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Biomedical subjects

S Choi

Publications and source records attributed to S Choi.

248 records · Page 14Linked to original sources
PubMed1977

Blood pressure in a high school population. I. Standards for blood pressure and the relation of age, sex, weight, height, and race to blood pressure in children 14 to 18 years of age.

This is a report on the initial from an ongoing study of blood pressure in ninth to twelfth grade students in the St. Louis metropolitan area. The purpose was to establish standards, to determine the incidence of hypertension, and to examine the relationship of blood pressure to age, weight, height, sex, and race. Subjects with persistent hypertension were to be investigated and checked annually as long as they were in high school. Students in the ninth grade at the beginning of the project were to be screened each year for four years.

Adolescent↗
PubMed1975

Leukocyte function in children with malignancies.

Blood was obtained on 414 occasions from 106 children with acute lymphocytic leukemia (ALL) or solid tumors. Resting and stimulated hexose monophosphate shunt (HMPS) activity and unstimulated and stimulated nitroblue tetrazolium (NBT) dye reduction were assessed on each sample. The values obtained were compared to similar determinations made on blood obtained from 178 healthy children. Resting HMPS activity of all patients with malignant diseases was significantly (p smaller than 0.01) greater, and ability to stimulate HMPSP activity significantly (p smaller than 0.01) less than that noted in healthy control patients. Unstimulated NBT dye reduction of leukocytes obtained from patients with malignant disorders was significantly (p smaller than 0.01) less than that observed in healthy control children. No significant differences were noted in HMPS activity or NBT dye reduction in patients with ALL, rhabdomyosarcoma, or other solid tumors who had bacterial infection when compared to uninfected patients, or when patients were categorized according to the type of chemotherapy provided. HMPS activity and NBT dye reduction of patients with ALL prior to treatment, in remission, and during episodes of relapse did not differ from each other. Thus, a functional impairment in leukocyte function was noted in patients with ALL even when their peripheral blood and bone marrow cells exhibited normal morphology.

Bacterial Infections↗
PubMed1975

Spontaneous renal subcapsular hematoma renal angiography as a diagnostic aid.

Prior to the development of angiography, a definite diagnosis of spontaneous subcapsular renal hematomaa was not often made preoperatively. The classic triad of blood loss, pain, and mass on the affected side is seldom presented by the patient. The one constant finding on scout film is an enlarged renal shadow, presenting a problem in differential diagnosis. Chief among cause of subcapsular renal hemorrhage are trauma, tumor, infarct, arteritis, and bleeding diathises. Selective renal arteriography gives specific information about the renal vascular supply and the state of the renal parenchyma not available by other means. Diagnosis of subcapsular renal hematom is facilitated by this modality. A correct diagnosis of subcapsular renal hematoma may well spare an otherwise innocent kidney. A review of current literature was undertaken, and three documented cases of spontaneous subcapsular hematoma diagnosed prior to surgery and confirmed at surgery are presented.

Adenocarcinoma↗
PubMedDate not supplied

Progress on development of the Nimbus-University of Pittsburgh axial flow left ventricular assist system.

Nimbus Inc. (Rancho Cordova, CA) and the University of Pittsburgh have completed the second year of development of a totally implanted axial flow blood pump under the National Institutes of Health Innovative Ventricular Assist System Program. The focus this year has been on completing pump hydraulic development and addressing the development of the other key system components. Having demonstrated satisfactory pump hydraulic and biocompatibility performance, pump development has focused on design features that improve pump manufacturability. A controller featuring full redundancy has been designed and is in the breadboard test phase. Initial printed circuit layout of this circuit has shown it to be appropriately sized at 5 x 6 cm to be compatible with implantation. A completely implantable system requires the use of a transcutaneous energy transformer system (TETS) and a diagnostic telemetry system. The TETS power circuitry has been redesigned incorporating an improved, more reliable operating topography. A telemetry circuit is undergoing characterization testing. Closed loop speed control algorithms are being tested in vitro and in vivo with good success. Eleven in vivo tests were conducted with durations from 1 to 195 days. Endurance pumps have passed the 6 month interval with minimal bearing wear. All aspects of the program continue to function under formal quality assurance.

Heart-Assist Devices↗
PubMedDate not supplied

The efficacy of treatment with triamcinolone acetonide in calcinosis cutis following extravasation of calcium gluconate: a preliminary study.

