QuestionSBA
QuestionChoice
Lactulose is an osmotic laxative. Excessive use of lactulose can cause electrolyte abnormalities, such as hypokalaemia, instead of hyperkalaemia.
52966
e
Lactulose
QuestionChoice
Omeprazole is a proton pump inhibitor, which can cause hyponatraemia and hypomagnesaemia but is not known to cause hyperkalaemia.
52963
b
Omeprazole
QuestionChoice
Furosemide is a loop diuretic which blocks the reabsorption of sodium, potassium and chloride. It can cause hypokalaemia instead of hyperkalaemia.
52964
c
Furosemide
QuestionChoice
Losartan is an angiotensin-receptor blocker used for the treatment of hypertension, diabetic nephropathy and heart failure. As it works on the renin-angiotensin-aldosterone system as a blocker, it can cause a reduced sodium and a raised potassium.
52962
a
Losartan
QuestionChoice
Indapamide is a thiazide-like diuretic which can cause hypokalaemia instead of hyperkalaemia.
52965
d
Indapamide
Concept
Chapter
# Summary

Hyperkalaemia is a potentially life-threatening electrolyte abnormality, defined as a serum potassium concentration greater than 5.5mmol/L. A potassium of 6.0-6.5 mmol/L is classed as moderate hyperkalaemia, and > 6.5 mmol/L is classed as severe. Causes include acute or chronic renal impairment, medications such as ACE inhibitors, adrenal insufficiency and rhabdomyolysis. Pseudohyperkalaemia is also common and occurs when there is haemolysis of the blood collected that causes potassium to leak from cells. Key investigations include an ECG, a blood gas to confirm hyperkalaemia is true, and U&Es for renal function. Management depends on the severity of hyperkalaemia and may include calcium gluconate or calcium carbonate to stabilise the myocardium and insulin-dextrose infusion to drive potassium into the cells, as well as treating the cause of hyperkalaemia. Potassium binders such as sodium zirconium cyclosilicate (Lokelma) may also be used. The main complication is cardiac conduction abnormalities, with possible findings including tall tented T waves, flattened P waves, bradyarrhythmias and QRS widening with bizarre morphology. 

# Definition

Hyperkalaemia is a common electrolyte abnormality that is defined as an abnormally high serum potassium. The normal range is 3.5-5.0 mmol/L, with a level of > 5.5 mmol/L generally described as hyperkalaemia. It is seen in around 1-10% of hospital inpatients and is often asymptomatic.

# Aetiology

- Impaired excretion of potassium
   - Acute kidney injury
   - Chronic kidney disease
   - Medications (ACE inhibitors, potassium sparing diuretics, NSAIDs, heparin, trimethoprim, ciclosporin)
   - Type 4 renal tubular acidosis
   - Hypoadrenalism (e.g. Addison's disease)
- Increased potassium intake
    - Oral intake (especially if combined with impaired excretion)
    - Excessive IV potassium
- Increased cellular release  
   - Metabolic acidosis
   - Hyperglycaemia
   - Rhabdomyolysis
   - Tumour lysis syndrome
   - Packed red blood cell transfusion
   - Digoxin toxicity
   - Beta blockers
   - Severe burns
   - Hyperkalaemic periodic paralysis

# Classification

The European Resuscitation Guidelines stratify severity of hyperkalaemia as follows:

||Serum potassium (mmol/L)|
|--------------------------|------------------------------------|
|**Mild**|5.5–5.9|
|**Moderate**|6.0–6.4|
|**Severe**|≥6.5|

# Signs and Symptoms

Hyperkalaemia is often asymptomatic and only detected on blood tests - there may be symptoms or signs of the underlying cause however (e.g. dark urine in rhabdomyolysis)

**Symptoms include:**

- Palpitations
- Fatigue
- Chest pain
- Shortness of breath
- Paralysis

**Signs include:**

- Arrhythmias (e.g. bradycardia)
- Reduced muscle power +/- flaccid paralysis
- Hyporeflexia

# Differential Diagnosis

**Pseudohyperkalaemia** is common and refers to an artifactual increase in potassium in the sample tested - causes of this include:

