Lymphatic mapping for Merkel cell carcinoma.
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Biomedical subjects
H Weinberg
Publications and source records attributed to H Weinberg.
Continuous tissue oxygen tension measurement as a monitor of free-flap viability.
Early recognition of vascular compromise within microvascular free-tissue transfers is essential if reexploration is to prove successful. Tissue oxygen tension is increasingly recognized to be a sensitive and reliable index of tissue perfusion, and preliminary studies suggest that it may be of value in the assessment of free-flap viability. We describe our investigation into the application of an implantable microcatheter oxygen sensor in the monitoring of free flaps used in head and neck and extremity reconstruction. In a preliminary study using the rabbit model, we sought to evaluate the response of oxygen tension as an index of tissue perfusion in myocutaneous (n = 20) and osteomyocutaneous flaps (n = 5) under conditions of arterial and venous occlusion. A clinical study was then undertaken to evaluate the role of this method in the monitoring of surface and buried free flaps. In 30 heterogeneous free-tissue transfers, sensors placed intraoperatively were used to provide continuous information about flap oxygen tension (mean monitoring period 3.2 +/- 0.8 days). The data generated were correlated with changes in clinical parameters and routine flap observations. Results for experimental and clinical data have confirmed the efficacy of continuous tissue oxygen measurements using this device as a method that provides an objective, recordable index of free-tissue transfer viability in a variety of circumstances and vascular events. Tissue oxygen tension is a suitable index by which to evaluate flap viability with the probe placed in muscle or bone but is unreliable when used for the monitoring of revascularized cutaneous flaps.
Animals↗
The development of a Marjolin's cancer in a human immunodeficiency virus-positive hemophilic man and review of the literature.
BACKGROUND: The malignant potential of chronic ulcers and scars secondary to a variety of injuries is well characterized in the medical literature. Furthermore, it has been reported that human immunodeficiency virus (HIV)-positive patients have a higher incidence of basal cell carcinoma (BCC) than the general population. OBJECTIVE: To describe a case of an unusually aggressive morpheaform BCC that developed in a 28-year-old HIV-positive patient. The tumor developed in a scar 25 years after the initial trauma (Marjolin's ulcer). METHODS: Description of a case and review of the literature of Marjolins ulcer. RESULTS: The tumor was removed in a seven-stage, 21-section, micrographically controlled excision. Intraoperatively, perineural invasion of the infraorbital nerve was observed. The postoperative defect was repaired using a full-thickness skin graft. CONCLUSION: Although most malignancies arising within chronic scars are SCCs, BCCs and a number of other tumors have been described. Mohs micrographic surgery was effective in treating this aggressive morpheaform BCC. A high degree of suspicion in any changing healed scar is recommended.
Adult↗
Beneficial effects of corticosteroids on ocular myasthenia gravis.
OBJECTIVE: To determine if moderate-or low-dose corticosteroid therapy can reduce the diplopia and frequency of deterioration to generalized disease in ocular myasthenia gravis. DESIGN: Retrospective record review. SETTING: Two university-based neuro-ophthalmology services. PATIENTS: All 32 patients with ocular myasthenia gravis, treated with prednisone, followed up for a minimum of 2 years were included. Patients were treated with 1 or more courses of daily prednisone (highest initial dose, 40-80 mg) gradually withdrawn over 4 to 6 weeks. Subsequently, in 6 patients, 2.5 to 20 mg of prednisone was given on alternate day. OUTCOME MEASURES: Diplopia in the primary position or downgaze diplopia and generalized myasthenia gravis after 2 years of follow-up. RESULTS: Diplopia, which was initially found in the primary position in 29 patients and in the downgaze position in 26 patients, was absent in 21 patients at 2 years. Generalized myasthenia gravis occurred in 3 patients at 2 years. Elevated serum acetylcholine receptor antibody levels and abnormal electromyography findings were not predictive of worsening. No patient experienced a major steroid complication. CONCLUSIONS: Moderate-dose daily prednisone for 4 to 6 weeks, followed by low-dose alternate-day therapy as needed, can control the diplopia in patients with ocular myasthenia gravis. The frequency of deterioration to generalized myasthenia gravis at 2 years may be reduced; 9.4% in this study compared with more than 40% previously reported frequency. Corticosteroids may be useful even when ocular motor dysfunction is not normalized.
Adrenal Cortex Hormones↗
Periadventitial delivery of heparin in the prevention of microvenous thrombosis.
