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J G Jones

Publications and source records attributed to J G Jones.

At least 91 records · Page 5Linked to original sources
PubMed1996

A method for producing the coherent frequency: a steady-state auditory evoked response in the electroencephalogram.

Transient and steady-state auditory evoked responses in the electroencephalogram are used to study the effect on the brain of graded changes in the concentration of general anesthetics. A method is described using modern signal processing techniques to improve the analysis of steady-state auditory evoked responses (SSAER). The SSAER was obtained using headphones to give 100-200 auditory click stimuli from 6.5 Hz.to 50.5Hz in 1-Hz steps. The resulting electroencephalogram signals were filtered and subject to Fourier analysis, after which a series of coherence indexes were derived based on waves with significant power in the fundamental but with minimal harmonic content. These were plotted against the range of stimuli and fitted with a third-order polynomial. The frequency at which the maximum coherence index was achieved (highest possible value = 1) was derived from polynomial interpolation. The repeatability of the method was examined in 10 awake subjects using runs of ascending then descending stimulating frequencies. The mean maximum coherence index was at 38 Hz, with the 95% confidence interval of 37.3 Hz-38.9 Hz. There was no difference between ascending and descending sweeps. The method provides an automatic analysis of the SSAER that obviates the need to make subjective decisions about which is the dominant wave, a major problem in the analysis of the transient auditory evoked responses.

Acoustic Stimulation↗
PubMed1996

The coherent frequency in the electroencephalogram as an objective measure of cognitive function during propofol sedation.

Ten volunteers were studied during six stages of propofol sedation, namely awake (no propofol), light sedation (small dose of propofol), deep sedation (large dose), deep sedation with stimulation of the ulnar nerve, then light sedation again (small dose), and awake (recovery). Light and deep sedation were defined in terms of performance on a test of cognitive function: the within-list recognition (WLR) test. At each stage, the steady-state auditory evoked potential was measured at different stimulating frequencies to derive the frequency needed to achieve the maximal coherence index. This frequency is called the "maximum coherent frequency". WLR performance correlated with infusion dose (r = -0.71), plasma propofol concentration (r = -0.75), and maximum coherent frequency (r = 0.75). When the correlations were examined for the propofol sedation stages only, there remained a strong correlation between WLR performance and maximum coherent frequency (r = 0.47, P < 0.005), but no significant correlations between infusion dose and WLR (r = -0.11) or infusion dose and plasma concentration (r = 0.13). These data suggest that maximum coherent frequency provides a better measure of depth of sedation than does the dose of propofol alone.

Anesthesia Recovery Period↗
PubMed1996

Plasma antioxidant potential in severe sepsis: a comparison of survivors and nonsurvivors.

OBJECTIVE: To determine the plasma antioxidant potential of patients in the intensive care unit (ICU) with severe sepsis and secondary organ dysfunction and relate these findings to outcome. DESIGN: A prospective, cohort study. SETTING: A nine-bed ICU in a university teaching hospital. PATIENTS: Fifteen consecutive patients, who were within 16 hrs of development of severe sepsis and secondary organ dysfunction. INTERVENTIONS: Plasma samples were obtained within 16 hrs of the onset of secondary organ dysfunction and subsequently on days 2, 3, 4, 6, 8, 10, and 15 until patients either left the ICU or died. Plasma antioxidant potential was determined by an ultraviolet spectrophotometric technique. MEASUREMENTS AND MAIN RESULTS: The mean initial plasma antioxidant potential was lower than our range for healthy volunteers (p < .05). Survivors had an initial plasma antioxidant potential that was greater than nonsurvivors (p < .01), and serial subset analysis demonstrated that survivors, despite having a low initial plasma antioxidant potential rapidly attained normal or supranormal values. While plasma antioxidant potential also increased in nonsurvivors over time, values in this subset never reached the normal range and remained below values in survivors at all time points studied (p < .05). CONCLUSIONS: Plasma antioxidant potential is initially decreased in patients with sepsis who develop organ dysfunction, and it increases over time. While we have no clear evidence to prove that this reduction has a causal relationship, failure to achieve a normal plasma antioxidant potential is strongly associated with an unfavorable outcome.

APACHE↗
PubMed1996

The phylogenetic position and ultrastructure of the uncultured bacterium Achromatium oxaliferum.

Achromatium oxaliferum is a large, morphologically conspicuous, sediment-dwelling bacterium. Nothing is known concerning its phylogeny and it has eluded all attempts at laboratory cultivation. The limited physiological description of A. oxaliferum has been based on morphological features of the bacterium such as the presence of intracellular sulphur inclusions. A. oxaliferum cells were purified from a wetland region close to Rydal Water (Cumbria, UK). Scanning and transmission electron microscopy revealed that a number of morphologically distinct A. oxaliferum cell-types, based on cell surface features and the size and abundance of calcite and sulphur inclusions within the cells, were present in a single sample of purified cells. PCR was used to amplify almost full-length 16S rRNA gene sequences from DNA extracted from A. oxaliferum cells directly purified from sediments. The PCR products were cloned and partial sequences (approx. 400 bp) were determined for seven of the clones. Three different sequence clusters were recovered from the clone libraries. A near full-length (1489 bp) 16S rRNA gene sequence was determined for a representative clone of the most dominant sequence-type (52% of the sequences). Comparative sequence analysis showed A. oxaliferum to form a deep branching lineage within the gamma-subdivision of the Proteobacteria. A. oxaliferum was related most closely to the Chromatium assemblage that includes sulphur-oxidizing symbiotic bacteria, purple sulphur bacteria, and sulphur- and iron-oxidizing thiobacilli. Phylogenetic inferences made using distance, parsimony and maximum likelihood methods all placed A. oxaliferum with this group of bacteria. Bootstrap support for a relationship with any particular lineage within the assemblage was weak. The seven clone sequences recovered from the A. oxaliferum cells however formed a monophyletic group well supported by bootstrap analysis (85-100% support depending on the analysis done). It was concluded that A. oxaliferum was related to organisms of the Chromatium assemblage but constituted a novel lineage within this group of bacteria. A. oxaliferum cells were confirmed as the source of the 16S rRNA sequence obtained, by the use of a fluorescently-labelled 16S rRNA-targeted oligonucleotide specific for the A. oxaliferum rRNA sequence.

