Biomedical subjects
Publications and source records attributed to D Dyson.
Methoxyflurane has a high blood/gas partition coefficient and a low vapor pressure. Mask inductions may be excessively slow, necessitating early high vaporizer control knob settings or additional injectable induction agent. Recoveries may be very prolonged. Methoxyflurane is extensively metabolized, and this may be associated with hepatotoxicity and nephrotoxicity.
Patients with stable, end-state renal disease should be premedicated with an opioid and induced with minimal doses of an ultrashort barbiturate or isoflurane. Supplemental systemic or epidural analgesics can be administered if necessary. Urine output should be monitored in the perioperative period. If oliguria exists, fluids and perhaps a diuretic such as furosemide, mannitol, or dopamine should be administered.
Atypical fibroxanthoma, a more recently recognised variant of malignant fibrous histiocytoma, is described arising at the site of an earlier squamous cell carcinoma, in a patient treated with radiotherapy 21 years previously. Distinction between atypical fibroxanthoma and a poorly-differentiated squamous cell carcinoma proved to be difficult by ordinary light microscopy and it was only after immunohistochemical staining that the second lesion was confirmed as atypical fibroxanthoma. The natural history, differential diagnosis and histological pitfalls of this poorly characterised mesenchymal lesion are discussed.
The Limulus lysate test was evaluated as a method for rapid detection of neonatal gram-negative bacterial meningitis. A total of 208 CSF samples were collected from 145 newborn infants suspected of having meningitis. Initial samples from all six babies with culture-proven gram-negative bacterial meningitis had positive Limulus tests within 30 minutes of incubation. Samples from 14 infants with gram-negative organisms isolated only in blood and/or urine as well as from four neonates with gram-positive organisms in CSF cultures and from 13 with gram-positive organisms in blood cultures all yielded negative Limulus tests. Thus, of 37 newborn infants with bacteria demonstrated in systemic cultures, only those six with gram-negative organisms in CSF had positive CSF Limulus tests. The CSF Limulus test was shown to be a rapid, reliable, and specific test for the detection on neonatal gram-negative bacterial meningitis.
Amniotic fluid (AF) lecithin/sphingomyelin (L/S) rations were obtained in 223 pregnancies. Gestations complicated by maternal diabetes (71), vascular disease (50), and fetal growth retardation (47) were included. Elevated L/S ratios at 34 to 36 weeks' gestation were observed to accompany maternal vascular disease; higher rat;os were also related to fetal sex (female) and race (black). Declining L/S rations were observed in 14 of 35 diabetic patients studied serially (40 per cent) and were accompanied by increased perinatal morbidity and deaths. These data suggest an urgent need for further studies concerning the clinical usefulness of a serial decline in the L/S ration as a predictor of fetal compromise.
Pentobarbital (1.0, 1.5, and 2.0 mg/kg intravenously [IV]) was administered to four adult cows to determine a dose suitable for producing standing sedation in adult cattle, and to evaluate its effects on cardiopulmonary function and rumen motility. The response was assessed after 15, 30, 60, and 90 minutes. The 1.0 and 1.5 mg/kg doses induced mild sedation at 15 and 30 minutes, and no sedation at 60 and 90 minutes. The 2.0 mg/kg dose produced moderate sedation at 15 and 30 minutes, and mild sedation at 60 minutes. The 2.0 mg/kg dose was judged to be the most suitable. The effects of pentobarbital (2.0 mg/kg IV) on heart rate, blood pressure, respiratory rate, blood gases, and rumen motility were measured in five cows during a 90 minute period. Respiratory rate was significantly depressed at 15, 30, and 60 minutes, but there were no significant changes in the other variables. Pentobarbital (2.0 mg/kg IV) is reliable in adult cattle for standing sedation of short duration.