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Biomedical subjects

Y Hojo

Publications and source records attributed to Y Hojo.

At least 91 records · Page 5Linked to original sources
PubMed1983

Graphical analysis of drug effects in the dog heart-lung preparation--with particular reference to the pulmonary circulation and effects of norepinephrine and 5-hydroxytryptamine.

Our new method for the graphical analysis of drug effects in the dog heart-lung preparation was extended to pulmonary circulation. The equilibrium points, at which the cardiac output (CO) curve and venous return (VR) curve cross each other in the right atrial pressure (RAP)-CO and left atrial pressure (LAP)-CO relations, were directly recorded on two X-Y recorders. The VR curves were obtained by inducing cardiac fibrillation and simultaneously occluding the pulmonary arterial trunk. The competence test, which was utilized previously for recording the CO curve in the RAP-CO relation (Ishikawa et al., 1978), was confirmed to be a good procedure for the CO curve in the LAP-CO relation. During the competence test, the mean pulmonary pressure (Pmp) which is the intercept of the pulmonary VR curve on the LAP axis in the LAP-CO relation was changed as much as the change in the systemic reservoir blood level, with little change in the slope of the pulmonary VR curve. When the reservoir blood level was 100 mm above the superior vena cava and the aortic pressure was 70 mmHg (control), the Pmp value was 136 +/- 7 mmH2O (n = 24). The slope of the pulmonary VR curve was not so different from that of the systemic VR curve in RAP-CO relation. Raising aortic pressure to 100 mmHg caused a shift of the equilibrium point to the right and slightly downwards, increased the Pmp value by 42.9 +/- 9.9 mmH2O (delta Pmp) and decreased the reservoir blood volume by 26.2 +/- 6.4 ml (delta V). The ratio delta V/delta Pmp was 0.66 +/- 0.11 ml/mmH2O. The continuous infusion of norepinephrine 4 micrograms/min caused a shift of the equilibrium point to the left and upwards, decreased the Pmp value by 67.1 +/- 19.1 mmH2O and increased the reservoir blood volume by 35.3 +/- 7.2 ml. The ratio delta V/delta Pmp was 0.56 +/- 0.16 ml/mmH2O. The continuous infusion of 5-hydroxytryptamine at the rate of 60 micrograms/min caused a shift of the equilibrium point almost vertically and downwards, increased Pmp value by 34.8 +/- 3.2 mmH2O and decreased the reservoir blood volume by 45.8 +/- 10.1 ml. The ratio delta V/delta Pmp was 0.88 +/- 0.10 ml/mmH2O.

Animals↗
PubMed1981

Alterations of circulatory responses to upright tilt in cardiac patients.

Circulatory responses to the upright tilt were studied in 20 normal subjects and 27 cardiac patients with ischemic heart disease or idiopathic cardiomyopathy. In normal subjects, the upright tilt caused obvious increases in heart rate and diastolic pressure, a slight decrease in systolic pressure and marked decreases in cardiac output and stroke volume. The circulatory changes during the tilt were less pronounced in the cardiac patients as compared with the normal subjects. The reductions of cardiac output and stroke volume and the increase in total peripheral resistance were all significantly diminished. A paradoxical increase in cardiac output during the tilt, an observation hitherto not well recognized, was observed in 5 cases with low cardiac index during the control period. Although several possibilities can be considered for the explanation of the diminished, sometimes paradoxical, circulatory responses to the tilt in cardiac patients, the improvement of the function of the diseased heart by preload reduction was proposed as an important factor. There was a significant negative correlation between the per cent changes of cardiac output and the per cent changes of PEP/LVET. It was suggested that the measurements of systolic time intervals during the tilt might be useful for evaluating the severity of the hemodynamic derangement in cardiac patients.

Adolescent↗
PubMed1978

Direct recording of cardiac output- and venous return-curves in the dog heart-lung preparation for a graphical analysis of the effects of cardioactive drugs.

The dog heart-lung preparations were prepared. The "equilibrium point", which could be defined as the point at which the cardiac output (CO)-curve and the venous return (VR)-curve crossed, when the CO and VR were plotted against the right atrial pressure, was recorded directly by utilizing an X-Y recorder. The CO-curve was obtained, as a locus of the equilibrium point, by raising and lowering the level of blood in the venous reservoir (competence test). The meaning of the procedure was shown to increase or decrease the mean systemic pressure, and to cause the corresponding parallel shift in the VR-curve. The VR-curve was obtained by changing myocardial contractility. When heart failure was induced by pentobarbital or by chloroform, the equilibrium point shifted downwards to the right, depicting the VR-curve. During development of the failure, the slopes of CO-curves decreased gradually. Effects of cinobufagin and norepinephrine were also analyzed. Utilization of the X-Y recorder enabled us to settle the uniform experimental conditions more easily, and to follow the effects of drugs continuously on a diagram equating the CO- and VR-curves (Gyton's scheme).

Animals↗