Potassium

Question 1

What is the normal serum potassium range?

Answer 1

3.5-5.5 mmol/L

Question 2

Where is potassium primarily located in the body?

Answer 2

Predominantly intracellular

Question 3

How is potassium concentration regulated?

Answer 3

Primarily regulated by the Na+/K+ ATPase pump and renal excretion and reabsorption.

Question 4

Define hypokalemia.

Answer 4

Serum potassium concentration <3.5 mmol/L.

Question 5

Name the main categories of hypokalemia causes.

Answer 5

1) GI losses: vomiting & diarrhoea
2) renal losses: Conns (hyperaldosteronism), thiazide & loop diuretics, omsotic diuresis, bartter & gittlemans
3) cell influx: insulin, salbutamol, refeeding syndrome, metabolic alkalosis
4) rarely tubular acidosis 1 & 2, or hypomagnesiaemia

Question 6

What are some common symptoms of hypokalemia?

Answer 6

Muscle weakness, cardiac arrhythmias, polyuria, and polydipsia, cramps, hypotonia

Question 7

what are hypokalameia ECG changes?

Answer 7

flattened/inverted T waves
prominent U wave
prolonged PR
ST depression

“hypUkalaemia”

Question 8

how do you treat hypokalaemia?

Answer 8

-if serum K+ between 3-3.5 = oral KCl (2 sandoK sablets)
-if serum K+ <3 = IV KCl (max rate 10mmol/hr cos of cardiac arrest risk)

Question 9

what is bartter syndrome

Answer 9

defect in thick ascending limb (triple transporter not working) causing hypokalemia, alkalosis (low K+ so low H+) & hypotension

Question 10

what is gitelmann syndrome

Answer 10

mild K+ transporting defect in DCT (Na+/Cl-) transporter not working (like thiazide diuretics)

Question 11

what happens in renal tubular acidosis generally

Answer 11

failure of body to acidify urine
-causes an absurd acidosis & hypokalameia in 1 & 2 - this is opposite of normal as acidosis normally occurs with hyperkalaemia

Question 12

what happens in renal tubular acidosis type 1?

Answer 12

-DCT defect
-failure of H+ excretion and subsequent acidosis (metabolic) and hypokalemia (failed H+/K+ pump)
-most severe

Question 13

what happens in renal tubular acidosis type 2?

Answer 13

-defect in PCT = milder
-cant reabsorb bicarbonate - leads to acidosis & hypokalameia

Question 14

what happens in renal tubular acidosis type 4?

Answer 14

aldosterone deficiency or resistance (mild) - acidosis & HYPERkalameia

Question 15

Define hyperkalemia

Answer 15

Serum potassium concentration >5.5 mmol/L

Question 16

What are the main categories of hyperkalemia causes?

Answer 16

1) artefact: haemolysis
2) excessive intake: blood transfusion, oral, parenteral
3)movement of potassium out of cells : acidosis, DNA (insulin shortage), rhabdomyolysis (damage)
3)decreased excretion : acute renal failure (oligouric phase), CKD (late)
4) drugs: spironolactone, ACEi, ARB, NSAIDs

others: addisons, type 4 renal tubular acidosis

Question 17

If urine dip positive for blood but no erythrocytes on microscopy?

Answer 17

myoglobin in urine (rhabdomyolysis)

Question 18

ECG changes associated with hyperkalaemia? mnemonic?

Answer 18

Peaked T waves, prolonged PR interval, widened QRS complex, loss of P waves. In severe cases, a sine wave pattern can develop.

Mnemonic: P waves gone, T waves tall, QRS wide

Question 19

when do you treat hyperkalaemia usually?

Answer 19

potassium >5.5 with ECG changes or potassium >6.5 regardless of ECG changes

Question 20

what is the first step if K+ >6,5 and asymptomatic?

Answer 20

repeat blood sample, may be artefact

Question 21

treatment of hyperkalaemia?

Answer 21

-10ml 10% calcium gluconate (cardioprotective - stabilised cardiac membrane)
-100 mls 20% dextrose + 10 units short acting insulin (actrapid)

other options: nebulised salbutamol, calcium resonium or dialysis

Question 22

what caution should be taken in correcting hyperkalemia in those on digoxin?

Answer 22

cardiac monitoring as calcium IV may precipitate arrythmias

Question 24

mnemonic for hyperkalaemia treatment?

Answer 24

10 10 10 100 20

10 mls 10% calcium gluconate
10 units actrapid
100 mls 20% dextrose