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
IV calcium gluconate is part of the management of hyperkalaemia.
How does it work?
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
The mainstay of hyperkalaemia treatment is with an insulin and dextrose infusion and IV calcium gluconate.
What other options are available
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
Oral calcium resonium is an option to treatment hyperkalaemia.
In what incidience is suitable for
Suitable for milder cases of hyperkalaemia
In a patient with hyperkalaemia and ECG changes.
What is the single most appropriate management
IV calcium gluconate - cardioprotective
What is the first line management in hyperkalaemia
Calcium gluconate - cardioprotective preventing arrhythmias
Then given IV insulin and dextrose
What is the mechanism of action of calcium gluconate in the management of hyperkalaemia
Calcium gluconate reduces excitability of cardiac myocytes thus reducing the likelihood of developing life threatening arrhythmias
How does rampiril cause hyperkalaemia
Rampiril is an example of an ACE inhibitor
Causes hyperkalaemia by blocking the aldosterone pathway thereby leading to a retention of potassium
If a patient has a diagnosis of hyperkalaemia from blood work.
What is the most important next line investigation
ECG - to check for arrhythmias
What is the mechanism of action of calcium resonium in the management of mild hyperkalaemia
Moves potassium out of the gut and into the stools
Works slowly
Give an example of a potassium sparing diuretics
Spironolactone
The mainstay of hyperkalaemia treatment is with an insulin and dextrose infusion and IV calcium gluconate.
Why is insulin and dextrose given (seems counterintuitive)
Insulin causes intracellular K+ shift and glucose to required to prevent hypoglycaemia
