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J G Jones

Publications and source records attributed to J G Jones.

At least 127 records · Page 7Linked to original sources
PubMed1993

The laryngeal mask.

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Anesthesia, General↗
PubMed1993

Umbilical cord clamping and preterm infants: a randomised trial.

OBJECTIVE: To investigate the clinical effects of regulating umbilical cord clamping in preterm infants. DESIGN: A prospective randomised study. SETTING: The Queen Mother's Hospital, Glasgow. SUBJECTS: 36 vaginally delivered infants over 27 and under 33 weeks' gestation. INTERVENTION: Holding the infant 20 cm below the introitus for 30 seconds before clamping the umbilical cord ("regulated" group, 17 patients), or conventional management ("random" group, 19 patients). MAIN OUTCOME MEASURES: Initial packed cell volume, peak serum bilirubin concentrations, red cell transfusion requirements, and respiratory impairment (assessed by ventilatory requirements, arterial-alveolar oxygen tension ratio over the first day in ventilated infants, and duration of dependence on supplemental oxygen). RESULTS: There were statistically significant differences between the two groups in mean initial packed cell volume (regulated group 0.564, random group 0.509) and median red cell transfusion requirements (regulated group zero, random group 23 ml/kg). 13 infants from each group underwent mechanical ventilation and showed significant differences in mean minimum arterial-alveolar oxygen tension ratio on the first day (regulated group 0.42, random group 0.22) and in median duration of dependence on supplemental oxygen (regulated group three days, random group 10 days). Differences in final outcome measures such as duration of supplemental oxygen dependence and red cell transfusion requirements were mediated primarily through arterial-alveolar oxygen tension ratio and also packed cell volume. CONCLUSIONS: This intervention at preterm deliveries produces clinical and economic benefits.

Bilirubin↗
PubMed1993

Penetration of an aerosol, produced by film atomization, through the carinal bifurcation.

We have measured the size of spots produced by atomization of simulated biofilm particles from a tracheal tube. Draughtsman's ink was atomized from 8.5-mm i.d. Portex tracheal tubes, using an airflow of 1 litre s-1, and trapped on vertical acetate sheets. The spots produced by these particles were compared with the spot size after entrainment and dissemination from an ink-lined tracheal tube through a bifurcating tracheobronchial tube towards a glass plate. Spot dimensions were measured by computer-assisted image analysis of a video image. The smallest particles observed on the acetate sheets were 4-17 microns in size. In the bifurcating tube experiment, large particles were deposited around the carinal bifurcation, but smaller particles traversed the bend. The smallest spot size observed (7 microns minimum; 17 microns median) corresponds to particles small enough to penetrate further into the lower respiratory tract. Travel via a tube similar to the carinal bifurcation suggests that fragments of biofilm entrained in the tracheal tube could be propelled deeper into the respiratory tract during the inspiratory phase of mechanical ventilation.

Aerosols↗
PubMed1993

Causes of oxyhaemoglobin saturation instability in the postoperative period.

Healthy, young patients tend to have stable patterns of oxygen saturation (SaO2) in the perioperative period, but unstable patterns of oxygen saturation data in the postoperative period have been described which are associated with wide fluctuations in the value of SaO2 over short periods of time and with a propensity for severe desaturation. This investigation was designed to study the cause of these unstable, hypoxaemic patterns. SpO2 was measured by pulse oximetry in an "at risk" patient group (n = 20) before and after operation and displayed as sequential distribution diagrams and centile plots. In 16 of these patients SpO2 was determined also at different values of PlO2 (21-50 kPa) before and after operation. Instability of SpO2, assessed over periods of 1 h, was common (n = 18) after operation; it was caused by both acute desaturations and a fluctuating baseline SpO2. The PlO2 vs SpO2 relationship was displaced after operation, with both lateral (rightwards) and downwards displacement. The result was to bring the PlO2 to or near to the steep part of the curve. In patients who displayed an unstable pattern of SpO2 over a short period of time (< 5 min), this was abolished by increasing PlO2. We postulate that the displacement of the PlO2 vs SpO2 curve increases the propensity to desaturation in those patients with impaired control by placing the steep part of the curve near to a PlO2 value of 21 kPa.

Adult↗
PubMed1993

Analysis of factors which affect the relationship between inspired oxygen partial pressure and arterial oxygen saturation.

