Reading a Chemistry, K / Potassium

Potassium is an intracellular cation although it is passed across cell membranes to alter cell polarity.  It plays a key role in cardiac rhythm and rate, the kidney's ability to handle sodium, and acid-base metabolism.  Potassium and sodium absorption and excretion are usually tied to one another, so excesses or deficiencies of one of these electrolytes often effects the other.

Increased potassium or "hyperkalemia" may occur due to:
-Artifact: due to sample clotting (K is released for platelets as they clot) or hemolysis especially in horses and pigs (since potassium is found in high concentrations inside of cells, when the cells are lysed the potassium leaks out making it appear that there is more potassium in the extracellular fluid than expected)
-Cell rupture: due to over-exercise, tissue necrosis, etc.
-Leukocytosis: very high WBC counts can result in hyperkalemia due to cell leakage.
-Drugs: Trimethoprim induces hyperkalemia by inhibiting sodium resorption in the cortical collecting ducts of the kidney.
-Metabolic acidosis: potassium gets redistributed as the body tries to deal with the acidosis.
-Decreased renal excretion: in cases of oliguria or anuria such as blocked toms.
-Ruptured urinary bladder: if this is the case Na and Cl will be low (hyponatremia and hypochloremia)
-Inherited conditions: such as Hyperkalemic polymyopathy of horses.

*Observe your patient: Hyperkalemia will result in cardiac malfunction and generalized muscle weakness. 

Decreased potassium or "hypokalemia" may occur due to:
-Artifact: lipemia may cause a pseudohypokalemia
-Decreased intake: due to dietary insufficiency, anorexia,
-Redistribution: this may occur due to hormones including insulin and catecholamine so it can be brought on via bolus glucose administration, stress, or excitement.
-Fecal loss: if large amounts of sodium are being absorbed in the large intestine large amounts of potassium may be lost.
 -Renal losses: Increased GFR in the kidney: this will decrease reabsorption leading to hypokalemia.  Increased sodium excretion by the kidney: potassium is excreted along with sodium.
-Metabolic alkalosis
-Mineralcorticoids: such as aldosterone increase renal tubular resorption of sodium can result in potassium excretion by the kidney.  This can be due to administration of drugs, neoplasia, or other disorders.

*Observe your patient: Hypokalemia can result in restlessness, generalized muscle weakness, cardiac arrhythmia and death.