Enhanced exercise-induced hyperkalemia in patients with syndrome X. (1/356)

OBJECTIVES: The purpose of this study was to determine whether patients with syndrome X have altered potassium metabolism. BACKGROUND: Patients with syndrome X have angina pectoris and exercise induced ST segment depression on the electrocardiogram despite normal coronary angiograms. Increasing evidence suggests that myocardial ischemia is uncommon in these patients. Altered potassium metabolism causing interstitial potassium accumulation in the myocardium may be an alternative mechanism for chest pain and ST segment depression in syndrome X. METHODS: We compared the magnitude of exercise-induced hyperkalemia in 16 patients with syndrome X (12 female and four male, mean +/- SD age 53 +/- 6 years) and 15 matched healthy control subjects. The participants underwent a bicycle test at a fixed load of 75 W for 10 min, and blood samples were taken for analysis of potassium, catecholamines and lactate before, during and in the recovery period after exercise. In five patients with syndrome X, the test was repeated during alpha1 adrenoceptor blockade. RESULTS: Baseline concentrations of serum potassium, plasma catecholamines and plasma lactate were similar in patients and control subjects. The rate of exercise-induced increment of serum potassium was increased in the patients (70 +/- 29 vs. 30 +/- 21 micromol/liter/min in control subjects, p < 0.001). Six patients, who stopped before 10 min of exercise, showed very rapid increments in serum potassium concentration. Compared to the control subjects, patients also demonstrated larger increments in rate-pressure product, plasma norepinephrine and lactate concentrations during exercise. The rate of serum potassium increment correlated with the rate of plasma norepinephrine increment in the patients (r = 0.63, p < 0.02), but not in the control subjects (r = 0.01, p = 0.97). Blockade of alpha1 adrenoceptors decreased systolic blood pressure at baseline, but did not influence the increment of serum potassium, plasma catecholamines and lactate. CONCLUSIONS: Patients with syndrome X have enhanced exercise induced hyperkalemia in parallel with augmented increases of circulating norepinephrine and lactate. The prevailing mechanisms behind the abnormal potassium handling comprise sources distinct from alpha1-adrenoceptor activation.  (+info)

Familial pseudohyperkalemia maps to the same locus as dehydrated hereditary stomatocytosis (hereditary xerocytosis). (2/356)

Familial pseudohyperkalemia is a "leaky red blood cell" condition in which the cells show a temperature-dependent loss of potassium (K) from red blood cells when stored at room temperature, manifesting as apparent hyperkalemia. The red blood cells show a reduced lifespan in vivo but there is no frank hemolysis. Studies of cation content and transport show a marginal increase in permeability at 37 degrees C and a degree of cellular dehydration, qualitatively similar to the changes seen in dehydrated hereditary stomatocytosis (hereditary xerocytosis). Physiological studies have shown that the passive leak to K has an abnormal temperature dependence, such that the leak is less sensitive to temperature than that in normal cells. We performed genetic mapping on the original family and found that the condition in this kindred maps to the same locus (16q23-ter) that we have previously identified for an Irish family with dehydrated hereditary stomatocytosis, which does not show the same temperature effects.  (+info)

A case of aldosterone-producing adenoma with severe postoperative hyperkalemia. (3/356)

