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Biomedical subjects

H Aström

Publications and source records attributed to H Aström.

At least 55 records · Page 3Linked to original sources
PubMed1985

Haemodynamic and metabolic responses to prolonged exercise after chronic beta 1-adrenoceptor blockade in hypertensive man.

The influence of chronic beta 1-adrenoceptor blockade on haemodynamic and metabolic responses was examined in eight young hypertensive subjects during a 40 min submaximal bicycle test at 50% of maximal capacity. The patients were randomly allocated to one placebo and one treatment period of 6 weeks. During treatment atenolol (Tenormin, 100 mg) was given twice daily. Arterial pressure, cardiac output, leg blood flow, oxygen uptake and different metabolites in the blood were determined. The heart rate was reduced by beta 1-adrenoceptor blockade by 30% during exercise, and the decrease was related to plasma concentration of the drug. Cardiac output was decreased by approximately 10%, but the negative chronotropic effect was partly compensated for by a higher stroke volume. Blockade leg blood flow was reduced by 10%, but more oxygen was extracted, giving an unchanged oxygen uptake. Blood concentration and leg uptake of glucose were not influenced by the treatment, but plasma free fatty acids were reduced by 30-40%. Leg lactate release was decreased to half the value in the unblocked situation. Plasma renin activity did not increase at the beginning of exercise, but after 40 min an increase was seen, though only to half of the pretreatment value. It is concluded that beta 1-adrenoceptor blockade during submaximal exercise reduces blood flow to the working muscles and that this reduction is the result of a lower cardiac output. Aerobic metabolism is unchanged as a result of increased oxygen extraction, but less fat is used as lipolysis is inhibited. Glucose uptake by the working muscles is unchanged by beta 1-blockade, but there is evidence for an increased carbohydrate metabolism. As for non-selective blockade, atenolol decreases lactate release but this could be the result of non-specific action on the beta 1-receptor and/or increased carbohydrate oxidation. Furthermore, the beta 1-adrenoceptors seem to have a major influence on the renin release during exercise.

Adrenergic beta-Antagonists↗
PubMed1984

Angina pectoris and blood lactate concentration during graded exercise.

Nineteen patients with angina pectoris referred for preoperative evaluation were studied by psychophysical scaling of the chest pain according to Borg and blood lactate determination at rest and during a graded exercise test. The exercise tests consisted of stepwise increments of 10 W every min. Anginal pain, systolic blood pressure, heart rate (HR), and blood lactate concentration were determined at the end of each work load. The exercise test was interrupted at a rated anginal pain level (RAP) of 5-6/9 ("strong"), and this load was referred to as Wmax. The patients were divided into three groups: A with a Wmax less than or equal to 74 W, B 75-124 W, and C greater than or equal to 125 W. At submaximal loads HR was almost identical at the same absolute work load in all three groups. The heart rate at Wmax varied, however, and averaged 98 (A), 118 (B), and 136 (C), respectively. Corresponding peak values for RAP were 3.8, 4.5, and 4.8. Blood lactate at rest ranged from 1.0-1.6 mmol X 1-1 and increased curvilinearly with intensity, which was also the case for RAP. RAP was almost linearly related to blood lactate in all three groups suggesting a causal relationship between these two parameters.

Aged↗
PubMed1983

Left ventricular function after long-term treatment with ventricular inhibited compared to atrial triggered ventricular pacing.

The long-term effect of ventricular inhibited (VVI) and atrial triggered ventricular (VAT) pacing on cardiac performance was determined by cardiac catheterization at rest and during exercise in 9 patients with high-degree AV block. Cardiac output (Q) increased at rest by 22% during VAT vs. VVI (5.5 vs. 4.5 l/min, p less than 0.01). An increased stroke volume constituted the difference (75 vs. 63 ml, p less than 0.05). Mean working capacity increased by 12% in the supine position with VAT vs. VVI (p less than 0.05). During exercise Q increased by 40% with VAT vs. VVI (10.2 vs. 7.3 l/min, p less than 0.01) due to an increase in heart rate. Most pressures were largely unchanged. Stroke work and atrial rate decreased during VAT vs. VVI, which may indicate a lower sympathetic activity with VAT vs. VVI. The study demonstrated that hemodynamics advantages of VAT are still obtainable after several years of VVI pacing.

Adult↗
PubMed1983

Left ventricular volumes with ventricular inhibited and atrial triggered ventricular pacing.

