Internal Medicine – Hyperkalemia: By Ben Schelew M.D.

By Adem Lewis / in , , , , , , , , , /

Potassium is a naturally occurring element
with an atomic number of 19. It is the major positive ion inside animal cells. Potassium
is critical for several physiologic functions including neurotransmission, muscle contraction,
and heart function. If potassium levels become too high – a
condition called hyperkalemia – many of the body’s functions can become dysfunctional.
Because this is a potentially lethal condition, hyperkalemia is something that you cannot
afford to miss. Our bodies have a large store of potassium
but we require dietary intake to maintain safe levels. Our kidneys filter potassium,
then secrete or reabsorb it depending on our body’s need. The causes of hyperkalemia can be divided
into three main categories: Dietary intake can be excessive (too much
in); Renal impairment can result in accumulation
(not enough out); or The ion can be transferred out of cells (shift). Excessive intake is rare and really limited
to iatrogenic causes – or caused by medical intervention. For instance, the overtreatment
of hypokalemia by overshooting desired potassium levels is a cause. Eating foods that are rich
in potassium, like bananas, is not a cause. In fact, even though monkeys love bananas,
they manage to avoid hyperkalemia! Renal causes are a common cause of hyperkalemia.
These may include acute or chronic renal failure and deficiencies of the hormone aldosterone,
which regulates potassium levels – as in Addison’s disease. Other things that can
affect renal function – like the effect of drugs on glomerular filtration, as in the
case of NSAIDs, ACE inhibitors, ARBs, or potassium sparing diuretics like spironolactone or amiloride
– can also cause high levels of potassium. Finally, potassium can be released from cells
into the serum. This can happen due to tissue damage like rhabdomyolysis, burns, or necrosis
from blood cells during a massive transfusion or hemolysis, or transported out of cells
in the case of acidosis, low insulin levels or beta-blocker therapy. There are really no signs or symptoms of hyperkalemia.
The ECG may show signs of hyperkalemia, including small P waves, peaked T waves, progressing
to widened QRS, and finally a sinusoidal shape. The most impactful therapy of hyperkalemia
is CALCIUM! Calcium stabilizes the myocardium preventing fibrillation. One gram of calcium
chloride or calcium gluconate is administered intravenously every few minutes until the
ECG reverts to normal. Then one can work on shifting it back into cells with insulin or
ventolin, or ridding it from the body with diuretics or using dialysis.

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