HYPERKALEMIA and HYPOKALEMIA

What are the most common causes of hyperkalemia?

Impaired renal function with increased potassium intake Tissue breakdown Blood transfusion Transcellular shift (e.g., hyperkalemic periodic paralysis, acidosis) Mineralocorticoid deficiency (e.g., as a result of type IV RTA, ACE-Is or ARB use, Addison disease)

What are the symptoms and signs of hyperkalemia, and at what levels of PK do they occur?

Muscle weakness and impaired cardiac conduction, associated with ventricular arrhythmias; these tend to occur at a PK > 7-8 mEq/L.

What are the electrocardiographic manifestations of hyperkalemia?

K = 6-7 mEq/L: Peaked T waves
K = 7-8 mEq/L: Flattened P wave, prolonged PR, depressed ST segment, peaked T waves
K = 8-9 mEq/L: No P, widened QRS, peaked T waves
K > 9 mEq/L: Sine wave pattern

How does the TTKG help to determine the cause of hyperkalemia?

TTKG should be >7 in hyperkalemic states, indicating appropriate renal excretion. A lower value indicates impaired renal K+ secretion and excretion.

What is the appropriate management of hyperkalemia?

IV calcium gluconate is used to stabilize the cardiac membrane.
Potassium is effectively shifted into the intracellular space following administration of insulin (with D50 to prevent hypoglycemia), β-agonists such as albuterol, or manipulation of the pH by administration of IV sodium bicarbonate. Potassium can be eliminated from the body in 1 of the 3 ways: forced diuresis with furosemide, GI binding and excretion with sulfonate resin, or by dialysis.

What are the most common causes of hypokalemia?

GI losses (e.g., diarrhea) Renal losses (mineralocorticoid excess, RTA, diuretic use, osmotic diuresis, metabolic alkalosis) Transcellular shift (e.g., hypokalemic periodic paralysis)

What are the symptoms of hypokalemia?

Muscle weakness and cramps, cardiac arrhythmias, intestinal ileus, impaired urinary concentrating ability, and polyuria

What is the transtubular potassium gradient (TTKG)?

TTKG is a measure of renal K+ secretion: where UK and PK are urinary and plasma [K+], and Uosm and Posm are urinary and plasma osmolality.

How is the TTKG used to diagnose the cause of the hypokalemia?

TTKG should be

What other laboratory test may be helpful in determining the cause of hypokalemia?

A spot urine [K+] ≤ 15 mEq/L suggests that the kidney is not the source of K+ loss.

What is the appropriate management of hypokalemia?

Gradual repletion of potassium, orally or IV. Route and rate depend on severity of hypokalemia and symptoms.

At what rate may potassium be safely administered via an oral route?

KCl, 40-60 mEq doses, up to several hundred mEq/d, as tolerated

At what rate may potassium be safely administered via an IV route?

KCl, ≤40 mEq/L, at a rate of ~10-20 mEq/h through a peripheral vein. In emergency situations (e.g., life-threatening paralysis or arrhythmias), KCl may be given at a higher concentration and faster rate, but only through a central vein.

How does one estimate the magnitude of a potassium deficit?

A decrease of 1 mEq/L in serum [K+] represents a total body K+ deficit of approximately 200-400 mEq. A further decrease of 1 mEq/L represents an additional deficit of 200-400 mEq.