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Biomedical subjects

R W Walker

Publications and source records attributed to R W Walker.

At least 55 records · Page 3Linked to original sources
PubMed1992

Chemotherapy with vincristine (VCR) and etoposide (VP-16) in children with low-grade astrocytoma.

Twenty patients, aged 6 months to 20 years, with low-grade astrocytoma (LGA) participated in a chemotherapy trial of vincristine (VCR) and etoposide (VP-16). Fourteen children had recurrent progressive disease at entry on study. Prior treatment consisted of surgical resection alone (6), surgical resection and irradiation (4), surgical resection, irradiation and chemotherapy (2), surgery and chemotherapy (1), and irradiation and chemotherapy (1). Six patients were treated at initial diagnosis of LGA because they were less than 5 years old (5) or for a second primary tumor (1). Four recurrent patients and 3 newly diagnosed patients underwent surgical debulking of their tumors immediately prior to study entry. Tumors were located in the optic nerve/chiasm/hypothalamus (8), brain stem/cerebellum (4), cerebral hemispheres (3), midline structures (3), and spinal cord (2). The treatment plan administered in an out-patient setting consisted of weekly VCR 1.5 mg/m2 for 7 to 8 weeks and VP-16 100 mg/m2 for 5 days repeated every 6 weeks for a total of 18 months of therapy. Responses were evaluated by computerized tomography or magnetic resonance imaging. Of the 20 patients, 1 exhibited a partial response maintained for 12+ months, 3 exhibited minor responses maintained for a period of 10+ to 35 months, and 11 maintained stable disease for 10 to 42 months. Of the 11 patients with stable disease, 2 were withdrawn early from the study without further therapy. Five of the 20 patients developed progressive disease; for 4 of these 5, this occurred during the first course of therapy. Subsequently, these 5 died due to tumor.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1992

Diabetes mellitus in The Gambia, west Africa.

A register of diabetic patients attending the Royal Victoria Hospital, Banjul, The Gambia, was kept and data on hospital admissions recorded over a 1-year period. Two hundred and sixty-nine patients (110 men, 159 women) were registered of whom 66 (25%) were receiving insulin. Seventy-five patients (28%: 40 men, 35 women) were newly diagnosed. There were significant differences in age (p less than 0.001) and obesity (p less than 0.001) between men and women and between patients with different types of diabetes. There were 95 hospital admissions (5.2%) related to diabetes, as were a fifth of medical out-patient attendances. Ketoacidosis was the major cause of death while foot infections were more common (p less than 0.01) in women. Diabetes imposed a heavy burden on the health services of The Gambia, a small developing country in West Africa; more than 3.6% of the annual health budget was spent on the treatment of diabetic patients.

Adult↗
PubMed1992

Amphotericin B-associated leukoencephalopathy.

We report instances of fatal leukoencephalopathy associated with the intravenous administration of the antifungal agent amphotericin B (AmB) to a 16-year-old girl treated for acute lymphoblastic leukemia and a 22-year-old man who underwent bone marrow transplantation for a myelodysplastic syndrome. Both received AmB in association with cranial irradiation and developed a subacutely evolving neurologic disorder characterized by personality change and confusion rapidly progressing to akinetic mutism. Neuroimaging studies disclosed diffuse nonenhancing abnormalities of the cerebral, particularly frontal, white matter that included hypodensity on CT and increased signal on T2-weighted MRI. Postmortem examinations demonstrated a diffuse, noninflammatory leukoencephalopathy with florid astrogliosis, demyelination, and infiltration of the hemispheric white matter by foamy macrophages. In neither case was there evidence of opportunistic infection or neoplastic infiltration of the nervous system. We review the evidence that polyene macrolide antibiotics such as AmB are potential leukotoxins.

Adolescent↗
PubMed1992

Childhood medulloblastoma.

The progress that has been made in the treatment of the patient with medulloblastoma is gratifying. Survival for those who fall into the lower risk category probably exceeds 75%. For this degree of success, however, patients and their families have had to pay a price in terms of suffering the deleterious late effects of treatment. With sophisticated neuroimaging techniques diagnoses are now being made in a timely fashion and surgical mortality has been reduced to almost zero in most major medical centers. Radiation therapy and chemotherapy regimens have been increasingly successful, and further refinements of treatment are to be expected with the completion of randomized cooperative group trials. It is time to focus on means of achieving similar, or even better results, with reduced doses of neuraxis radiation, whenever possible, especially in the younger patient.

Age Factors↗
PubMed1992

Peripartum cardiac failure in The Gambia.

