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Biomedical subjects

S Bevegård

Publications and source records attributed to S Bevegård.

At least 55 records · Page 3Linked to original sources
PubMed1977

Effect of saluretic therapy on muscle content of water and electrolytes in relation to hemodynamic variables.

Muscle content of water and electrolytes (needle biopsy), intraarterial BP and cardiac output (dye dilution technique) were measured in 12 patients with essential hypertension before and after 4 months of mefruside therapy (25 mg/day). Before therapy there were no significant differences in muscle tissue electrolyte and water content compared with normotensive subjects. No correlation was found between central hemodynamic variables and the electrolyte and water content of muscle tissue either before or after therapy. After 4 months of mefruside therapy, muscle tissue water showed a mean decrease which was not significant. Serum potassium and muscle potassium content decreased significantly but there was no significant change in intracellular potassium concentration. Intracellular sodium concentration increased significantly, while muscle sodium content showed a mean increase which was not statistically significant. The change in intracellular sodium concentration showed a significant negative correlation with the decrease in mean arterial BP. The change in total cellular water content showed a significant negative correlation to the changes in total peripheral vascular resistance. Saluretic therapy seems to induce counterregulatory mechanisms that interfere with the hypotensive effect.

Adult↗
PubMed1977

Effect of changes in blood volume distribution on circulatory variables and plasma renin activity in man.

In 8 healthy subjects the pressure around the lower body was changed to 40 mmHg above (LBPP) and below (LBNP) atmospheric, thereby altering the amount of blood pooled in the lower body. Heart rate, intraarterial blood pressure, central venous pressure, cardiac output (dye dilution technique) and forearm blood flow (venous occlusion plethysmography) were measured. Plasma renin activity was determined with a radioimmunological method. 6 subjects maintained a relative circulatory steady state during LBNP. LBNP caused significant decrease in central venous pressure (CVP), stroke volume and cardiac output (Q) with an unchanged mean arterial pressure (MAP). Heart rate (HR) increased significantly. Calculated total peripheral vascular resistance (TPVR) and regional vascular resistance (RVR) in the forearm were significantly increased when measured 5-9 min after the onset of LBNP, whereas plasma renin activity (PRA) showed a definite increase only after 19 min of LBNP stimulation. No correlation was found between the changes in PRA and TPVR or RVR. Increasing the pressure around the lower body (LBPP) resulted in a slight but significant increase in MAP as well as a significant but transient increase in CVP. No significant changes were found in HR, Q or TPVR. In the forearm a decrease in RVR was demonstrated. PRA was not significantly changed. The results demonstrate that peripheral vascular resistance and PRA are both influenced by changes in blood volume distribution, possibly elicited via intrathoracic receptors sensitive to changes in central blood volume and/or CVP. The results also suggest that PRA does not play any significant part in the vasoconstriction during LBNP stimulation.

Atmospheric Pressure↗
PubMed1977

Blood pressure and heart rate regulating capacity of the carotid sinus during changes in blood volume distribution in man.

The influence of changes in blood volume distribution on the carotid baroreflex was studied in 18 subjects. Blood volume distribution was changed by varying the pressure around the lower body above and below ambient, thereby varying the amount of blood pooled in this region and exerting a secondary influence on the central blood volume. The carotid arterial stretch receptors were stimulated by varying the pressure in air-tight box enclosing the neck. To obtain a standardized carotid sinus stimulus (SCS) the pressure in the box was varied sinusoidally between - 10 and - 40 mmHg with a fixed freqency of 0.03 Hz. The effects on heart rate and blood pressure were assessed by harmonic analysis performed off-line on a digital computer. During lower body negative pressure of -40 mmHg (LBNP -40), i.e. during a procedure known to reduce the central blood volume, SCS induced an augmented effect on the blood pressure regulating capacity but not on the heart rate response. Expressing the blood pressure regulating capacity as peak-to-peak changes in systolic arterial pressure, the response during LBNP -40 mmHg was almost twice the control value. The opposite stimulus-lower body postive pressure-influenced the SCS-induced effects only slightly but on the average a minor reduction in both blood pressure and heart rate regulating capacity was found compared with the control condition, though the difference did not reach significant levels. The results support the hypothesis that changes in blood volume distribution modify the function of the carotid baroreflex, possibly via intrathoracic receptors sensitive to changes in central blood volume and/or central venous pressure.

