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Biomedical subjects

I Chesner

Publications and source records attributed to I Chesner.

12 recordsLinked to original sources
PubMed1998

Near-infrared spectroscopy in the assessment of cerebral oxygenation at high altitude.

Hypoxia plays a key role in the pathogenesis of acute mountain sickness (AMS), but individual susceptibility is variable and cerebral symptoms do not always correlate with PaO2 measurements. Cerebral hypoxia may be more relevant than PaO2. We studied trends in cerebral regional oxygen saturation by the technique of near-infrared spectroscopy in 20 subjects ascending rapidly to 4680 m. Subjects were enrolled in a placebo-controlled, double-blind trial of medroxyprogesterone for the prevention of AMS. The fall in cerebral oxygen saturation was less than in the periphery. At 4680 m, cerebral oxygenation correlated with peripheral saturation but not with PaCO2 or with cerebral symptoms scores. At 4680 m, subjects on medroxyprogesterone had higher cerebral and peripheral saturation compared with those on a placebo. We conclude that cerebral oxygenation monitored with the Critikon 2020 system provided important information on the complex relationship of hypoxia to AMS and that other factors, such as changes in blood flow or capillary permeability, may be equally important.

Adult↗
PubMed1994

Prevention of rebleeding from oesophageal varices: two-year follow up of a prospective controlled trial of propranolol in addition to sclerotherapy.

A prospective randomised trial comparing propranolol and sclerotherapy to sclerotherapy alone was conducted over a 2-year follow up in a district hospital setting of unselected patients. Rebleeding and survival were analysed. Thirty-nine patients were randomised to propranolol plus sclerotherapy and 34 to sclerotherapy alone. The two groups were clinically comparable. There was no significant difference in the cumulative percent of patients free of rebleeding; 54% of the sclerotherapy group rebled compared to 52% of the group treated with propranolol plus sclerotherapy (Hazard ratio 1.09 (0.54-2.22) and p = 0.81, NS). Two-year actuarial survival was also not significantly different, with 77% of the propanolol plus sclerotherapy group surviving, compared to 74% of sclerotherapy alone (Hazard ratio 1.08 (0.35-2.22) and p = 0.79, NS). The mean time to eradication of varices was not significantly different between the two groups (propranolol plus sclerotherapy 222 days, sclerotherapy alone 243 days), nor did the rate of variceal recurrence differ (72.7 vs 72 days). This study did not show long-term improvement in rebleeding or survival using propranolol in addition to a regular sclerotherapy programme.

Adolescent↗
PubMed1990

Use of automatic computerised pump to maintain constant intragastric pH.

We used continuous variable rate infusions of famotidine in eight normal volunteers under fasting conditions to raise intragastric pH to 5.0. An intragastric glass electrode continuously monitored acidity and this information was automatically computed to regulate an intravenous infusion system (GastroJet). The computer was programmed to aim for pH 6.0, increasing and lowering infusion rates accordingly. Two regimens were compared with placebo (10 mg bolus followed by infusion or infusion of famotidine alone). Volunteers were admitted to an investigation ward and each study was preceded by a standard normal meal. Hydration was maintained with intravenous fluids. During placebo treatment the median pH was 1.5 and the pH was less than 5.0 for 98% of the time. All volunteers responded to famotidine but dosage requirements varied (range 41 mg to 126 mg). The median pH rose to 6.5 when infusions of famotidine followed boluses and to 6.6 when infusions alone were used - the pH was less than 5.0 for 20% and 16% of the time respectively (p less than 0.05 Wilcoxon compared with placebo). Mean drug use was greater with boluses (98 mg v 87 mg p = 0.03: paired Student's t test) and onset was not apparently faster. Blood famotidine concentrations followed infusion rate changes. Famotidine infused by GastroJet maintains a high fasting intragastric pH and priming boluses are probably unnecessary.

Adult↗
PubMed1988

Human gastric perfusion: evidence for non-uniformity of blood flow.

