Hyperkalaemia

Question 1

Define Hyperkalaemia

Answer 1

Defined as a serum potassium concentration >= 5.5mmol/L

Normal range: 3.5-5.5 mmol/L

Question 2

Potassium is primarily found where?

a) Intracellularly
b) Extracellularly

Answer 2

a) Intracellularly (~98% of K+ in the body)

Question 3

Potassium is predominantely secreted by?

Answer 3

The kidneys

Question 4

What is the most abundant intracellular cation

Answer 4

Potassium

Question 5

What 3 mechanisms regulate potassium levels

Answer 5

Aldosterone

Acid-base balance

Insulin levels

Question 6

Why is metabolic acidosis associated with hyperkalaemia

Answer 6

Hydrogen and potassium ions compete with each other for exchange with sodium ions (Sodium potassium ATPase) across cell membranes and in the distal tubule

Acidosis results in decreased cellular uptake of potassium as potassium is released in exchange for hydrogen ions

Question 7

Hyperkalaemia causes can be broadly categories into 2 categories.

Name them

Answer 7

Because of impaired potassium excretion

Because of increased K release from cells

Question 8

Name some of the causes that cause hyperkaelamia secondary to impaired potassium excretion

Answer 8

Acute kidney injury

Chronic kidney disease

Medications e.g. ACE inhibitors, Potassium sparing diuretics e.g. spironolactone, heparin, trimethoprim

Addison’s disease

Question 9

Name three potential causes that cause hyperkaelamia secondary to increased potassium release from cells

Answer 9

Lactic acidosis

Insulin deficiency

Rhabdomyolysis

Question 10

What kind of symptoms do the majority of patients with hyperkalaemia have

Answer 10

Patients are usually asymptomatic however in severe cases they may have arrhythmias

Question 11

The majority of patients with hyperkalaemia are asymptomatic.

If they do have symptoms what are they?

Answer 11

Fatigue

Generalised weakness

Chest pain

Palpitations

Question 12

The majority of patients with hyperkalaemia are asymptomatic.

If they do have signs what are they?

Answer 12

Arrhythmias

Reduced power

Reduced reflexes

Question 13

How is hyperkalaemia diagnosed

Answer 13

Hyperkalaemia is diagnosis by anything that detects serum potassium i.e. U+Es, ABG/VBG.

If you need rapid assessment then us VBG/ABG

Question 14

What investigations help in assessing hyperkalaemia

Answer 14

Bloods (anything that detects serum potassium)

• U&Es
• VBG/ABG
• Urinary potassium

Other

• ECG - to check for arrhythmias

Question 15

What are the typical ECG features seen in hyperkalaemia

Answer 15

Peaked or ‘tall tented’ T waves

Prolonged PR interval (> 200 ms)

Widening of the QRS interval (> 120 ms)

Small, or absent, P waves

Eventually leads to Sine wave pattern (terminal sign) and asystole i.e. flatline

Question 16

What is asystole:

a) Shoackable wave length
b) Non-shockable wave length

Answer 16

b) Non-shockable wave length

Question 17

The treatment of hyperkalaemia is dependent on the plasma concentration of potassium and the presence/absence of ECG changes.

When would you need urgent treatment in mild hyperkalaemia

Answer 17

Do not need urgent treatment.

Changes in diet and contributing drugs should be enough

Question 18

The treatment is hyperkalaemia dependent on the plasma concentration of potassium and the presence/absence of ECG changes.

When would you need urgent treatment in moderate hyperkalaemia

Answer 18

If there is ECG changes present

Question 19

The treatment for hyperkalaemia is dependent on the plasma concentration of potassium and the presence/absence of ECG changes.

When would you need urgent treatment in severe hyperkalaemia

Answer 19

Always required - even in the absence of ECG changes

Question 20

What is the serum potassium level range in mild hyperkalaemia

Answer 20

5.5-6 mmol/L

Question 21

What is the serum potassium level range in moderate hyperkalaemia

Answer 21

6 - 6.4 mmol/L

Question 22

What is the serum potassium level range in severe hyperkalaemia

Answer 22

>= 6.5 mmol/L

Question 23

What is the mainstay of treatment for hyperkalaemia

Answer 23

Insulin and dextrose infusion

AND

IV calcium gluconate

Question 24

IV insulin and dextrose is used in the management of hyperkalaemia.

How does it work?

Answer 24

Insulin (e.g. actrapid 10 units) and dextrose (e.g. 50mls of 50%)

Insulin drives the glucose into the cells, potassium is taken with it, thus reducing serum potassium levels

Dextrose is given to prevent any hypoglycaemia associated with insulin administration

Question 25

IV calcium gluconate is part of the management of hyperkalaemia.

How does it work?

Answer 25

10ml of 10% calcium gluconate (or chloride) over 10 mins

Cardioprotective – stabilises the cardiac muscles cells reducing the risk of arrhythmias

Does not lower serum potassium levels, merely stablises the myocardium

Question 26

The mainstay of hyperkalaemia treatment is with an insulin and dextrose infusion and IV calcium gluconate.

What other options are available

Answer 26

Nebulised salbutamol – temporarily drives potassium into cells.

IV fluids –increases urine output, which encourages potassium loss from the kidneys

Oral calcium resonium – moves potassium out of the gut and into the stools. It works slowly and is suitable for milder cases of hyperkalaemia.

Sodium bicarbonate (IV or oral) – only used by renal specialist

Dialysis – required in severe or persistent cases associated with renal failure

Question 27

Oral calcium resonium is an option to treatment hyperkalaemia.

In what incidience is suitable for

Answer 27

Suitable for milder cases of hyperkalaemia

Question 28

In a patient with hyperkalaemia and ECG changes.

What is the single most appropriate management

Answer 28

IV calcium gluconate - cardioprotective

Question 29

What is the first line management in hyperkalaemia

Answer 29

Calcium gluconate - cardioprotective preventing arrhythmias

Then given IV insulin and dextrose

Question 30

What is the mechanism of action of calcium gluconate in the management of hyperkalaemia

Answer 30

Calcium gluconate reduces excitability of cardiac myocytes thus reducing the likelihood of developing life threatening arrhythmias

Question 31

How does rampiril cause hyperkalaemia

Answer 31

Rampiril is an example of an ACE inhibitor

Causes hyperkalaemia by blocking the aldosterone pathway thereby leading to a retention of potassium

Question 32

If a patient has a diagnosis of hyperkalaemia from blood work.

What is the most important next line investigation

Answer 32

ECG - to check for arrhythmias

Question 33

What is the mechanism of action of calcium resonium in the management of mild hyperkalaemia

Answer 33

Moves potassium out of the gut and into the stools

Works slowly

Question 34

Give an example of a potassium sparing diuretics

Answer 34

Spironolactone

Question 35

The mainstay of hyperkalaemia treatment is with an insulin and dextrose infusion and IV calcium gluconate.

Why is insulin and dextrose given (seems counterintuitive)

Answer 35

Insulin causes intracellular K+ shift and glucose to required to prevent hypoglycaemia