Left ventricular (LV) volumes were assessed with equilibrium radionuclide angiocardiography at rest and during exercise in nine patients with high-degree AV block treated with ventricular inhibited (VVI), which was subsequently changed to atrial triggered ventricular pacing (VAT). The ventricular rates were similar at rest but higher on exercise during treatment with VAT (102 ppm) than with VVI (71 bpm). The LV end-diastolic volume tended to be larger with VAT than with VVI pacing, both at rest (185 vs. 145 ml) and during exercise (220 vs. 162 ml). The LV end-systolic volume also tended to be larger at rest (110 vs. 81 ml) and during exercise (149 vs. 83 ml). The LV ejection fractions were similar at rest but on exercise they decreased to significantly lower levels with VAT (0.35), while remaining unchanged with VVI (0.47). One mechanism for this difference could be an enhanced contractile state in VVI pacing compared with VAT pacing.

Adult↗
PubMed1982

Intra-operative variations in carotid artery blood flow and cardiac output: the effects of changes in blood volume and carbon dioxide during surgery under neurolept anesthesia.

Seven patients were operated on for stenosis of the internal carotid artery (ICA) with endarterectomy under neurolept anesthesia. The ICA blood flow was found to be unchanged after reconstruction following an operative blood loss of one fifth of the patient's blood volume despite variations in cardiac output. The relationship between carbon dioxide tension and cerebral blood flow remained unchanged during hypovolemia. It is concluded that the autoregulation of the cerebral blood flow is maintained under neurolept anesthesia.

Aged↗
PubMed1981

Effect of beta-adrenoceptor blockade on exercise performance and metabolism.

1. Carbohydrate and lipid metabolism and the capacity to perform prolonged submaximal physical exercise were studied in six young healthy subjects treated in a randomized double-blind fashion for 2 days with either placebo, the non-selective beta-adrenoceptor antagonist propranolol (80 mg b.i.d.) or the cardioselective agent metoprolol (100 mg b.i.d.). On day 3, 1 h after the last dose, the subjects exercised for 30 min periods followed up 10 min rest up to the point of exhaustion. 2. The capacity to perform exercise was decreased with both beta-adrenoceptor antagonists. However, at an equal degree of beta 1-adrenoceptor blockade, all subjects could exercise for a longer period of time on the cardioselective agent as compared with the non-selective drug. 3. Blood glucose levels decreased during exercise irrespective of the type of treatment, but the attenuation occurred most rapidly on propranolol. At exhaustion the average non-esterified fatty acid levels had increased 256% on placebo, 148% on metoprolol and 65% on propranolol. A significant positive correlation was found between changes in non-esterified fatty acid levels during exercise and total working time. It is concluded that beta-adrenoceptor blockade diminishes the capacity for prolonged sub-maximal exercise at least in part by reducing the availability of substrates to the working muscles.

Adult↗
PubMed1981

Haemodynamic effects of withdrawal of long-term treatment with beta-adrenoceptor blocking agents in subjects with essential hypertension.

1. After 10 years of beta-adrenoceptor blockade in five female patients with essential hypertension, the beta-adrenoceptor-blocking agent was withdrawn, and the women were then followed up for 1 year, with measurements of cardiac output and peripheral resistance. 2. Blood pressure remained low during the first year after withdrawal in spite of the fact that the heart rate increased within the first few days. 3. Cardiac output was found to increase during the first year after withdrawal, although total peripheral resistance was essentially unchanged. 4. The maintenance of low blood pressure after withdrawal of the antihypertensive drug might indicate a regression of structural changes in the resistance vessels during successful long-term antihypertensive treatment. 5. Minimal resistance in hands and calves did not increase during the year after withdrawal.

Adrenergic beta-Antagonists↗
PubMed1981

Central haemodynamics during halothane and enflurane anaesthesia in vascular surgery.

Central haemodynamics were studied before and during reconstructive vascular surgery in 18 patients receiving halothane or enflurane anaesthesia (nine patients in each group). In both groups cardiac output (CO), stroke volume (SV), oxygen uptake (VO2) and arterial blood pressure fell significantly after induction of anaesthesia, whereas the arterio-venous oxygen difference (AVD) and the total peripheral resistance (TPR) remained unchanged. In spite of an average intraoperative blood loss of 600 ml, which had not been substituted for, surgery brought about an increase in CO, SV and VO2, while the AVD and TPR remained unchanged. Following transfusion of 900 ml of blood, CO and SV showed a further significant increase in both groups, whereas VO2 was unchanged and the AVD and TPR fell significantly. The pulmonary capillary venous pressure (PPCV) was stable during induction of anaesthesia and surgery but increased after blood transfusion. The changes in SV and PPCV were analyzed in relation to the concept of ventricular function curves. It is concluded that there were no fundamental differences in central haemodynamics between halothane and enflurane anaesthesia either before or during surgery. In both groups the changes in CO and SV were due mainly to a reduced demand of oxygen transport and expected changes in sympatho-adrenergic tone rather than to myocardial depression.