The adoption of pulse oximetry in anaesthesia and intensive care has resulted in oxyhaemoglobin saturation (SaO2) becoming an important and widely used clinical descriptor of gas exchange, although its full potential has not been realized. We have explored the effect of impaired gas exchange on the relationship between PIO2 and SaO2. A curve of oxygen content vs PIO2 for an ideal lung was constructed using the oxygen dissociation curve and allowing for the effect of dissolved oxygen in plasma. A plot of PIO2 vs SaO2 was derived from this content curve. The effect of impaired gas exchange (shunt and V/Q effects) on this relationship was then modelled using for shunt the equation Qs/Qt = (Cc' O2-CaO2)/(Cc' O2-CvO2) and for V/Q, a graphical method using the equation V/Q = k(Cc' O2-CvO2)/ (PIO2-PAO2) and the oxygen content curve to model the effect of a spread of V/Q ratios. A total of nine compartments were used to model the scatter of V/Q, and the size of these compartments were determined by their relative blood supply. Plots of PIO2 vs SaO2 were derived for different values of shunt and V/Q. The PIO2 vs SaO2 curve reflected the shape of the oxygen dissociation curve but lay to the right by PIO2-PAO2. Shunt caused a depression of the plateau of this curve with relatively little lateral movement, whereas a low mean V/Q ratio caused a marked rightwards lateral displacement. Increased IogSD Q caused a flattening of the relationship. The combined effect of shunt and a spread of V/Q ratios caused both lateral and vertical displacements. Thus a series of simple measurements of PIO2 and SaO2 gave information about both shunt and V/Q abnormality.

Humans↗
PubMed1993

A measure of consciousness and memory during isoflurane administration: the coherent frequency.

The coherent frequency (CF) of the auditory evoked response (AER) is derived using auditory clicks presented at frequencies in the range 5-47 Hz. CF and psychological performance were measured while seven subjects breathed isoflurane in doses increasing from 0% to 0.2%, 0.4% and 0.8% end-tidal concentration and then decreasing to 0%. With increasing doses of isoflurane, CF decreased and there was a decrease in within-list recognition (WLR) and category recognition (CR) scores. There was a correlation between changes in CF and WLR (P < 0.05) and between CF and category recognition (CR) (P < 0.05). A painful stimulus given in conjunction with 0.4% isoflurane caused an increase in CF, WLR and CR in some subjects. This did not reach statistical significance for the group as a whole, apart from the short word interval scores in the WLR which indicated an increase in attention (P < 0.01). Subjects did not respond with 0.8% isoflurane, either before or after painful stimulation. Reduction of end-tidal isoflurane from 0.8% to 0% caused an increase in the CF and improved performance on the psychological tests. A category generation task on recovery showed no evidence of implicit learning of words presented in conjunction with 0.8% isoflurane.(ABSTRACT TRUNCATED AT 250 WORDS)

Anesthesia, Inhalation↗
PubMed1993

Predictors of self-reported psychopathology in children abused repeatedly by a parent.

OBJECTIVE: This study was designed to test the influence of gender, type of abuse, and other factors on the development of psychopathology in abused children. METHOD: Forty-one children who had been abused repeatedly either physically or sexually by a parent or parent figure were given the revised Diagnostic Interview for Children and Adolescents. RESULTS: Logistic regression analyses showed: conduct disorder was predicted by male gender and increasing age regardless of type of abuse; post-traumatic stress disorder was predicted by number of stressors other than abuse and not by sexual abuse versus physical abuse. Predictors of somatization, psychotic symptoms, suicidal ideation, and separation anxiety also were identified. CONCLUSIONS: Gender, age, and stressors other than abuse contribute to the prediction of psychiatric disorder in abused children. Early interventions with young abused boys could help prevent development of violent behavior or conduct disorder; case work to reduce other stressors and treatments designed to reduce the impact of stressors may ameliorate developing post-traumatic stress disorders and other emotional disorders in abused children.

Adolescent↗
PubMed1993

Small bolus injections of intravenous midazolam for upper gastrointestinal endoscopy: a study of 788 consecutive cases.

1 A recent audit of upper gastrointestinal endoscopy carried out by the Royal College of Surgeons of England has shown that the majority of endoscopists use a bolus injection rather than a slow intravenous titration of benzodiazepine for intravenous sedation. In this study we have confirmed the theoretical premise that a reduced dose of midazolam is required when given as a bolus. A mean dose of 4.65 mg midazolam intravenously has been found to be effective and safe in sedating patients under 70 years (n = 552). The dose of midazolam needed is reduced in older patients: patients over 70 years (n = 236) needed a mean dose of 1.89 mg. 2 Topical pharyngeal anaesthesia was not required with these doses of midazolam, and it was our impression that the examination was equally well tolerated with a similar degree of anterograde amnesia as in the previous study. 3 Our data, together with the results of the audit, would suggest many endoscopists are employing unnecessarily large and at times potentially dangerous doses of intravenous sedation in elderly patients and that the vast majority of upper gastrointestinal endoscopies can be performed successfully, without topical pharyngeal anaesthesia, using a bolus injection techniquewith a reduced dosage of sedative agent.

Adolescent↗
PubMed1993

The rightward gas vesicle operon in Halobacterium plasmid pNRC100: identification of the gvpA and gvpC gene products by use of antibody probes and genetic analysis of the region downstream of gvpC.

