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Maintenance of potassium balance during long-term diuretic therapy in chronic heart failure patients with thiazide-induced hypokalemia: comparison of potassium supplementation with potassium chloride and potassium-sparing agents, amiloride and triamterene.
The relative efficacy of potassium chloride, amiloride and triamterene in maintaining potassium and magnesium balance was evaluated in 23 hypokalemic (S-K less than or equal to 3.5 mmol/l) patients with chronic heart failure receiving diuretic therapy. Amiloride and triamterene were administered in a randomized, crossover manner, followed by potassium chloride in an open manner. During a 5-month treatment with hydrochlorothiazide 50 mg twice/day, potassium chloride 1 g twice/day was not as effective as amiloride 5 mg or triamterene 75 mg twice/day in maintaining serum potassium and magnesium and total-body potassium, while amiloride and triamterene seemed to be equally effective. During all three supplementations, a decrease in serum potassium to a hypokalemic level was observed in some patients. The need for higher doses of potassium chloride, amiloride and triamterene was clearly concentrated to the same patients, and correction was easily reached by increasing the respective doses.
Action potential conduction block of nerves in vitro by potassium citrate, potassium tartrate and potassium oxalate.
OBJECTIVES: Potassium salts in desensitising formulations are believed to act by blocking nerve conduction. The aim of this study was to assess the ability of some organic potassium salts to block action potential conduction and to compare their effects with potassium chloride and potassium nitrate. MATERIALS AND METHOD: Potassium citrate, oxalate or tartrate were added to Krebs' solutions to raise the potassium concentration to 8-64 mM. The test solutions were applied to rat spinal nerves in a bath while monitoring the compound action potentials evoked by electrical stimulation. RESULTS: All potassium salts attenuated the compound action potential in a dose-dependent manner. There were no significant differences between the effects of potassium tartrate and potassium citrate solutions (p>0.1) which caused significantly greater compound action potential attenuation than the same concentrations of potassium oxalate (p<0.05). On the basis of the potassium ion concentration required to cause 50% attenuation of the compound nerve action potential, the relative potencies of the potassium salts were: citrate = tartrate> oxalate>chloride =nitrate. CONCLUSION: Potassium citrate and potassium tartrate were more effective than other potassium salts in blocking nerve conduction and may be more effective dentinal desensitising agents.
Potassium secretion by rat distal colon during acute potassium loading: effect of sodium, potassium intake and aldosterone.
1. Potassium secretion by the distal colon before and during intravenous infusion of a potassium load was measured in vivo in groups of rats treated in various ways: A, normal control; B, adrenalectomized; C, sodium depleted; D, on potassium-rich diet for 7 days; E, after 72 h aldosterone (1 microgram/h); F, after 72 h aldosterone (10 micrograms/h). 2. Potassium infusion produced no increase of secretion in the adrenalectomized rats but in all the other groups it increased by 2- to 3-fold. Secretion during infusion correlated well with the basal (pre-infusion) rate and in groups C and D reached 140 +/- 15 and 173 +/- 17 nmol min-1 cm-1 respectively compared with 28 +/- 6 nmol min-1 cm-1 in the controls (A). The passive paracellular pathway for potassium was unaffected by the infusion. Amiloride (100 mumol/l) did not significantly affect potassium secretion rate either before or during the acute potassium infusion. The potassium channel blocker, tetraethylammonium chloride, reduced both basal and the secretion rate during infusion. 3. Transepithelial potential difference (PD), active sodium absorption and sodium fluxes were similar in normal controls and rats fed the potassium-rich diet. However, the PD was partially amiloride sensitive in the latter group although amiloride insensitive in the normal group. In sodium-depleted rats, the PD was elevated and totally amiloride insensitive. 4. In both aldosterone-treated groups (E and F), basal potassium secretion rate was high and similar, and during potassium infusion rose 3-fold to 114 +/- 24 (E) and 105 +/- 5 (F) nmol min-1 cm-1. However, the PD was not elevated significantly in group E and was only partially amiloride sensitive, whereas in those infused at the higher rate (F) the PD was increased and was totally amiloride sensitive. 5. The high potassium secretion rates developed by this epithelium in sodium-restricted and potassium-enriched dietary states appear to depend on the presence of an amiloride-insensitive transcellular potassium pathway which is induced at a lower level of aldosterone stimulation than is the amiloride-sensitive transcellular sodium pathway.
