Electrolyte Replacement
Goals: K>4, Mg>2, Phos>3
Potassium:
10 meq increases K by 0.1
KCl (IV or PO)- IV: usually 10 meq/hr. Can give 20/hr IV. (max 40/hr via central line but this is rarely done)
- PO: 100% bioavailability
In DKA give KPhos instead of KCl because pts get HYPERchloremia and HYPOphosphatemia, and they're already getting NaCl in their IVFs
Magnesium:
1 gram increases Mag by 0.1
- MagSO4 (IV) can give as bolus
- MagOxide (PO) 80% bioavailability. Comes only in 400 mg tabs. Large doses cause diarrhea. Give with meals.
Give PO for background replacement and IV boluses to tweak AM labs
Phosphorous
- KPhos (IV) 15 mmol = 22 meq K
- NaPhos (IV) 15 mmol = 20 meg Na
- NeutraPhos (PO) 1 packet = 8 mmol Phos + 7 mmol Na + 7 mmol K
- NeutraPhos-K (PO) 1 packet = 8 mmol Phos + 7 mmol Na + 14 mmol K
- mild (Phos=2.5-2.9) - give 0.32 mmol/kg
- mod (Phos-2-2.5) - give 0.32-0.64 mmol/kg
- severe (Phos<2) - give 0.64-1 mmol/kg
- PO 60-80% biolavailable. Better for background replacement. Give TID with meals.
- Fleet's enema is NaPhos
- If pt needs K, give KPhos. Otherwise give NaPhos. NaPhos will not significantly add to hypernatremia if good renal fx.
- Phos important for wound healing, burns, diaphragm, Goes down early in refeeding syndrome.
Calcium
- CaCl (12 meq) needs central line
- Ca gluconate (4 meq) - often depleted after blood products (EDTA). Give 1-2 g.
Bicarbonate
- Calculate HCO3 deficiency = 0.5 * kg * (24 - HCO3)
- In non-AG met acidosis, replace over 12-24h (or 1/2 in 12h)
- In AG met acidosis, don't give HCO3 (because acidosis not due to decr HCO3 and extra HCO3 can result in incr CO2/acid in tissues)
- 1 amp = 1 meq/mL NaHCO3 in 50 mL = 50 meq (add to IVFs)
- 5% solution (drip)
Remember the sodium. 3 amps added to 1L = 150 meq, so in that case add to D5 instead of NS (154 meq Na) or 1/2NS (77 meq Na)
To protect kidneys from IV contrast, 3 amps in D5 at 3cc/kg/hr over 1-2 h
Drugs that cause electrolyte abnormalities
Hypokalemic drugs
- lasix/loop diruetics
- beta lactams (K, Mg)
- amphoB (K, Mg, renal tox)
Hyperkalemic drugs
- ace inhib spironolactone (decr Na)
- heparin (wk aldo agonost, decr Na)
- bactrim (Trimethoprim)
- dig toxicity is worse with low K but may result in incr K