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Biomedical subjects

J G Jones

Publications and source records attributed to J G Jones.

At least 19 recordsLinked to original sources
PubMed1995

Visualisation of changes in regional cerebral blood flow (rCBF) produced by ketamine using long TE gradient-echo sequences: preliminary results.

Autoradiographic studies have shown that low dose ketamine produces increases in regional glucose utilisation and blood flow in the hippocampus, cerebral cortex, and olfactory lobe in the rat brain, probably due to antagonism at the NMDA receptor. Functional MRI using deoxyhaemoglobin contrast can be used to study changes in regional cerebral blood flow (rCBF). Long TE gradient-echo sequences were used to study changes in rCBF produced by low dose ketamine in rats anaesthetised with nitrous oxide, supplemented with either halothane (HAL) or fentanyl/fluanisone/midazolam (FFM) combination. Images from rats in the FFM group showed a 10-14% increase in signal intensity in the hippocampus, cerebral cortex, and olfactory lobe following either a single bolus or a low dose infusion of ketamine (p < .05). These changes were significantly reduced in the HAL group (p < .005). Halothane is known to attenuate the changes in regional glucose utilisation produced by the noncompetitive NMDA antagonist dizocilpine (MK-801), and its effects on ketamine-induced changes in rCBF seen in this study may be due to a similar effect. The potential use of functional MRI in studying the effect of pharmacological interventions on rCBF is discussed.

Anesthetics, Dissociative↗
PubMed1995

Effect of pulse dexamethasone therapy on the incidence and severity of chronic lung disease in the very low birth weight infant.

We conducted a prospective, randomized, double-blind trial to assess the efficacy and safety of pulse doses of dexamethasone on survival without supplemental oxygen in very low birth weight infants at high risk of having chronic lung disease. Seventy-eight infants with birth weights < or = 1500 gm who were ventilator dependent at 7 days of postnatal age were randomly assigned to receive pulse doses of dexamethasone, 0.5 mg/kg per day, divided twice daily (n = 39), or an equivalent volume of saline solution placebo (n = 39), for 3 days at 10-day intervals until they no longer required supplemental oxygen or assisted ventilation, or reached 36 weeks of postmenstrual age. At study entry, the groups did not differ by birth weight, gestational age, or severity of lung disease. At 36 weeks of postmenstrual age, there was both a significant increase in survival rates without oxygen supplementation (p = 0.03) and a significant decrease in the incidence of chronic lung disease (p = 0.047) in the group that received pulse therapy. Supplemental oxygen requirements were less throughout the study period in the group that received repeated pulse doses of dexamethasone (p = 0.013). The total numbers of deaths and the durations of supplemental oxygen, ventilator support, and hospital stay did not differ between groups. Recorded side effects in the pulse therapy group were minimal and included an increase in the use of insulin therapy for hyperglycemia (p < 0.05). We conclude that in this population of very low birth weight infants, treatment with pulse doses of dexamethasone resulted in improvement in pulmonary outcome without clinically significant side effects.

Adult↗
PubMed1995

Cerebral blood flow distribution during induced hypotension with haemorrhage, trimetaphan or nitroprusside in rats.

Local cerebral blood flow (CBF) during three types of profound hypotension were compared using the quantitative autoradiographic [14]-C iodo-antipyrine method. Rats were rendered hypotensive to a mean arterial pressure of 30 mm Hg for 30 min by haemorrhage, trimetaphan or nitroprusside during 0.8% halothane anaesthesia. During haemorrhagic hypotension, mean local CBF was reduced significantly in all except two pontine regions. This reduction in flow ranged from 83% to 41% compared with the normotensive control group, with the neocortex and telencephalon most affected. During trimetaphan-induced hypotension, local CBF was reduced to the same degree and in the same pattern as that during haemorrhagic hypotension. In contrast, during nitroprusside-induced hypotension, local CBF in many regions of the brain was well maintained (57-101%); although local CBF was significantly below control in all cortical and telencephalic regions, it was significantly greater in the majority of these regions than in the other two hypotensive groups. We conclude that local CBF was significantly reduced in the neocortex and telencephalon by hypotension of this degree induced by all three methods, but nitroprusside preserved local CBF significantly better than the other methods, in these, as in most other regions.

Anesthesia, General↗
PubMed1995

A method of costing anaesthetic practice.