- Prolonged tourniquet time
- Difficult venepuncture
- Excessive fist clenching
- Delayed specimen processing
- Contamination with potassium EDTA anticoagulant in FBC bottles
- Thrombocytosis
- Leukocytosis

# Investigations

- **Blood gas** to confirm hyperkalaemia rapidly and check acid-base status and lactate
- **ECG** to look for cardiac conduction abnormalities associated with hyperkalaemia. ECG changes include tall-tented T waves, PR prolongation, p wave flattening and QRS broadening.
- **U&Es** to confirm hyperkalaemia, check sodium (may be an associated hyponatraemia e.g. in adrenal insufficiency) and renal function

# Management 

**Conservative management:**

- Stop any potassium-containing fluids
- Address any underlying causes e.g. stop any contributing medications where possible, manage constipation
- Consider advising the patient on a low potassium diet (e.g. in patients with chronic kidney disease) - dietician referral may be helpful
- Patients with ECG changes may require cardiac monitoring
- Mild-moderate cases of hyperkalaemia without ECG changes may be managed by addressing the underlying cause alone

**Medical management:**

- Patients with ECG changes or severe hyperkalaemia require treatment
- Give 10 ml of IV 10% calcium carbonate or 30ml of IV 10% calcium gluconate immediately
- This does not reduce serum potassium but acts to stabilise the myocardium and reduce the risk of arrhythmias
- Further doses may be given if required
- Give an insulin and glucose infusion (e.g. 10 units of Actrapid in 50 ml of 50% glucose over 15-30 minutes
- This reduces serum potassium by shifting potassium into cells, however does not eliminate potassium from the body
- Nebulised salbutamol may be given in addition which has the same effect
- Potassium binders may be considered to eliminate potassium via the gut, especially in patients with chronic or refractory hyperkalaemia
- Newer agents such as sodium zirconium cyclosilicate (Lokelma) are better tolerated than older resins (e.g. sodium polystyrene sulfonate)
- Furosemide may also be useful to increase urinary potassium excretion especially in patients with fluid overload
- Consider sodium bicarbonate for patients with acidosis and hyperkalaemia
- Medical treatment may be required to correct the cause of hyperkalaemia (e.g. IV fluids for a pre-renal AKI or rhabdomyolysis)

**Interventional management:**

- Refractory hyperkalaemia despite medical therapy is an indication for emergency dialysis

# Complications

The main complication of hyperkalaemia is cardiac conduction abnormalities and arrhythmias which in the most severe cases may cause cardiac arrest - changes in order of increasing severity are:

1. Tall tented T-waves
2. Flattened P-waves
3. Prolonged PR interval
4. Widened QRS complexes
5. Idioventricular rhythms (bradycardia of ventricular origin)
6. Sine wave pattern (pre-terminal rhythm)
7. Ventricular fibrillation/asystole

# References

[BNF Treatment Summary - Hyperkalaemia](https://bnf.nice.org.uk/treatment-summaries/hyperkalaemia/)

[The Renal Association - Treatment of Acute Hyperkalaemia in Adults](https://www.ukkidney.org/sites/default/files/RENAL%20ASSOCIATION%20HYPERKALAEMIA%20GUIDELINE%20-%20JULY%202022%20V2_0.pdf)

[Patient UK - Hyperkalaemia in adults](https://patient.info/doctor/hyperkalaemia-in-adults)

[Whittington Hospital Hyperkalaemia Guideline](https://www.whittington.nhs.uk/document.ashx?id=6250)

[Life in the Fast Lane - Hyperkalaemia](https://litfl.com/hyperkalaemia-ecg-library/)
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ECG changes seen in someone with hyperkalaemia.
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10653
An 87-year-old man presents with a 3 day history of palpitations. On examination, his heart rate is 110 bpm. The remainder of the examination is unremarkable. A venous blood gas confirms a potassium of 7.2 mmol/L (3.5 - 5.3 mmol/L) and an ECG shows sinus tachycardia with peaked T waves. He is given calcium gluconate and insulin-dextrose.
 
Which of his regular medications should be held?
a