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Biomedical subjects

L Gullestad

Publications and source records attributed to L Gullestad.

At least 91 records · Page 5Linked to original sources
PubMed1994

Magnesium status in healthy free-living elderly Norwegians.

OBJECTIVE: Magnesium (Mg) status has previously not been properly assessed among healthy elderly subjects. METHODS: Thirty-six healthy elderly subjects participated. Their Mg status was assessed by serum Mg, basal urinary Mg output, and with a Mg loading test (30 mmol infused during 8 hours; urine sampled 24 hours), and compared with 53 healthy younger subjects. Their dietary intake was assessed by a quantified food frequency questionnaire. Fourteen of the subjects received 300 mmol Mg to study the effect on Mg status. RESULTS: With the exception of vitamin D in women, average energy and nutrient intakes were adequate. All subjects had serum Mg levels within the reference value of the laboratory. Basal urinary Mg excretion was 3.3 +/- 1.1 mmol/day and 24-hour Mg retention after a Mg load was 28 +/- 16% compared to 6 +/- 11% in younger controls, suggesting Mg deficiency in the elderly. In the 14 subjects who received oral Mg supplementation there was a statistically significant increase in basal urinary Mg excretion and creatinine clearance, and decreases in Mg retention, serum Mg and serum creatinine. CONCLUSIONS: This study suggests that a significant subclinical Mg deficit, not detected by serum Mg, was present in many of these healthy elderly subjects. Mg supplementation improved Mg status and renal function.

Aged↗
PubMed1994

The magnesium loading test: reference values in healthy subjects.

The magnesium loading test is a useful tool in the diagnosis of magnesium deficiency. In order to establish a reference range in normal subjects, 88 healthy men and women aged between 18 and 66 years were given 30 mmol magnesium intravenously during eight hours as a loading test, urine was collected from start of infusion for 24 h for measurement of magnesium excretion. The magnesium mean retention was 6.3 +/- 10.3% of the loading dose, and the 0.025 and 0.975 fractiles were -19.5% and 27.5%, respectively. There was no significant difference between the sexes or in the different age groups studied. There was no correlation between the magnesium retention and serum magnesium or with basal urinary magnesium excretion. An excess excretion of magnesium was observed the postload day compared to baseline, but the excretion 24 and 48 h after the magnesium loading were closely correlated, suggesting that 24 h urinary sampling is sufficient. In order to examine the reproducibility of the test 23 of the subjects underwent two magnesium loading tests 4 weeks apart. The mean difference between two repeat magnesium loading tests was 2.0% with a SD of 8.1% and a 95% confidence interval of -1.6-5.5%. Normal saline did not affect baseline magnesium excretion. Concomitant administration of ethanol or physical exercise caused greater variation in magnesium excretion, whereas furosemide was without effect. The 8 h magnesium loading test with 24 h urine sampling seems to be fairly reproducible, is adequate for clinical use, but the normal range is wide.

Adolescent↗
PubMed1993

The effect of magnesium versus verapamil on supraventricular arrhythmias.

Magnesium has previously been used in the treatment of various arrhythmias, but few randomized and prospective studies are available. In a single-blind study, the efficacy and safety of intravenous magnesium sulfate (bolus doses of 5 + 5 mmol followed by infusion of 0.04 mmol/min) versus verapamil (5 + 5 mg followed by 0.1 mg/min) was evaluated in 57 patients with supraventricular arrhythmias (supraventricular tachycardia, atrial fibrillation, and atrial flutter) of recent onset (less than 1 week). Fifteen (58%) of the patients receiving magnesium (n = 26) converted to sinus rhythm within 4 h, and 16 (62%) within 24 h. Verapamil caused a lower ventricular rate, but only six (19%) of the patients (n = 31) converted to sinus rhythm within 4 h (p < 0.01) and 16 (52%) within 24 h (NS). No side effects were observed during magnesium infusion, whereas six patients receiving verapamil had to be withdrawn from further study medication due to symptomatic side effects (hypotension in three, cardiac failure in three). Magnesium appears to be an effective and safe drug for the treatment of supraventricular arrhythmias. The overall efficacy for conversion to sinus rhythm is at least as effective as with verapamil, and its action is more rapid.

