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Why Does Potassium Increase In Acidosis?

Effects Of Ph On Potassium: New Explanations For Old Observations

Effects Of Ph On Potassium: New Explanations For Old Observations

Go to: Abstract Maintenance of extracellular K+ concentration within a narrow range is vital for numerous cell functions, particularly electrical excitability of heart and muscle. Potassium homeostasis during intermittent ingestion of K+ involves rapid redistribution of K+ into the intracellular space to minimize increases in extracellular K+ concentration, and ultimate elimination of the K+ load by renal excretion. Recent years have seen great progress in identifying the transporters and channels involved in renal and extrarenal K+ homeostasis. Here we apply these advances in molecular physiology to understand how acid-base disturbances affect serum potassium. The effects of acid-base balance on serum potassium are well known.1 Maintenance of extracellular K+ concentration within a narrow range is vital for numerous cell functions, particularly electrical excitability of heart and muscle.2 However, maintenance of normal extracellular K+ (3.5 to 5 mEq/L) is under two potential threats. First, as illustrated in Figure 1, because some 98% of the total body content of K+ resides within cells, predominantly skeletal muscle, small acute shifts of intracellular K+ into or out of the extracellular space can cause severe, even lethal, derangements of extracellular K+ concentration. As described in Figure 1, many factors in addition to acid-base perturbations modulate internal K+ distribution including insulin, catecholamines, and hypertonicity.3,4 Rapid redistribution of K+ into the intracellular space is essential for minimizing increases in extracellular K+ concentration during acute K+ loads. Second, as also illustrated in Figure 1, in steady state the typical daily K+ ingestion of about 70 mEq/d would be sufficient to cause large changes in extracellular K+ were it not for Continue reading >>

Metabolic Acidosis

Metabolic Acidosis

Practice Essentials Metabolic acidosis is a clinical disturbance characterized by an increase in plasma acidity. Metabolic acidosis should be considered a sign of an underlying disease process. Identification of this underlying condition is essential to initiate appropriate therapy. (See Etiology, DDx, Workup, and Treatment.) Understanding the regulation of acid-base balance requires appreciation of the fundamental definitions and principles underlying this complex physiologic process. Go to Pediatric Metabolic Acidosis and Emergent Management of Metabolic Acidosis for complete information on those topics. Continue reading >>

Potassium And Acidosis

Potassium And Acidosis

Balance among electrically charged atoms and molecules is essential to maintaining chemical equilibrium in your body. Potassium is the most abundant, positively charged atom inside your cells. Because acids and potassium both have a positive electrical charge in your body, their concentrations are interdependent. Medical conditions that cause an overabundance of acids in your blood, known as acidosis, may affect your blood potassium level, and vice versa. Video of the Day Metabolic acidosis is an abnormally low blood pH caused by overproduction of acids or failure of your kidneys to rid the body of acids normally. With metabolic acidosis, your blood has an abnormally high level of positively charged hydrogen atoms, or hydrogen ions. To reduce the acidity of your blood, hydrogen ions move from your circulation into your cells in exchange for potassium. The exchange of hydrogen for potassium ions helps relieve the severity of acidosis but may cause an abnormally high level of blood potassium, or hyperkalemia. Drs. Kimberley Evans and Arthur Greenberg reported in a September 2005 article published in the "Journal of Intensive Care Medicine" that there is a 0.3 to 1.3 mmol/L increase in blood potassium for every 0.1 decrease in pH with metabolic acidosis. Metabolic Acidosis Recovery Correction of the underlying medical problem responsible for metabolic acidosis typically leads to normalization of your blood pH. Although blood potassium is typically elevated with metabolic acidosis, a substantial amount of your total body potassium stores can be lost through the kidneys, causing a total body deficit. As your blood pH returns to normal, potassium moves from your bloodstream back into your cells. If your total body potassium stores have been depleted, your blood concentration Continue reading >>

Potassium Balance In Acid-base Disorders

Potassium Balance In Acid-base Disorders

INTRODUCTION There are important interactions between potassium and acid-base balance that involve both transcellular cation exchanges and alterations in renal function [1]. These changes are most pronounced with metabolic acidosis but can also occur with metabolic alkalosis and, to a lesser degree, respiratory acid-base disorders. INTERNAL POTASSIUM BALANCE Acid-base disturbances cause potassium to shift into and out of cells, a phenomenon called "internal potassium balance" [2]. An often-quoted study found that the plasma potassium concentration will rise by 0.6 mEq/L for every 0.1 unit reduction of the extracellular pH [3]. However, this estimate was based upon only five patients with a variety of disturbances, and the range was very broad (0.2 to 1.7 mEq/L). This variability in the rise or fall of the plasma potassium in response to changes in extracellular pH was confirmed in subsequent studies [2,4]. Metabolic acidosis — In metabolic acidosis, more than one-half of the excess hydrogen ions are buffered in the cells. In this setting, electroneutrality is maintained in part by the movement of intracellular potassium into the extracellular fluid (figure 1). Thus, metabolic acidosis results in a plasma potassium concentration that is elevated in relation to total body stores. The net effect in some cases is overt hyperkalemia; in other patients who are potassium depleted due to urinary or gastrointestinal losses, the plasma potassium concentration is normal or even reduced [5,6]. There is still a relative increase in the plasma potassium concentration, however, as evidenced by a further fall in the plasma potassium concentration if the acidemia is corrected. A fall in pH is much less likely to raise the plasma potassium concentration in patients with lactic acidosis Continue reading >>

On The Relationship Between Potassium And Acid-base Balance

On The Relationship Between Potassium And Acid-base Balance

The notion that acid-base and potassium homeostasis are linked is well known. Students of laboratory medicine will learn that in general acidemia (reduced blood pH) is associated with increased plasma potassium concentration (hyperkalemia), whilst alkalemia (increased blood pH) is associated with reduced plasma potassium concentration (hypokalemia). A frequently cited mechanism for these findings is that acidosis causes potassium to move from cells to extracellular fluid (plasma) in exchange for hydrogen ions, and alkalosis causes the reverse movement of potassium and hydrogen ions. As a recently published review makes clear, all the above may well be true, but it represents a gross oversimplification of the complex ways in which disorders of acid-base affect potassium metabolism and disorders of potassium affect acid-base balance. The review begins with an account of potassium homeostasis with particular detailed attention to the renal handling of potassium and regulation of potassium excretion in urine. This discussion includes detail of the many cellular mechanisms of potassium reabsorption and secretion throughout the renal tubule and collecting duct that ensure, despite significant variation in dietary intake, that plasma potassium remains within narrow, normal limits. There follows discussion of the ways in which acid-base disturbances affect these renal cellular mechanisms of potassium handling. For example, it is revealed that acidosis decreases potassium secretion in the distal renal tubule directly by effect on potassium secretory channels and indirectly by increasing ammonia production. The clinical consequences of the physiological relation between acid-base and potassium homeostasis are addressed under three headings: Hyperkalemia in Acidosis; Hypokalemia w Continue reading >>

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