Potassium

Kalium

What is another name for potassium?

What type of ion is potassium?

Major intracellular cation

2%

How much potassium is found in plasma?

Most life-threatening electrolyte when abnormal

Why is potassium clinically important?

• Heart contraction

• Neuromuscular excitability

• Intracellular fluid (ICF) volume regulation

• Hydrogen ion (acid-base) balance

Main functions of potassium?

3.5–5.2 mmol/L

Normal potassium range?

6.5 mmol/L

Critical value for hyperkalemia?

2.25 mmol/L

Critical value for hypokalemia?

ECG changes

What happens at 6–7 mmol/L K⁺?

Loss of muscle excitability

What happens at 8 mmol/L K⁺?

Cardiac arrest

What happens at 10 mmol/L K⁺?

Arrhythmia and paralysis

Severe hypokalemia effect (<3.4)?

↑ K⁺ (0.5% RBC hemolysis → +0.5 mmol/L)

Effect of hemolysis on potassium?

Plasma values slightly lower (0.1–0.7 mmol/L)

Effect of anticoagulants on potassium?

↑ K⁺ by 10–30%

Effect of muscle activity?

↑ potassium

Effect of prolonged serum-RBC contact?

Effect of prolonged tourniquet use?

Impaired renal excretion

Most common/almost/always cause of hyperkalemia?

a. ↓ Aldosterone response
b. Renal failure
c. ↓ Distal sodium delivery

Three mechanisms of reduced renal potassium excretion?

1.     Decreased renal excretion

2.     Extracellular shift

3.     Increased intake

4.     Drugs (tacrolimus, cyclosporine)

Causes of hyperkalemia?

1. Gastrointestinal loss

2. Renal loss

3. Intracellular shift

Causes of hypokalemia?

Falsely elevated potassium due to specimen issues

What is pseudohyperkalemia?

• Hemolyzed specimen

• Thrombocytosis

• Prolonged tourniquet

• Fist clenching

• Blood stored in ice

• IV fluid contamination

• High blast count (leukemia)

• Leukocytosis

• Recentrifugation of SST

Causes of pseudohyperkalemia?

Potassium via light emission

What does EFP measure?

Electrode used for potassium?

Valinomycin gel electrode

Principle of AAS?

Absorption of radiation by atoms

Lockhead & Purcell

Colorimetry