PURPOSE: In spite of advances in technique and instrumentation, microvascular free tissue transfer remains associated with a persistent risk of flap failure. The use of systemic anticoagulants to overcome the formation of vasoocclusive thrombi at reactive anastomotic sites is associated with a high rate of flap hematoma and is ill advised in the operative setting. The purpose of this study was to investigate the use of a biodegradable, nontoxic polymer gel (polyvinyl alcohol, PVA) to effect a sustained localized release of perivascular heparin around thrombogenic venous anastomoses. MATERIALS AND METHODS: A modified adventitial inclusion model was created in the femoral vein of 64 adult female Sprague-Dawley rats. Animals were divided into four experimental groups: 1) no treatment (controls), 2) periadventitial PVA gel contained in a vicryl chamber, 3) periadventitial PVA gel mixed with heparin, and 4) systemic heparin (intravenous pump). Patency rates in the femoral vein were checked at 10 minutes, 1 hour, 1 day, and 4 days after surgery. Systemic coagulation parameters and histology (scanning electron microscopy, SEM) were assessed in representative animals from all groups. RESULTS: Patency rates for experimental groups showed a significant improvement in animals treated with PVA/heparin and systemic heparin over controls. Wound hematomas occurred in 7 of 16 animals in group 3, and in 4 of 16 animals in group 4. Activated partial thromboplastin times were elevated in group 4 only (> 150 seconds). CONCLUSIONS: Continuous release of periadventitial heparin using a polymeric delivery system may represent an efficient means of attenuating the reactivity of microvenous anastomoses without affecting systemic coagulation parameters. In this model, however, its use was associated with a high rate of local wound hematoma.
Animals↗
Thrombolysis at a controlled pressure prolongs the survival of skin flaps treated with superoxide dismutase.
The role of thrombolysis in reestablishing patency in the microcirculation following ischemia, and thereby improving the efficacy of agents attenuating reperfusion injury, such as the oxygen free radical scavenger, superoxide dismutase (SOD), was investigated in a rat model. Abdominal skin flaps were subjected to normothermic ischemia induced by complete occlusion of the pedicle for periods of 12, 13, 14, 16, 18, 20, 22, and 24 hr. In Group 1 (n = 64), all animals received flap washout using 100,000U urokinase (manual injection) followed by 7,500 IU SOD given intra-arterially immediately prior to reperfusion. Animals in Group 2 received flap washout consisting of 100,000U urokinase given via a pressurized delivery system, followed by 7,500 IU SOD. Results demonstrated a statistically significant improvement in flap survival in Group 2. The authors concluded that thrombolytic therapy may be useful in improving the delivery of agents, such as SOD, which attenuate reperfusion injury in skin flaps.
Animals↗
Increased patency of artificial microvascular grafts using arteriovenous fistula loops: a two-stage procedure for lengthening the pedicle of free-tissue transfer.
The effect of a high-flow system on the patency of artificial microvascular grafts (AMG) was investigated using arteriovenous (A-V) fistula loops made of polytetrafluoroethylene (PTFE) in a clinically useful longer length. At a second stage, the A-V loops, matured for 7 days, were used as recipient conduits for free-tissue transfer. The patency rates of 5-cm long PTFE A-V fistula loops were compared with 5-cm and 1-cm long interpositional micrografts in a rat model. The patency rate of the loops at 7 days was 80 percent, compared to 0 percent for both the 5-cm and 1-cm interpositional grafts. A-V fistula loops matured for 7 days in vivo were divided in their midsections and used as arterial and venous conduits (each 2.5 cm long) for free epigastric flaps (3 x 6 cm) raised from the contralateral groin. Sixty-seven percent (8/12) of the free flaps were viable at 7 days. The A-V fistula loop in a high-flow system has a beneficial effect in maintaining patency of AMGs. PTFE fistula loops matured for 7 days can be used as arterial and venous conduits for microsurgical tissue transfer in rats.
Animals↗
Combination therapy for salvaging a failing, experimental skin flap.
The failing free flap remains a major problem for the reconstructive surgeon. Many and varied pharmacologic agents have been utilized to reverse the effects of ischemia in these flaps. Treatments have been aimed at inhibiting presumed causative factors in the no-reflow phenomenon. Therapy has generally been single in nature and designed to affect only one of these presumed factors. In this study, several pharmacologic agents were utilized individually or in combination therapy as postischemic washouts, in an effort to attack the multiple causative factors in the no-reflow phenomenon and to improve flap survival in a rat abdominal skin flap model. The treatment agents included lactated Ringer's, superoxide dismutase, and urokinase, with each used independently as a postischemic perfusion washout. Combination therapy utilized an initial postischemic perfusion with urokinase, followed by a second perfusion washout with superoxide dismutase. After 18 hr of primary ischemia, there was increased flap survival in the animals undergoing perfusion washout with either superoxide dismutase alone or with combined urokinase and superoxide dismutase washouts, compared to all other treatments (p < 0.001). It was found that flaps undergoing combined urokinase and superoxide dismutase postischemic perfusion washouts demonstrated significantly improved survival after 20 hr of primary ischemia, compared to all other therapies (p < 0.05). By demonstrating improved survival when a thrombolytic agent is used in conjunction with an oxygen free radical scavenger, these findings may have implications in the treatment of clinically failing free flaps.