The extreme halophile Halobacterium halobium synthesizes intracellular gas-filled vesicles that confer buoyancy. A cluster of 13 genes on the 200-kb endogenous plasmid pNRC100 has been implicated in the biosynthesis of gas vesicles. Here, we show that two gas vesicle proteins are encoded by genes in the rightward operon, gvpA and gvpC, by Western blotting (immunoblotting) analysis with antibodies directed against LacZ-GvpA and LacZ-GvpC fusion proteins. Our results are consistent with previous data showing that the gvpA gene product is the major gas vesicle protein and demonstrate for the first time that the gvpC gene product is also present in H. halobium gas vesicles. Northern (RNA) blotting analysis showed two RNA species, an abundant 0.35-kb transcript of gvpA and a minor 2.5-kb transcript of gvpAC, and a third gene 3' to gvpAC, named gvpN. The gvpN gene encodes a hypothetical acidic protein with a molecular weight of 39,000 and a nucleotide binding motif. We used a site-directed mutagenesis method involving double recombination in Escherichia coli to insert a kanamycin resistance cassette just beyond the stop codon of gvpN. Introduction of the mutated gene cluster into an H. halobium mutant with a deletion of the entire gas vesicle gene cluster resulted in gas vesicle-positive transformants; this result suggests that gvpN is the last gene of the rightward gas vesicle transcription unit. We discuss the design and utility of the kanamycin resistance cassette for the mutagenesis of other genes in large operons.

Archaeal Proteins↗
PubMed1993

Cognitive function during moderate hypoxaemia.

The effect of hypoxaemia (mean SpO2 78%) on cognitive function was measured in two groups of twelve normal subjects. A series of psychometric tests was administered to each subject in the same sequence and consisted of the Reitan trail-making test, a digit symbol substitution test, a visuospatial orientation test and the simple unprepared reaction-time test. Psychomotor performance was assessed in a double-blind manner while the subjects were breathing first air and then either air or a hypoxic mixture. While there was improvement in time for the trail-making test during a repeat study breathing air, there was significant deterioration of time to completion of the test in conditions of hypoxia. A significant learning effect in the orientation test was seen in the control group but this did not occur in hypoxic subjects. Hypoxaemia was shown to cause a significant impairment of simple unprepared reaction time compared with controls. All the changes in cognitive function were small and there were no subjective differences in the air or hypoxic groups. The usefulness of the Reitan trail-making and the simple unprepared reaction-time test in the assessment of psychomotor performance deficit under conditions of hypoxaemia has been demonstrated by this study in normal subjects. It was concluded that a mean oxygen saturation of 78% caused only minor changes in cognitive function in normal subjects.

Adult↗
PubMed1993

Oxygen saturation during hemodialysis.

The aim of this study was to examine the saturation patterns of cuprofane and polysulfone membranes in hemodialysis patients, and to correlate that with permeability of the alveolar membrane, unloading of CO2 over the membranes, and production of oxygen free radicals. Polysulfone membranes did not have the same desaturation pattern as the cuprofane membranes. Both membranes were equally effective in the unloading of CO2, and so alveolar hypoventilation does not explain oxygen desaturation during hemodialysis. White blood cells have a central role in the parallel development of early leucopenia and hypoxemia. The precise mechanism is still unknown because there were no changes in permeability of the alveolar membrane or production of oxygen free radicals.

Biocompatible Materials↗
PubMed1993

The effect of propofol anaesthesia on free radical-induced lipid peroxidation in rat liver microsomes.

In order to assess the in vivo significance of the free radical scavenging properties of propofol the effect of propofol anaesthesia on the sensitivity of rat liver microsomes to radical-induced lipid peroxidation has been examined. Microsome peroxidation was initiated with a combination of reduced nicotinamide adenine dinucleotide phosphate and ferric ions, and assessed by measuring the changes in oxygen tension in the microsome suspension. In comparison to animals receiving 10% intralipid, saline or midazolam, microsomes prepared from animals anaesthetized with propofol demonstrated a significantly increased resistance to lipid peroxidation. Thus, the median delay in onset of the maximum rate of oxygen consumption in animals receiving a bolus of propofol was 23.1 min (range 14.4-32.3), in comparison to delays in the animals receiving intralipid, saline or midazolam of 1.9 (0.5-4.1), 2.4 (2.0-3.7) and 3.0 (1.8-6.1) min respectively (P < 0.01 in each case, Mann Whitney U-test). More prolonged anaesthesia with either repeated boluses or an infusion of propofol also delayed the onset of lipid peroxidation (45.6 (27.2-60) and 18.3 (9.2-60) min respectively). We conclude that the free radical scavenging properties of propofol are biologically significant at anaesthetic doses.

Anesthesia, Intravenous↗