Hyperkalaemia Flashcards
Define Hyperkalaemia
Defined as a serum potassium concentration >= 5.5mmol/L
Normal range: 3.5-5.5 mmol/L
Potassium is primarily found where?
a) Intracellularly
b) Extracellularly
a) Intracellularly (~98% of K+ in the body)
Potassium is predominantely secreted by?
The kidneys
What is the most abundant intracellular cation
Potassium
What 3 mechanisms regulate potassium levels
Aldosterone
Acid-base balance
Insulin levels
Why is metabolic acidosis associated with hyperkalaemia
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
Hyperkalaemia causes can be broadly categories into 2 categories.
Name them
Because of impaired potassium excretion
Because of increased K release from cells
Name some of the causes that cause hyperkaelamia secondary to impaired potassium excretion
Acute kidney injury
Chronic kidney disease
Medications e.g. ACE inhibitors, Potassium sparing diuretics e.g. spironolactone, heparin, trimethoprim
Addison’s disease
Name three potential causes that cause hyperkaelamia secondary to increased potassium release from cells
Lactic acidosis
Insulin deficiency
Rhabdomyolysis
What kind of symptoms do the majority of patients with hyperkalaemia have
Patients are usually asymptomatic however in severe cases they may have arrhythmias
The majority of patients with hyperkalaemia are asymptomatic.
If they do have symptoms what are they?
Fatigue
Generalised weakness
Chest pain
Palpitations
The majority of patients with hyperkalaemia are asymptomatic.
If they do have signs what are they?
Arrhythmias
Reduced power
Reduced reflexes
How is hyperkalaemia diagnosed
Hyperkalaemia is diagnosis by anything that detects serum potassium i.e. U+Es, ABG/VBG.
If you need rapid assessment then us VBG/ABG
What investigations help in assessing hyperkalaemia
Bloods (anything that detects serum potassium)
- U&Es
- VBG/ABG
- Urinary potassium
Other
- ECG - to check for arrhythmias
What are the typical ECG features seen in hyperkalaemia
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
What is asystole:
a) Shoackable wave length
b) Non-shockable wave length
b) Non-shockable wave length
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
Do not need urgent treatment.
Changes in diet and contributing drugs should be enough
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
If there is ECG changes present
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
Always required - even in the absence of ECG changes
What is the serum potassium level range in mild hyperkalaemia
5.5-6 mmol/L
What is the serum potassium level range in moderate hyperkalaemia
6 - 6.4 mmol/L
What is the serum potassium level range in severe hyperkalaemia
>= 6.5 mmol/L
What is the mainstay of treatment for hyperkalaemia
Insulin and dextrose infusion
AND
IV calcium gluconate
IV insulin and dextrose is used in the management of hyperkalaemia.
How does it work?
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
