ISSN:0001-6101    

DOI:10.1111/j.0954-6820.1981.tb02633.x

出版商:Blackwell Publishing Ltd    

年代:1981

数据来源: WILEY

摘要:

AbstractA short review is given of the ionic fluxes associated with the action potential in Purkinje fibres, and in sinus and AV‐node, and of the influence of variations in the extracellular concentrations of K+, Na+, Ca2+and Mg2+on basic electrophysiological parameters.Variations in serum potassium concentration often play an important role in the genesis of arrhythmias by changing several electrophysiological parameters, whereas only extreme variations in the serum calcium level produce electrophysiological effects of clinical importance. Hypo‐ and hypernatremia within the ranges observed clinically most probably do not produce significant electrophysiological changes. Variations in extracellular magnesium concentration seem to have effects on electrophysiological parameters particularly when they occur simultaneously with changes in the concentrations of calcium and potass

ISSN:0001-6101    

DOI:10.1111/j.0954-6820.1981.tb02634.x

出版商:Blackwell Publishing Ltd    

年代:1981

数据来源: WILEY

摘要:

AbstractThe maintenance of normal electrical activity in the myocardium is an ATP‐dependent process. Consequently failure to maintain the tissue reserves of ATP above a critical level, as occurs during ischaemia and post ischaemic reperfusion, results in the development of ionic imbalance. The ions involved include Na+, K+, Mg2+. Under conditions of low flow ischaemia an accumulation of K+in the T‐tubules may account for the genesis of some of the arrhythmias that occur during the ischaemic episode. Electrical uncoupling, another late event in an ischaemic episode, is probably due to an intracellular accumulation of Ca+.The contribution of an altered pattern of electrolyte distribution to the genesis of arrhythmias during myocardial ischaemia is discussed, with reference to the mechanisms whereby these ionic imbalances can be minimized or preven

ISSN:0001-6101    

DOI:10.1111/j.0954-6820.1981.tb02635.x

出版商:Blackwell Publishing Ltd    

年代:1981

数据来源: WILEY

摘要:

AbstractAtrial fibrillation is highly favoured by an accelerated atrial muscle repolarization. In hyperthyroidism, this occurs without changes in resting membrane potential level of the atrial muscle cells and without changes of the ionic composition of the cell. In patients prone to atrial fibrillation but without signs of hyperthyroidism, accelerated atrial repolarization can also be demonstrated. In such patients, a decreased atrial muscle potassium content seems responsible for the electrophysiological changes that highly favours the occurence of atrial fibrillation.

ISSN:0001-6101    

DOI:10.1111/j.0954-6820.1981.tb02636.x

出版商:Blackwell Publishing Ltd    

年代:1981

数据来源: WILEY

摘要:

AbstractTo avoid errors in plasma potassium determination clenching of the fist should be avoided and heparinized blood should be used. The patient should be fasting and samples taken at the same time of the day. When evaluating intracellular potassium from plasma potassium acid based status should be considered. The clinical status should also be considered, since severely ill patients may have a low transmembrane potential leading to loss of cell potassium and increase in plasma potassium. Measurements of exchangable sodium and potassium with radioactive tracers or whole body potassium (40K) are inprecise for determination of absolute cellular concentrations but more suitable for longitudinal studies. Determination of red cell electrolytes is of limited value, since these cells are not typical for the body cells. Electrolyte determination in leukocytes may give more accurate information. Muscle water and electrolytes can be determined in needle biopsy material. The concentration of intracellular electrolytes are expressed in relation to different bases of reference (FFS, GFFS, alkali‐soluble protein, phosphorous, and intracellular water); the advantages and fallacies in using these references are discusse

ISSN:0001-6101    

DOI:10.1111/j.0954-6820.1981.tb02637.x

出版商:Blackwell Publishing Ltd    

年代:1981

数据来源: WILEY

摘要:

AbstractThe results of measurements of body sodium, chloride and potassium by isotope dilution or whole body counting in patients with heart disease are reviewed. In patients with cardiac oedema exchangeable sodium and chloride are increased while body potassium tends to be decreased or normal. The findings in normonatraemic hypochloraemia, hypokalaemia and metabolic alkalosis, in diuretic hyponatraemia and in dilutional hyponatraemia are reviewed and their possible consequences in terms of changes in electrolyte gradients are discussed.The limitations and usefulness of measurements of exchangeable electrolytes in heart disease are mentioned.