It is known that some patients with primary aldosteronism show postoperative hyperkalemia, which is due to inability of the adrenal gland to secrete sufficient amounts of aldosterone. However, hyperkalemia is generally neither severe nor prolonged, in which replacement therapy with mineralocorticoid is seldom necessary. We report a case of a 46-year-old woman with an aldosterone-producing adenoma associated with severe postoperative hyperkalemia. After unilateral adrenalectomy, the patient showed episodes of severe hyperkalemia for four months, which required not only cation-exchange resin, but also mineralocorticoid replacement. Plasma aldosterone concentration (PAC) was low, although PAC was increased after rapid ACTH test. Histological examination indicated the presence of adrenocortical tumor and paradoxical hyperplasia of zona glomerulosa in the adjacent adrenal. Immunohistochemistry demonstrated that the enzymes involved in aldosterone synthesis, such as cholesterol side chain cleavage (P-450scc), 3beta-hydroxysteroid dehydrogenase (3beta-HSD), and 21-hydroxylase (P-450c21), or the enzyme involved in glucocorticoid synthesis, 11beta-hydroxylase (P-450c11beta), were expressed in the tumor, but they were completely absent in zona glomerulosa of the adjacent adrenal. These findings were consistent with the patterns of primary aldosteronism. Serum potassium level was gradually decreased with concomitant increase in PAC. These results suggest that severe postoperative hyperkalemia of the present case was attributable to severe suppression of aldosterone synthesis in the adjacent and contralateral adrenal, which resulted in slow recovery of aldosterone secretion. It is plausible that aldosterone synthesis of adjacent and contralateral adrenal glands is severely impaired in some cases with primary aldosteronism, as glucocorticoid synthesis in Cushing syndrome.  (+info)

Hyperkalaemic paralysis--a bizarre presentation of renal failure. (4/356)

Paralysis due to hyperkalaemia is rare and the diagnosis may be overlooked in the first instance. However it is rapidly reversible and so long as electro-cardiography and serum potassium measurement are urgently done in all patients presenting with paralysis, it will not be missed. A case of hyperkalaemic paralysis is described and a review of the emergency management discussed.  (+info)

Activation and inactivation of the voltage-gated sodium channel: role of segment S5 revealed by a novel hyperkalaemic periodic paralysis mutation. (5/356)

Hyperkalaemic periodic paralysis, paramyotonia congenita, and potassium-aggravated myotonia are three autosomal dominant skeletal muscle disorders linked to the SCN4A gene encoding the alpha-subunit of the human voltage-sensitive sodium channel. To date, approximately 20 point mutations causing these disorders have been described. We have identified a new point mutation, in the SCN4A gene, in a family with a hyperkalaemic periodic paralysis phenotype. This mutation predicts an isoleucine-to-phenylalanine substitution at position 1495 located in the transmembrane segment S5 in the fourth homologous domain of the human alpha-subunit sodium channel. Introduction of the I1495F mutation into the wild-type channels disrupted the macroscopic current inactivation decay and shifted both steady-state activation and inactivation to the hyperpolarizing direction. The recovery from fast inactivation was slowed, and there was no effect on channel deactivation. Additionally, a significant enhancement of slow inactivation was observed in the I1495F mutation. In contrast, the T704M mutation, a hyperkalaemic periodic paralysis mutation located in the cytoplasmic interface of the S5 segment of the second domain, also shifted activation in the hyperpolarizing direction but had little effect on fast inactivation and dramatically impaired slow inactivation. These results, showing that the I1495F and T704M hyperkalaemic periodic paralysis mutations both have profound effects on channel activation and fast-slow inactivation, suggest that the S5 segment maybe in a location where fast and slow inactivation converge.  (+info)

Hyperkalemia in patients infected with the human immunodeficiency virus: involvement of a systemic mechanism. (6/356)

