Biomedical subjects

R Coxon

Publications and source records attributed to R Coxon.

42 records · Page 3Linked to original sources

PubMed1983

Prenalterol, an oral beta-1 adrenoceptor agonist, in the treatment of chronic heart failure.

The haemodynamic effects of prenalterol, a new beta-1 agonist, were studied in 10 patients with chronic heart failure. Following intravenous prenalterol infusions of 1 mg, 2.5 mg and 5 mg at 15 min intervals, oral slow release prenalterol 20 mg, 30 mg and 50 mg was given at 2 h intervals and then 50-100 mg bid for one month. There were no significant changes in heart rate or blood pressure. Cardiac output increased significantly from control of 4.4 +/- 0.91/min to a maximum of 5.8 +/- 1.81/min (p less than 0.01) following the 5 mg prenalterol infusion and this increase was maintained following oral prenalterol on Days 1 and 2 and at 1 month. Significant increases in stroke volume and stroke work indices and reduction in systemic vascular resistance were also observed. Maximum increases in cardiac output and stroke work index following intravenous prenalterol correlated significantly with maximum increases observed following oral prenalterol on Day 2. Non-invasive evaluation showed no change in echocardiographic left ventricular end-diastolic dimension but a significant reduction in left ventricular end-systolic dimension on Day 30. PEP/LVET was significantly reduced from control of 0.56 +/- 0.15 to 0.47 +/- 0.12 (p less than 0.05) on Day 2 and 0.49 +/- 0.09 (p less than 0.05) at 1 month. Treadmill exercise duration was significantly improved for the group at 1 month and no adverse effects were noted. Oral slow release prenalterol is a potentially useful new drug for patients with chronic heart failure.

Administration, Oral↗

PubMed1982

Hemodynamic effects of captropril in chronic heart failure: efficacy of low-dose treatment and comparison with prazosin.

The acute hemodynamic effects and long-term therapeutic actions of low doses of the oral angiotensin-converting enzyme (ACE) inhibitor captopril (CPT) were evaluated in 18 patients with severe chronic congestive heart failure (CHF). Increasing doses of 1, 2.5, 6.25, 12.5, and 25 mg of CPT were given at 2-hour intervals. Increased stroke volume index (SVI) and reduced mean pulmonary capillary wedge (PCW) pressure occurred at 1 hour (p less than 0.05) with an associated decline of blood pressure. Maximal hemodynamic improvement for the group was seen at 6 and 7 hours following the 6.25 and 12.5 mg doses when SVI was elevated 35% and mean PCW pressure decreased 40% from control. CPT in doses of 12.5 to 50 mg every 8 hours was continued long term in these 18 CHF patients. Four patients died, and one was noncompliant; drug therapy was withdrawn in two patients with symptomatic hypertension and in one patient who experienced an alteration in taste. The remaining 10 patients showed significant improvement in symptoms and treadmill exercise duration at 3 months after CPT therapy was started. Moreover, repeat hemodynamic measurements were similar to optimal measurements obtained during the initial study. In a further study, the acute hemodynamic and hormonal effect of sequentially randomized 5 mg prazosin and 25 mg CPT were compared in 10 CHF patients. While both drugs reduced PCW pressure and vascular resistance, CPT effects were greater. Further, CPT alone effected a small rise in cardiac index and minor decline in heart rate, and CPT diminished aldosterone levels and increased plasma renin activity while prazosin did not.

Aldosterone↗

PubMed1982

Prazosin and captopril in chronic heart failure: comparison of acute haemodynamic and hormonal effects.

Ten patients with severe chronic heart failure were given prazosin 5 mg and captopril 25 mg in random order on consecutive days. Small increases in cardiac index and reductions in heart rate were effected by both drugs, but these alterations and the accompanying increases in stroke volume index were significant only following captopril. Both drugs significantly reduced mean pulmonary capillary wedge pressure and mean right atrial pressure and also systemic vascular resistance and blood pressure, the effect of captopril being greater than that of prazosin. Following captopril, plasma aldosterone levels were significantly reduced and plasma renin activity increased from control values, whereas prazosin did not alter these hormone indices.

Aged↗

PubMedDate not supplied

Echo-planar imaging of the brain at 3.0 T: first normal volunteer results.

OBJECTIVE: To present the first echo-planar brain images of diagnostic quality obtained at 3.0 T and to point out some of the problems experienced in performing it. MATERIALS AND METHODS: The results presented were obtained on volunteers using an in-house designed and constructed 3.0 T EPI imager. RESULTS: The results demonstrate the feasibility of obtaining snapshot imaging comprising up to 256 x 256 pixels and corresponding to a spatial resolution of 0.75 x 0.75 mm2 with a slice thickness of 2.5 mm. CONCLUSION: Potentially augmented diagnostic information can be obtained with high field EPI of the brain. Some susceptibility artifact is apparent at the bone-air interfaces as expected at 3.0 T.

Artifacts↗

PubMedDate not supplied

Echo-volumar imaging (EVI) of the brain at 3.0 T: first normal volunteer and functional imaging results.

OBJECTIVE: Our goal was to present the first echo-volumar brain images obtained at 3.0 T, together with the first functional imaging results using echo volumar imaging. MATERIALS AND METHODS: The results presented were obtained on volunteers using an in-house designed and constructed 3.0 T echo-planar/volumar imager. RESULTS: The results demonstrate the feasibility of obtaining snapshot volumar images comprising up to 64 x 64 x 8 voxels corresponding to a spatial resolution of 3.0 x 3.0 x 2.5 mm3. Results are also presented showing local cortical changes in signal in response to an external visual stimulus for both the left and the right brain hemispheres. CONCLUSION: The snapshot acquisition of a whole-volume data set has a number of advantages when considering motional effects or functional image changes that may involve time delays or phase effects within different cortical regions. Instantaneous acquisition of the whole data set means accurate phase information may be straightforwardly obtained.

Brain↗

PubMedDate not supplied

Nitroglycerin in a transdermal therapeutic system in chronic heart failure.

Nitroglycerin (NTG) in a transdermal therapeutic system (TTS) was evaluated in 16 patients with severe chronic heart failure. Eight patients were given NTG TTS with an in vivo release rate of 5 mg/24 h. No significant changes in heart rate or blood pressure were observed. Pulmonary capillary wedge (PCW) pressure was reduced significantly from a control value of 29 +/- 4 mm Hg to 17 +/- 2 mm Hg after 1 h (p less than 0.01), and significant reduction was maintained for 24 h. The system was then removed and PCW pressure rose to 27 +/- 2 mm Hg after 2 h. NTG TTS, 10 mg/24 h, was applied and PCW pressure was again reduced significantly. Significant reduction in systemic vascular resistance and increases in cardiac and stroke volume indices occurred on the first day at 4 h but were not maintained. In another eight patients, the haemodynamic effects of NTG TTS (5 mg/24 h), oral isosorbide dinitrate (20 mg), and topical NTG ointment (1 inch) were compared. Significant reductions in PCW pressure were achieved with each method of treatment, but no significant alterations in other haemodynamic measurements were observed. Haemodynamic reevaluation of 10 patients treated with NTG TTS for 3 months showed partial attenuation of the reduction in PCW pressure compared with the initial response.

Administration, Topical↗