Electrolyte abnormalities

Question 1

Clinical presentation of hyperkalaemia. Which symptoms are particularly worrying?

Answer 1

Generally non-specific, but may include

• muscle weakness,
• fatigue,
• **Chest symptoms e.g. palpitations, pain, dyspnoea, paresthesia. **

Question 2

What levels of potassium is normal? When is it mildly, moderately, and severely elevated?

Answer 2

Normal: 3.5 to 5.0 mmol/L.

Mild: Above 5.5
Moderate: Above 6-6.4
Severe: Above 6.4

K+ is crucial for maintaining cell membrane potential, nerve impulse transmission, muscle contraction, heart function, enzymatic processes, and regulating fluid and electrolyte balance, as well as acid-base homeostasis.

Question 3

How are potassium levels usually regulated?

Answer 3

By renal excretion and, to a lesser extent, by gastrointestinal excretion and transcellular shifts.

Question 4

What is the largest store of potassium in the body?

Answer 4

Muscles

Potassium is predominantly stored intracellularly, with about 98% of the body’s potassium stored within cells.

Question 5

List the most common causes of hyperkalaemia.

Consider patient RFs/PMH/DH

Answer 5

• Renal Failure: Acute or chronic failure leads to reduced potassium excretion.
• Medications: ACE inhibitors, ARBs, heparin, potassium-sparing diuretics, NSAIDs decrease renal potassium excretion. Beta-blockers can inhibit cellular uptake of potassium.
• Obstructive Uropathy

Question 6

Which endocrine conditions are most likely to cause hyperkalaemia?

Answer 6

• Addison’s disease
• Diabetes: DKA/ insulin deficiency

Question 7

Which medications commonly indicated in cardiovascular conditions might cause hyperkalaemia?

Answer 7

• ACEis, ARBs, potassium-sparing diuretics (educing excretion)
• beta-blockers (prevents K+ from entering cells)

Question 8

What are some acute causes of hyperkalaemia

Answer 8

• metabolic acidosis
• rhabdomyolysis
• tumour lysis syndrome
• Transfusions (blood, potassium supplements)

Question 9

Why does acidosis cause hyperkalaemia?

Answer 9

It causes hydrogen ions enter cells in exchange for potassium, raising extracellular potassium levels.

> compensatory mechanism

Question 10

What is the most initial ECG change in hyperkalaemia? What severity does it usually indicate?

Answer 10

Mild to Moderate Hyperkalaemia (Potassium 5.5-6.5 mmol/L):
* Tall, peaked T waves: The most common early sign, particularly noticeable in the precordial leads.

ECG changes may not always correlate with the severity of hyperkalaemia. Some patients may exhibit significant hyperkalaemia without classic ECG changes; hence, rely on both serum potassium levels and clinical presentation.

Question 11

What are more severe/worrying ECG signs in hyperkalaemia?

Answer 11

• Prolonged PR interval
• P wave flattening/disappears
• Widening of the QRS complex/eventually VF

Question 12

Which two bedside investigations are important for hyperkaelaemia?

Answer 12

• ECG
• Glucose/ketones in case of diabetes-related

Question 13

What are some blood tests to investigate for hyperkalaemia?

Answer 13

• UnEs (K+ and renal function)
• Blood Gas Analysis: To assess for acidosis, which can contribute to hyperkalaemia.

Question 14

Life-threatening complications of hyperkalaemia

Answer 14

• Cardiac arrythmias
• Renal failure

Question 15

List 3 emergency management options for hyperkalaemia.
What are the indications of each treatment?

Answer 15

• IV calcium gluconate (indicated immediately with ECG changes/cardiac symptoms)
• Short-acting Insulin/with glucose or dextrose (to shift K+ intracelllularly)
• Nebulised salbutamol may help shift K+ intracellularly

Manage underlying cause e.g. drug adjustments, medical condition.

Question 16

How does calcium gluconate work in hyperkalaema?

Answer 16

Stabilises the cardiac membrane.

**Calcium gluconate works within minutes but does not lower serum potassium levels. **Always administer before other treatments if ECG changes are present.

Question 17

What is a medication that can enhance renal excretion of potassium in the context of hyperkalaemia?

Answer 17

Loop diuretics e.g. furosemide?

Question 18

How might refractory hyperkalaemia be managed? e.g. all drug therapies are failing.

Answer 18

Haemodialysis.

Question 19

What is the main mechanism of pseudohyperkalaemia? (e.g. iatrogenic during blood taking)

Answer 19

Cell lysis due to improper technique/ prolonged time in tube. e.g. forceful aspirationg or rough handling of blood sample, using a tight torniquet for a prolonged period of time, fist clenching.