Arrhythmias, Cardiac↗
PubMed1993

Variable effects of beta-adrenoceptor blockade on muscle blood flow during exercise.

The role of beta-adrenoceptors in exercise-induced muscle hyperaemia was investigated. Exercise was performed with a small and a large muscle mass: knee extension (KE) and bicycle exercise (BE). Seven healthy subjects performed light and maximal KE and eight subjects performed stepwise dynamic BE to exhaustion before and after acute i.v. administration of propranolol (0.15 mg kg-1). Leg blood flow was measured by a bolus dye dilution technique. During KE at low and high power leg blood flow was reduced by 8.7 and 10.5% after propranolol was administered, mean arterial blood pressure (MAP) was reduced at low, but not at high power resulting in increased leg vascular resistance (LVR) during high intensity. During BE propranolol reduced leg blood flow and increased LVR at low power, but not at high power. At high BE intensity LVR did not change with increasing power and was slightly decreased after propranolol was administered. In this situation oxygen uptake was close to maximum and the concentration of catecholamines was 3-5 times higher compared with KE. There was no significant effect of propranolol on lactate release or arterial-femoral venous (a-fv) differences for adrenaline or noradrenaline. We conclude that beta-adrenoceptors modulate local vasodilation in skeletal muscles during exercise independently of local muscle energy demand, but that the effect is highly dependent on active muscle mass since alpha-adrenergic activity during maximal BE seemed to disguise any effect of propranolol on LVR.

Adrenergic beta-Antagonists↗
PubMed1992

[Sudden cardiac death. Significance of beta blockaders].

Sudden death accounts for about 15-20% of all natural fatalities in the industrially developed world. Most of the victims have a substrate of extensive myocardial injury caused by coronary heart disease, cardiomyopathy and hypertensive heart disease. In most cases, the immediate cause of death is triggered by ventricular tachycardia which degenerates into ventricular fibrillation. Changes in myocardial electrical properties may be critically modified by ischemia, imbalance in the autonomic nervous system, electrolytic disorders, and haemodynamic factors. We review the causes of sudden cardiac death, giving special attention to the effect of beta-adrenoceptor blockade as a preventive measure.

Adrenergic beta-Antagonists↗
PubMed1992

[Myocardial disease in diabetes mellitus].

Diabetes mellitus is associated with excessive cardiovascular morbidity and mortality. Patients with diabetes mellitus suffer premature and severe atherosclerosis, and the relative impact is greater in women than in men. Clinical, experimental and pathological studies support the existence of a specific cardiomyopathy associated with diabetes mellitus. The cardiomyopathy plays an essential role in the pathogenesis of primary myocardial involvement, resulting in ventricular dysfunction, diminished cardiac pump performance and eventually overt heart failure. The authors discuss coronary heart disease and diabetic cardiomyopathy and indicate relevant treatment regimens.

Cardiomyopathies↗
PubMed1992

Differential effect of selective beta 1 and nonselective beta-adrenoceptor blockade on epinephrine and atropine response in normal humans.