Potassium maintenance. Potassium supplements or potassium sparing agents.
This paper reviews and presents data from a series of studies evaluating the extent of potassium depletion that occurs in various disease states and a comparison of the efficacy of potassium supplementation or potassium sparing diuretics in its correction. Changes in serum potassium levels are common after diuretics but are relatively minor in most people if small doses of diuretics are used. Total body potassium deficit is uncommon in people treated with a diuretic for hypertension and the fall in serum potassium results from alkalosis and a shift of potassium into the cell. Potassium sparing diuretics correct the potassium abnormality more readily than potassium supplements. Evidence is also presented that suggests that a high salt, low potassium diet may be an important cause of hypokalemia in people given diuretics.
Plasma potassium in patients with terminal renal failure during and after haemodialysis; relationship with dialytic potassium removal and total body potassium.
BACKGROUND: Chronic haemodialysis (HD) patients may present with severe predialysis hyperkalaemia which is improved by dialytic treatment. However, factors influencing the behaviour of postdialysis plasma potassium (plasma K) are not well known. METHODS: In this prospective study 14 patients (7 female, 7 male) on chronic HD were investigated during a standardized 4-h HD with a 2 m2 high-flux dialyser and up to 6 h postdialysis. Dialytic potassium removal was measured by dialysate collection. Total body potassium (TBK) was measured by whole-body counting of 40K. RESULTS: Plasma K declined from 5.65 to 3.62 mmol/l on HD. In spite of a total dialytic removal of 107 mmol of potassium plasma K rose to 5.01 mmol/16 h postdialysis. TBK, as adjusted for age, was 38.2 and 49.0 mmol/kg BW in female and male patients respectively, i.e. in the normal range. Of a total potassium removal of 107 mmol on HD only 42% originated from the extracellular space. Dialytic potassium removal was best correlated with removal of intracellular potassium but also with extracellular potassium content and with the product of plasma K x TBK. The 6-h postdialysis plasma K was correlated with the predialysis value but not with TBK or dialytic potassium removal. CONCLUSION: A rather high dialytic removal of potassium (which is correlated with plasma K x TBK) does not necessarily prevent a rapid postdialysis rebound of plasma K. Therefore patients with marked hyperkalaemia should be monitored closely postdialysis. TBK can be normal in haemodialysis patients who are well nourished.
[Serum potassium and urine potassium concentrations following single and repeated potassium load].
Levels of potassium concentration have been determined after single and repeated oral application of potassium. The maximum level of serumpotassium concentration was found about 2 hours after intake of 120 mval potassium. The concentration of potassium did not return to basic values within 24 hours. The concentration of potassium in urine increased during the first 4 hours. 6 to 12 hours later the maximum level is achieved. This leads to the conclusion that enterally applicated potassium is shifted into the intracellular space and is later released into the extracellular space. Repeated application of potassium in diminished dosages leads to reduced increased of serum and urin potassium concentration. The increase in concentration remains relatively constant during the whole period of application. For longterm therapy with oral potassium an application of a minimum dosage of 40 mval potassium in an 8 to 12 hours rhythm is reasonable.
Potassium recycling in the renal medulla: effects of acute potassium chloride administration to rats fed a potassium-free diet.
