IV Potassium Replacement
Maximum concentration: peripheral IV ≤10 mEq/100 mL; central line ≤20 mEq/100 mL. Maximum infusion rate: ≤10–20 mEq/hr (peripheral); ≤40 mEq/hr (central, with continuous ECG monitoring). NEVER give IV potassium as a push — fatal cardiac arrhythmia. Verify: renal function (GFR) and urine output before and during infusion. Pain and burning at peripheral IV site is common — dilute further or use central line.
Magnesium Sulfate
Indications: hypomagnesemia, pre-eclampsia/eclampsia, torsades de pointes, severe asthma. Concentration: 1–2 g/50–100 mL D5W (general replacement); 4–6 g loading dose for eclampsia over 20–30 min. Maximum rate: 1–2 g/hr for replacement; can go faster for eclampsia loading dose. Monitor: respiratory rate (>12), deep tendon reflexes (loss = early toxicity), urine output (>25 mL/hr). Antidote: calcium gluconate.
Phosphate Replacement
Indications: hypophosphatemia (refeeding syndrome, DKA, malnutrition). Two forms — sodium phosphate and potassium phosphate (choose based on K+ level). General dose: 15–30 mmol IV over 2–4 hours (varies by severity). Risk: calcium-phosphate precipitation — DO NOT mix calcium and phosphate in same IV line. Monitor: serum phosphate, calcium, creatinine. Recheck levels 2–4 hours post-infusion.
Calcium Administration
Two forms: calcium gluconate (safer peripherally, gentler; for replacement) and calcium chloride (3× more elemental calcium; for cardiac arrest — central line preferred). Calcium gluconate: 1–2 g in 50–100 mL over 20–30 min. Calcium chloride: 1 g IV push in cardiac arrest. Extravasation causes severe tissue necrosis — watch IV site. Do not mix with bicarbonate or phosphate (precipitation). Monitor: ECG for bradycardia, hypotension, and arrhythmias.
Monitoring Parameters
Before replacement: verify lab value (repeat if unexpected), assess symptoms, check renal function, verify IV access. During infusion: cardiac monitoring for K+ and Mg replacement, vital signs, IV site, symptom assessment. After replacement: recheck electrolyte levels (timing per protocol — typically 1–4 hours after completion). Document: pre-lab, dose given, time, rate, route, patient response, post-lab.
Important Notes
- Calcium chloride and calcium gluconate are NOT interchangeable dose-for-dose — know which form is ordered and why.
- Magnesium infusion: check DTRs (patellar reflex) every 1–2 hours — loss of reflex precedes respiratory arrest.
Clinical Tips
- In DKA, phosphate often falls with insulin treatment — anticipate and monitor proactively.
- Simultaneous hypokalemia and hypomagnesemia are common — magnesium must be replaced first or potassium cannot be corrected.
Summary
Electrolyte replacement requires precise calculations, appropriate concentration and rate selection, and vigilant monitoring. Understanding the pharmacology and nursing implications of each electrolyte prevents life-threatening complications.