Sympathetic stimulation with epinephrine (EPI) combined with parasympathetic blockade with atropine was studied in 10 healthy volunteers premedicated with placebo or three different beta-adrenoceptor blockers: atenolol (62.5 micrograms/kg, beta 1-selective), propranolol (62.5 micrograms/kg, nonselective), and pindolol (7.5 micrograms/kg, nonselective with intrinsic sympathomimetic activity, ISA). EPI infusion (0.06 microgram/kg/min) after placebo increased heart rate (HR) and systolic blood pressure (SBP) and decreased diastolic BP (DBP). Pretreatment with atenolol reduced the HR increase, and caused similar changes in BP. In contrast, pretreatment with propranolol and pindolol decreased HR and increased BP. Combined EPI and atropine (15 micrograms/kg) after placebo increased HR by 40% without causing BP changes. Similar HR changes were observed after administration of all beta-adrenoceptor blockers, but whereas a marked pressor response was observed after propranolol and pindolol a blunted response was observed after atenolol. Propranolol and pindolol reduced myocardial oxygen demand estimated by the HR x BP product after EPI, but this response was abolished by atropine. Serum potassium decreased from 3.9 +/- 0.2 to 3.2 +/- 0.3 mM after EPi and atropine. This effect was less after atenolol, and potassium increased after premedication with propranolol and pindolol. Our results show that nonselective beta-adrenoceptor blockade has a favorable effect on potassium homeostasis and oxygen demand parameters during EPI infusion but causes a marked pressor response, contrary to a beta 1-selective agent, during combined sympathetic stimulation and parasympathetic blockade. They also highlight the importance of the vasodilator cholinergic system as a defense mechanism in such situations.

Adrenergic beta-Antagonists↗
PubMed1992

Oral magnesium supplementation improves metabolic variables and muscle strength in alcoholics.

Magnesium deficiency is common among chronic alcoholics, but the knowledge of oral magnesium supplementation to this group is limited. We, therefore, randomized 49 chronic alcoholics, moderate to heavy drinkers for at least 10 years to receive oral magnesium or placebo treatment for 6 weeks according to a double-blind protocol. Effects on metabolic variables and muscle strength were analyzed. Significant reduction of aspartate-aminotransferase (ASAT), alanine-aminotransferase (ALAT) and gamma-glutamyl-transpeptidase (GGT) were seen after magnesium, whereas no change was observed with placebo. Bilirubin decreased in both groups. Serum Na, Ca, and P increased significantly during magnesium therapy compared with no statistically significant change in the placebo group. Serum K and Mg increased slightly after magnesium supplementation and decreased in the placebo group, resulting in a significant difference between the two groups at the end of the study. Muscle strength increased significantly during magnesium treatment, contrasting to no change with placebo. Blood pressure, heart rate, hematological variables, serum lipids (cholesterol, HDL, TG), glucose tolerance, and creatinine were unchanged in the two groups after treatment. Alcohol consumption was similar before and during the trial and does not explain the differences between the two groups The results shows that short-term oral magnesium therapy may improve liver cell function, electrolyte status, and muscle strength in chronic alcoholics.

Administration, Oral↗
PubMed1992

Magnesium deficiency diagnosed by an intravenous loading test.

Magnesium deficiency is common but difficult to diagnose and to assess in clinical practice. The use of a magnesium loading test was therefore evaluated to diagnose magnesium deficiency in 661 hospitalized patients with medical conditions assumed to interfere with magnesium uptake and excretion. Thirty millimoles of magnesium sulphate were administered intravenously during 8 h as a loading test and related to the urinary excretion in the following 24 h. A group of 30 patients without any known predisposition for magnesium deficiency and a group of 27 healthy volunteers served as controls. The mean (with 95% confidence interval) magnesium retention was 4 (-2-10)% in the control group of patients and 3 (-2-8)% in healthy subjects. A significantly higher retention was observed in all the groups of the patients: atrial fibrillation 18 (11-25)%, other arrhythmias 18 (11-24)%, hypertension 27 (20-33)%, coronary artery disease 25 (20-30)%, congestive heart failure 31 (26-37)%, cerebrovascular events 38 (24-51)%, gastrointestinal disorders 22 (14-29)%, diabetes mellitus 16 (9-22)%, and alcoholics 33 (29-36)%. The percentage of patients with a retention greater than mean + 2 SD of the two control groups varied between 22% and 54% among the different patient groups. The mean serum magnesium among the patient groups was similar to the control group of patients, except for the alcoholics, hypertensives and young healthy controls, who had significantly reduced levels. Magnesium retention was significantly correlated to age and renal function, and among the alcoholics negatively correlated to serum magnesium.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1991

[Cholesterol-lowering effect of oat].