ISSN:0001-6101    

DOI:10.1111/j.0954-6820.1981.tb02638.x

出版商:Blackwell Publishing Ltd    

年代:1981

数据来源: WILEY

摘要:

AbstractThis paper is intended to give a review of the etiology and symptoms of potassium deficiency in man, as an introduction to the section on potassium and cardiac arrhythmias of this symposium. A review is given of different conditions where hypokalemia and /or total potassium deficiency is or might be part of the clinical picture, such as conditions with insufficient dietary intake, gastrointestinal potassium losses (e.g. vomiting, fistulas, malabsorption, abuse of laxatives and diarrhea), and renal potassium losses (e.g. primary and secondary hyperaldosteronism, Cushing's syndrome, intake of licorice, diabetic coma, renal disease, diuretic treatment and l‐dopa treatment). Common symptoms of hypokalemia and/or potassium deficiency are reviewed as well, such as general and unspecific symptoms (e.g. tiredness, lack of concentration, lack of appetite and vomiting), and symptoms from the heart, kidneys and skeletal muscl

ISSN:0001-6101    

DOI:10.1111/j.0954-6820.1981.tb02639.x

出版商:Blackwell Publishing Ltd    

年代:1981

数据来源: WILEY

摘要:

AbstractThiazide diuretics are widely accepted as the cornerstone of antihypertensive treatment programs. Hypokalemia is a commonly encountered metabolic consequence of chronic thiazide therapy. We treated 38 patients (22 low renin, 16 normal renin) with moderate diastolic hypertension with hydrochlorothiazide (HCTC) administered on a twice daily schedule. Initial dose was 50 mg and the dose was increased at monthly intervals to 100 mg, 150 mg and 200 mg daily until blood pressure normalized. The serum K during the control period was 4.5 ± 0.2 mEq/I an on 50, 100, 150 and 200 mg HCTZ daily 3.9 ± 0.3, 3.4 ± 0.2, 2.9 ± 0.2, and 2.4 ± 0.3 mEq/I, respectively. Corresponding figures for whole body K were 4107 ± 208, 3722 ± 319, 3628 ± 257, 3551 ± 336, and 3269 ± 380 mEq, respectively.In 13 patients we observed the effects of HCTZ therapy (100 mg daily) on the occurrence of PVC's during rest as well as during static and dynamic exercise. During rest we observed 0.6 ± 0.08 PVC beats/min ± SEM and during static and dynamic exercise 0.6 ± 0.06 and 0.8 ± 0.15, respectively. Corresponding figures during HCTZ therapy 100 mg daily were 1.4 ± 0.1, 3.6 ± 0.7 and 5.7 ± 0.8, respectively.The occurrence of PVC's correlated significantly with the fall in serum K+observed r = 0.72, p<0.001.In conclusion we found that thiazide diuretics cause hypokalemia and depletion of body potassium. The more profound hypokalemia, the greater the propensity for the occ

ISSN:0001-6101    

DOI:10.1111/j.0954-6820.1981.tb02640.x

出版商:Blackwell Publishing Ltd    

年代:1981

数据来源: WILEY

摘要:

AbstractArrhythmias induced by digitalis are believed to be secondary to changes in ion concentrations in the myocardial cells or changes in the transcellular ion gradient.Both diuretic induced hypokalemia and digitalis inhibit the membrane‐Na+K+ATPase activity which cause a decrease of the intracellular potassium concentration. This may explain the risk of cardiac arrhythmias during digitalis treatment and during severe hypokalemia, and may further explain the increase for myocardial sensitivity for digitalis when hypokalemia is present.The myocardial uptake of digitalis however is markedly increased at low extracellular potassium concentration and this may be the explanation of the interaction between digitalis and hypokalemia.Not only the myocardial digoxin kinetic is changed during hypokalemia but the renal excretion rate of digoxin is markedly reduced during hypokalemia leading to increased serum digoxin concentration and thereby the risk of digitalis intoxicatio

ISSN:0001-6101    

DOI:10.1111/j.0954-6820.1981.tb02641.x

出版商:Blackwell Publishing Ltd    

年代:1981

数据来源: WILEY

摘要:

AbstractReviews of large series of patients with digitalis‐induced arrhythmias create a seeming paradox: Hypokalemia is infrequently associated with digitalis‐induced arrhythmias but the clinical benefit of supplementation of potassium for most digitalis‐induced arrhythmias is obvious. Examination of the electrophysiologic abnormalities induced by digitalis coupled with the electrophysiologic effects dependent on the ratio of intracellular to extracellular concentrations of potassium clarifies the issue. We present evidence that supports additive effects of the toxicity of digitalis and abnormal ratios of concentrations of potassium inside and outside the cardiac cell using metabolic alkalosis as a marker of intracellular potassium depletion. Patients with metabolic alkalosis and normokalemia with “therapeutic” concentrations of digoxin had significantly greater prevalance of arrhythmias than did patients without alkalosis. We presume this effect of alkalosis to be mediated by effects on extra‐to intracellular ratios o

ISSN:0001-6101    

DOI:10.1111/j.0954-6820.1981.tb02642.x

出版商:Blackwell Publishing Ltd    

年代:1981

数据来源: WILEY