A neurocutaneous island flap model: an experimental study in rats

Neurocutaneous flaps have been popularized recently in clinical reconstructive surgery. However, controversies exist concerning their anatomy and physiology. The particular role of neural vasculature in the survival of these skin flaps is also quite undefined in the experimental setting, and additional studies on this subject are necessary. The goal of this study was to describe a neurocutaneous flap in a rat model and to investigate its blood supply. Thirty male Sprague-Dawley rats weighing 300 to 350 g were used in this study, which was conducted in two stages. During the first stage, the lower extremities of 10 rats were dissected for the anatomic study of the neurocutaneous flap. A constant cutaneous nerve innervating the anterolateral thigh skin was exposed. It arose either from the saphenous nerve or the superficial epigastric nerve and was accompanied by a constant longitudinal arterial plexus. The tiny neural vessels were conveyed by the superficial fascia along their course. A 30 x 30-mm cutaneous island flap, which was based only on the cutaneous nerve with its accompanying vessels and a strip of superficial fascia, was raised on the anterolateral thigh skin using an operating microscope. The well-perfused skin territory was marked after sodium fluorescein injection. The stained skin territory was located centrally and medially on the whole island flap, and it was approximately 10 x 20 mm. This finding was confirmed by the qualitative assessment of the vascularity for this skin territory in microangiography. After studying the pedicle anatomy and determining the optimal viable skin island, the second stage of the study was performed. The remaining 20 rats were divided into two groups. In the experimental group (N = 10), a neurocutaneous island flap (10 x 20 mm) was outlined on the anterolateral aspect of the thigh at its middle third. It was designed in such a way that its short and long axes lay in the center of the distance between the anterior superior iliac spine and the anterior aspect of the knee joint. After identification and dissection of the neurovascular pedicle, the flap was raised in a lateral-to-medial direction without including the deep fascia. At this point the flap remained connected only by the pedicle and a strip of superficial fascia surrounding it. It was sutured in the same place. In the control group (N = 10), the pedicle of the flap was severed and the skin island was sutured back as a composite graft. All the experimental flaps survived well. In the control group, none of the flaps survived except one that was partially viable. The flaps in the experimental group were reelevated as neurocutaneous island flaps on day 7 for microangiographic study, and specimens were processed for histologic staining. Microangiography revealed the extent of neural vasculature and vascularization of the skin through cutaneous perforators. Histologic investigation demonstrated the neural vessels that were related closely to the superficial fascia. The authors propose a neurocutaneous island flap model in the lower extremity of the rat in which the survival of the flap depended mainly on the neural arterial supply. It was also demonstrated that the superficial fascia played a role as a connective tissue framework for conveying tiny neural blood vessels to reach the skin. This model may serve as a reproducible and reliable neurocutaneous island flap model for additional studies in this field.     

Delayed prefabricated arterial composite venous flaps: an experimental study in rabbits

Prefabrication of composite arteriovenous flaps with implantation of an autologous graft (cartilage) or an alloplastic material (porous polyethylene) was studied in 40 rabbits. Abdominal flaps based on bilateral epigastric pedicles were elevated. An ear cartilage graft or a porous polyethylene implant was inserted under the flap. Two weeks after the operation, 10 flaps with cartilage graft and 10 flaps with porous polyethylene were raised, converted to arteriovenous flaps, and resutured in place in the experimental groups. In the other 20 rabbits of the control groups, the flaps (10 with cartilage graft and 10 with porous polyethylene) were raised and resutured in place as conventional axial flaps. At the end of the second and fourth week postoperatively, samples were obtained from the flap tissues (including a part of the graft or implantation material) and were prepared for histologic examination in all rabbits. The viable areas of all flaps were assessed at the end of fourth week after the second operation. The mean survival rates were 99.4%, 99.7%, 99.5%, and 99.8% in the arteriovenous and control flaps prefabricated with cartilage graft and the arteriovenous and control flaps prefabricated with porous polyethylene respectively. The features of wound healing in the experimental and control groups were similar. The study showed that arteriovenous perfusion can nourish a prefabricated flap containing an implanted material (autologous or alloplastic) and these 2-week delayed composite flaps have a similar survival rate to delayed prefabricated conventional axial flaps.     

Fiberoptic bronchoscopy during noninvasive positive-pressure ventilation in patients with chronic obstructive lung disease with hypoxemia and hypercapnia

OBJECTIVES: To assess the feasibility and safety of non invasive positive-pressure ventilation (NIPPV) via a face mask to performing fiberoptic bronchoscopy (FOB) in patients with COPD contraindicating FOB in spontaneous ventilation. STUDY DESIGN: Clinical, prospective, open, non comparative trial of feasibility. PATIENTS: Ten consecutive COPD patients (71 +/- 5 year-old, PaO2 = 53 +/- 13 mmHg and PaCO2 = 67 +/- 11 mmHg), without any sign of acute respiratory failure, admitted to the intensive care unit for pneumonia requiring a bronchoalveolar lavage (BAL). Including were: PaO2 < 70 mmHg despite nasal O2 delivered at 3 L.min-1, PaCO2 > 50 mmHg, improvement of SpO2 with NIPPV before FOB. METHODS: Topical anaesthesia of the nose and pharynx was obtained with a 5% lidocaine spray. NIPPV was administered using a ventilatory support system Evita 4 (Dr?ger) applied through a full facial mask secured to the patient with elastic straps. Patients were first allowed to acclimate for 5 min with NIPPV (IPAP = 16 cmH2O, EPAP = 0 and trigger of 0.3 cm H2O while a FIO2 kept at 0.7). A T-adapter Medisize (Péters) was attached to the facial mask. The tip of the FOB was inserted through the nose. Topical anaesthesia of the vocal cords was obtained with 1% lidocaine solution (3 mL). The FOB was inserted into the trachea up to a bronchial sub-segment. BAL was performed by instillation of 100 mL of saline solution. After FOB, the NIPPV was maintained for 5 min. Heart rate, SpO2 were measured continuously and arterial pressure at 2 min intervals. Arterial blood gas values were obtained just prior NIPPV and after 15 min and 60 min NIPPV disconnection. RESULTS: FOB duration was 11 +/- 4 min. SpO2 significantly improved during FOB (from de 91 +/- 4.7% to 97% +/- 1.7) without decrease of oxygen saturation lower than 90%. There were no changes in PaCO2 and PaO2 during the hour following the end of procedure. FOB under NIPPV was performed in all patients without complications and was very well tolerated in eight patients. After NPPV disconnecting, one patient required again NIPPV for 15 min. No patient required endotracheal intubation within 24 hours. All patients survived. CONCLUSION: Application of NIPPV during FOB is a safe technic for maintaining adequate gas exchange in hypoxaemic and hypercapnic COPD patients not in acute respiratory failure. After the end of the procedure a close surveillance in the intensive care unit is essential.     

Tri-dimensional automatic segmentation of PET volumes based on measured source-to-background ratios: influence of reconstruction algorithms.

A method for automatic volume segmentation of functional imaging based on a relationship between source-to-background ratio and the iso-activity level to be used is described. Such method, which has been established with radioactive spheres in a phantom, is independent of the a priori knowledge of the lesion of interest and is valid for small (>2 ml) and/or poorly contrasted (S/B>1.5) lesions. Accuracy varies slightly with the image reconstruction algorithm used.