Use of oat-supplement has been advocated to reduce serum cholesterol concentration. In order to study the effect of a daily dietary supplement of oats on lipid levels we performed three controlled clinical trials in healthy Norwegians and patients with hypercholesterolemia. The studies lasted 3-5 weeks, and oats were added to the diet in bread, breakfast cereals, porridge or crispbread. The serum cholesterol concentrations were reduced by 2.5-5% in four of the five groups with an oat-supplemented diet. No effect was found in the group who ate crispbread. Lipid levels remained unchanged in the three control groups. We conclude that oat products have a small but significant cholesterol-lowering effect when given as a supplement to the ordinary Norwegian diet.

Adult↗
PubMed1991

Intrapericardial left atrial aneurysm diagnosed by transoesophageal echocardiography and nuclear magnetic resonance imaging.

A case of intrapericardial left atrial aneurysm is described in a 38-year-old woman, who presented with invalidating paroxysmal atrial fibrillation. The diagnosis was suspected by 2D-echocardiography, and confirmed by transoesophageal echocardiography and magnetic resonance imaging. Chest X-ray, right and left ventricular and coronary angiography were normal. The aneurysm was surgically removed, and the patient has subsequently remained free from symptoms.

Adult↗
PubMed1991

Effects of selective beta 2-adrenoceptor blockade on serum potassium and exercise performance in normal men.

1. The differential effects of beta-adrenoceptor subtypes on potassium fluxes and exercise capacity were compared in eight healthy young men using single oral doses of the selective beta 2-adrenoceptor antagonist ICI-118551, the selective beta 1-adrenoceptor antagonist atenolol or the non-selective beta-adrenoceptor antagonist propranolol. The study was randomized, double-blind and placebo controlled. 2. Potassium in the venous effluent from the exercising muscles increased progressively with increasing exercise intensity. This response was augmented by propranolol, whereas neither atenolol nor ICI-118551 modified the response. After exercise potassium concentration fell exponentially with no difference between the treatment regimens. 3. Cumulative work was significantly reduced by ICI-118551 (6.4%, P = 0.04) and by propranolol (12.4%, P less than 0.01), whereas the reduction with atenolol (5.6%) did not reach statistical significance. 4. Atenolol and propranolol reduced peak heart rate by 23% and 29%, and peak systolic blood pressure by 9% and 11% respectively during maximal exercise. ICI-118551 caused a non-significant reduction in heart rate during submaximal exercise, with a significant reduction at maximum exercise (6% reduction), whereas systolic blood pressure was not different from placebo. Diastolic blood pressures were similar across all treatment regimens. 5. Similar glucose concentrations were obtained at baseline and at exhaustion during all treatment regimens. Lactate concentrations were comparable for any given exercise intensity irrespective of treatment regimens. Propranolol reduced lactate concentrations from the exercising muscles at maximum exercise in proportion to the reduction of maximal exercise capacity. 6. The subjective perception of fatigue was not affected by either beta 1- or beta 2-adrenoceptor blockade.(ABSTRACT TRUNCATED AT 250 WORDS)

Adrenergic beta-Agonists↗
PubMed1989

[Beta blockaders and physical performance. Limiting factors].

Beta blockers are known to cause reduced exercise performance in hypertensive and healthy subjects. Additive effects of selective blockade of beta-1 and beta-2 receptor subtypes seems to account for the total reduction in exercise capacity observed with non-selective beta-1,2 blockade. The mechanism is as yet undefined. The magnitude of the reduction is dependent of type of exercise and level of fitness. Hemodynamic parameters, substrate delivery to the working muscles, mental factors, and interference with potassium homeostasis may be involved.

Adrenergic beta-Antagonists↗
PubMed1989

Effect of beta-adrenergic blockade on hormonal responses during continuous and intermittent exercise.

