Biomedical subjects
Publications and source records attributed to A Poon.
Basal cell carcinomas (BCCs) of the caruncle are rare. We report a case of a primary BCC of the caruncle in a 74-year-old man who was seen with a medial interpalpebral lesion. He had a history of sun exposure and multiple malignant neoplasms of the skin. The lesion was excised and histological examination showed a BCC of the caruncle. The clinical history, examination findings, and histological features are given.
Constant infusion of factor VIII (FVIII) into patients with haemophilia A after major surgery has been recommended as optimal treatment to avoid peaks and valleys in the circulating levels of FVIII and to allow the use of much lower doses of FVIII than are historically required. One of our young patients with severe (< 0.01 U/ml FVIII) haemophilia suffered a subdural haematoma for which he received treatment with 815190 recombinant FVIII (rFVIII) units over a period of 52d. 2 weeks after admission, because of low FVIII levels and the presence of FVIII inhibitors, the infusion rate was increased to > 100 U/kg/h for 14d. During this time the FVIII level fluctuated between 0.6 and 4.2 U/ml. For some period it was not possible to detect ristocetin co-factor activity in this patient's plasma and the von Willebrand factor (VWF) level and VWF multimer pattern resembled those of a patient with von Willebrand's disease. Subsequently, when the rFVIII dose was increased 2-fold, this was not reflected by the plasma level of FVIII although antibodies were not detected. The data suggest that the prolonged infusion of very high levels of rFVIII which is deficient in von Willebrand factor can result in depletion of VWF from existing stores, producing a laboratory picture which is consistent with the diagnosis of von Willebrand's disease. Further, in the absence of complexing with VWF, FVIII appears to be cleared from the circulation at an increased rate. This is expensive and potentially compromising. Therefore, when administering very high doses of FVIII concentrates devoid of VWF for prolonged periods of time, ristocetin cofactor and VWF levels should be monitored.
PURPOSE: The construction and use of a surgical snare in retrieving and securing posterior chamber intraocular lenses is described. METHODS: The snare consists of a 10-O polypropylene suture threaded into a 25-gauge retrobulbar needle. This is used after a pars plana vitrectomy to retrieve the dislocated intraocular lens. The needle attached to the polypropylene suture is used to secure the lens haptic 1.5 mm behind the limbus. Two snares are used to secure the two lens haptics. CONCLUSIONS: The snare is easy to make with readily available materials. The use of this snare involves less intraocular and extraocular manipulations than other described methods.
Spinal administration of adenosine analogs and an adenosine kinase inhibitor produces antinociception in thermal threshold tests. In the present study, we determined the effects of N6-cyclohexyladenosine (adenosine A1 receptor selective), 2-[p-(2-carboxyethyl)phenylethylamino]-5'-N-ethyl-carboxamidoadeno sine (CGS-21680) (adenosine A2A receptor selective), and 5'-N-ethylcarboxamidoadenosine (NECA) (non-selective), on formalin induced nociceptive responses (flinching/lifting and licking/biting) using two concentrations of formalin (2% and 5%). We also examined the antinociceptive effects of 5'-amino-5'-deoxyadenosine, an adenosine kinase inhibitor, and deoxycoformycin, an adenosine deaminase inhibitor, under these conditions. Adenosine A1 receptor agonists, but not the A2A selective agent, produced significant antinociception, as did 5'-amino-5'-deoxyadenosine, but not deoxycoformycin. The extent of antinociception produced was greater with the lower stimulus intensity. The effects of NECA and 5'-amino-5'-deoxyadenosine were inhibited by caffeine, indicating the involvement of cell surface adenosine receptors in their actions. We conclude (a) that the adenosine A1, but not the A2A, receptor is involved in spinally mediated antinociception, (b) that adenosine kinase is more important than adenosine deaminase in regulating endogenous adenosine levels in the spinal cord, and (c) that stimulus intensity is an important determinant of the efficacy of purines in the spinal cord.
PURPOSE: We evaluated the incidence of clinically significant refractoriness to platelet transfusions in children with acute leukemia. PATIENTS AND METHODS: We reviewed the complete transfusion records up to July 1993 of all 213 patients diagnosed with acute leukemia at our institution over the 4-year period 1987 to 1990. The transfusion protocol called for all patients requiring transfusion of red cell and/or platelet concentrates to initially receive components that were not leukocyte reduced. Patients suspected clinically to be refractory to platelets were tested for anti-human leukocyte antigen (HLA) antibodies and those that tested positive were switched to HLA-matched platelets. RESULTS: Of 184 patients diagnosed with acute lymphoblastic leukemia (ALL), 133 (72%) required platelet support, whereas all 29 patients with acute myeloid leukemia (AML) were transfused with platelets. The incidence of clinically suspected refractoriness to non-leukocyte-reduced platelets, which was confirmed by a positive test for anti-HLA antibodies and which resulted in a switch to HLA-matched platelets, was nine of 29 (31%) for patients with AML but only three of 133 (2.3%) for patients with ALL. CONCLUSIONS: The results of this study indicate that clinically significant platelet refractoriness requiring transfusion of HLA-matched platelets occurs infrequently in childhood ALL. For this group of patients, use of leukocyte-depleted cellular components for the purpose of preventing platelet refractoriness cannot be justified. This approach may be appropriate for children with AML.