BACKGROUND: The appearance of hyperkalemia has been described in human immunodeficiency virus (HIV)-positive patients treated with drugs with amiloride-like properties. Recent in vitro data suggest that individuals infected with HIV have alterations in transcellular K+ transport. METHODS: With the objective of examining the presence of alterations in transmembrane K+ equilibrium in HIV-positive patients, we designed a prospective, interventional study involving 10 HIV-positive individuals and 10 healthy controls, all with normal renal function. An infusion of L-arginine (6%, intravenously, in four 30-min periods at 50, 100, 200, and 300 ml/hr) was administered, and plasma and urine electrolytes, creatinine, pH and osmolality, total and fractional sodium and potassium excretion, transtubular potassium gradient, plasma insulin, renin, aldosterone, and cortisol were measured. RESULTS: A primary disturbance consisting of a significant rise in plasma [K+] induced by L-arginine was detected in only the HIV patients but not in the controls (P < 0.001 between groups). A K+ redistribution origin of the hyperkalemia was supported by its rapid development (within 60 min) and the lack of significant differences between HIV-positive individuals and controls in the amount of K+ excreted in the urine. The fact that the HIV-positive individuals had an inhibited aldosterone response to the increase in plasma K+ suggested a putative mechanism for the deranged K+ response. CONCLUSIONS: These results reveal that HIV-infected individuals have a significant abnormality in systemic K+ equilibrium. This abnormality, which leads to the development of hyperkalemia after the L-arginine challenge, may be related, in part, to a failure in the aldosterone response to hyperkalemia. These results provide a new basis for understanding the pathogenesis of hyperkalemia in HIV individuals, and demonstrate that the risk of HIV-associated hyperkalemia exists even in the absence of amiloride-mimicking drugs or overt hyporeninemic hypoaldosteronism.  (+info)

The effect of potassium chloride infusion of parotid salivary flow and composition in conscious sheep. (7/356)

The composition and flow of parotid saliva in conscious sheep was measured before, during and after the intravenous infusion of 0-43 M-KCl or 0-43 M-NaCl at 2 ml./min for 2 hr. The salivary flow rate was depressed during the infusion of potassium chloride into both intact sheep and adrenalectomized sheep. As the salivary flow was unchanged by sodium chloride infusion it was concluded that the potassium ion was responsible for the decrease in flow and that this effect was not mediated through any of the adrenal hormones. The highly significant negative correlation between plasma potassium concentration and salivary flow throughout all potassium infusions indicated that the extent to which the salivary flow was depressed varied with the degree of hyperkalaemia. Except for situations where mineralocorticoid levels were likely to be elevated the concentrations of sodium and potassium in the saliva were positively correlated with the plasma concentrations of these ions. The salivary bicarbonate concentration of the saliva was negatively related to flow. The chloride concentration of the saliva was negatively correlated with salivary flow during all potassium chloride infusions.  (+info)

Changes in renal haemodynamics and electrolyte excretion during acute hyperkalemia in conscious adrenalectomized sheep. (8/356)

The p-aminohippurate (PAH) clearance, inulin clearance and the excretion of electrolytes by 10 adrenalectomized sheep were measured before, during and after the infusion of 0-43 M-KCl at 2 ml./min for 2 hr. The PAH clearance increased as the plasma potassium concentration increased up to approximately 6-0 m-mole/l. Further increases in plasma potassium were associated with a progressive return of the PAH clearance to or below the pre-infusion levels. At its maximum the PAH clearance was 1-228 +/- 0-032 (S.E. of mean) times the pre-infusion levels. The inulin clearance increased to reach a mazimum coincident with or subsequent to the maximum PAH clearance. The maximum level of inulin clearance during the hyperkalaemia was 1-158 +/- 0-020 times the pre-infusion clearance. The increments in the clearance of potassium and of bicarbonate rose rapidly to exceed the increment in inulin clearance during the hyperkalaemia in all experiments. The increments in the clearance of sodium and of chloride exceeded the increment in inulin clearance in more than half the experiments. It was concluded that although hyperkalaemia was associated with increased glomerular filtration much of the increased excretion of sodium, chloride and bicarbonate was derived from depressed tubular reabsorption of the ions. When the infusion experiments were repeated on the same animals the sheep demonstrated an improved ability to control the rise in plasma potassium concentration which was similar to potassium adaptation described in other species. There were no apparent differences between sheep maintained on 1-5 mg and 5 mg deoxycorticosterone acetate daily in their adaptation to potassium loading and the effect was tentatively attributed to the level of steroid maintenance being chronically high. The toxicity of hyperkalaemia was not lessened by this adaptation to potassium loading.  (+info)