Hypophosphatemia

Background

CNS
- Weakness
- Circumoral and fingertip paresthesias
- Decreased DTRs
- Decreased Mental Status
Cardiac
- Impaired myocardial function

Internal redistribution
- Refeeding of malnourished
- DKA
- Nonketotic hyperglycemia
- Receiving hyperalimentation
- Acute respiratory alkalosis
- Hungry bone syndrome
Decreased intestinal absorption
- Inadequate intake
- Antacids containing aluminum or magnesium
- Steatorrhea and/or chronic diarrhea
Increased urinary excretion
- Vitamin D deficiency or resistance
- Primary renal phosphate wasting (rare genetic disorders)
- Fanconi syndrome
  - Multiple myeloma
- Osmotic diuresis (most often due to glucosuria)
- Proximally acting diuretics (e.g. acetazolamide and some thiazide diuretics)
- Acute volume expansion
- Intravenous iron administration
Renal replacement therapy

Serum phosphate 1 mg/dl to 2 mg/dl
- Able to take PO
  - Minimize or eliminate all dextrose-containing IV solutions
  - Aggressively treat acidosis
  - 1 tab K-phos neutral 250mg Q hour x 5 doses
    - Each tab contains phosphorus 8 mmol, Na 13 mEq, K1.1 mEq
  - Recheck serum phosphate after last dose, and repeat dosing if continues to be <2 mg/dl
- NOT able to take PO
  - Minimize or eliminate all dextrose-containing IV solutions
  - Aggressively treat acidosis
  - Give 15 mmol of IV potassium phosphate over 2.5 hours (contains 22 mEq K)
    - Peripheral administration may cause burning at injection site
    - Consider central venous administration, if available
    - Repeat dosing regimen if serum phosphate remains <2 mg/dl
Serum phosphate <1 mg/dl
- Minimize or eliminate all dextrose-containing IV solutions
  - Exceptions: vasopressors, sedatives, analgesics, antibiotics, blood products, NS
- Aggressively treat acidosis
- Give 45 mmol of IV potassium phosphate over 7 hours (contains 66 mEq of K)
  - Peripheral administration may cause burning at injection site
  - Consider central venous administration, if available
- If patient can tolerat PO, ALSO follow steps 1 above
- Recheck serum phosphate after infusion
  - Repeat IV administration if <1 mg/dl
  - Consider oral administration if >1mg and <2 mg/dl