Scott B. Gustafson

Chitosan Dressing Provides Hemostasis in Swine Femoral Arterial Injury Model

Objective. Chitosan dressings have been shown to be effective in improving survival of severe parenchymal injuries in an animal model andin treating prehospital combat casualties. Our goal was to test the efficacy of chitosan acetate dressings in providing durable hemostasis in a high-flow arterial wound model. Methods. A proximal arterial injury was created with 2.7-mm vascular punches in both femoral arteries of fourteen anesthetized swine. By using a crossover design, 48-ply gauze (48PG) or a chitosan dressing (HC) was applied with pressure to the injury for 3 minutes andthen released. If hemostasis was not maintained for 30 minutes, a second identical attempt was made by using the same dressing type. If hemostasis was still not achieved, the dressing was considered an acute failure andthe alternate dressing type was applied. If failure of hemostasis occurred between 30 and240 minutes after application, the dressing was considered a chronic failure andthe artery was ligated. Results. All 25/25 (100%) of the HC tests and3/14 (21%) of the 48PG maintained hemostasis for 30 minutes. At 240 minutes, 21/25 (84%) of the HC tests and1/14 (7%) of the 48PG maintained hemostasis. Statistical analysis by Fischers exact test shows a significant (p < 0.001) difference in hemostatic efficacy between the 48PG andHC groups in this model, both at 30 minutes andat 240 minutes. Conclusion. Chitosan acetate hemorrhage control dressings provided superior hemostasis to 48 ply gauze in high inguinal femoral arterial injuries. Chitosan-based dressings may provide prehospital treatment options for hemostasis in patients with severe hemorrhagic arterial injuries.

Characterizing light propagation in bone for photodynamic therapy of osteosarcoma

This work aims at characterizing how light propagates through bone in order to efficiently guide treatment of osteosarcoma with photodynamic therapy (PDT). Optical properties of various bone tissues need to be characterized in order to have a working model of light propagation in bone. Bone tissues of particular interest include cortical bone, red and yellow marrow, cancellous bone, and bone cancers themselves. With adequate knowledge of optical properties of osseous tissues, light dosimetry can determine how best to deliver adequate light to achieve phototoxic effects within bone. An optical fiber source-collector pair is used for diffuse reflectance spectroscopic measurements in order to determine the scattering and absorption properties of bone tissues. Native absorbers of interest at visible and near-IR wavelengths include water and oxygenated and deoxygenated hemoglobin. A cylindrically symmetric Monte Carlo model is then used, incorporating these results, in order to predict and guide the delivery of light within bone in order to achieve the desired phototoxic effect in PDT.

Clinical results of photodynamic therapy for the treatment of sarcoid tumors in equids

Sarcoids are a locally invasive cutaneous fibroblastic neoplasia and are the most common skin tumor of equids. Myriad treatments are described in the literature including surgery, topical blistering agents, cryosurgery, immunotherapy, and intralesional chemotherapy. Recurrence or progression of the disease after treatment is common. Two years ago the authors began clinical trials investigating the feasibility of photodynamic therapy for the treatment of sarcoid tumors. The tumor or surgical margins were treated using topical or intra-lesional delta-aminolevulinic acid (ALA) as a photosensitizing agent. The ALA was left in situ for a period of time allowing buildup of protoporphyrin IX (the photosensitizer) prior to irradiation with a 635-nm diode laser. We have initial results in 10 patients with 18 lesions and have seen decrease in tumor size or complete remission in 13 of 18 lesions. Recurrence or progression has been noted in 7 lesions. Results of these trials and follow-up information on clinical patients will be presented for review.

Characterizing the Optical Properties of Bone Using a Multi-Fiber Array and Diffuse Reflectance Spectroscopy

A multi-fiber array is used for diffuse reflectance spectroscopic measurements of visible and near-IR light in bone. Optical properties are determined by fitting resulting spectra versus source-collector fiber separation and spectra of native absorbers.