The modifying effect on exercise performance and neuroendocrine response of the nonselective beta blocker timolol (10 mg b.i.d. for 5 days) and the beta 1-selective beta blocker metoprolol (100 mg b.i.d. for 5 days) was studied. The hormones studied were growth hormone, prolactin, cortisol, renin, epinephrine, dopamine, and norepinephrine. The response was studied during short-term maximal dynamic exercise, using two different exercise protocols; continuous (n = 11) and intermittent (n = 9) bicycle ergometry, in normal healthy young men. Accumulated work on placebo was nearly identical in the two studies, but was significantly reduced by 10.4% and 6.6% with timolol and by 4.7% and 6.7% with metoprolol, during continuous and intermittent exercise, respectively. During continuous exercise, accumulated work was 5.8% lower (p less than 0.05) with timolol than with metoprolol. The hormonal plasma concentrations of all hormones except renin were higher during continuous exercise than during intermittent exercise. Beta blockade had no effect on baseline hormonal levels, but the response was markedly changed during exercise. Maximum epinephrine, cortisol, and prolactin responses increased after beta blockade; dopamine remained nearly unchanged; while the renin responses were attenuated. Norepinephrine concentrations were slightly increased during continuous exercise by beta blockade and rose in direct proportion to the increase in workload. During intermittent exercise, maximum norepinephrine levels were significantly reduced by beta blockade compared with placebo. Thus the effect of beta 1-selective and nonselective beta receptor blockade on circulating hormones does not seem to explain the reduced exercise capacity following beta blockade.

Adrenergic beta-Antagonists↗
PubMed1989

Interaction of naloxone and timolol on maximal exercise capacity and the subjective perception of fatigue.

The effect on exercise performance and on the subjective perception of fatigue of the opioid receptor blocker naloxone, the nonselective beta-blocker timolol, and the combination of these two was studied in a double-blind randomized cycle ergometry test in healthy young men. Cumulative work at exhaustion was reduced by 25% after timolol (P less than 0.002) and by 34% after naloxone/timolol (P less than 0.02) but not after naloxone, compared with placebo. Naloxone alone had no influence on the subjective perception of fatigue (Borg scale rating), but significantly higher ratings were obtained by timolol and by naloxone/timolol. The present study does not support the hypothesis that opioid peptides are of importance for maximal exercise capacity and subjective perception of fatigue during short-term dynamic exercise in healthy young men.

Adult↗
PubMed1989

The importance of potassium and lactate for maximal exercise performance during beta blockade.

Changes in femoral vein pH, lactate, glucose and potassium were studied in a double-blind randomized, short-term, dynamic cycle ergometry exercise test on six healthy male subjects after administration of non-selective (timolol), beta-1-selective (atenolol) beta blocker or placebo. The exercise intensity was increased in steps of 200 kpm/min every 2 min until exhaustion. During submaximal exercise, potassium concentrations in blood from the exercising leg muscles increased progressively with increasing exercise intensity, and was significantly higher for any given exercise level following timolol as compared to placebo administration. The potassium concentrations following atenolol were in-between those of timolol and placebo. Despite reduced working capacity after non-selective beta blockade, almost identical potassium concentrations were reached at exhaustion irrespective of treatment regimens (placebo: 6.3, range 5.8-6.8 mmol/l; atenolol: 6.5, range 6.1-7.3 mmol/l and timolol: 6.4, range 6.2-6.8 mmol/l). The increase in s-lactate concentrations was similar across all treatments, and rose in proportion to the increase in the exercise intensity. A biphasic increase in lactate was observed with identical breaking points (anaerobic threshold) irrespective of treatment regimens. There was no difference in glucose concentrations between the treatment regimens. The marked increase in serum potassium during maximal exercise coincides with leg muscle fatigue and may, by its effect on the muscle cell membrane potential, limit the maximal working capacity following beta blockers. The rise in serum potassium may curtail the use of maximal exercise test as an index of cardiac performance in healthy young subjects.

Adrenergic beta-Antagonists↗