๐ Potassium (Kโบ)
Goal: 4.0โ5.0 mEq/L (โฅ 4.0 in cardiac patients)
| Kโบ Level | Replacement | Expected โ |
| 3.5โ3.9 | KCl 40 mEq PO ร 1 | โ ~0.4 mEq/L |
| 3.0โ3.4 | KCl 40 mEq PO ร 2 (or 20 mEq IV ร 2) | โ ~0.8 mEq/L |
| 2.5โ2.9 | KCl 20 mEq IV ร 3โ4 + 40 mEq PO | Variable |
| < 2.5 | KCl 40 mEq IV (10 mEq/hr peripheral, 20 mEq/hr central) + telemetry | Check q2h |
โ ๏ธ Always check Mgยฒโบ. Hypomagnesemia prevents Kโบ correction. Fix Mg first. Max peripheral IV rate: 10 mEq/hr (burning). Max central: 20 mEq/hr. Telemetry if Kโบ < 3.0.
๐ก Magnesium (Mgยฒโบ)
Goal: โฅ 2.0 mg/dL (โฅ 2.0 in cardiac/ICU)
| Mgยฒโบ Level | Replacement |
| 1.5โ1.9 | MgO 400 mg PO BID ร 2 days (or MgSOโ 2g IV ร 1) |
| 1.0โ1.4 | MgSOโ 2g IV ร 2 doses |
| < 1.0 | MgSOโ 4g IV over 4h + recheck. Telemetry. May need 8โ12g total over 24h. |
โ ๏ธ Key facts: IV Mg causes flushing/warmth (warn patient). Oral Mg causes diarrhea (MgO worst, Mg glycinate better tolerated). Renal patients: reduce dose -Mg is renally cleared. 50% of hypoK is from concurrent hypoMg.
๐ข Phosphate (POโ)
Goal: 2.5โ4.5 mg/dL
| POโ Level | Replacement |
| 2.0โ2.4 | Neutra-Phos 2 packets PO (or K-Phos 2 tabs PO) |
| 1.5โ1.9 | Na-Phos or K-Phos 15 mmol IV over 2h |
| < 1.5 | Na-Phos or K-Phos 30 mmol IV over 4โ6h (max 7 mmol/hr) |
โ ๏ธ Choose Na-Phos vs K-Phos based on Kโบ level. K-Phos if K is also low (repletes both). Na-Phos if K is normal/high. IV phosphate can cause hypocalcemia -check Ca. Reduce dose in renal failure.
๐ต Calcium (Caยฒโบ)
Goal: iCa 1.1โ1.3 mmol/L / Total Ca 8.5โ10.5 mg/dL (corrected for albumin)
| Scenario | Replacement |
| Mild (asymptomatic) | Calcium carbonate (Tums) 1โ2g PO TID with meals + Vitamin D |
| Moderate (symptomatic) | Calcium gluconate 1โ2g IV over 10โ20 min |
| Severe / symptomatic | Calcium gluconate 1โ2g IV bolus โ continuous infusion 0.5โ1.5 mg/kg/hr |
| Cardiac arrest / severe | Calcium CHLORIDE 1g IV push (central line only -3ร more elemental Ca) |
โ ๏ธ Always check Mg first. HypoMg โ impaired PTH โ refractory hypoCa. Correct albumin: add 0.8 per 1g albumin below 4.0. CaCl via central line ONLY (tissue necrosis if infiltrates). Ca gluconate safe peripherally.
๐ด Sodium (Naโบ) -Correction Limits
See Hyponatremia topic for full management
โค 8
mEq/L rise in 24h
(max safe correction rate)
โค 10โ12
mEq/L rise in 48h
(be even more cautious if chronic)
ODS
Osmotic demyelination syndrome
if corrected too fast
Hyponatremia: NS for hypovolemic, fluid restrict for euvolemic (SIADH), diuretics for hypervolemic. HTS 3% for severe symptoms (seizure, coma) -100 mL bolus, recheck Na in 2h. Hypernatremia: Free water deficit = 0.6 ร wt ร ((Na/140) โ 1). Replace slowly -max correction 10 mEq/24h to avoid cerebral edema.