[Deficiency of potassium in blood simulating autonomic dystonia].
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Nutritional therapy can be impaired if imbalances in water and electrolyte status have led to gross disorders of the cardiovascular, pulmonary, renal, metabolic, and central nervous systems. Restauration and maintenance of the functional extracellular fluid volume is the primary therapeutic goal in water and electrolyte resuscitation. Hyper- and hypoosmolar disturbances are automatically corrected by intrinsic regulatory mechanisms. Potassium deficiency or overload, or potassium disequilibrium between the intracellular and extracellular space can lead to dangerous cardiac arrhythmias. Hyper- and hypokalemia usually develop within days or even weeks and should not be corrected within a few hours. If life threatening hyperkalemia develops during acute renal failure, 20 ml 10% calcium gluconate solution can be given intravenously in order to avoid ventricular fibrillation or cardiac arrest. The discrimination between prerenal disease, acute tubular necrosis and other causes of acute renal failure is based on special investigations, such as urinary osmolality, urinary sodium concentration, clearance of creatinine, osmolar solutes, free water, and fractional sodium excretion. The clinical examination of a patient should be the basis of assessing his water and electrolyte state. Laboratory findings which are in disagreement with the clinical state have to be repeated, critically interpreted, but not completely rejected. Third space losses make fluid balance difficult.
Sixty-four Sprague-Dawley rats (initially weighing 200-225 grams) were divided into three groups. Group 1, the experimental group, was fed a potassium depleted diet for 42 days, followed by a potassium repleted diet for up to an additional 14 days. Group 2, the dietary control group, received a potassium deficient diet, but was continuously supplemented by drinking water containing potassium chloride 150 meq/L. Group 3, the control group remained on normal rat chow and tap water during the entire investigation. Quantitative morphometric analysis was used to assess the percent of myocardium occupied by lesion. These data were analyzed by an analysis of variance (ANOVA) for repeated measures, comparing the three groups with one another; a second analysis compared the myocardial lesions of the dietary experimental group during the potassium depletion and repletion periods. At the end of the dietary depletion period (day 42) focal areas of cardiac myocyte necrosis and mononuclear infiltrate were found in the experimental group. Morphometric assessment on day 42 revealed a volume fraction (Vv) of 8.61 (+/- 4.41)%, which was significantly greater (p = 0.0018), as compared with both control groups. Lesion area significantly regressed in two and one half days after potassium was supplemented in the dietary experimental group to 0.58 (+/- 0.34)% Vv (p = 0.0005). Six days after potassium was replaced in the diet, there was no significant difference between the experimental and control groups, and only a limited connective tissue scar was noted in the experimental group. The mechanism of the rapid regression of lesions and the production of only limited connective tissue scar is suggested but requires further elucidation.
Hypokalemia poses a common diagnostic challenge with many potential etiologies. Multiple factors may contribute to this electrolyte deficiency in any given patient. Gastrointestinal potassium wasting usually is identifiable by an associated increase in fluid losses via biliary tract or bowel. A urinary potassium excretion of 20 mEq or more per day in the presence of a low serum potassium (less than 3.5 mEq/L) suggests inappropriate potassium wasting. Although diuretic therapy (loop diuretics, thiazides) undoubtedly is the most common cause of a potassium deficit, one also must consider abnormalities of the pituitary-adrenal axis, renal disorders including tumors, other drugs, and a variety of less well-defined entities. Potassium deficiency may produce both functional and structural defects in the kidneys, myocardium, skeletal muscle, central nervous system, and gastrointestinal tract. Treatment is aimed at replacing potassium intravenously or orally or preventing further potassium loss (spironolactone, triamterene); when associated with a metabolic alkalosis (chloride deficiency), the replacement should be potassium chloride.
-Normotensive salt sensitivity, a putative precursor of hypertension, might be quite frequent in African Americans (blacks) and less frequent in Caucasian Americans (whites), but only when dietary potassium is deficient and not when maintained well within the normal range. We tested this hypothesis in 41 metabolically controlled studies of 38 healthy normotensive men (24 blacks, 14 whites) who ate a basal diet low in sodium (15 mmol/d) and marginally deficient in potassium (30 mmol/d) for 6 weeks. Throughout the last 4 weeks, NaCl was loaded (250 mmol/d); throughout the last 3, potassium was supplemented (as potassium bicarbonate) to either mid- or high-normal levels, 70 and 120 mmol/d. Salt sensitivity, defined as an increase in mean arterial blood pressure >/=3 mm Hg with salt loading, was deemed "moderate" if increasing </=10 mm Hg and "severe" if increasing more. When dietary potassium was 30 mmol/d, salt loading induced a mean increase in blood pressure only in blacks (P<0.001), and salt sensitivity occurred in most blacks but not whites (79% vs 36% (P<0.02). Supplementing potassium only to 70 mmol/d attenuated moderate salt sensitivity similarly in blacks and whites; 120 mmol/d abolished it, attenuated severe salt sensitivity, which occurred in a quarter of affected blacks, and suppressed the frequency and severity of salt sensitivity in blacks to levels similar to those observed in whites. These observations demonstrate that in most normotensive black men but not white men, salt sensitivity occurs when dietary potassium is even marginally deficient but is dose-dependently suppressed when dietary potassium is increased within its normal range. Such suppression might prevent or delay the occurrence of hypertension, particularly in the many blacks, in whom dietary potassium is deficient.