Animals↗
Reappraisal of the inferior epigastric flap: a new neurovascular flap model in the rat.
An anatomic, histologic, and electrophysiologic study was carried out in order to determine the distribution and cutaneous sensory territory of the epigastric nerve in the rat. Results for nerve staining (Sihler's method) and electrophysiologic nerve mapping indicate that the neurosome of the epigastric nerve has a different autonomy than the vascular territory of the inferior epigastric artery. Based on these findings, an experimental model for neurovascular free-tissue transfer is proposed.
Abdomen↗
Motor cortex activity and predicting side of movement: neural network and dipole analysis of pre-movement magnetic fields.
Neuromagnetic fields were recorded from human subjects during the performance of left and right voluntary finger movements. Modeling of current dipole sources indicated symmetric activation of both motor cortices beginning 600 ms prior to movement onset. This activity became lateralized to the contralateral hemisphere 200-300 ms prior to movement onset, the period during which an artificial neural network showed increased ability to predict side of movement within single trials. The results describe the mechanism of lateralization of cortical brain activity preceding voluntary movement and provide further evidence of the involvement of ipsilateral motor cortex in unilateral movements.
Contingent Negative Variation↗
Free flap monitoring: a review of current practice.
Individual techniques for the postoperative monitoring of free flaps vary considerably. In order to establish the currently preferred protocols, a survey was conducted among micro-surgeons in North America using a mailed questionnaire. Data were received from 95 centers for the monitoring of 2,825 free flaps performed during 1994. Results indicate that rates for flap salvage and overall success with free tissue transfer are closely related to surgical experience (number of cases performed per month). Ninety percent of microsurgeons routinely use monitoring devices, with external and laser doppler having achieved greatest popularity. An account is given of the preferred postoperative regimens for flap surveillance, and the overall results are discussed.
Clinical Competence↗
Glutathione disulphide as a marker of reperfusion injury in ischaemic skin flaps.
Estimation of the oxidised form of glutathione (GSSG) in an ischaemic/reperfused organ is frequently employed as an indicator of oxidative stress created by the production of oxygen free radicals during the reperfusion period. The time course of oxidative stress and tissue damage in 19 ischaemic/reperfused guinea-pig island skin flaps was evaluated. No-flow ischaemia was induced in the flaps for 6 h in 7 animals, and for 8 h in 9 animals (a further 3 animals served as controls without ischaemia). Arterial and venous blood samples were obtained directly from the flap pedicle at baseline, 10, 30, and 60 min following reperfusion. Results suggest that a second focus of oxidative injury, possibly mediated by activated neutrophils, contributes to the overall process of reperfusion injury. Plasma levels of GSSG allow for a more sensitive quantification of oxidant stress within reperfused ischaemic flaps, and may serve as a useful tool in skin flap research.
Animals↗
Use of the guinea pig flank flap in skin flap research.
A variety of flaps in laboratory animals have been designed that propose to parallel the behavior of human skin under different experimental conditions. In the search for a readily available and affordable island skin flap model that combines reliable anatomy with a pedicle of substantial size, we have designed in the guinea pig a cutaneous flap based on the superficial circumflex iliac artery and vein. In 22 adult female Hartley guinea pigs, an 8 x 4 cm flank flap based on the superficial circumflex iliac pedicle was raised, and its characteristics were evaluated for applications to skin flap research. Dermofluorometric studies were performed that confirm the vascularity of this flap, and 100% survival of the flap was seen 5 days after surgery in all animals. Of particular benefit was the demonstration that both afferent and efferent blood samples can be taken from the pedicle directly, which allows for the direct quantification of plasma markers after physiologic insults to the skin flap, such as burn or ischemia. This anatomically reliable and easily dissected flap lends itself well to preliminary skin flap research and may contribute to standardization of a model for further studies examining the behavior of skin microcirculation under adverse physiologic conditions.
Animals↗
Improved efficacy of urokinase further prolongs ischemic skin-flap survival.
Salvage of a free-tissue transfer, when postoperative vascular compromise is detected, depends largely upon the restoration of a patent microcirculation. The therapeutic efficacy of thrombolytics infused directly into the failing flap has been clearly demonstrated. In this experiment, the authors investigated whether the method of selective administration of urokinase to failing skin flaps in 68 Sprague-Dawley rats had any effect on flap survival. In one group of animals, postischemic flaps were perfused with 100,000 IU of urokinase given by manual injection, and via a pressurized delivery system (150 mmHg) in the other group. Flap survival was assessed at 7 days. A significantly greater survival was seen in flaps treated with urokinase by controlled pressure infusion (p < 0.01). This simple method is suggested to increase the efficacy of urokinase used in the context of flap salvage.
