after completion of the microvascular anastomoses. Static and dynamic IR thermography is a promising, objective method for intraoperative and postoperative monitoring of free-flap reconstructions in head and neck surgery and to detect perfusion failure, before macroscopic changes in the tissue surface are obvious. A lack of significant decrease of the temperature difference compared to surrounding tissue following completion of microvascular anastomoses and an atypical rewarming following a thermal challenge are suggestive of flap perfusion failure.

Microsurgical free flaps are today considered state of the art in head and neck reconstruction after composite tumor resections. Free flaps provide superior functional and aesthetic restoration with less donor-site morbidity. This article details our approach to this challenging and complex procedure. Free tissue transfer can be viewed as consisting of 4 essential stages: (1) defect assessment, (2) preparation of recipient vessels, (3) flap selection and harvest, and (4) flap inset and microsurgical anastomoses. The essential details of each step are highlighted. Meticulous attention to each step is important because each plays a crucial role in the overall success of the procedure. Workhorse flaps in our practice are the anterolateral thigh, radial forearm, fibula, and jejunum flaps. Unique issues related to postoperative care and monitoring of head and neck free flaps are discussed. The management of complications, in particular those threatening flap survival, are reviewed in detail.

Intraoperative and postoperative free flap monitoring by means of oxygen tension measurement was carried out in 11 patients. We used an invasive flexible microcatheter that allowed for measurement of oxygen tension in all types of free flaps. Two cases of the measured flaps were buried free flaps which do not allow monitoring by clinical assessment. All flaps monitored in this study survived. One case of displacement of the microcatheter occurred. In one patient, the tissue pO2 monitor successfully detected early vascular thrombosis with subsequent reoperation and salvage of the free flap.

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

There is an increasing demand for successful free tissue transfer, with postoperative monitoring of flaps a key to early salvage. Monitoring methods have ranged from clinical techniques to invasive options, of which two are particularly applicable to buried flaps (Cook-Swartz Doppler probe and microdialysis). The evidence for these options has been represented largely in separate cohort studies, with no single study comparing these three techniques. We aim to perform this comparison in a single cohort of patients. A prospective, consecutive cohort study comparing clinical monitoring, microdialysis and the implantable Doppler probe was undertaken. In 20 patients receiving 22 flaps, 21 flaps were monitored with microdialysis, 18 flaps with clinical observation, and 21 flaps with the Cook-Swartz Implantable Doppler probe. Exclusion was based on applicability and availability intra-operatively. Efficacy was assessed through sensitivity, specificity, positive, and negative predictive values. Nineteen of 22 flaps had no suspected anastomotic problems; 3 of 22 flaps were explored for anastomotic problems, with two salvaged and one lost. The implantable Doppler and microdialysis were found to detect flap statistically earlier than clinical assessment, with microdialysis better at detecting flap compromise: 100% specificity (confidence interval 31-100%) when compared to the implantable probe and clinical assessment (67%: 13-98% and 33%: 2-87%, respectively). Each of the Cook-Swartz Doppler probe, microdialysis and clinical assessment was found suitable for monitoring in free tissue transfer. The implantable Doppler and microdialysis offer the potential for earlier detection of flap compromise.

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.

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.