According to the hypothesis of potassium recycling in the renal medulla, a portion of potassium in fluid in the medullary collecting duct is reabsorbed, trapped in the medullary interstitium by countercurrent exchange, and secreted in either the pars recta or descending limb of the juxtamedullary nephron. To examine the effects of an acute change in potassium balance on recycling, we performed a micropuncture study on the exposed papilla of 8 chloride. A second group of 6 rats was studied under identical conditions and infused with potassium chloride and amiloride. In the first group, the fraction of filtered potassium remaining at the end of the juxtamedullary descending limb increased with time to values over 100% concomitantly with the rise in urinary excretion of potassium. A strong association was found between those two variables (P less than 0.025). In the second group, in which the increase in urinary fractional excretion of potassium was prevented by amiloride, the rise in fractional of filtered potassium remaining at the end of the juxtamedullary nephron was abolished. These findings are interpreted as providing further support for the hypothesis of medullary recycling of potassium.
Total body potassium, potassium retention and potassium intake in protein energy malnutrition.
The total body potassium (TBK) and potassium retention were measured during the early stages of recovery of malnourished children on three levels of potassium intake. A potassium intake of 2 mEq/kg/day resulted in significantly greater potassium retention than one of 3 mEq/kg/day. A higher level of intake (15 mEq/kg/day) did not result in an absolute increase in potassium retention and is not recommended because of its theoretical dangers, although it may have stimulated an increase in potassium capacity.
Effect of external potassium concentration on potassium uptake and potassium permeability of chicken enterocytes.
1. The effects of external potassium concentration on potassium uptake and potassium permeability have been investigated in isolated chicken enterocytes. 2. Ouabain-sensitive K+ uptake exhibited simple saturation kinetics with an apparent affinity constant, KT, of approximately, 1 mM K+. In the presence of ouabain, K+ uptake relates linearly with its external concentration, and the apparent diffusion constant, KD, was 1.3 nmol mg-1 protein mM-1 min-1. 3. Membrane potential, evaluated from the transmembrane TPP+ distribution ratio, was lower than the potassium equilibrium potential. 4. Estimated potassium permeability is decreased by low external potassium concentration and unaffected by high external potassium concentration.
[Intravenous loading by potassium aspartate and potassium chloride in the normal subject. Modifications of blood potassium, urinary potassium and the electrocardiogram].
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[Determination of the potassium ionic activity of potassium aspartate solution by using the potassium sensitive glass electrode. An electrophysiological study of the effect of L-potassium aspartate on renal tubular function of the rat. 3].
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[Further research on the role of prostanoids in controlling renal function in humans in normal potassium balance and acute experimental potassium depletion. II: Studies of potassium depletion].
The renal function was evaluated by clearance (cl.) method during hypotonic polyuria and successive relative antidiuresis induced by lysine-8-vasopressin (LVP) administration. Four 15 min and two 60 min cl. periods were performed during hypotonic polyuria and antidiuresis, respectively. Glomerular filtration rate was estimated by creatinine cl.; the osmotic cl. (Cosm'CH2O), the absolute and fractional excretions of water, sodium, potassium and chloride were determined by usual methods. The urinary PGE2, 6-keto-(-)PGF1 alpha and TxB2 concentrations were determined by RIA method. The study protocol was applied on 22 healthy women in acute potassium depletion obtained by natriuretic treatment combined with replacement on quantitative basis of net salt and water urinary losses either in normal potassium diet intake (50 meq/d) or in a low one (less than or equal to 10 meq/d). In Group D3 (n = 6) in the presence of a greater potassium cumulative deficit (198.4 +/- 22.2 meq), as compared to normal potassium balance, a significant reduction of kaliemia and a significant increase of PRA were present. During hypotonic poliuria, besides a marked renal potassium conservation, a significant decrease of creatinine cl., fractional chloride reabsorption (apparently at the diluting segments) and of urinary 6KPGF and TxB2 excretions, were observed. Urinary PGE2 excretion was n.s. reduced.
[The "anomalous" relationship between the concentration of potassium in the medium and the membrane potential of muscle fibers with a decreased intracellular potassium concentration. II. Rate of forward and reverse K42 transport through muscle fiber membranes in saccharose-sulfate solutions with potassium concentrations of 2.5 and 75 mM].
