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Biomedical subjects

S G Cooper

Publications and source records attributed to S G Cooper.

At least 19 recordsLinked to original sources
PubMed1992

Minimally invasive management of transposition of the great arteries in the newborn period.

This study reports on a predominantly noninvasive management program for neonatal transposition of the great arteries [TGA] incorporating balloon atrial septostomy [BAS] under echocardiographic control. BAS was performed in 25 consecutive patients presenting with TGA between April 1988 and April 1990. Structural and coronary anatomy was evaluated echocardiographically with angiographic supplementation only when additional data were required. This information was correlated, where possible, with direct anatomic findings and subsequent course. BAS was performed through the umbilicus in 17 patients (85% of patients in whom this approach was attempted). Thirteen patients did not require ventilation during BAS. There were minimal complications and satisfactory septostomies in all cases. Coronary anatomy was correctly predicted in all patients where anatomic correlation was available. Without invasive investigation 9 patients underwent neonatal arterial switch procedures and 2 underwent palliative procedures. BAS under echocardiographic control proved safe, effective, minimally traumatic and mostly possible via the umbilical vein. The umbilical vein, where patent, permitted rapid safe access for BAS. Echocardiographic diagnosis of the coronary artery, and structural and functional anatomy was reliable and allowed minimally invasive preoperative management in many patients.

Cardiac Catheterization↗
PubMed1992

Tangential breast irradiation: simple improvements.

A series of studies using phantom and in vivo dosimetry measurements with diodes and thermoluminescent dosimetry were undertaken to establish whether simple methods are available to obtain improvements in homogeneity of dose in the treated breast, and reductions of dose to tissues outside it, when using tangential 6MV photon fields. These studies confirmed that the use of an appropriate lung density correction factor in the planning process is likely to cause a reduction in the amount of wedge compensation predicted to be necessary to produce reasonable dose homogeneity in the central axis of the beam. This was shown to be of value in eliminating potential areas of overdosage in the chest wall medial and lateral to the breast mound, and also in reducing unwanted doses to the contralateral breast and lung. Further reductions in dose to contralateral breast were confirmed to occur when the majority, or all, of the wedge compensation predicted necessary is placed on the lateral field and when the lateral tangential field is angled anteriorly in such a way as to align the posterior beam edges. Skin does above, below, and over the breast mound were observed to depend critically upon angle of incidence of the beam, with its consequent effect upon electron build-up, and the position of the breast contour in the beam. Skin doses above and below the breast mound were shown to exceed over the mound itself. This differential effect was observed to increase with increasing wedge compensation. In some situations skin doses below the breast mound nearly reached prescribed dose within the breast. The design and use of simple lead attenuators to reduce these areas of high dosage is discussed.

Breast Neoplasms↗
PubMed1991

Continuous subcutaneous insulin infusion (CSII) and insulin antibodies in rabbits.

Using prepubertal male New Zealand White rabbits, continuous subcutaneous insulin infusion (CSII), delivered by either an external or an implantable infusion device, resulted in significantly higher insulin antibody (I-Ab) production than bolus injection (BII). We tested the influence during CSII of (1) the insulin species, (2) the insulin diluent, (3) the materials of which the infusion devices were made and (4) the incubation of insulin in a syringe on the backs of rabbits ('sham-infusion'), with the following results: (1) beef and sulphated beef insulins produced high levels of I-Abs, while porcine and human insulins produced moderate levels; (2) with all insulins used, 0.9% NaCl and 0.9% NaCl with 24-26 mmol NaHCO3 added, produced high levels of I-Ab. A buffer containing 0.7% NaCl, 0.136% sodium acetate trihydrate and 0.1% methyl-p-hydroxybenzoate and a buffer containing 16 mg/ml glycerol and 2 mg/ml phenol, produced highly significantly lower I-Abs (P less than 0.001); (3) insulin glass syringes produced much lower I-Ab levels than in standard polypropylene syringes and (4) polypropylene syringes in a 'sham-infusion' technique, resulted in intermediate levels of insulin antibodies [(P less than 0.02) vs CSII; (P less than 0.005) vs BII]. Our data suggest that insulin immunogenicity is influenced by all four factors tested. We suggest that benefits of CSII therapy may be attenuated unless a best possible control of these factors is achieved.

Animals↗
PubMed1990

Total respiratory compliance in infants and young children with congenital heart disease.

The multiple occlusion technique was used to measure total respiratory system compliance (Crs) in 62 infants and young children with congenital heart disease (age range, 2 days to 2 years). Measurements were found to be reproducible in nine infants in whom repeat measurements were possible (maximum deviation between measurements less than 10%). The incidence of failure to obtain accurate results was no greater than when studying infants without cardiopulmonary disease. However, in the presence of severe growth retardation or alinearity of volume-pressure data, results may be difficult to interpret in individuals. Results of Crs were related to non-invasive assessments of cardiac disease severity using chest radiography and echocardiography. After the effects of growth had been taken into account, a significant negative relationship was found between Crs and the right pulmonary artery to aortic ratio, which reflects pulmonary vascular engorgement (P = 0.003, R2 = -0.40). However, no significant relationship was found between Crs and chest X-ray score (P = 0.27).