This paper identifies the main factors involved in the cost of elective general anaesthetic practice. The costs of anaesthesia were divided into overheads and running costs, which are sensitive to the duration of anaesthesia, and fixed costs which are incurred by each patient but are not sensitive to the duration of anaesthesia. The overhead costs consisted of salaries, capital equipment and maintenance costs. The overhead cost of a consultant anaesthetist combined with a technical assistant's salary, monitoring equipment and anaesthetic machine was estimated at 45.05.h-1 pounds (using 1993 salary scales and prices). The fixed costs of pre-operative assessment and nursing care in recovery were the same for all patients, 20.60 pounds per patient. For the majority of anaesthetics the combined cost of the anaesthetist, overheads and postoperative care was about 70% of the total cost, the remainder being the running costs which included drugs, anaesthetic gases, vapours, intravenous fluids, sterile equipment and other disposable items. Four sample anaesthetics were costed in two ways: both methods used the same overhead and fixed cost per patient but one added the cost of all the individual drugs and consumables used, whereas the other grouped these together using a charge sheet which can be computerised and used prospectively to cost anaesthesia. There was close agreement between the costs derived with the two methods. The cost of a 30 min delay in the start of an operating session was 27.30 pounds (anaesthetist, assistant and nurse salary (9.50.h-1 pounds)) which is more than the cost of 2 h of propofol infusion anaesthesia.(ABSTRACT TRUNCATED AT 250 WORDS)

Analgesia↗
PubMed1995

Flow cytometric determination of pre-transfusion red cell volume in fetuses and neonates requiring transfusion based on RhD+ dilution by transfused D- red cells.

We report a case of feto-maternal haemorrhage and describe a new flow-cytometric method of determining a fetus's or infant's pre-transfusion red cell volume (RCV). We validate this method against an established technique, employing fetal haemoglobin (HbF) dilution, for determining the RCV in fetuses and neonates requiring intravascular transfusion. We discuss advantages and other potential applications of this new method.

Blood Transfusion, Intrauterine↗
PubMed1995

Medical management of sinusitis: educational goals and management guidelines. The International Conference on sinus Disease.

The primary goal of sinusitis management is resolution of infection, leading to patency of the ostiomeatal complex. Antibiotics and decongestants are the cornerstones of therapy for acute sinusitis. Diagnosis of acute sinusitis is based on the history and physical findings. Sinusitis is considered to be acute or recurrent acute if infection resolves without residual mucosal damage. Choices for first-line antibiotic therapy include adequate dosages of trimethoprim-sulfamethoxazole, loracarbef, and amoxicillin-clavulanate. Decongestants and mucoevacuants may reduce tissue edema, facilitate drainage, and maintain ostial patency. Topical corticosteroids are useful additional therapy in allergic rhinosinusitis and as an aid in the long-term management of chronic sinusitis. Parenteral corticosteroids have no role in first-line management of acute or recurrent acute sinusitis.

Chronic Disease↗
PubMed1995

The PIO2 vs. SpO2 diagram: a non-invasive measure of pulmonary oxygen exchange.

A non-invasive method for measuring pulmonary oxygen exchange is described using a plot of inspired oxygen partial pressure (PIO2) vs. oxygen saturation (SpO2). This method was assessed using nine normal subjects and 35 patients undergoing major surgery, including five thoracotomies. In each patient PIO2 was varied to produce a range of values of SpO2 between 85% and 99%. A model based on the inspired to arterial oxygen difference involving the shunt equation, solved by simultaneous numerical methods, was used to show how the PIO2 vs. SaO2 relationship could be used to derive two parameters of oxygen exchange, the PIO2-Pco2 difference and the Virtual Shunt. The model allows the inspired to arterial difference in PO2 to be divided into (a) an inspired to 'ideal' alveolar difference attributable to the balance between alveolar ventilation and oxygen uptake; (b) an 'ideal' alveolar to end-capillary difference attributable to inhomogeneity in ventilation/perfusion ratios; and (c) end-capillary to arterial difference attributable to true shunt, which was termed 'virtual shunt' because of the uncertainties of assuming fixed values for haemoglobin concentration and arteriovenous oxygen content difference. The coefficient of determination showed that there was a good fit of the model to the data. Because the method is model-based it enables extrapolation to different PIO2 values as well as the study of the evolution of changes in gas exchange under varying conditions.

Adult↗
PubMed1994

Orientation-conserved transfer of symmetric Krebs cycle intermediates in mammalian tissue.