Post-mortem injection studies have demonstrated marked differences in the course and distribution of arterioles in the stomach, but evidence of differential perfusion in man is lacking. Using the non-invasive laser Doppler technique, we studied 38 patients referred for gastroscopy for dyspeptic symptoms. Flux measurements were made at nine sites: distal oesophagus, cardia, mid-body and antrum on lesser and greater curves, and pre- and post-pylorus. In all cases the stomach was macroscopically normal. Flux in the proximal stomach was significantly greater than that in the antrum, (P less than 0.001, Student's t test). This in vivo study demonstrates a flow gradient related to the previously demonstrated anatomical differences.

Blood Flow Velocity↗
PubMed1987

Immunogold-silver technique applied to showing malignant B cell infiltration of gastrointestinal tract in patients with chronic lymphocytic leukaemia and non-Hodgkin's lymphoma.

Gastric, duodenal, and rectal biopsy specimens from 20 patients with chronic lymphocytic leukaemia (CLL) and non-Hodgkin's lymphoma (NHL), not primarily of gastrointestinal origin, were examined using the immunogold-silver staining (IGSS) technique. In paraffin sections the presence of kappa and lambda surface immunoglobulin in lymphoid infiltrates was shown. Using this technique, nine patients were shown to have infiltration of the gastrointestinal mucosa by monoclonal B cells at one or more sites. In a further case a lymphoid aggregate was shown to express both kappa and lambda surface light chains, suggesting that it had a benign nature.

Adult↗
PubMed1986

Effect of acetazolamide on exercise performance and muscle mass at high altitude.

The effect of acetazolamide (Az) on exercise performance and muscle mass in acclimatised subjects at an altitude of 4846 m was assessed in 11 subjects and compared with the effect of placebo on 10 other subjects. Exercise performance at 85% maximum heart rate fell by 37% in the Az group and by 45% in controls (p less than 0.05). Weight loss was greater in the placebo group at high altitude (p less than 0.01) and this correlated with the fall in exercise performance (p less than 0.001). During the expedition anterior quadriceps muscle thickness fell by 12.9% in the control group and 8.5% in the Az group (p less than 0.001), while biceps muscle thickness fell by 8.6% in controls and 2.3% in the Az group (p less than 0.001). Measurements of skin-fold thickness indicated a loss of 18% of total body fat in the placebo group and 5% in the Az group by the end of the expedition (p less than 0.001). Calorie intakes at altitudes above 3000 m were low and similar for the two groups. The Az group had fewer symptoms of acute mountain sickness but differences between the two groups were not statistically significant. Acetazolamide is therefore useful for climbers and trekkers who are acclimatised to high altitudes. It could be most useful at extreme altitudes, where maintenance of exercise performance and muscle mass are important.

Acetazolamide↗
PubMed1985

Practical assessment of the NBT-PABA pancreatic function test using high performance liquid chromatography determination of p-aminobenzoic acid in urine.

A practical method for determining p-aminobenzoic acid in urine by high-performance liquid chromatography has been assessed. The technique is quick, requires no extraction steps and has good precision. Using this method, healthy individuals had a p-aminobenzoic acid excretion index of 94% +/- 18 (mean +/- 1 SD). Patients with proven, severe chronic exocrine pancreatic dysfunction had index values of less than 5-25%. Unlike chemical methods available, there were no interferences in any of the urines tested, nor did 12 compounds tested interfere with the analysis.

4-Aminobenzoic Acid↗
PubMed1984

Low plasma C4 concentrations: association with microangiopathy in insulin dependent diabetes.

Plasma C4 concentrations were measured in insulin dependent diabetics with and without microangiopathy and in controls. The diabetics had significantly lower C4 values than controls (p less than 0.001), and patients with insulin dependent diabetes and microangiopathy had lower values than those without this complication (p less than 0.001). There was a 7.1-fold increase in the prevalence of complications in the diabetics with low C4 values. Of 41 diabetics whose rate of albumin excretion was measured, 13 had increased rates and 11 of these had low C4 concentrations. Low plasma C4 concentration in insulin dependent diabetes is strongly associated with microvascular disease and may identify diabetics with a particular propensity to develop this complication.

Adolescent↗