Base Sequence↗
PubMed1996

The effects of hypoxaemia and recommendations for postoperative oxygen therapy.

Hypoxaemia following surgery is common and may be prolonged and severe. The thresholds for deleterious effects of hypoxaemia on the heart and central nervous system are reviewed and the problems of assessment of the adequacy of tissue oxygenation are outlined. Recommendations for postoperative oxygen therapy are made.

Brain↗
PubMed1996

The effect on the heart of hypoxaemia in patients with severe coronary artery disease.

The aim of the study was to examine the effect of spontaneous nocturnal hypoxaemia on myocardial ischaemia in patients with severe coronary artery disease. This was a prospective study of continuously measured oxygen saturation and ECG overnight in patients prior to coronary artery bypass graft surgery. Fifteen patients with angiographically proved coronary artery disease were studied between October 1992 and September 1993. All patients had episodes of hypoxaemia with oxygen saturation < 94% and eight of the 15 patients had episodes where oxygen saturation < 85%. An episode was defined as a period of hypoxaemia not less than 2.5 min in duration, the longest total duration of hypoxaemia in one patient being 355 min. Twelve of the 15 patients showed a drop in ST segment of 1 mm or more lasting from 5-700 min. The hypoxaemic and ischaemic episodes apparently occurred at random. No causal relationship could be shown between hypoxaemia and ischaemia.

Adult↗
PubMed1996

The airways and anaesthesia II. Pathophysiology.

We pointed out in the first of these two articles that the commonest cause of an anaesthetic disaster in young healthy patients is a loss of airway patency then a failure to intubate occurring unexpectedly in the absence of head or neck pathology. Upper airway obstruction is a very common complication of general anaesthesia and all anaesthetists must be trained in the management of this problem. Less obvious are the changes that can occur in the lower airways which can impair gas exchange by increasing ventilation-perfusion mismatch. This article is concerned with these pathophysiological changes that occur during general anaesthesia.

Airway Obstruction↗
PubMed1996

Squamous cell carcinoma in mature cystic teratoma in a young woman: a diagnostic and management dilemma.

Mature cystic teratomas of the ovary are one of the most common ovarian neoplasms found in reproductive age women. The most common type of malignancy associated with ovarian mature cystic teratomas is squamous cell carcinoma. The frequency of this type of malignant degeneration is age related and is most common in the fifth and sixth decade of life. A case of a squamous cell carcinoma which developed in a mature cystic teratoma in a 25-year-old female is presented and issues regarding the diagnosis and management of this rare complication are discussed.

Adult↗
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

Pulse dexamethasone does not impair growth and body composition of very low birth weight infants.

OBJECTIVE: Evaluation of repeated pulses of dexamethasone (PDEX), given to improve cardiopulmonary outcome, on growth of very low birth weight (VLBW, < 1500 g) infants. METHODS: In this prospective, double-blind, randomized clinical trial, VLBW infants mechanically ventilated at 1 week of age received intravenous PDEX or saline placebo (P) for 3 days, every 10 days, until no supplemental oxygen or ventilation was required or 36 weeks postmenstrual age (PMA). Weight gain, fluid intake, caloric intake, and serum glucose were monitored throughout the study. Nutritional assessment at 36 weeks PMA consisted of weight, length, head circumference, skinfold thickness measures, body composition by total body electrical conductance, and bone mineral content (BMC) by single beam photon absorptiometry. RESULTS: 37 PDEX and 31 P infants survived at least 36 days and completed the protocol. Average daily weight gain, fluid intake and caloric intake were not different between groups. The pattern of weight gain (g/kg/day, mean +/- SD) was different: PDEX infants showed significant growth delay during (3.0 +/- 11.4) and immediately after (7.8 +/- 8.7) each pulse, with subsequent growth acceleration (18.3 +/- 8.2) until the next steroid pulse. In contrast, growth rate of P infants was constant (12.6 +/- 3.7) (p = 0.04). Hyperglycemia requiring insulin therapy occurred only in the PDEX group (10/37). The catch-up growth noted between pulses in the PDEX group was explained only in part by insulin therapy. At 36 weeks PMA, there were no differences between groups in body size, composition, or BMC. CONCLUSION: PDEX negatively affected glucose metabolism and growth patterns during and immediately after drug exposure. However, assessment near term gestational age showed similar body composition and size in both groups.

Body Composition↗
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↗