Electrolyte Replacement
Electrolyte Replacement
David Ray Velez, MD
Table of Contents
General Approach
| Lyte | Replacement | Dose | Will Raise | Notes |
| K | KCl | 10 mEq | 0.05-0.1 mEq/L | Preferred Over K-Phos |
| Ca | Ca-Gluconate | 1 g | 0.5 mg/dL | If Mild |
| CaCl | 1 g | 1.5 mg/dL | If Severe/Symptomatic | |
| Mg | Mg-Sulfate | 1 g | 0.2 mg/dL | IV Preferred |
| Phos | Na-Phos | 15 mmol | 0.4 mg/dL | Preferred Over K-Phos |
| K-Phos | 15 mmol | 0.4 mg/dL | Also Gives 22 mEq K |
Goal of Replacement
- Goal: Normal Serum Electrolyte Levels
- Generally Attempt to Achieve the Middle of the Normal Range, Not the Lower Limit, to Allow for Ongoing Losses (Ex: K Goal 4.0, Not 3.5)
MNEMONIC: Approximate Goal Electrolyte Levels: “2-3-4” (2 Mg, 3 Phos, 4 K)
Route
- Enteral (PO) Replacement:
- Generally Preferred if Able to Tolerate Oral Intake (Not Magnesium)
- Slower Correction Limits the Risk of a Sudden Significant Increase
- Intravenous (IV) Replacement:
- Preferred Route if Deficiency is Severe
- More Rapid Correction
Replacements
Potassium
- Potassium Chloride (KCl)
- Correction: Every 10 mEq will Increase Serum K 0.05-0.1 mEq/L
- IV and PO Dosing are Equivalent
- Rechecking After Replacement:
- IV – Immediately After the Final Dose
- PO – Should Wait One-Hour to Recheck to Allow Absorption
Calcium
- Calcium Gluconate
- IV Correction: Every 1 g will Increase Total Calcium 0.5 mg/dL (iCal 0.15 mg/dL)
- Preferred for Mild Asymptomatic Deficiencies
- Calcium Chloride (CaCl2)
- IV Correction: 1 g will Increase Total Calcium 1.5 mg/dL (iCal 0.45 mg/dL)
- Provides Three Times the Amount of Elemental Calcium per Gram as Calcium Gluconate
- Preferred for Severe or Symptomatic Deficiencies
- Corrosive to Veins and Requires a Central Line
- IV Correction: 1 g will Increase Total Calcium 1.5 mg/dL (iCal 0.45 mg/dL)
Magnesium
- Magnesium Sulfate (MgSO4)
- Correction: Every 1 g will Increase Serum Mg 0.2 mg/dL
- IV Preferred – Enteral Absorption Has Variable Bioavailability
- Rechecking After Replacement: Wait 8-12 Hours to Allow Gradual Redistribution to Tissues
Phosphate
- Sodium Phosphate (Na Phos)
- IV Correction: Every 15 mmol with Increase Serum PO4 0.4 mg/dL
- Preferred Choice Over K Phos
- Rechecking After Replacement: Wait 2-4 Hours
- Enteral Dosing:
- Variable Bioavailability – Dose Should Be Tripled
- 250 mg PO is Equivalent to 8 mmol
- Generally Given in 3-4 Doses Over the Day
- Potassium Phosphate (K Phos)
- Same Correction as Na Phos
- Also Provides 22 mEq K per 15 mmol
Normal Requirements
Requirements Per Day
- Potassium (K): 0.5-1 mEq/Kg/Day
- Sodium (Na): 1-2 mEq/kg/Day
- Chloride (Cl): 2-3 mEq/Kg/Day
Normal Levels
- Sodium (Na): 135-145 mEq/L
- Chloride (Cl): 96-106 mmol/L
- Potassium (K): 3.5-4.5 mEq/L
- Calcium (Ca): 9.0-11.0 mg/dL
- Ionized Calcium (iCal): 4.5-5.5 mg/dL (1.16-1.31 mmol/L)
- Phosphate (PO4): 3.0-4.5 mg/dL
- Magnesium (Mg): 1.5-2.5 mEq/L