PURPOSE: To describe the patterns of visual loss associated with pituitary macroadenomas compressing the anterior visual pathway. METHOD: A prospective survey of 29 patients with pituitary macroadenomas who presented to the neurosurgical unit at St Vincent's Hospital, Melbourne. Selected patients had histologically verified pituitary macroadenomas, and visual defects (acuity, colour and/or field loss) consistent with anterior visual pathway compression. RESULTS: All patients had visual field defects detected on perimetry, and the majority were asymmetrical. Bitemporal defects were most common but field defects ranged from monocular defects to generalised constriction. Four patients (13.8%) did not report visual symptoms, and of those who had symptoms, blurred vision was the most common complaint. Ninety-six per cent of eyes had field loss, 56% had decreased colour vision, 46% had decreased acuity, 31% had optic disc pallor, and 2% had an ophthalmoplegia. CONCLUSIONS: Patients with visual pathway compression by pituitary macroadenomas may be asymptomatic despite having field defects. Perimetry is the most sensitive method of identifying compression, followed by colour vision, visual acuity, then the presence of optic atrophy. Automated static threshold perimetry appears to show early field defects better than manual kinetic perimetry. All patients with pituitary macroadenomas should have thorough ophthalmological examinations, including perimetry to document visual deficits secondary to compression.
A case is presented of a child with mosaic Down syndrome, who presented at birth with a transient leukemia and later progressed to megakaryoblastic leukemia. Evidence is presented that both leukemias were of megakaryoblastic lineage and evolved from a trisomic hematopoietic precursor. This case is unique in the poor course of the initial transient neonatal leukemia with improvement following chemotherapy. It also highlights the form of leukemia and associated myelodysplasia that occurs in children with Down syndrome. This form of leukemia and transient leukemia are interrelated and are unique to children with Down syndrome.
The prevalence of hazardous drinking of alcohol in orthopaedic inpatients and its impact on patient management was determined. A prospective survey was performed on acute and arranged admissions in the orthopaedic wards at St Vincent's Hospital, Melbourne, over a 3 month period. At-risk drinking was measured by the AUDIT questionnaire, a score of eight or more suggesting hazardous drinking and a score of 20 or more suggesting dependence. A separate questionnaire recorded relevant details of the admission, complications during hospital stay, degree of difficulty nursing the patient and any past history of alcohol problems. Thirty-four (36%) of 94 patients were drinking at hazardous levels. Of these, 62% gave no prior history of problems with alcohol. Thirty-four per cent of 53 acute admissions and 39% of 41 arranged admissions were harmful drinkers suggesting that trauma may not be the only contribution to problem drinking in the orthopaedic setting. Hazardous drinking occurred in both male and female groups aged less than 55 years and in males greater than 55 years. Hazardous drinking was associated with more inpatient complications (chi 2 = 6.6, d.f. = 1, P = 0.01) and greater nursing difficulty (chi 2 = 5.5, d.f. = 1, P = 0.02). A third of the patients in the orthopaedic wards drink alcohol at hazardous levels, whether they are acute or arranged admissions. Hazardous drinking is associated with more complications and greater difficulty in nursing patients.
Gas gangrene of the liver is a very unusual cause of graft failure, and gas gangrene caused by Enterobacter cloacae is also exceedingly rare. Although Clostridial infection could not be excluded in this case, the literature and our case show that Enterobacter cloacae can be present in gas gangrene tissue whether or not it is the only infecting organism.
Q-MED is an automated history-taking system that uses speaker-independent continuous speech as its main interface modality. Q-MED is designed to allow a patient to enter her basic symptoms by engaging in a dialog with the program. Error-recovery mechanisms help to eliminate findings resulting from misrecognitions or incorrect parses. An evaluation of the natural language parser that Q-MED uses to map user utterances to findings showed an overall semantic accuracy of 87 percent; Q-MED asks more specific questions to capture findings that were not volunteered, or that were unable to be parsed in their initial, open-ended form.
