Biomedical subjects

A Bryan

Publications and source records attributed to A Bryan.

9 recordsLinked to original sources

PubMed1998

Hemodynamic performance of the 21-mm St. Jude BioImplant prosthesis using dobutamine Doppler echocardiography.

This study examines the hemodynamic performance of small size St. Jude BioImplant aortic prostheses using dobutamine echocardiography. Eleven patients (3 women, mean age 75 years) who had undergone aortic valve replacement with a size 21-mm St. Jude BioImplant aortic prostheses at 10.8 +/- 5.1 months (SD) previously were studied. Dobutamine infusion was started at a rate of 5 microg/kg/min and increased to 10 microg/kg/min, and subsequently to 20 microg/kg/min at 15-minute intervals. Pulsed and continuous-wave Doppler studies were performed at rest and at the end of each stage. Effective orifice area, mean gradient, and the performance index across each prosthesis were calculated and cardiac output was determined by Doppler measurement of flow in the left ventricular outflow tract. Stress dobutamine increased heart rate and cardiac output by 51% and 56%, respectively (both p <0.0001), and the mean transvalvular gradient increased from 30.1 +/- 7.5 mm Hg at rest to 49.3 +/- 11.5 mm Hg at maximum stress (p <0.0005). The performance index increased progressively from 0.29 +/- 0.05 at rest to 0.40 +/- 0.10 at maximum stress (p <0.0005). Regression modeling analyses demonstrated that the maximum stress gradient was independent of all variables except the resting gradient (p = 0.03). Body surface area had no effect on the changes in cardiac output, effective orifice area, or transprosthetic gradient at maximum stress. Thus, these data demonstrate that the size 21-mm St. Jude BioImplant prosthesis exhibits suboptimal hemodynamic performance with transvalvular gradients consistent with mild to moderate aortic stenosis, both at rest and under stress conditions.

Adrenergic beta-Agonists↗

PubMed1996

Detection and prevention of myocardial damage during open heart surgery.

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Biomarkers↗

PubMed1994

Recovery after oral surgery with halothane, enflurane, isoflurane or propofol anaesthesia.

We have compared the recovery characteristics of four different techniques for maintenance of anaesthesia in 99 day-case patients admitted for oral surgery. All patients received propofol for induction of anaesthesia followed by halothane, enflurane, isoflurane or propofol infusion for maintenance of anaesthesia. Each patient was subjected to a battery of psychometric tests which included Spielberger state, trait, mood stress and mood arousal questionnaires, Maddox-Wing test and five-choice serial reaction time. All tests were performed before operation and at 0.5, 1, 2, 4, 24 and 48 h after operation. Performance in the reaction time test decreased significantly in the immediate postoperative period, returning almost to preoperative values by 4 h. However, only those patients who received enflurane or propofol had returned to their performance level before surgery by 4 h, although all four groups had achieved this target by 24 h. There was a further improvement in performance at 48 h. Anxiety and stress were high before surgery and decreased rapidly in the postoperative period. The Maddox-Wing test demonstrated a significant impairment in performance in the first 1 h after surgery, which returned to normal by discharge at 4 h. There were no significant differences between the four groups in these latter tests.

Adult↗

PubMed1992

Frozen phonology thawed: the analysis and remediation of a developmental disorder of real word phonology.

A 5-year-old boy presented with very deviant phonological production, as well as some delay in acquisition of vocabulary for comprehension. Investigations showed that, in contrast to his very limited phonological system in word production and naming, he was able to repeat a variety of non-words with reasonable accuracy using a variety of syllable structures. A period of therapy aimed at improving his phonological segmentation skills resulted in dramatic improvement in real word production to the same level that he showed with non-words. This improvement was specific to the domain of treatment--real word phonology--demonstrating that the effects were a result of the therapy regimen. The reasons for this dissociation between the phonology of real words and non-words are discussed. It is concluded that the child's pattern of performance is incompatible with theories which assume that a single phonological representation is used both for word recognition and for output. His deficit appears to lie in a failure to update the underlying phonological representations used to drive spoken output as his phonological abilities develop--his lexical phonology was 'frozen'.

Child, Preschool↗

PubMed1985