Aged↗
PubMed1981

Leg haemodynamics during different forms of anaesthesia in patients undergoing reconstructive vascular surgery.

In the present study the effects of three different anaesthetics (halothane, n = 9, enflurane, n = 9, and neurolept, n = 11) on leg circulation were studied during vascular reconstruction with a reversed femoropopliteal saphenous vein bypass graft. Leg vascular resistance showed significant differences between the three anaesthetic groups. Thus, during the pretransfusion period, leg resistance in the neurolept group was significantly higher than in the halothane and enflurane groups, although the blood volume did not differ significantly between the groups. Though leg resistance after blood transfusion decreased significantly more in the neurolept group compared with the two other groups, the resistance after transfusion was still significantly higher in the neurolept group. Inducing pharmacological vasodilatation caused significant increases in common femoral arterial and bypass blood flows in all groups, but the increases were significantly more pronounced in the neurolept group. It is concluded that leg haemodynamics are influenced in different ways according to the anaesthetic agents used. This, in turn, might contribute to a better understanding and a more correct interpretation of the results of intraoperative flow and pressure measurements, and, consequently, to improvement of the reconstructive procedure.

Aged↗
PubMed1979

Influence of beta-adrenoceptor blockade on leg blood flow and lactate release in man.

Nine healthy male volunteers were studied at rest and during exercise before and after acute local beta-blockade in one leg. Oxygen uptake, arterial pressure, heart rate, leg blood flow and arterial-femoral venous differences for oxygen and lactate were determined. In addition, five subjects were studied at rest during adrenaline infusion to test the blockade; in this situation the increase in leg blood flow and decrease in resistance seen in the control leg were prevented in the blocked leg. During exercise, the beta-blockade did not influence leg blood flow. At rest, lactate release was abolished from the blocked leg, and during exercise the release was reduced by 50%. These findings demonstrate that acute betareceptor blockade does not interfere with the exercise-induced vasadilation but has metabolic consequences reflected by a reduction in the release of lactate from the leg.

Adrenergic beta-Antagonists↗
PubMed1979

Blood volume in angina pectoris.

Blood volume was measured in 60 consecutive male patients with disabling angina pectoris undergoing preoperative investigation for coronary bypass surgery. Of these patients, 58 had a lower blood volume than predicted. There was a decrease in blood volume of 21% (1.3 litres) from the predicted normal value (P less than 0.001). Seventeen per cent of the patients were on diuretics, 30% were on digitalis, and 48% were on beta-blocking drugs at the time of the study. There was no correlation between this medical treatment and the deviation in blood volume. In patients without signs of myocardial insufficiency the decrease in blood volume was most prominent, while in those with an enlarged heart and a raised left ventricular preload (at rest) the deviation was less.

Adult↗
PubMed1979

Circulatory and metabolic effects of acute beta 1-blockade in severe pre-eclampsia.

Five mg of a beta 1-adrenoceptor antagonist (atenolol) was given i.v. to 5 women with severe pre-eclampsia in the 3rd trimester of pregnancy. There was a significant decrease of both mean systolic blood pressure, from 171 to 155 mm Hg, and mean diastolic blood pressure, from 116 to 107 mm Hg. The mean maternal heart rate decreased significantly from 90 to 74 and mean fetal heart rate significantly from 145 to 138 beats per min. There were no significant changes in the plasma levels of cyclic AMP, insulin, glucose, free fatty acids, 3-hydroxy-butyrate or glycerol.

Adolescent↗
PubMed1979

LEg venous oxygen saturation in the evaluation of intra-operative blood flow during arterial reconstructive surgery.

In twenty-four patients, undergoing a femoro-popliteal saphenous vein bypass graft for symptomatic atherosclerotic occlusion of the superficial femoral artery, oxygen saturation values for the femoral and popliteal veins were compared to the directly measured blood flows in the common femoral artery and in the bypass graft, respectively. Blood flow and venous oxygen saturation increased significantly after transfusion of 900 ml of blood. Pharmacological vasodilation caused a significant increase in blood flow both before and after transfusion, whereas the changes in venous oxygen saturation were significant only before blood transfusion. A close statistical relationship was found between initial femoral venous oxygen saturation and initial blood flow in the common femoral artery as well as between initial popliteal venous oxygen saturation and initial byapss blood flow. However, especially at low saturation values, the evaluation of blood flow was very uncertain. Whole leg and lower leg oxygen uptakes were not altered by intraoperative changes in blood volume. It is concluded that blood flow in the common femoral artery and the bypass graft can be roughly estimated from analysis of oxygen saturation in the femoral and popliteal veins, respectively. Furthermore, by determining leg venous oxygen saturation both before and after flow augmentation, induced by pharmacological vasodilation, a conception of the load on the vascular system may be obtained.

Aged↗