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Biomedical subjects

J B Liu

Publications and source records attributed to J B Liu.

118 records · Page 7Linked to original sources
PubMed1988

Vasodilating mechanism and response to physiological pressor stimuli of acute doses of carvedilol compared with labetalol, propranolol and hydralazine.

There is conflicting evidence regarding the main mechanism of the vasodilating effect with carvedilol at therapeutic doses, and to examine this, single doses of carvedilol 50mg and 100mg were compared with labetalol 400mg, propranolol 160mg, propranolol 80mg plus hydralazine 50mg and placebo in healthy subjects. Dose-response studies (required to increase heart rate or systolic blood pressure by 25 beats/min and 20mm Hg, respectively) were performed with phenylephrine, angiotensin and isoprenaline after each drug, and placebo administration and the effects of physiological pressor stimuli were compared. Phenylephrine systolic pressure dose-response curves were shifted by labetalol (dose ratio 2.4) and both carvedilol doses (dose ratios 50mg 1.9, 100mg 20.2). The slight shift to the right of the angiotensin dose-response curves with hydralazine plus propranolol (dose ratio 1.4) and carvedilol 50mg (dose ratio 1.4) was not significant. beta-Blockade was greatest with propranolol 160mg, followed by carvedilol 100mg, propranolol 80mg plus hydralazine 50mg, carvedilol 50mg and was least with labetalol 400mg (isoprenaline dose ratios required to increase heart rate by 25 beats/min were 55.2, 27.2, 20.2, 14.2, 11.5, respectively). Blood pressure rise with cold pressor and isometric exercise was inhibited most by labetalol. At these acute doses carvedilol displayed some alpha-blockade, but the lower ratio of alpha-blockade to beta-blockade differed from that seen with labetalol, which may account for the different haemodynamic responses at rest and during physiological pressor stimuli with the 2 drugs. There was no definite evidence of direct vasodilator effect.

Adrenergic beta-Antagonists↗
PubMedDate not supplied

Superficial masses with color flow Doppler imaging.

Color Doppler imaging findings and spectral waveforms were reviewed for 21 superficial masses in which color Doppler imaging revealed flow. This series included 5 benign hyperplastic lymph nodes, 5 malignant masses, 2 staphylococcus abscesses, and 9 pseudoaneurysms. Benign hyperplastic nodes had a vascular pattern consisting of prominent central flow with a branching radial pattern, reflecting the morphology of lymph nodes. One metastasis from melanoma demonstrated abundant peripheral flow and central avascularity, while the other 4 malignant masses and the 2 abscesses had sparse internal flow. All pseudoaneurysms had a to-and-fro imaging and spectral pattern (into the mass during systole, out during diastole), and/or a swirling pattern on real-time images (8 of 9 each). Doppler spectral analysis revealed continuous forward flow during diastole for all other masses and abscesses. Waveforms appeared similar for benign and malignant masses, and for abscesses. Conventional image-directed Doppler examinations performed prior to color Doppler studies failed to reveal flow in 2 partially thrombosed pseudoaneurysms, 1 malignant mass, and 1 abscess. Benign hyperplastic nodes, malignant masses, and pseudoaneurysms had distinctive color Doppler image appearances in this series, although demonstration of flow within a mass does not eliminate the possibility of abscess. Proper use of color and spectral Doppler analysis of superficial masses involves more than mere detection or exclusion of flow.

Abscess↗
PubMedDate not supplied

Intravascular ultrasound as an alternative to positive-contrast vena cavography prior to filter placement.

PURPOSE: In a nonconsecutive series of patients, intravascular ultrasound (IVUS) was investigated for safety and efficacy as an alternative to positive-contrast vena cavography for evaluating the inferior vena cava (IVC) prior to filter placement. MATERIALS AND METHODS: In a 6.5-year period, 30 patients (15 women, 15 men) ranging in age from 22 to 98 years old (mean, 56 years) underwent vena cava filter placement without conventional positive-contrast vena cavography, after IVUS evaluation of the IVC with use of a 6.2-F, 12.5- or 20-MHz monorail catheter system. The rationale for using IVUS included contraindications to iodinated contrast material in 14 patients with renal insufficiency and in four patients with previous life-threatening anaphylactoid reaction to iodinated contrast material; limitations to radiation exposure in four pregnant patients; and inability to otherwise image the IVC of eight morbidly obese patients who exceeded the weight limits of available angiographic equipment. IVUS completely replaced positive-contrast vena cavography, although not fluoroscopy in the four pregnant patients and in the 18 patients with contrast material contraindications. In two of the eight obese patients, IVUS was the only imaging modality. RESULTS: In all 30 patients, IVUS successfully determined the patency of the filter delivery route veins and the vena cava, the absence of thrombus, the location of renal veins, the absence of anatomical variants, and the vena cava diameter at the desired filter deployment level. Successful filter placement was confirmed in all 30 patients either with plain film alone (n = 12), IVUS alone (n = 3), computed tomography alone (n = 1), external ultrasound alone (n = 1), IVUS and another imaging modality (n = 10), or by combinations of other imaging modalities (n = 3). There were no complications. CONCLUSIONS: IVUS is a safe and effective alternative to conventional positive-contrast vena cavography for imaging the IVC prior to filter placement in patients with contraindications to iodinated contrast material or ionizing radiation.

Adult↗