Aorta↗
PubMed1990

Low dose rate teletherapy using a telecaesium 137 unit radiobiological, physical and clinical considerations.

Low dose rate teletherapy aims to combine the supposedly superior results obtained with low dose rate implants with the convenience and staff protection characteristics of external beam therapy. Previous investigators have used telecobalt units to produce dose rates of 1.1 to 1.8 Gy/hr to treat in daily sessions lasting 6-10 hours to total doses of 60-70 Gy. These studies have not discounted the possibility that much of the advantage of interstitial implants results from the low dose rates used per se, and from the fact that the total dose is delivered in a short overall time. The relationship between total dose, dose rate and volume giving normal tissue and anit-tumour effects, however, remains ill-defined. At the Newcastle Mater Misericordiae Hospital a Caesium teletherapy unit has been modified to treat at low dose rates and a study has been designed with a view to establish which permutations of total dose and dose rate are isoeffective for acute mucosal and acute skin reactions in the dose rate range between 0.8 and 9.6 Gy/hr (1.3 and 16 cGy/min).

Cesium Radioisotopes↗
PubMed1989

Nephrocutaneous fistula diagnosed by computed tomography.

We present an unusual case of isolated nephrocutaneous fistula secondary to renal calculi with perirenal infection. The usefulness of computed tomography (CT), with its depiction of the extent of involvement and its characterization of the disease process, is described and the literature is reviewed.

Adult↗
PubMed1989

Balloon dilation of pulmonary venous pathway obstruction after Mustard repair for transposition of the great arteries.

Percutaneous balloon dilation was attempted in three patients with mid baffle pulmonary venous pathway obstruction after the Mustard operation for transposition of the great arteries. The procedure was unsuccessful in a 3 year old boy. Evidence for relief of obstruction in the other two patients (7 and 14 years old, respectively) consisted of angiographic demonstration of improved caliber at the site of the pulmonary venous pathway narrowing, improvement in the Doppler spectral signal at this site from an "obstructed" to a "normal" pattern as well as symptomatic improvement. Balloon dilation was performed twice in one of these patients. The Doppler and symptomatic improvement were sustained in both patients at short-term follow-up (5 and 6 months, respectively). This technique may offer effective relief of pulmonary venous pathway obstruction in some patients with this complication of the Mustard operation.

Adolescent↗
PubMed1989

Treatment of recoarctation: balloon dilation angioplasty.

Balloon dilation of recoarctation of the aorta was performed 47 times in 44 patients 49 +/- 54 months after surgical repair. The initial operation was performed in the neonatal period in 29 patients (66%). The age at balloon dilation was 4.9 +/- 5.3 years (range 2 months to 20 years) and weight was 18 +/- 15 kg (range 2 to 72). Systolic pressure difference across the recoarctation site decreased from 37 +/- 16 to 14 +/- 11 mm Hg and coarctation/aortic diameter ratio increased from 0.45 +/- 0.14 to 0.85 +/- 0.16 immediately after balloon dilation regardless of the nature of the previous operation (subclavian flap [n = 12], resection with end to end anastomosis [n = 21], patch angioplasty [n = 4] or multiple operations [n = 5]). In the ascending aorta, systolic pressure decreased from 120 +/- 25 to 113 +/- 20 mm Hg. In the descending aorta, systolic pressure increased from 85 +/- 15 to 100 +/- 19 mm Hg and pulse pressure increased from 22 +/- 7 to 36 +/- 8 mm Hg. At repeat cardiac catheterization in 21 patients (48%) 12 +/- 8 months after balloon dilation, there was further reduction in systolic pressure difference from 17 +/- 11 to 12 +/- 9 mm Hg with no further change in coarctation/aortic diameter ratio. Aneurysm formation was evident in one patient (2%) immediately after balloon dilation; the aneurysm was unchanged at repeat study 15 months later. A "new" aneurysm was apparent in 2 (10%) of the other 20 patients restudied to date. The occurrence of aneurysm in these three patients was unrelated to balloon size. There were no procedure-related deaths. Three patients (7%) had femoral artery occlusion. Balloon dilation affords good relief of obstruction without adverse sequelae from aortic wall disruption at medium-term follow-up.

Angioplasty, Balloon↗
PubMed1989

Aneurysm of the ductus arteriosus.

Two neonates with aneurysms of the ductus arteriosus were seen. One suffered a fatal spontaneous rupture of the aneurysm, and the second (in which it was an incidental finding) the aneurysm was monitored by echocardiography, and seemed to resolve spontaneously.

Aneurysm↗