General Principles

Do no harm — electrolyte correction can cause significant morbidity if done wrong.
Treat the patient, not just the number.
Rate of change matters: rapid shifts (hours) are more dangerous than slow, chronic changes (days–weeks).
Always evaluate clinical scenario and symptoms before intervention.

Sodium Disorders

Etiology: Usually due to lack of free water (not salt overload). Common in bedbound, infants, patients with altered thirst.
Symptoms: Nonspecific (lethargy, weakness, irritability, nausea). Severe (Na >160) → seizures, coma.
Treatment:
- If able, allow patient to drink water (best physiologic correction).
- IV fluids if unable: start with normal saline if hypovolemic (even though Na 154, it is relatively hypo for someone with Na >170).
- Correct slowly unless seizures/coma (then give enough to stabilize, then slow down).
- Calculate free water deficit for planned correction.

First step: Check for pseudohyponatremia → correct Na for glucose (and consider lipids, protein).
Symptomatic (seizure/coma):
- Treat immediately with 3% saline, 100 mL bolus, may repeat ×3.
- Goal: improve symptoms, not normalize number.
- Do not exceed 0.5–1 mEq/L/hr correction (max ~10–12 mEq in 24h).
- Once Na ~125, seizures/coma should stop. If not, reconsider diagnosis.
Asymptomatic/mild:
- Assess volume status:
  - Hypovolemic (diuretics, GI losses): give isotonic fluids.
  - Euvolemic (SIADH): fluid restrict.
  - Hypervolemic (CHF, cirrhosis, renal failure): fluid restrict, consider loop diuretics.
Disposition: Admit if symptomatic, Na <120, or requiring aggressive correction.
Avoid rapid correction: Risk of central pontine myelinolysis (locked-in syndrome).

Causes: Renal failure (most common), ACE inhibitors/ARBs, missed dialysis.
ECG findings: Peaked T waves → PR prolongation → absent P waves → QRS widening → sine wave → asystole.
- Can also present as bradycardia without classic ECG changes.
Treatment (order matters):
1. Calcium (chloride or gluconate): stabilizes myocardium.
2. Shift K into cells:
  - Insulin + glucose
  - Bicarbonate (if acidotic)
  - Beta-agonist (e.g., albuterol)
3. Remove K:
  - Hemodialysis (definitive, esp. ESRD)
  - Slow options: sodium zirconium cyclosilicate (Lokelma), patiromer (Veltassa), old agent: kayexalate (not fast, risk of GI necrosis).

Causes: Diuretics (most common), GI losses, insulin/glucose shifts, periodic paralysis.
Symptoms: Weakness, fatigue, ectopy/PVCs, polyuria, ileus. Severe (<2.5) → paralysis, respiratory failure.
Always check magnesium: must replete Mg to correct K.
Treatment:
- Oral replacement if mild/asymptomatic.
- IV replacement if severe or symptomatic (add Mg if low/unknown).
- Repletion takes time (patients are massively K-depleted).

Causes: Hyperparathyroidism (benign) or malignancy (bad).
Symptoms: “Stones, bones, groans, psychiatric overtones”: kidney stones, bone pain, constipation, lethargy, confusion, coma.
ECG: Shortened QT interval.
Treatment:
- IV fluids (NS) — first-line.
- Bisphosphonates, calcitonin → longer-term (oncology).

Causes: Renal failure (↑ phosphate binds Ca), post-parathyroidectomy, pancreatitis.
Symptoms: Tetany, seizures, carpopedal spasm, Chvostek/Trousseau signs.
Treatment:
- IV or oral calcium depending on severity.
- Avoid overly aggressive replacement in renal failure (risk of calcium-phosphate precipitation).

Causes: Alcoholism, poor nutrition, GI/renal losses.
Symptoms: Neuromuscular irritability, tremors, seizures, refractory hypokalemia/hypocalcemia.
Treatment: Oral or IV magnesium.

Causes: Renal failure, iatrogenic (excess Mg supplementation, e.g., preeclampsia).
Symptoms: Decreased reflexes, hypotension, bradycardia, respiratory depression, cardiac arrest.
Treatment: Stop Mg, IV calcium for stabilization, dialysis if severe.

Treat the symptoms, not just the lab number.
Correct slowly unless life-threatening symptoms.
Always check for co-abnormalities:
- Correct Na for glucose.
- Replace Mg with K.
ECG is your friend in K, Ca, and Mg disorders.
When in doubt: hydrate, stabilize the heart, correct cautiously.