Metabolism of [2-13C]-, [3-13C]-, and [1,2,3-13C]propionate in perfused rat livers and [2-13C]-acetate in perfused rat hearts has been examined in tissue extracts by 13C NMR. Label from [2-13C]-propionate was preferentially incorporated into the C2 carbon of lactate, alanine, and aspartate in liver tissue while label from [3-13C]propionate appeared preferentially in the C3 carbon of those same molecules. These data suggest that 13C may not be completely randomized in the symmetric citric acid cycle intermediates succinate and fumarate as is normally assumed but that some fraction of those intermediates may be transferred between enzymes in this span of the cycle with conservation of spatial orientation, consistent with recent results obtained in yeast [Sumegi et al. (1990) Biochemistry 29, 9106-9110]. This was confirmed by performing similar experiments with [1,2,3-13C]propionate. Time-dependent asymmetry was also observed between the intensities of the glutamate C2 and C3 resonances and between the aspartate C2 and C3 resonances in 13C NMR spectra of intact hearts and heart extracts during early perfusion with [2-13C]-acetate. A model is presented which predicts that isotopic asymmetry is observed only during the first 2-3 turns of the cycle pools when isotope enters the cycle via acetyl-CoA even if all symmetric cycle intermediates retain a unique molecular orientation on each pass through the citric acid cycle.

Acetates↗
PubMed1994

A method for obtaining 13C isotopomer populations in 13C-enriched glucose.

13C NMR analysis of 13C-enriched glucose containing multiple isotopomers is hampered by chemical shift similarities of several carbon resonances and by the presence of two anomeric forms. A convenient and quantitative method of enzymatically oxidizing glucose to gluconate in tissue and perfusate extracts is presented. The six carbon resonances of the resulting 13C-enriched gluconate are fully resolved at high pH, thereby allowing a determination of the fractional population of each 13C isotopomer by 13C NMR. The utility of this method is demonstrated using the effluent from an isolated perfused liver containing 13C-enriched glucose produced by hepatic metabolism of sodium [1,2,3-13C3]propionate via the citric acid cycle and gluconeogenesis. An analysis of the gluconate C2 and C5 resonances in this sample showed that pentose phosphate activity was insignificant during this perfusion protocol. As demonstrated, this method provides a means of fully describing 13C isotopomer populations in enriched glucose samples where isotope may be derived from multiple metabolic pathways, thus expanding the scope of experimental design and enrichment strategies.

Animals↗
PubMed1994

Effects of oxidant exposure on substrate utilization and high-energy phosphates in isolated rat hearts.

The effects of a xanthine oxidase-mediated free radical-generating system containing purine and iron-loaded transferrin or solutions containing hydrogen peroxide and iron-loaded transferrin on substrate utilization and high-energy phosphates were evaluated by nuclear magnetic resonance (NMR) spectroscopy in isolated perfused rat hearts. Hearts were supplied with lactate, acetate, and glucose, and the contribution of each substrate to acetyl coenzyme A was measured in control hearts and in the presence of a free radical-generating system. Perfused hearts were monitored by 31P NMR, and tissue extracts were analyzed by 13C NMR. Free radicals decreased the phosphocreatine and beta-ATP peak areas and reduced contractile function. Under control conditions, lactate, acetate, and endogenous sources were the major contributors of acetyl coenzyme A units, with only 5% originating from glucose. In the presence of a xanthine oxidase-mediated free radical-generating system, the glucose contribution increased to 54%, while contributions from acetate and endogenous sources were significantly reduced. Both 13C and 31P NMR analyses showed no significant accumulation of glycolytic sugar phosphates, suggesting little inhibition of glyceraldehyde-3-phosphate dehydrogenase. The increased contribution of glucose to the tricarboxylic acid cycle relative to acetate and endogenous sources is consistent with activation of pyruvate dehydrogenase. In contrast, hearts exposed to a hydrogen peroxide-based free radical-generating system showed an increase in lactate utilization, a decrease in acetate utilization, and no change in glucose utilization compared with control hearts. Glycolytic sugar phosphates were found to accumulate, suggesting possible inhibition of glyceraldehyde-3-phosphate. Thus, different radicals or their metabolites may have varying effects on myocardial metabolism.

Acetates↗
PubMed1994

Unique dermatological complication of rhM-CSF treatment.

A patient is presented who developed cutaneous papular histiocytic infiltrates after treatment with monocyte colony stimulating factor (rhM-CSF). This is the first reported complication of this type after treatment with this new cytokine.

Humans↗
PubMed1994

Free radicals in anaesthesia and intensive care.

This review aims to outline the nature and origin of free radicals, or oxidants, in biological systems and to summarise their involvement in diseases of interest to anaesthetists, with particular reference to reperfusion injury (of the gut, brain, myocardium and transplanted organs), shock/trauma, inflammation/sepsis and halothane hepatitis. In-vitro and animal studies examining the role of free radicals and antioxidants in the pathophysiology and treatment of these conditions are presented. Some of the evidence from clinical studies supporting the use of antioxidant therapy in patients is also presented.

Anesthesia↗