Twenty-seven patients with peripartum cardiac failure were seen at the Royal Victoria Hospital, Banjul over a 2-year period while one further patient presented 6 months after delivery with a cerebral embolus secondary to a dilated cardiomyopathy. Five (18%, P less than 0.001) patients had twin pregnancies. Seventeen (63%) patients attended for follow-up, of whom eight had evidence of continuing cardiac dysfunction and required treatment with diuretics; two patients were known to have died. In five asymptomatic patients the electrocardiogram had reverted to normal and three patients had further pregnancies without relapse. The bipolar distribution of onset of symptoms in relation to pregnancy was suggestive of two different pathological processes. There was no evidence that cultural habits played any significant part in the aetiology of peripartum cardiac failure in The Gambia.

Adolescent↗
PubMed1991

Pneumocystis carinii pneumonia in patients with primary brain tumors.

All histologically documented episodes of Pneumocystis carinii pneumonia in adult patients with primary brain tumors treated at Memorial Sloan-Kettering Cancer Center, New York, NY, since 1981, were retrospectively reviewed. Pneumocystis carinii pneumonia was histologically documented 11 times in 10 patients. During the same 8-year interval, approximately 587 adults were seen at the center for a brain tumor, 90% of whom received ongoing therapy. Therefore, in at least 1.7% (10/587) of our patients with brain tumors, P carinii pneumonia developed. The median duration of dexamethasone therapy at the onset of P carinii pneumonia symptoms was 2.75 months. Symptoms began during tapering of steroid therapy in eight episodes. Bronchoscopy was diagnostic in the eight cases in which it was performed. Four episodes (40%) were fatal. Trimethoprim-sulfamethoxazole prophylaxis may be indicated in some patients with brain tumors, especially during tapering of steroid therapy.

Adult↗
PubMed1991

Antagonism of intense atracurium-induced neuromuscular block in children.

Antagonism of intense neuromuscular block induced by atracurium 0.5 mg kg-1 was attempted in four groups of six children using one of two doses of neostigmine (0.05 mg kg-1 and 0.1 mg kg-1) or of edrophonium (0.5 mg kg-1 and 1.0 mg kg-1) when the first twitch of the post-tetanic count (PTC1) was 10% of control. For comparison with normal practice, a fifth group received neostigmine 0.05 mg kg-1 when the first twitch of the train-of-four was 10% of control. Total recovery time from PTC1 10% to a train-of-four ratio of 0.8 was not reduced by early administration of the anticholinesterases, compared with conventional administration of neostigmine at T1 10%. However, recovery from intense block was faster after neostigmine than edrophonium (P less than 0.01). Doubling the doses of the anticholinesterases did not reduce the recovery time and had the effect of increasing variability. We conclude that there is no clinical advantage in attempting to antagonize intense neuromuscular block in children using normal or increased doses of neostigmine or edrophonium.

Atracurium↗
PubMed1991

Neurologic complications of leukemia.

In any patient with leukemia and new neurologic findings, the first entity that must be considered is direct invasion of the nervous system. If that is not a consideration, one must systematically consider cerebrovascular disorders, CNS infections, or metabolic abnormalities as the cause. Finally, one must not overlook radiotoxicity, chemotoxicity, or both in the differential diagnosis. Although some neurologic disorders are stereotyped in their presentation and are relatively easy to recognize, others continue to perplex the physician. Symptoms may be multifactorial in origin, compounding the problem. Leukemia is a systemic disease that may affect the nervous system at any site and at any time during the illness. Now that cure is possible and even to be expected in these diseases, it has become even more important to recognize and alleviate any neurologic morbidity.

Brain Neoplasms↗
PubMed1990

Myotonic and neuromuscular blocking effects of increased doses of suxamethonium in infants and children.

The myotonic effects and duration of action of several doses of suxamethonium were determined in 24 infants and 16 children during thiopentone-fentanyl-nitrous oxide anaesthesia. Infants received suxamethonium 2, 3 or 4 mg kg-1; children received 1 or 2 mg kg-1. The increase in muscle tone during onset of neuromuscular block was independent of dose. Onset of block was faster in children who received suxamethonium 2 mg kg-1 compared with those who received 1 mg kg-1, and in infants given 2 mg kg-1 than in children given the same dose. Compared with adults given suxamethonium 1 mg kg-1, infants required 3-4 mg kg-1 and children at least 2 mg kg-1 to produce 6-8 min of neuromuscular block. These results provide a clear indication for increasing the intubating doses of suxamethonium in infants and children, and a explanation for the unduly high rate of "masseter spasm" in some paediatric centres.

Anesthesia, General↗
PubMed1990

Obstetrical risk management: establishing documents of defense.

The practice of obstetrics is high risk for the obstetrician. We are the target for plaintiffs and their attorneys for any outcome--maternal or neonatal--that is less than perfect. Thus obstetricians should learn how to practice inexpensive, high-quality defensive medicine by increasing knowledge of risk management and improving charting skills. This article attempts to achieve these objectives, thus reducing the obstetrician's vulnerability to being a legal "sitting duck"!

