Hypokalaemia

Question 1

Under what level is classed as:

• Mild
• Moderate
• Severe

Answer 1

< 3.5 mmol/L

< 3 mmol/L

<2.5 mmol/L

Question 2

Pathophysiology:

Why is muscle excitability lowered?

Answer 2

Low serum K

An increased gradient from ICF to ECF

Increased leakage from ICF

Hyperpolarisation of myocyte membrane (inc. cardiac)

Harder to reach action potential

Reduces muscle excitability

Question 3

Pathophysiology:

How does it affect GFR?

Why does bicarbonate levels increase? - think carefully!

Does it lower or increase insulin secretion?

What cardiac drug does it worsen the toxicity of?

Answer 3

Lowered GFR

First, hypokalemia results in the shift of hydrogen ions intracellularly. The resulting intracellular acidosis enhances bicarbonate reabsorption in the collecting duct. Second, hypokalemia stimulates the apical H+/K+ ATPase in the collecting duct.

Lowered insulin secretion - opposite for hyper - they could get hyperglycaemia

Digoxin

Question 4

Causes:

GI loss - causes?

Diuretics - which types? - 2

What acid-base imbalance can cause this?

What diabetic complication results in this?

Answer 4

D&V
Fistula

Thiazides
Loop

Metabolic alkalosis

First, hypokalemia results in the shift of hydrogen ions intracellularly. The resulting intracellular acidosis enhances bicarbonate reabsorption in the collecting duct. Second, hypokalemia stimulates the apical H+/K+ ATPase in the collecting duct.

DKA - K leaves cells and is lost in the urine

Question 5

S+S:

CV:

• They may be asymptomatic but have ECG changes!
• They get arrhythmias. What are some symptoms of this?

They have confusion and lethargy as APs are slowed. - They have similar symptoms of having damage to a nerve. What symptoms will they have?

Organ-specific - how does it affect the following? (think about what it is)

• Resp
• GI
• Urinary

Answer 5

Altered HR
Palpitations
Light-headed

Paraesthesia 
Flaccid weakness 
Hyporeflexia
Myalgia 
Tetany 
Cramps 
Rhabdomyolysis 

Shallow breathing and resp failure

Constipation

Polyuria

Question 6

Investigations:

What ECG changes do they have? - think about it slowing everything down

What needs to be done to distinguish between renal and non-renal losses?

Answer 6

P widening
T flattening or inversion
ST depression
Prominent U

Urine K

Question 7

Management:

K replacement:

What is important to remember when giving supplementation?

Answer 7

You have to give it slowly