Neonatal hypocalcemia is not an uncommon condition, especially in the premature neonate. It is effectively treated by intravenous administration of calcium gluconate. Complications of extravasation during intravenous infusion include localized calcification and occasionally necrosis. When this occurs, however, there is no specific mode of treatment except supportive management and skin graft. This experiment was designed to evaluate the efficacy and safety of treatment with triamcinolone acetonide in calcinosis cutis following extravasation of calcium gluconate. Initially, 2 cc of 10% calcium gluconate was injected subcutaneously into two rabbits at seven sites on the shaved skin of the back. Another two rabbits were injected at the same sites with 0.5 cc of triamcinolone acetonide (10 mg/dl) after injection of 2 cc of 10% calcium gluconate. As a control, 2 cc of normal saline was injected into another rabbit in the same manner. These five rabbits were observed over the next 7 weeks and underwent pathologic examination at various intervals (on days 1, 3, 8, 15, 30, 37, 45). In the 10% calcium gluconate injected rabbits, nodules and large ulcerated lesions developed after 15 days. Multiple, linear, ulcerative and indurated masses were noted on day 37. The lesions healed progressively with a decrease in ulceration, and after 2 months, the masses disappeared gradually. Histologically, on day 15 calcium deposits were seen in the walls of the arteries, veins, dermis, and muscle fibers and epidermal necrosis was seen at the injection sites. From day 37 discharge of calcium deposits began to take place by means of transepidermal elimination. After 2 months, the calcium and mucin deposition was observed focally in the dermis. In the rabbits injected with 10% calcium gluconate and triamcinolone acetonide, mild erythema and induration were seen after day 15 at the injection sites; this gradually disappeared. After 30 days the injection sites were normal in appearance. Histologically, at day 15 calcium deposition was seen in the upper dermis, but after 1 month the injection sites were histologically normal. We suggest that intralesional injection of triamcinolone acetonide for the treatment of calcinosis cutis following extravasation of calcium gluconate is effective, probably due to its antiinflammatory effect and its role in facilitating the resorption of calcium in the tissue.

Administration, Topical↗
PubMedDate not supplied

Aortic nonanastomotic pseudoaneurysm eroding lumbar vertebra--a case report.

Nonanastomotic pseudoaneurysms are uncommon complications of prosthetic grafts, which are mostly associated with axillofemoral grafts. The case presented describes a pseudoaneurysm secondary to a previously placed end-to-side aortobifemoral bypass. Back pain developed 3 years after the original bypass and was not relieved with narcotics and muscle relaxants. The patient also complained of a 20-pound weight loss, night sweats, and frequent emesis. Approximately 1 year after the onset of back pain, left leg claudication developed. He eventually underwent magnetic resonance imaging of the lumbosacral spine, which depicted a tumorlike mass eroding the vertebral bodies of L2 and L3. Full oncologic workup was pursued preoperatively. The patient also underwent aortography, computed tomography of the abdomen and pelvis, and an inferior venacavogram to elucidate the relationships between the mass and the major vascular structures. On exploration, no malignancy was present. A hole in the native aorta approximately 2 cm above the level of the end-to-side aortic anastomosis was discovered. This was contiguous with the vertebral bodies and the left psoas muscle. The pseudoaneurysm was repaired by conversion of the proximal anastomosis to an end-to-end aorto right iliac and left femoral bypass. All of the preoperative symptoms resolved after repair of the pseudoaneurysm. Chronic aortic rupture or pseudoaneurysms are difficult to diagnose due to the unusual clinical presentations. Despite complete radiologic evaluation, preoperative diagnosis may be difficult or impossible without a high degree of suspicion. Surgical repair will depend on the cause of the pseudoaneurysm--all but infected aneurysms may be repaired in line by creating a proximal anastomosis above the level of the pseudoaneurysm. Atypical back pain in patients with previous aortic reconstructions should alert the clinician to the possibility of vascular involvement. Patients with aortic pseudoaneurysms should undergo prompt repair to avert the potential risk for rupture when the surrounding structures are no longer able to contain the pulsatile flow.

Anastomosis, Surgical↗
PubMedDate not supplied

Combined transcatheter arterial embolization and regional chemotherapy for locally advanced carcinoma of the breast. A preliminary investigation.

