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💧 Water & Electrolyte Disturbances
Essential Clinical Guide for Medical Students
🎓 Community Medicine • First Year
📊 Total Body Water (TBW) Basics
Adult Male TBW
~60% of Body Weight
Infants: Higher • Women: Slightly Lower
🔬 Intracellular vs Extracellular Ions
🧫 INSIDE CELLS (ICF):
⚡ Cation: Potassium (K⁺)
⚡ Anions: Phosphates, Proteins
💧 OUTSIDE CELLS (ECF):
⚡ Cation: Sodium (Na⁺)
⚡ Anions: Chloride (Cl⁻), Bicarbonate (HCO₃⁻)
⚡ Cation: Potassium (K⁺)
⚡ Anions: Phosphates, Proteins
💧 OUTSIDE CELLS (ECF):
⚡ Cation: Sodium (Na⁺)
⚡ Anions: Chloride (Cl⁻), Bicarbonate (HCO₃⁻)
📋 Daily Requirements (70 kg Adult)
| Component | Per kg | Total Daily |
|---|---|---|
| 💧 Water | 35–45 mL/kg | 2.45–3.15 L |
| 🧂 Sodium | 1.5–2 mmol/kg | 105–140 mmol |
| ⚡ Potassium | 1.0–1.5 mmol/kg | 70–105 mmol |
🩸 Volume Disturbances
📉 Hypovolaemia
Definition: Reduction in circulating blood volume
Common Causes:
• Loss of sodium-containing fluids
• Acute blood loss
• Sequestration of fluids
• Loss of sodium-containing fluids
• Acute blood loss
• Sequestration of fluids
Lab Finding: ↑ Serum urea (low urine flow → ↑ tubular reabsorption)
✅ Management:
IV isotonic (normal) saline to expand ECF volume
IV isotonic (normal) saline to expand ECF volume
📈 Hypervolaemia
Definition: Sodium and water excess
Note: Rare in patients with normal cardiac & renal function
✅ Management:
• Restrict dietary sodium (50–80 mmol/24h)
• Fluid restriction
• Diuretic therapy (pivotal role)
• Restrict dietary sodium (50–80 mmol/24h)
• Fluid restriction
• Diuretic therapy (pivotal role)
🧂 Sodium Disorders
⬇️ HyponatraemiaNa⁺ < 135 mmol/L
🔍 Causes:
- Renal losses: Diuretics (especially thiazides)
- Adrenocortical failure
- GI losses: Vomiting, Diarrhoea
- Skin losses: Burns
⚠️ CRITICAL: Correction rate should NOT exceed 10 mmol/L/24hrs
Rapid correction → Osmotic demyelination (myelinolysis) → Permanent brain damage!
Rapid correction → Osmotic demyelination (myelinolysis) → Permanent brain damage!
⬆️ HypernatraemiaNa⁺ > 145 mmol/L
🔍 Causes:
- Renal losses: Loop diuretics + water restriction
- Glycosuria (hyperosmolar state)
- GI losses: Colonic diarrhoea
- Skin losses: Excessive sweating
- Diabetes insipidus (central/nephrogenic)
🚨 Clinical: Dizziness → Delirium → Weakness → Coma → Death (if untreated)
✅ Management (if acute):
IV 5% dextrose or 0.45% saline at 50–70 mL/hr
IV 5% dextrose or 0.45% saline at 50–70 mL/hr
⚡ Potassium Dynamics
🔄 K⁺ Moves INTO Cells With:
✅ Extracellular alkalosis
✅ Insulin • Catecholamines (β₂) • Aldosterone
🔄 Opposite factors cause K⁺ efflux → Hyperkalaemia
⬇️ Hypokalaemia (K⁺ < 3.5 mmol/L)
📉 Reduced Intake
Dietary deficiency, K⁺-free IV fluids
Dietary deficiency, K⁺-free IV fluids
🔄 Redistribution
Alkalosis, Insulin, β-agonists
Alkalosis, Insulin, β-agonists
🚽 Urinary Loss
Cushing's, Glucocorticoids
Cushing's, Glucocorticoids
🤢 GI Loss
Vomiting, NG aspiration, Diarrhoea
Vomiting, NG aspiration, Diarrhoea
⚠️ Clinical Features:
• Muscular weakness & fatigue
• Ventricular ectopic beats / arrhythmias
• ⚡ Potentiates digoxin toxicity!
• Muscular weakness & fatigue
• Ventricular ectopic beats / arrhythmias
• ⚡ Potentiates digoxin toxicity!
✅ IV Replacement Guidelines:
• Standard: ≤ 10 mmol/hour
• Severe/Life-threatening: Up to 20 mmol/hour with continuous ECG monitoring
• Always dilute • Use infusion pump • Monitor site
• Standard: ≤ 10 mmol/hour
• Severe/Life-threatening: Up to 20 mmol/hour with continuous ECG monitoring
• Always dilute • Use infusion pump • Monitor site
⬆️ Hyperkalaemia (K⁺ > 5.0 mmol/L)
🍽️ Increased Intake
Dietary K⁺, K⁺-containing IV fluids
Dietary K⁺, K⁺-containing IV fluids
🔄 Redistribution
Acidosis, Insulin deficiency, β-blockers, TLS
Acidosis, Insulin deficiency, β-blockers, TLS
🚫 Reduced Excretion
AKI, CKD, Addison's disease
AKI, CKD, Addison's disease
🚨 ⚠️ Silent Killer: May have NO symptoms until cardiac arrest!
🚑 Emergency Treatment (K⁺ > 6.5 mmol/L)
1
🛡️ Stabilise Cardiac Membrane
💡 Works within minutes - cardiac protection
IV Calcium Gluconate 10mL of 10%💡 Works within minutes - cardiac protection
2
🔄 Shift K⁺ Into Cells
• Inhaled β₂-agonist (salbutamol)
• IV Glucose 50mL 50% + Insulin 5-10 IU
• IV Sodium Bicarbonate
💡 Onset: 15-30 minutes
• Inhaled β₂-agonist (salbutamol)
• IV Glucose 50mL 50% + Insulin 5-10 IU
• IV Sodium Bicarbonate
💡 Onset: 15-30 minutes
3
🗑️ Remove K⁺ From Body
• IV Furosemide + Normal Saline
• Ion-exchange resin (oral/rectal)
• Dialysis (definitive for renal failure)
💡 Actually eliminates potassium
• IV Furosemide + Normal Saline
• Ion-exchange resin (oral/rectal)
• Dialysis (definitive for renal failure)
💡 Actually eliminates potassium
🎯 Test Your Knowledge
Remember: Electrolyte management isn't just about numbers—it's about understanding the patient's overall clinical picture!
❓ Quick FAQ
Why correct hyponatraemia slowly?
When do I use central vs peripheral IV for potassium?
What's the first step in severe hyperkalaemia?
📚 Keep Learning, Future Doctor!
#ElectrolyteMaster#MedicalStudent#CommunityMedicine#ClinicalPharmacology#PatientSafety#IraqHealthcare#DrAliAlSaedi
"In medicine, balance is everything. Master electrolytes, master life." 💙
⚠️ Disclaimer: Educational content only. Always follow institutional protocols and consult senior clinicians.
⬆️
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