We report a case of pediatric acute non-lymphocytic leukemia (ANLL) with monosomy 7 occurring in a child successfully treated for acute lymphoblastic leukemia (ALL) nine years earlier. Acquired monosomy 7 is currently recognized as a distinct therapy-related cytogenetic abnormality which nonrandomly occurs as a late complication of cytotoxic therapy used in the treatment of both malignant and nonmalignant disease. Most commonly, this occurs as a disorder of bone marrow morphology and function characterized as a myelodysplastic syndrome (MDS) or ANLL. This case report emphasizes the need for continued evaluation of long-term survivors of childhood cancer to identify and minimize therapy-related side effects without compromising successful management.
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Simple closure, the conventional operation for perforated acute duodenal ulcers, is associated with symptomatic relapse in a large proportion of patients. In order to assess the role of immediate definitive surgery, 78 fit patients with perforated acute ulcers were prospectively randomized to undergo either closure alone or proximal gastric vagotomy with closure (PGV). Patients taking potentially ulcerogenic drugs or who had severe stress were excluded from the study. Both groups were comparable with respect to age, sex, general medical health, duration of perforation, length of ulcer history, and presence of duodenal scarring. There was no hospital mortality. Minor complications occurred in 7.3% after closure and 10.8% after PGV. At 3 years follow-up, the cumulative recurrence rates were 36.6% and 10.6% after closure and PGV, respectively (p = 0.001). Eighty-five per cent of recurrences after closure were symptomatic, and half of them required reoperation. Duodenal scarring itself did not appear to influence the outcome after closure. PGV was not associated with dumping, diarrhea or other unwanted side effects. Although less than that in chronic ulcers, there is a substantial risk of symptomatic relapse after closure of perforated acute duodenal ulcers. With judicious patient selection, PGV effectively reduces this risk without incurring disabling side effects associated with other ulcer operations.
Twenty-four patients with Down syndrome and leukemia were studied. A strong male predominance (79%) was found. Age ranged between 18 months and 15 years (mean: 5 6/12); 54% of the patients were less than 4 years of age at the time of diagnosis. A preleukemic phase was noted in 6/24 patients. This phase, characterized essentially by thrombocytopenia, lasted from 2-8 months. Patients with preleukemia had unusual blast cell morphology and involvement of more than one cell line (dyserythropoiesis, hypolobulated megakaryocytes) and were probably M7 leukemias. All patients demonstrated severe methotrexate toxicity at standard methotrexate doses. Toxicity, manifesting as mouth ulcerations and bone marrow depression was seen regardless of the route of administration (oral, intrathecal or intravenous). A 30%-50% reduction of the standard dose was tolerated. Methotrexate absorption and clearance were studied in two patients and were found to be normal. We postulate that the observed toxicity of methotrexate may be due to a gene dosage effect for enzymes known to be on chromosome 21 and intervening in purine metabolism. Increased purine synthesis implies greater tetrahydrofolic acid demands and therefore greater sensitivity to an antifolate agent.
In order to validate a previously derived set of risk factors, 259 consecutive patients who had simple closure or definitive operation for perforated duodenal ulcers were studied prospectively. Major medical illness, preoperative shock, and longstanding perforation (more than 24 hours) correctly predicted the outcome in 93.8% of patients. Most importantly, 16 patients (6.2%) who died after operation could be identified (no false-negative error). The mortality rate increased progressively with increasing numbers of risk factors: 0%, 10%, 45.5%, and 100% in patients with none, one, two, and all three risk factors, respectively. These findings underscore the importance of patient selection and the feasibility of a risk grading system in guiding surgical management. Definitive surgery can be done safely in good-risk patients. Simple closure is preferable in those patients with uncomplicated perforations if any risk factor is present. Truncal vagotomy and drainage may be required if there is coexisting bleeding or stenosis. Nonoperative treatment deserves re-evaluation in patients with all three risk factors because of their uniformly dismal outcome after operation.
Megakaryoblastic leukemia and transient leukemia in Down's syndrome have been reviewed using case reports from the literature and our own experience at the Hospital for Sick Children. The following conclusions have been reached: (1) approximately 20% of leukemia (excluding transient leukemia) in Down's syndrome is acute megakaryoblastic leukemia; (2) approximately 20% of all leukemia in Down's syndrome is transient leukemia; (3) transient leukemia in Down's syndrome is acute megakaryoblastic leukemia; (4) recurrence of acute megakaryoblastic leukemia occurs in 20% of the cases of transient leukemia; and (5) the incidence of acute megakaryoblastic leukemia in Down's syndrome is estimated to be 400 times that in normal children. These observations suggest that a specific form of leukemia, namely acute megakaryoblastic leukemia, has a remarkable association with Down's syndrome.
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