Although chronic potassium deficiency is a common clinical problem, the hemodynamic consequences of chronic sustained potassium depletion have not been clearly delineated. In this study, the hemodynamic consequences of chronic potassium depletion were evaluated in the conscious rat. Potassium-depleted rats had a decrease in mean arterial pressure which was caused by a decrease in systemic vascular resistance. In association with these changes in systemic hemodynamics, renal blood flow (RBF) was also decreased. The decreased renal blood flow was caused by an increased renal vascular resistance (RVR). Because plasma renin activity was increased the role of angiotensin II as a renal vasoconstrictor was evaluated by utilizing two angiotensin antagonists. Although the administration of saralasin to potassium-depleted rats did not alter systemic hemodynamics, RVR was decreased and RBF was increased. Similar results were obtained with the converting enzyme inhibitor teprotide. Because products of endoperoxide metabolism may cause renal vasoconstriction, the role of prostaglandins and thromboxanes as renal vasoconstrictors were evaluated by utilizing cyclo-oxygenase and thromboxane synthetase inhibitors. None of these agents altered systemic hemodynamics. Following the administration of indomethacin, RVR was decreased and RBF was increased in potassium-depleted rats. Similar results were obtained with another cyclo-oxygenase inhibitor, meclofenamate, and with imidazole, an inhibitor of thromboxane synthetase. Because neither angiotensin II nor products of endoperoxide metabolism could alone account for the increased renal vascular resistance of potassium depletion, studies were performed in potassium-depleted rats treated with indomethacin plus either saralasin or teprotide. In these potassium-depleted animals, renal blood flow was restored to normal. In conclusion, the decrease in renal blood flow and the increase in renal vascular resistance in potassium depletion is mediated by angiotensin II and a product of prostaglandin endoperoxide metabolism, most likely, thromboxane.
Potassium depletion in rats augments the specific renal lesions of phosphate loading. Since it has been shown that phosphate loading increases the specific cardiac lesions of potassium deficiency (12), it is concluded that the similar types of electrolyte imbalance (potassium depletion-phosphate load) act conversely in the two organs.
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An H(+)-K(+)-adenosinetriphosphatase (H(+)-K(+)-ATPase) contributes to potassium reabsorption by the collecting ducts of the rat kidney. mRNAs for two isoforms of the H(+)-K(+)-ATPase, HK alpha 1 and HK alpha 2, have been found in the rat kidney. To evaluate whether the HK alpha 1 and HK alpha 2 proteins are present in the rat kidney, microsomes enriched in HK alpha 1 or HK alpha 2 were isolated using the MiniMac magnetic separation system with antibodies directed against either HK alpha 1 (HK 12.18) or HK alpha 2 (AS 31.7). Immunoblots of rat kidney microsomal protein isolated with HK 12.18 revealed a band approximately 94 kDa in size that comigrated with the G1 fraction of the stomach. Immunoblots of rat kidney microsomal protein isolated with AS 31.7 revealed a band slightly greater than 94 kDa that comigrated with a band obtained from rat colonic microsomal protein. To examine the effect of perturbations in potassium metabolism, the abundance of the HK alpha 1 and HK alpha 2 isoforms was compared in rats fed a normal or potassium-deficient diet. A low-potassium diet increased the abundance of HK alpha 2, whereas that of HK alpha 1 was not altered. These data suggest that HK alpha 2 might be the isoform responsible for potassium conservation by the kidney.
OBJECTIVE: To describe profound hypokalemia in a comatose patient with diabetic ketoacidosis. METHODS: We present a case report, review the mechanisms for the occurrence of hypokalemia in diabetic ketoacidosis, and discuss its management in the setting of hyperglycemia and hyperosmolality. RESULTS: A 22-year-old woman with a history of type 1 diabetes mellitus was admitted in a comatose state. Laboratory tests revealed a blood glucose level of 747 mg/dL, serum potassium of 1.9 mEq/L, pH of 6.8, and calculated effective serum osmolality of 320 mOsm/kg. She was intubated and resuscitated with intravenously administered fluids. Intravenous administration of vasopressors was necessary for stabilization of the blood pressure. Intravenous infusion of insulin was initiated to control the hyperglycemia, and repletion of total body potassium stores was undertaken. A total of 660 mEq of potassium was administered intravenously during the first 12.5 hours. Despite such aggressive initial repletion of potassium, the patient required 40 to 80 mEq of potassium daily for the next 8 days to increase the serum potassium concentration to normal. CONCLUSION: Profound hypokalemia, an uncommon initial manifestation in patients with diabetic ketoacidosis, is indicative of severe total body potassium deficiency. Under such circumstances, aggressive potassium repletion in a comatose patient must be undertaken during correction of other metabolic abnormalities, including hyperglycemia and hyperosmolality. Intravenously administered insulin should be withheld until the serum potassium concentration is (3)3.3 mEq/L.
Evidence for interactions between amino acid and electrolyte metabolism is reviewed. Variations in dietary sodium, potassium, and chloride concentrations affect acid-base balance and also influence the severity of the lysine-arginine antagonism. High dietary levels of Na and K salts of metabolizable organic acids alleviate, whereas excessive dietary chloride exacerbates, the antagonism. Potassium deficiency causes depletion of intracellular potassium and increased intracellular accumulation of basic amino acids. These variations in electrolytes, which alter acid-base balance, also influence the metabolism of glutamic acid and the excretion of nitrogen. It is hypothesized that basic amino acids as well as glutamic acid and glutamine may have an important role in metabolic regulation of acid-base balance.