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Biomedical subjects

C McDonald

Publications and source records attributed to C McDonald.

162 records · Page 9Linked to original sources
PubMedDate not supplied

Outcomes after "unroofing" of a myocardial bridge of the left anterior descending coronary artery in children with hypertrophic cardiomyopathy.

The importance of myocardial bridging of a coronary artery in the setting of hypertrophic cardiomyopathy is controversial, although we have previously reported an association with myocardial ischemia and sudden death in children. We report five symptomatic children in whom symptoms or evidence of myocardial ischemia resolved or improved after supraarterial myotomy alone.

Adolescent↗
PubMedDate not supplied

Late-onset 21-hydroxylase deficiency: reliable diagnosis by steroid analysis of random urine collections.

The feasibility of performing steroid analysis by capillary gas chromatography on random urine samples for the detection of mild late-onset 21-hydroxylase deficiency was evaluated. Comparisons were made of basal excretions of androgen and 17 alpha-hydroxyprogesterone metabolites with plasma levels (basal and stimulated) of 17 alpha-hydroxyprogesterone and testosterone in six patients with the disorder. The following steroid metabolite excretion ratios were determined for normal controls and affected individuals. 1) 17 alpha-hydroxypregnanolone/tetrahydrocortisone + tetrahydrocortisol + 5 alpha-tetrahydrocortisol (cortisol metabolites) (normal 0.017-0.10, affected 0.17-0.42); 2) pregnanetriol/cortisol metabolites (normal 0.03-0.15, affected 0.17-0.99); 3) pregnanetriolone/cortisol metabolites (normal 0.02-0.014, affected 0.08-0.20); 4) androsterone + etiocholanolone/cortisol metabolites (normal 0.26-1.02, affected 0.34-1.47). Among the 21-deoxy steroid ratios, there was no overlap between affected and unaffected individuals. Two of six affected individuals had androsterone + etiocholanolone/cortisol metabolite ratios in the normal range. This method provides excellent discrimination between normal and affected individuals, precluding the need for an ACTH-stimulation test. It is anticipated that it will be increasingly used for diagnosis of the condition.

Adolescent↗
PubMedDate not supplied

Solubilities of trimethoprim and sulfamethoxazole at various pH values and crystallization of trimethoprim from infusion fluids.

Solubilities of sulfamethoxazole (SMX) and trimethoprim (TMP) have been measured in the absence and presence of various concentrations of hydroxypropyl beta-cyclodextrin (HPCD) in buffers over a range of pH values. The solubilities of TMP increased linearly in the presence of HPCD at pH values of 7.0, 7.5, 8.9, and 9.9 indicating the formation of 1 to 1 complexes, whose association values increase as pH does and as the ionization of TMP decreases. For SMX at pH 7.0, a 1:1 complex is formed, but at pH 7.5 HPCD has little effect on the solubility of the highly ionized SMX, presumably since only un-ionized molecules can form inclusion complexes with the HPCD. At pH 7.0 when solubilities of TMP and SMX are measured in the same system containing buffer and HPCD, a massive decrease in the solubility of TMP is found, while that of SMX decreases slightly. A slightly soluble complex of TMP/SMX may be formed. When TMP/SMX injection is diluted 1;10 with phosphate buffer (pH 7.8), an immediate massive precipitation which is mostly TMP is observed. The presence of 10% w/v HPCD in the buffer delays and modifies the precipitation of TMP and SMX but does not prevent it. Mixing the injection (1 to 10) with normal saline (pH 9.5) gives a steadily increasing precipitation of TMP with time, but no discernible change in the concentration of SMX. However, in normal saline containing 10% w/v HPCD there is no crystallization of either drug over a 5 day period.

Buffers↗
PubMedDate not supplied

Recovery of Salmonella spp. from refrigerated preenrichment cultures of dry food composites.

Refrigerated preenrichment 72 h and selective enrichment cultures arising from 25 g analytical units of dry foods can be used to increase the analytical flexibility and productivity of laboratories for the detection of foodborne Salmonella spp. by AOAC method 994.04. Results of this intralaboratory study using artificially contaminated dry foods validate the extended application of the refrigerated preenrichment approach to dry food composites (375 g). All samples found to be contaminated by AOAC/Bacteriological Analytical Manual methods were identified readily from the homologous, refrigerated preenrichment broth cultures. This extended application of the refrigeration approach was recently adopted First Action by AOAC and was included as a modification to method 994.04. In addition, ancillary work on the diagnostic value of prolonged (48 h) incubation of lysine iron (LI) agar as described in the AOAC Official Method 967.26 led to a recommendation that the 48 h period of incubation be revoked in favor of a 24 h incubation of inoculated LI medium.

Cold Temperature↗
PubMedDate not supplied

The effect on syringe performance of fluid storage and repeated use: implications for syringe pumps.

Syringe stiction has been reported to cause syringe pump malfunction, hence the effect on syringe performance of syringe use and the formulations used in the syringe were investigated. The force required for syringe plunger motion (at 2.5 mm min-1), when filled with soybean oil emulsion (SBOE) and with water, and the extraction of silicone oil from syringes by these fluids, were measured for Primo, Talus and Terumo 10 mL, and Terumo 50 mL syringes. The breakloose, average extrusion and maximum force required to maintain plunger motion increased after storage of SBOE for 7 days in all syringes tested (p < 0.05). The storage of water increased the breakloose force of all syringes, but only increased the maximum force of Talus syringes, and both the average extrusion and maximum forces of Terumo 10 mL syringes. The mechanism for this is most likely swelling of the elastomer of the piston due to sorption of fluid. The force was found to increase logarithmically with repeated syringe use. Electrothermal atomization atomic absorption spectroscopy was used to measure the silicone oil content of syringe extractions. Three extractions were performed: repeated flushing, vigorous washing, and storage for 7 days with occasional agitation. Up to 69.4% of the silicone oil present in the syringes was extracted with both water and SBOE when they were stored or washed. In contrast to water, SBOE also extracted the lubricant when the syringe was filled and flushed immediately. If syringes are refilled, stored filled before use, or used over a prolonged period, particularly with a SBOE formulation, syringe striction may occur during infusion with a syringe pump.

Drug Storage↗
PubMedDate not supplied

Air medical transport services in North Carolina.

Air medical transport is an important component of contemporary prehospital care for patients with time-sensitive conditions and those whose clinical needs exceed the expertise of local providers. Early contact with trained flight dispatchers facilitates air transport. Appropriate stabilization, effective communication, and transfer of medical documents ensure that transports are appropriate, timely, and safe.

Air Ambulances↗
PubMedDate not supplied

Pharmacological management of asthma.

Asthma management is changing, and there are many potential new drugs undergoing early and late phase trials. Nonetheless, it is unlikely that any dramatic alterations in therapy will occur within the next 3 years. The asthma treatment paradigm has altered over the past 10 or so years, with the emphasis on symptom relief from short acting beta agonists giving way to preventive treatment of underlying airway inflammation with inhaled corticosteroids. More recently, long acting beta agonists have been demonstrated to reduce the need for increasing doses of inhaled steroids in patients with poorly controlled asthma. This article reviews these trends.

Administration, Inhalation↗