The measurements were made of the unidirectional potassium fluxes, the rate constants and the permeability coefficient. At external potassium 2.5 mM, the outflux and influx are 10--15, and 22-29 micromol/h g d. wt, respectively, and the net flux is comparable with the unidirectional fluxes. At external potassium 75 mM, the unidirectional fluxes increase up to 70--80 micromol/h, g d. wt. and the net flux does not exceed 0.1 of the unidirectional one. The outflux rate constant/influx rate constant ratio for both the potassium concentrations is about 1.5 times below the Ussing's ratio. This effect cannot be accounted for the single file phenomenon since it is independent of the direction and value of the net potassium flux. The discrepancy between the measured membrane potential and EK may, to some extent, be due to peculiarities of potassium movement.
[Further research on the role of prostanoids in controlling renal function in humans in normal potassium balance and acute experimental potassium depletion. III: Effects of indomethacin in potassium depletion].
The renal function was evaluated by clearance (cl.) method during hypotonic polyuria and successive relative antidiuresis induced by lysine-8-vasopressin administration. Four 15 min and two 60 min cl. periods were performed in hypotonic polyuria and antidiuresis, respectively. Glomerular filtration rate was estimated by creatinine cl., the osmotic cl. (Cosm' CH2O), the absolute and fractional excretions of water, sodium, potassium and chloride were determined by usual methods. The urinary PGE2, 6-keto-PGF1 alpha and TxB2 excretions were determined by RIA method. The study protocol was applied on 14 healthy women in acute potassium depletion, treated with indomethacin (100 mg i.m. at the end of the oral water load). In Group D3 (n = 6) in the presence of a greater potassium cumulative deficit (198.4 +/- 22.2 meq), in hypotonic polyuria, indomethacin induces significant effects as an increase of fractional hydro-electrolytic reabsorptions and as a decrease of urinary prostanoid excretion. The indomethacin tubular action in potassium depletion differs significantly from that observed in normal potassium balance.
Intracellular granules of the renal medulla in a case of potassium depletion due to renal potassium wasting. Electron microscopic comparison with renal medullary granules in the potassium-depleted rat.
An electron microscopic comparison was made of intracellular granules of the renal papilla and inner medulla in two types of potassium depletion: one in a 47-year-old white male with chronic potassium-wasting renal disease and the other in the experimentally depleted rat. The granules in both cases were composed of small and large vesicles; myelin figures; small particles; and dense bodies, with a partial, or complete, single limiting membrane. Ultrastructurally, the constituent elements of the granules were essentially the same in the two types of potassium depletion. It was concluded that the intracellular granules in the human tissue were the result of potassium depletion and a counterpart to those in the potassium-depleted rat.
[The "anomalous" relationship between the concentration of potassium in the medium and the membrane potential of muscle fibers with a decreased intracellular potassium concentration. I. Movement of potassium, accompanying ions and water].
A study was made of the electrogenesis on (Na+C1)-free muscles in potassiumsulfate media, with the membrane potential not corresponding to Ek. It was found that the potassium content in these muscles may change: at 2.5 mM external potassium, the internal potassium content decreases, whereas at 75 mM it increases. Undoubtedly, some other ions (phosphates?) apart from K+ do penetrate the muscle membrane. The evidence obtained disprove a previous idea that under the condition described it is potassium alone which is involved in potential genesis.
[The "anomalous" relationship between the concentration of potassium in the medium and the membrane potential of muscle fibers with a decreased intracellular potassium concentration. III. Change in the membrane potential during prolonged muscle incubation in saccharose-sulfate media containing 2.5 or 75 mM of potassium].
At the external potassium concentration 2.5 mM, The value Em--Ek diminishes, but at 75 mM it increases, although the potassium fluxes are nearly balanced and nosignificant changes in internal potassium occur. The contribution of other ions to the electrogenesis is examined. An attempt is made to describe the movement of these ions by the Goldman equations. The permeability coeficients should have been much higher than potassium coefficient, and besides it should be admitted that the coefficients and the internal activity of ions discussed may vary with time.