Blood flow analyses by intraoperative transit-time flow measurements of free flaps for head and neck reconstructions: A prospective single-center study.

BACKGROUND: The behavior of blood flow changes within free flaps following microvascular anastomosis is not well described in the literature. The aim of this study was to determine the immediate blood flow behavior of different free flaps as reference values for various clinical applications. METHODS: Intraoperative transit-time flow measurements were performed on patients receiving free flap transfer in the head and neck area comprising radial forearm flaps (RFF), peroneal artery perforator flaps (PAP), anterolateral thigh flaps (ALT), vastus lateralis flaps (VLF), parascapular flaps (PSF), latissimus dorsi flaps (LDF), fibula free flaps (FFF), deep circumflex iliac artery flaps (DCIA), and scapular flaps (SF). In accordance with a structured protocol, measurements took place at the pedicle directly before flap harvesting and at the recipient vessels 1 h after flap transfer. Heart rate, transplant weight, and other patient characteristics were recorded and analyzed. RESULTS: A total of 129 were enrolled, comprising 66 RFF, 8 ALT, 6 PAP, 11 VLF, 3 PSF, 2 LDF, 24 FFF, 7 DCIA, and 2 SF. In most of the transplant groups, arterial perfusion increased after anastomosis at the recipient site. The arterial pulsatility index developed indirectly proportionally to arterial blood flow, whereas venous blood drainage did not show any statistically significant changes. Muscle flaps had the highest arterial perfusion before flap transfer. Composite transplants with hard and soft tissue presented the greatest increase in arterial perfusion. The lowest arterial blood flow after anastomosis was measured in PAP and RFF. In contrast, RFF and PAP presented the highest arterial perfusion per 100 g transplant weight. CONCLUSIONS: Arterial perfusion changed, whereas venous blood flow did not show any statistically significant variations in any transplant group. Perfusion of free flaps does not only depend on the recipient vessel and the recipient bed, but also on flap-specific anatomy and physiology.

Alterations in Surgically Created Intimal Lesions: An Observation Study in the Aortic Rat Model.

BACKGROUND: Intimal injury in microvessels due to common risk factors such as atherosclerosis or inadequate manipulation are known to have a major impact on developing thrombosis and eventually vascular obstruction. Understanding of these injuries is therefore of great significance to prevent far-reaching consequences such as flap loss in free tissue transfer. It was the aim of this study to evaluate artificially induced intimal lesions with focus on alteration in size and configuration. METHODS: Intimal defects were created surgically in the abdominal aorta of 30 male Wistar rats. After planimetric measurement of the defect sizes, configuration of defects were classified as round, horizontal, or vertical. Seven days postoperatively, the rats underwent a second-look surgery. Finally, the abdominal aorta was harvested, and the endothelial defects were reevaluated concerning size and configuration using a defined pattern. RESULTS: The mean defect size created intraoperatively was 1.68 ± 0.6 mm2. The classification of the defects configurations resulted in 43.3% round, 20% horizontal, and 36.7% vertical defects. Reevaluation at 7 days after surgery showed defect shrinkage in 96.7% in total and 42.8% averaging due to reendothelialization. A shift in defect configuration was detected in 56.7%, the strongest being in vertical defect configurations (100%). Vascular occlusion did not occur in any of the specimen. CONCLUSION: Intimal injuries undergo a fast repair process in terms of size reduction and configuration modification due to reendothelialization. Especially vertical defects, representing a great risk for thrombus formation, convert into lower risk horizontal defect configurations. In high-flow vessels such as the rat aortas, small endothelial damage seems to have no significant impact to produce complete vascular occlusion. Still, all efforts should be made to avoid any kind of intimal injury.

Comparison of a high-definition three-dimensional digital camera system with a conventional state-of-the-art operation microscope for microsurgical anastomoses.

Since its clinical implementation, microvascular surgery has depended on the continuous improvement of magnification tools. One of the more recent developments is a high-definition three-dimensional (3D) digital system (exoscope), which provides an alternative to the state-of-the-art operating microscopes. This study aimed to evaluate the advantages and disadvantages of this technology and compare it with its predecessor. The study included 14 surgeons with varying levels of experience, none of which had used a 3D optical system previously. Six of these surgeons performed five arterial and five venous anastomoses in the chicken thigh model with both the VITOM 3D exoscope-guided system and the Pentero operating microscope. These anastomoses were then evaluated for their quality and anastomosis time. The participants and the other eight surgeons, who had used the digital 3D camera system for microsurgical training exercises and vascular sutures, answered a questionnaire. The anastomosis time and number of complications were lower with the conventional microscope. Participants rated the image quality with the conventional microscope as higher, whereas the field of view and ergonomics were favorable in the digital 3D camera system. Exoscopes are optics suitable for performing simple microvascular procedures and are superior to classical microscopes ergonomically. Thus far, they are inferior to classical microscopes in terms of image quality and 3D imaging.

Infantile human labial glands: Distribution of aquaporins and claudins in the context of paracellular and transcellular pathways.

Human labial glands consist of saliva-secreting cells which are formed by serous and predominantly mucous glandular cells. The following excretory duct system converts the isotonic saliva into a hypotonic fluid. Liquids are transported across the membrane of epithelial cells by paracellular or transcellular mode of action. We studied aquaporins (AQP) and tight junction proteins in the endpieces and duct system of human labial glands of 3-5-month-old infants for the first time. AQP1, AQP3, and AQP5 represent the transcellular transport; tight junction proteins like claudin-1, - 3, - 4, and - 7 regulate the permeability of the paracellular pathway. Specimens of 28 infants were included in this study and analyzed histologically. AQP1 was present in myoepithelial cells and in endothelial cells of small blood vessels. AQP3 showed basolateral plasmamembrane localization in glandular endpieces. AQP5 was localized at the apical cytomembrane in serous and mucous glandular cells and at the lateral membrane in serous cells. Ducts remained unstained with the antibody to AQP1, AQP3, and AQP5. Claudin-1, - 3, - 4, and - 7 were expressed mainly in the lateral plasmamembrane of serous glandular cells. In the ducts, claudin-1, - 4, and - 7 were detected at the basal cell layer, claudin-7 also at the lateral cytomembrane. Our findings provide new insights into the localization of epithelial barrier components necessary for regulating saliva-modification in infantile labial glands.

Effects of endothelial defects and venous interposition grafts on the acute incidence of thrombus formation within microvascular procedures.

Endothelial defects (ED) and the usage of interposition vein grafts (IVG) are known risk factors for free flap failure. This experimental study aimed to compare both situations of thrombus formation and fluorescence angiographic behavior. Indocyanine green videoangiography (ICGVA) with the FLOW 800 tool was systematically performed in groups I = ED, II = IVG, and III = ED and IVG (each n = 11). ICGVA was able to detect thrombosis in five animals and safely ruled it out in 26 with two false-positive cases (sensitivity, specificity, and positive and negative predictive values were 100%, 90%, 62%, and 100%, respectively). The difference between visually and ICGVA-assisted ED measurements was significant (p = 0.04). The areas of thrombosis showed no significant difference. Moreover, ICGVA detected a decrease of all parameters at the ED area and/or within the IVG section in all groups. The presence of an endothelial defect had a higher impact on thrombus formation than the IVG usage. ICGVA is qualitatively able to detect endothelial defects and clinically evident thrombosis. However, the quantitative values are not yet attributable to one of the clinical scenarios that may jeopardize free flap transfer.