Blood and electrolytes
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Objective:
This page enlists composition of blood and some key electrolytes in blood systems and provide the the reader an idea on imbalances of electrolytes in blood and drugs used to manage the imbalances.
Key words:
Blood, components of blood
Blood and electrolytes
Electrolyte Normal Range And ECG changes.
Sodium (Na⁺) 135–145 mEq/L
Potassium (K⁺) 3.5–5.0 mEq/L
Chloride (Cl⁻) 98–106 mEq/L
Bicarbonate (HCO₃⁻) 22–28 mEq/L
Calcium (total Ca²⁺) 8.5–10.5 mg/dL
Magnesium (Mg²⁺) 1.7–2.4 mg/dL
Phosphate (PO₄³⁻) 2.5–4.5 mg/dL
Ionized calcium 1.12–1.32 mmol/L
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Hyperkalemia
Hyperkalemia is an higher serum potassium concentration, generally K⁺ >5.0–5.5 mEq/L.
Common causes:
• Renal failure/CKD
• ACE inhibitors, ARBs, spironolactone, NSAIDs
• Metabolic acidosis or insulin deficiency
• Tissue breakdown
• Pseudohyperkalemia due to hemolysis
Clinical features:
Often asymptomatic; severe cases may cause muscle weakness, paralysis, and life-threatening cardiac arrhythmias.
Hyperkalemia: Classification by Severity
🟢 Normal K⁺: 3.5–5.0 mEq/L
🟡 Mild: 5.1–5.9 mEq/L
🟠 Moderate: 6.0–6.4 mEq/L
🔴 Severe: ≥6.5 mEq/L
ECG changes:
Peaked T waves → prolonged PR → loss of P waves → widened QRS → sine-wave pattern.
Key point:
Severe hyperkalemia is a medical emergency, particularly when ECG abnormalities are present.
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Effect of electrolytes on the Heart — Why Balance is Life-Saving
Heart runs on electricity, and electrolytes like potassium, calcium, and magnesium are its fuel. Even a small imbalance can change the EKG — and sometimes stop the heart.
Potassium (K⁺)
Low (Hypokalemia): Causes depressed ST, inverted T waves, and a U wave. Can trigger dangerous arrhythmias.
High (Hyperkalemia): Produces tall peaked T waves, widened QRS, and prolonged PR interval. Severe cases can cause cardiac arrest.
Calcium (Ca²⁺)
Low (Hypocalcemia): Prolonged QT interval, raising risk of life-threatening V-Tach.
High (Hypercalcemia): Shortens QT, widens T waves — speeding up electrical conduction.
Magnesium (Mg²⁺)
Low (Hypomagnesemia): Depressed ST, prolonged QT — can worsen arrhythmias, especially in alcoholics or ICU patients.
High (Hypermagnesemia): Widened QRS, prolonged PR — slowing the heart’s electrical signals.
These subtle changes on an EKG can mean the difference between stability and sudden cardiac arrest. That’s why doctors check electrolytes in every ER chest pain, kidney disease, and ICU patient.
Takeaway: A balanced diet, hydration, and monitoring during illness or medication use (like diuretics) protect not just your health — but your heartbeat itself.
Acute pharmacological management of hyperkalemia
The acute pharmacological management of hyperkalemia (elevated serum potassium levels), dividing interventions by their physiological mechanisms.
Calcium gluconate 10%: 10 mL IV over 2-5 min (cardiac protection)
Regular insulin: 10 units IV + 25 g dextrose IV.
Albuterol: 10-20 mg nebulized.
Sodium bicarbonate: 50-100 mEq IV if metabolic acidosis.
Furosemide: 20-40 mg IV (if appropriate).
Sodium zirconium cyclosilicate or Patiromer to remove potassium.
Hemodialysis for severe hyperkalemia, especially in kidney failure or oliguria.
Summary of Interventions
1. Myocardial Membrane Stabilization (Immediate Protection)
Medication: Calcium gluconate 10%
Dose/Route: 10 mL IV over 2–5 minutes.
Mechanism: It does not lower serum potassium. Instead, it antagonizes the toxic effects of high potassium at the cardiac cell membrane. This stabilizes the resting membrane potential, preventing lethal arrhythmias (e.g., ventricular fibrillation) in patients with toxic ECG changes like peaked T-waves.
2. Intracellular Potassium Shifting (Temporary Shifts)
These therapies work quickly to redistribute potassium from the blood into the cells, lowering serum levels while definitive elimination is arranged:
Regular Insulin + Dextrose: 10 units IV regular insulin administered alongside 25 grams of IV dextrose (glucose). Insulin drives potassium into cells by upregulating the Na⁺/K⁺ ATPase pump; dextrose is co-administered to prevent severe hypoglycemia.
Albuterol (Salbutamol): 10–20 mg nebulized. This beta-2 adrenergic agonist also stimulates the \(Na^{+}/K^{+}\) Albuterol (Salbutamol): 10–20 mg nebulized. This beta-2 adrenergic agonist also stimulates the Na⁺/K⁺pump to promote intracellular shifting.
Sodium Bicarbonate: 50–100 mEq IV. This is reserved strictly if the patient has concurrent metabolic acidosis, driving an exchange of hydrogen ions out of cells for potassium ions moving in.
3. Potassium Elimination (Definitive Removal)
To lower total body potassium levels, the excess ions must be excreted:
Furosemide: 20–40 mg IV. A loop diuretic that increases potassium excretion via urine, used if renal function is preserved and the patient is not volume-depleted.
Potassium Binders: Sodium zirconium cyclosilicate (SZC) or Patiromer. These are oral gastrointestinal cation exchange agents that bind potassium in the gut to remove it via feces.
Hemodialysis: The ultimate definitive treatment reserved for severe hyperkalemia, particularly when complicated by acute kidney injury, chronic kidney disease (ESRD), or oliguria (poor urine output) where medical therapies fail or are contraindicated.
References
1. Jayasinghe, R., Kovoor, P. (2002). Drugs and the QTc interval. Australian Prescriber-an independent review. 25(3): 63-65. DOI: 10.18773/austprescr.2002.058.
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Most of the information in this page are collected from Google AI Overview. These are for informational purposes only. For medical advice or diagnosis, consult a professional. AI responses may include mistakes. Learn more
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