Adult↗
PubMed1977

Carotid baroreceptor function in hypertensive patients.

Carotid baroreceptor function has been studied in twenty-five patients with essential hypertension and in ten normotensive control subjects of corresponding age. The carotid baroreceptors were stimulated by increasing the transmural pressure over the carotid arteries by the application of negative pressure in a box enclosing the neck. Stimulation elicited significant decreases in intra-arterial blood pressure, heart rate and cardiac index in both hypertensive and normotensive subjects. Both groups also showed a significant decrease in stroke index and a significant increase in total peripheral vascular resistance index. The response to carotid sinus stimulation did not differ significantly between the two groups. In fourteen of the hypertensive subjects, carotid baroreceptor function was studied after 4 months of saluretic therapy, mefruside, and in nine of these patients after additional treatment with a beta-receptor blocking drug, alprenolol, for another 4 months. Both mefruside and alprenolol induced a significant decrease in mean arterial blood pressure but the response to the carotid baroreceptor stimulation was not significantly altered. The findings indicate that the carotid baroreceptor is re-set to the actual blood pressure level, with little or no change in gain in hypertensive subjects both without and during hypotensive therapy.

Adult↗
PubMed1976

Respiratory function, cardiovascular dimensions and work capacity in boys with bronchial asthma.

Twenty boys with bronchial asthma, aged 8-13 years, were studied with regard to the size of their respiratory and circulatory organs and to their excercise tolerance. The boys were divided into two groups (A and B) depending on the severity of their subjective symptoms. Normal values were found for TLC, VC, and FRC in both groups, whereas the group with the most severe asthma had a slightly increased RV. In both groups THb, blood and heart volumes were normal. A quite normal relationship between these variables was observed as well as with work capacity (W170 and VO2 max) with no intergroup differences. Respiratory rate was lower and ventilation was increased in group B, both in submaximal and maximal exercise. Thus, tidal volume in maximal exercise exceeded 50 per cent of vital capacity in this group. These boys also had the highest blood lactate concentration at submaximal and maximal exercise. In half of the boys asthma-like attacks were elicited by the excercise. The symptoms subsided without treatment shortly after work. The frequency and intensity of attacks were similar in the two groups.

Adolescent↗
PubMed1976

Circulatory effects of dihydroergotamine in patients with disturbed sympathetic vasomotor control with special reference to postural hypotension.

In five patients with postural hypotension (disturbed sympathetic vasomotor control) the effect of intravenous and oral administration of dihydroergotamin (DHE) has been studied. The therapeutic effect of oral administration of DHE has also been compared to the effect of treatment with an antigravity suit. Following intravenous administration of DHE, systemic and central venous pressure increased in all cases. The effect on cardiac output was negligible and consequently the calculated total peripheral vascular resistance increased. Orthostatic tolerance increased in all cases. During long-term oral administration the effect was comparable to that obtained with an antigravity suit. The increased orthostatic tolerance is explained by a constrictive effect on both capacitance and resistance vessels. In order to analyze the influence of a functional denervation on the effect of DHE on peripheral circulation, a study has also been performed during epidural anaesthesia of the lower body in 11 patients. In the legs which were deprived of sympathetic tone intravenous administration of DHE caused constriction of resistance vessels. In the intact forearm there was a decrease of tone in the resistance vessels. The results indicate that DHE - apart from its well-known venoconstrictive effect - also may constrict resistance vessels when they are subjected to a low sympathetic nervous outflow.

Administration, Oral↗