Animals↗
Evaluation of a continuous systemic infusion of iloprost, a stable PGI-2 analog, on the survival of experimental skin flaps.
Numerous investigators have attempted to enhance the survival of ischemic experimental skin flaps using various pharmacologic manipulations. Recently, the authors' laboratory demonstrated the beneficial effect of iloprost, a stable PGI2 analogue, as a post-ischemic perfusion washout, in improving the survival of ischemic skin flaps. The rat unilateral abdominal skin flap, based on the superficial epigastric vessels, was utilized in this study involving 30 animals. The animals were divided into three different treatment groups, with ischemic periods of 16 and 18 hr. Perfusion washouts were performed at the completion of the various ischemic periods. Alzet osmotic pumps were used to deliver a continuous systemic infusion of iloprost for 7 days postoperatively. The groups consisted of the following: Group 1 (single ILO)--perfusion washout with iloprost only; Group 2 (continuous LD ILO)--low-dose systemic iloprost infusion (0.066 mcg/kg/min) and perfusion washout with iloprost; and Group 3 (continuous HD ILO)--high-dose systemic iloprost infusion (0.1 mcg/kg/min) and perfusion washout with iloprost. The percentage of flap survival was assessed on postoperative day 7. Skin flaps of the animals receiving the continuous systemic infusion of iloprost were noted to have varying percentages of survival, while skin flaps undergoing perfusion washout only were found to have either complete survival using a continuous systemic infusion of iloprost, compared to iloprost perfusion washout alone. In addition, the hypotensive side effects of systemic iloprost infusion limit its use in the rat skin-flap model.
Animals↗
A standardized model of microvenous thrombosis.
A standardized model of venous thrombosis is necessary when evaluating potential antithrombotic or thrombolytic agents in microsurgery. Previous studies have shown the adventitial "tuck" model to be advantageous in terms of the vascular reactivity achieved and the relative ease of performance. However, variability exists in the current design, due to the lack of standardized dimensions of the adventitial flap. Two variations of this model are presented which attempt to overcome this problem, and their reproducibility is compared to the inversion graft model of venous thrombosis in the rat femoral vein. The "femoral vein flap" is suggested as a suitable model to simulate anastomotic thrombosis during microvenorrhaphy.
Abdominal Muscles↗
Additional benefit of heparin in the thrombolytic salvage of ischemic skin flaps.
Microvascular thrombosis is known to play an important part in the cessation of flow seen in a flap following ischemia and revascularization. Its reversal, using thrombolytic therapy, is associated with higher rates of successful flap salvage. Although this procedure restores patency to the microcirculation, the damaged endothelial cell layer remains highly thrombogenic and a definite risk of rethrombosis exists in the early period of reperfusion. In an inferior epigastric flap model in a rat, we investigated the effect of additional heparin (subcutaneous and intravenous administration) following a standardized urokinase washout (100,000 iu) of the ischemic flaps. Flap survival was assessed at 1 week and morphological changes in the microcirculation were observed using electron microscopy. Results showed a significant increase in flap survival in the group receiving intravenous heparin following urokinase washout and suggest that systemic heparin may play a beneficial role in the early reperfusion period following thrombolytic flap salvage.
Animals↗
Vascularized bone flaps in oromandibular reconstruction. A comparative anatomic study of bone stock from various donor sites to assess suitability for enosseous dental implants.
OBJECTIVE: To identify donor sites from which vascularized bone may be harvested capable of accepting osseointegrated implants of the minimum dimensions required to ensure long-term implant stability. DESIGN: An anatomic study of the most commonly employed donor sites for vascularized bone in oromandibular reconstruction was conducted on 28 cadavers. SETTING: Academic tertiary referral center. PARTICIPANTS: Twenty-eight freshly embalmed, adult white cadavers (16 male, 12 female) were dissected. INTERVENTION: The ipsilateral fibula, iliac crest, radius, and lateral border of the scapula were harvested and multiply sectioned at predetermined sites. OUTCOME MEASURE: Implantability was determined for each section based on measurements of height, width, and cross-sectional area utilizing computer planimetry. RESULTS: The iliac crest was the most consistently implantable donor site, followed by the scapula, fibula, and radius (83%, 78%, 67%, and 21% of sections from each donor site satisfying the criteria for implantability). Consistent regional differences in implantability were encountered at each donor site except the scapula. CONCLUSIONS: Following ablation of oromandibular malignant neoplasms, restoration of stable retentive dentition is a prerequisite to a successful functional oral rehabilitation. This is best achieved with enosseous implants, capable of supporting a stable dental prosthesis, placed directly into vascularized bone flaps at the time of mandibular reconstruction. The implications of the results obtained in this study for gender, donor site selection, and orientation of the vascularized bone flap are discussed.
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