Makindo Medical Notes | Metabolic alkalosis

🩺 Cause	🤒 Clinical Features	🔬 Diagnostic Tests	💊 Management
🤮 Vomiting / NG Suction	Loss of HCl → dehydration, postural hypotension	ABG: ↑pH, ↑HCO₃⁻ U&E: ↓Cl⁻, ↓K⁺	IV 0.9% NaCl + K⁺ replacement Stop suction / treat vomiting
💊 Diuretics (Loop / Thiazide)	Weakness, dizziness, dehydration	ABG: ↑pH, ↑HCO₃⁻ Electrolytes: ↓K⁺, ↓Cl⁻	Stop / adjust diuretic IV saline + KCl supplements
🧬 Hyperaldosteronism	HTN, muscle weakness, thirst, polyuria	ABG: ↑pH, ↑HCO₃⁻ Electrolytes: ↓K⁺, ↑Na⁺ Renin: ↓, Aldosterone: ↑	Treat cause (e.g., adrenal adenoma) Spironolactone / eplerenone
💉 Excess Bicarbonate	Confusion, paraesthesia, cramps, fluid overload	ABG: ↑pH, ↑HCO₃⁻ Electrolytes: ↑Na⁺, ↓K⁺	Stop bicarbonate Treat underlying acidosis cause
⚡ Hypokalaemia	Weakness, palpitations, arrhythmias (PVCs)	ECG: U waves, flat T waves Serum: ↓K⁺	Potassium replacement (oral / IV) Treat underlying cause
💧 Contraction Alkalosis	Dehydration (dry mouth, low BP)	ABG: ↑pH, ↑HCO₃⁻ U&E: ↓Cl⁻, ↓K⁺ Urine Cl⁻: low	IV 0.9% NaCl + KCl Correct volume loss
🥛 Milk-Alkali Syndrome	Nausea, vomiting, confusion, kidney stones	ABG: ↑pH Electrolytes: ↑Ca²⁺, ↑HCO₃⁻ Creatinine ↑	Stop Ca²⁺ / antacids IV fluids Severe hypercalcaemia → bisphosphonates

📝 Key Clinical Pearls

🔄 Compensation is usually by hypoventilation (↑PaCO₂).
🧪 Urine chloride helps: low (<15 mmol/L) suggests vomiting/diuretics, high (>20 mmol/L) suggests mineralocorticoid excess.
⚠️ Hypokalaemia and hypochloraemia are hallmarks and must be corrected.

🩺 Case 1 — Vomiting-Induced Alkalosis

A 45-year-old woman presents with 5 days of persistent vomiting from severe gastritis. She is weak, dizzy, and hypotensive. Labs: pH 7.50, HCO₃⁻ 36 mmol/L, K⁺ 2.8 mmol/L, Cl⁻ low. Management: 💧 IV 0.9% saline and potassium replacement to correct volume and electrolyte deficits. Treat underlying cause of vomiting. Avoid: ❌ Continuing NG suction or antiemetics alone without fluid/electrolyte correction.

🩺 Case 2 — Diuretic-Induced Alkalosis

A 72-year-old man with chronic heart failure on furosemide presents with weakness and muscle cramps. Vitals stable. Labs: pH 7.48, HCO₃⁻ 34 mmol/L, K⁺ 3.0 mmol/L. Management: 💊 Review diuretic dose, replace potassium and magnesium, consider adding potassium-sparing diuretic (spironolactone, amiloride). Avoid: ❌ Escalating loop diuretic dose without electrolyte monitoring.

🩺 Case 3 — Post-Hypercapnic Alkalosis

A 65-year-old man with COPD on home oxygen is admitted with acute hypercapnic respiratory failure. After aggressive ventilation in ICU, his PaCO₂ normalises but labs now show pH 7.52, HCO₃⁻ 36 mmol/L, K⁺ 3.4 mmol/L. Management: 🏥 Careful weaning of ventilation, electrolyte correction (K⁺, Cl⁻), acetazolamide may be considered to promote renal bicarbonate excretion. Avoid: ❌ Over-ventilation leading to sudden CO₂ drop; avoid bicarbonate administration.

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Metabolic alkalosis

🌡️ Analysis of Blood Gas (Metabolic Alkalosis)

🔎 Aetiology

📋 Causes and Management

📝 Key Clinical Pearls

🩺 Case 1 — Vomiting-Induced Alkalosis

🩺 Case 2 — Diuretic-Induced Alkalosis

🩺 Case 3 — Post-Hypercapnic Alkalosis

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