Hyperkalaemia Flashcards
what are the ranges of potassium?
Normal- 3.5-5.5 mmol/L
hyperkalaemia- >5.5 mmol/L
mild- 5.5-5.9 mmol/L
moderate- 6.0-6.4 mmol/L
severe- >6.5 mmol/L
describe the pathophysiology of hyperkaleamia
About 98% of total body potassium (K+) is Intracellular and off this, 75% is contained in skeletal muscle cells.
The remaining 2% extracellular component is maintained within a tight range of 3.5 to 5.5 mEq/L (1 mmol equals 1 mEq K+) by the body.
The main mechanism by which this trans-cellular ratio is maintained is through the sodium-potassium (Na-K) adenosine triphosphatase (ATPase) pump. It uses ATP to drive K+ into cells in exchange for sodium (Na).
The resulting K+ gradient creates a resting membrane potential that determines cardiac and neuromuscular cell excitability and signal conduction
Because the extracellular K+ level is proportionally so much less than the intracellular level, even a small change in the extracellular level significantly alters the resting membrane potential.
This leads to decrease muscle contractile strength, evident in the typical clinical presentation (see below)
what are the causes of hyperkalaemia?
imbalance between intake + excretion
