13. Potassium disorders

Question 1

Where is potassium mainly contained?

Answer 1

Within cells

Question 2

What are the classic features of changes in potassium?

Answer 2

Changes in the ECG

Question 3

How does potassium change in hyperkalaemia

Answer 3

Tall tented T wave
Small P wave
Broad QRS

Question 4

What are the different reasons for a high potassium

Answer 4

Kidney function is reduced
Redistribution
Increased intake

Question 5

What kidney problems cause hyerkaelemia?

Answer 5

Renal failure
ACE inhibitors- (reduced aldosterone, reduced K excretion)
Potassium sparing diuretics (sporonolactone)
Addison’s disease

Question 6

What is good to keep in mind for low serum sodium, high serum potassium

Answer 6

Addisons disease

Question 7

Explain redistribution hyperkalaemia

Answer 7

Metabolic Acidosis causes potassium to move out of the cell to maintain electroneutrality within the cell

Question 8

Discuss hyperkaelemia due to increased intake

Answer 8

Unlikely unless there is also impaired renal excretion
Over supplementation of IV fluids or TPN
Blood transfusion- potassium rich cells

Question 9

What is pseudohyperkalaemia?

Answer 9

High potassium on blood results although potassium is not actually that high within the body.

Question 10

What are the causes of pseudohyperkalaemia

Answer 10

Caused due to haemolysis when blood is being taken
Delayed centrifugation (RBC leaks out of cells)
Sample contamination
Increased platelet or white cell count

Question 11

Someones bloods show high potassium- what is teh first step

Answer 11

Look at drugs, heamolysis, renal failure, addisons,

Question 12

What are the less common causes?

Answer 12

Tumour lysis syndorme
Rhabdomyolsis
Metabolic acidossis

Question 13

What are the extremely extremely rare causes?

Answer 13

If youve got here get a second opinion. Paralysis diseases, pseduohyperkaelemia

Question 14

What can be given to correct potassium imbalance

Answer 14

Insulin (also give with glucose)
Salbutamol (nebulised)
Dialysis

Question 15

How do you tell between kidney injury and dehydrtion?

Answer 15

Urea and creatinine should be proportionately high (e.g. both doubled)

Question 16

What are the ECG chanegs on hypokalaemia?

Answer 16

Flattened T wave
U wave
Smaller QRS
Prolonged QT

Question 17

What causes hypokalaemia?

Answer 17

GI loss (Intestinal fistula, overuse of laxatives, V&D)
Increased renal excretion

Question 18

What causes hypokalaemia?

Answer 18

GI loss (Intestinal fistula, overuse of laxatives, V&D)
Increased renal excretion
redistriution

Question 19

What renal causes are there of hypokalaemia?

Answer 19

Diuretics
Magnesium syndrome- low potassium, low calcium
cushings syndrome- (excess cortisol causes)
Conn’s syndrome- (excess aldosterone causes)
Bartter’s or Gitelmans (rare)
Renal tubuar acidosis (rare)

Question 20

How does redistribution cause hypokaelmia

Answer 20

Insulin (high dose)
B2 agonsits (salbutamol)
Metabolic alkalosis

Question 21

What are the most common causes of hypokalaemia?

Answer 21

Vomiting, diorrea?
Surgery (fistula)
Drugs?
Metabolic alkalosis
Excess urinary loss? (renal vs gut loss)
Loop or thiazide diuretics

Question 22

At what rate should you give potassium?

Answer 22

Do not give IV potassium faster than 20mmol/hour
Monitor with ECg if giving faster than 10mmol

NEVER EVER EVER GIVE BOLUS POTASSIUM