Seventeen patients with carcinoma of the breast received a combination of transcatheter arterial embolization and regional chemotherapy before surgery. A gelatin powder mixed with an anticancer agent and blood clotting factors (own technique) was selectively injected into the internal mammary artery, the lateral thoracic artery, and the thoracodorsal artery. Marked regression of both primary tumor and metastatic regional lymph nodes was observed. The potential of this method as presurgical treatment is discussed.

Adult↗
PubMedDate not supplied

Epikeratoplasty for myopia: 2-year results and a proposed nomogram.

BACKGROUND: Epikeratoplasty for myopia is a relatively safe and reversible surgical technique that can result in large refractive corrections. However, it is also claimed that long-term stability and predictability are not satisfactory due to refractive regression and undercorrection. METHODS: In an effort to improve predictability and stability of epikeratoplasty for myopia, we followed 24 cases for 2 years and isolated factors affecting the postoperative refractive results. RESULTS: We found that better refractive results were achieved at 24 months postoperatively for cases in which the power of preoperative myopia was lower. Our investigations also disclosed no significant correlation between the surgical outcome at 24 months and patients' sex, age, and preoperative keratometric readings. CONCLUSION: On the basis of our observations, we propose a new nomogram where higher powers of minus keratolenses, compared to the traditional prescription chart, should be selected for those with high preoperative myopia to result in improved long-term results with epikeratoplasty for myopia. This nomogram has not yet been clinically tested.

Adult↗
PubMedDate not supplied

Infantile Krabbe disease: complementary CT and MR findings.

This case report of the infantile form of Krabbe disease in a 2 1/2-month-old boy illustrates the complementary findings that may be seen on CT and MR scans. The key finding on the CT scan was increased density in a bilateral symmetrical distribution involving the thalami with extension into the centrum semiovale. The MR scan, on the other hand, more clearly showed demyelination in the brain stem and cerebellum. In cases in which this involvement is minimal or absent, the MR scan may fail to detect an abnormality, and a CT scan will, therefore, still be necessary to detect characteristic abnormalities.

Brain↗
PubMedDate not supplied

Continued development of the Nimbus/University of Pittsburgh (UOP) axial flow left ventricular assist system.

Nimbus and the University of Pittsburgh (UOP) have continued the development of a totally implanted axial flow blood pump under the National Institutes of Health (NIH) Innovative Ventricular Assist System (IVAS) program. This 62 cc device has an overall length of 84 mm and an outer diameter of 34.5 mm. The inner diameter of the blood pump is 12 mm. It is being designed to be a totally implanted permanent device. A key achievement during the past year was the completion of the Model 2 pump design. Ten of these pumps have been fabricated and are being used to conduct in vitro and in vivo experiments to evaluate the performance of different materials and hydraulic components. Efforts for optimizing the closed loop speed control have continued using mathematical modeling, computer simulations, and in vitro and in vivo testing. New hydraulic blade designs have been tested using computational fluid dynamics (CFD) and flow visualization. A second generation motor was designed with improved efficiency. To support the new motor, a new motor controller fabricated as a surface mount PC board has been completed. The program is now operating under a formal QA system.

Animals↗
PubMedDate not supplied

Controller for an axial-flow blood pump.

An axial-flow ventricular assist device (VAD) under development at the authors' facility is intended for use as a long-term implantable device. At high speeds axial-flow VADs can collapse the native ventricle and damage the heart muscle, lung tissue, and blood. A prototype algorithm was developed to maintain physiologic perfusion to the vital organs while preventing ventricular collapse, through analysis of the electrical current waveform of the motor. The premise of the control algorithm is that the hemodynamics of the patient are reflected in the shape of this waveform. This approach is intended to eliminate the need for invasive sensors, thus effectively using the pump itself as a transducer. The control algorithm regulates the speed of the pump by comparing the motor-current waveform with reference waveforms using a matched filter. The matched filter was evaluated by its classification and differentiation performance. Thus far, the authors have been able to classify the waveforms into one of the four physiologic regions (below, within, or above the optimal range, and ventricular suction) with over 90% reliability. Ongoing work is directed toward improving the detection of ventricular suction, as this condition must be strictly avoided.

Algorithms↗