Humans↗
PubMed1989

Carboplatin-associated thrombotic microangiopathic hemolytic anemia.

Thrombotic microangiopathic hemolytic anemia has been associated with several chemotherapeutic agents. The authors describe a patient who developed this syndrome while receiving carboplatin, an analog of cisplatin. The clinical course was marked by encephalopathy and multifocal neurologic deficits. Progressive brainstem dysfunction culminated in coma and respiratory arrest. Pathologic examination revealed widespread microvascular thrombosis, particularly severe in the heart, kidney, and brain. Although the pathogenesis of chemotherapy-related thrombotic microangiopathy remains unclear, an elevated von Willebrand factor antigen and pathologic evidence of endothelial hyperplasia in this patient suggest that an abnormality of the endothelium is related to the development of the clinical syndrome.

Anemia, Hemolytic↗
PubMed1989

Reduced incidence of the somnolence syndrome in leukemic children with steroid coverage during prophylactic cranial radiation therapy. Results of a pilot study.

Chemotherapeutic regimens for childhood acute lymphoblastic leukemia (ALL) include a remission induction period with high, daily doses of prednisone among other agents. A period of central nervous system (CNS) prophylaxis follows, during which steroids are often tapered entirely before cranial radiation (CRT) is completed or even initiated. The somnolence syndrome (SS) has been described 4 to 6 weeks after completion of CRT in up to 60% of the children with doses as low as 1800 cGy. A pilot study of continuous steroid coverage during CRT in childhood ALL was conducted. From July 1984 to July 1986, 38 children entered on Children's Cancer Study Group ALL protocols received CRT of 1800 cGy (180 cGy x 10). All patients received oral prednisone throughout the entire course of CRT at daily doses varying from 3.0 to 60.0 mg/m2. The overall incidence of the SS was 13% (five patients). The development of the syndrome was steroid dose-dependent: greater than or equal to 15 mg/m2/d (one of 32 patients), 3% incidence; less than 15 mg/m2 (four of six patients), 67% incidence. The presence of headache during CRT was also steroid dose-related: greater than or equal to 15 mg/m2, one of 32 patients; less than 15 mg/m2, six of six patients. Of the seven patients with headache during CRT, five developed the SS. The two patients (both of the less than 15 mg/m2 group) who did not develop the SS were the only cases treated with increased steroid doses at the onset of headache symptoms. Steroid coverage at a dose of greater than or equal to 15 mg/m2 during CRT appears to significantly reduce the incidence of acute radiation reactions and the SS. A prospective randomized study is planned to confirm these initial findings.

Adolescent↗
PubMed1989

Fatal necrotizing encephalopathy complicating treatment of malignant gliomas with intra-arterial BCNU and irradiation: a pathological study.

We describe the neuropathologic findings at autopsy in six patients who developed a progressive encephalopathy complicating the treatment of malignant gliomas with combined intra-arterial 1,3-bis(2-chloroethyl)-1-nitrosourea (BCNU) and cerebral irradiation. Four brains were free of tumor and one contained a microscopic focus of residual glioma. In only one case was there evidence of tumor progression. A disseminated process characterized by miliary foci of necrosis with mineralizing axonopathy was present in all cases, restricted to the internal carotid distribution of the perfused hemisphere and involving primarily though not exclusively the white matter, which was diffusely and severely edematous. This was combined in 3 cases with a histologically dissimilar, massive necrotizing leukoencephalopathy indistinguishable from pure radionecrosis. Much of the toxicity of this therapy is mediated by vascular injury, but the disseminated necrotizing lesion probably reflects, at least in part, direct neural damage.

Brain Diseases↗
PubMed1989

Leptomeningeal gliomatosis with spinal cord or cauda equina compression: a complication of supratentorial gliomas in adults.

Seven patients with supratentorial gliomas developed leptomeningeal gliomatosis (LMG) without symptomatic recurrence at the primary tumor site. In all, severe back and radicular pain, often simulating disc disease, preceded the development of spinal cord or cauda equina dysfunction. In 4 instances, intracranial hypertension due to hydrocephalus developed prior to spinal involvement. Cytological examination of the CSF revealed malignant cells in only 2/7 but a myelogram was diagnostic in all 7. All patients received spinal irradiation (RT) and 5 received chemotherapy. Two patients with low-grade gliomas improved transiently; 5 with malignant gliomas responded poorly, became paraplegic over 4 months and eventually died of LMG. When fatal LMG occurs in young adults suffering from supratentorial glioma, the primary tumor is often quiescent. Hydrocephalus is often the first manifestation of LMG and, when it is detected, a myelogram and CSF cytology study should be performed in the hope that diagnosis and treatment of spinal cord lesion at a very early stage will prove beneficial. Irradiation of the entire spinal canal is probably required as there is a high risk of rapid development of new lesions in non irradiated segments of the spinal canal.

Adolescent↗