Phosphate Balance

Question 1

What is the normal phosphate level?

Answer 1

The normal range for phosphorus is 2.7 to 4.5 mg/dL. The
symptoms of paresthesias, myopathy, delirium, seizures, and
coma correspond to hypophosphatemia.
Barash PG, Cullen BF, Stoelting RK, Cahalan MK, Stock MC,
Ortega R. Clinical Anesthesia. 7th ed. Philadelphia, PA:
Lippincott Williams and Wilkins; 2013: 355.

Question 2

How does respiratory alkalosis affect the renal

excretion of phosphate?

Answer 2

Respiratory alkalosis decreases the renal excretion of
phosphate.
Barash PG, Cullen BF, Stoelting RK, Cahalan MK, Stock MC,
Ortega R. Clinical Anesthesia. 7th ed. Philadelphia, PA:
Lippincott Williams and Wilkins; 2013: 355.

Question 3

How does fluid volume expansion affect the renal

excretion of phosphate?

Answer 3

Volume expansion increases the renal excretion of phosphate.
Barash PG, Cullen BF, Stoelting RK, Cahalan MK, Stock MC,
Ortega R. Clinical Anesthesia. 7th ed. Philadelphia, PA:
Lippincott Williams and Wilkins; 2013: 355.

Question 4

What are the three primary factors that influence the

renal reabsorption of phosphate by the kidneys?

Answer 4

Dietary intake, parathyroid hormone, and insulin-like growth
factor.
Barash PG, Cullen BF, Stoelting RK, Cahalan MK, Stock MC,
Ortega R. Clinical Anesthesia. 7th ed. Philadelphia, PA:
Lippincott Williams and Wilkins; 2013: 355.

Question 5

Where is the majority of the body’s phosphorus

located?

Answer 5

About 90% of the body’s phosphorus is found in bone. Almost
10% is located in the intracellular fluid. The <1% remaining is
found in the extracellular fluid.
Barash PG, Cullen BF, Stoelting RK, Cahalan MK, Stock MC,
Ortega R. Clinical Anesthesia. 7th ed. Philadelphia, PA:
Lippincott Williams and Wilkins; 2013: 355.

Question 6

What is a potential effect of administering phosphate

to patients who are hypocalcemic?

Answer 6

The administration of phosphate to hypocalcemic patients could
exacerbate the hypocalcemia.
Barash PG, Cullen BF, Stoelting RK, Cahalan MK, Stock MC,
Ortega R. Clinical Anesthesia. 7th ed. Philadelphia, PA:
Lippincott Williams and Wilkins; 2013: 356.

Question 7

How does hyperventilation affect the phosphate

level?

Answer 7

Respiratory alkalosis from hyperventilation decreases
phosphate levels. Respiratory alkalosis is also presumed to be
the cause of hypophosphatemia associated with gram-negative
sepsis and salicylate poisoning.
Barash PG, Cullen BF, Stoelting RK, Cahalan MK, Stock MC,
Ortega R. Clinical Anesthesia. 7th ed. Philadelphia, PA:
Lippincott Williams and Wilkins; 2013: 355-356.

Question 8

What is ‘refeeding syndrome’?

Answer 8

Carbohydrate loading can induce hypophosphatemia via an
insulin-mediated uptake of phosphorus. This is the most
common form of hypophosphatemia seen in hospitalized
patients.
Barash PG, Cullen BF, Stoelting RK, Cahalan MK, Stock MC,
Ortega R. Clinical Anesthesia. 7th ed. Philadelphia, PA:
Lippincott Williams and Wilkins; 2013: 356.

Question 9

How does hypophosphatemia affect hematologic

function?

Answer 9

Hypophosphatemia results in dysfunction of red and white blood
cells as well as platelets. Because the phagocytic, chemotaxic,
and bactericidal activity of the white blood cells is diminished,
hypophosphatemia can contribute to a patient’s susceptibility to
sepsis.
Barash PG, Cullen BF, Stoelting RK, Cahalan MK, Stock MC,
Ortega R. Clinical Anesthesia. 7th ed. Philadelphia, PA:
Lippincott Williams and Wilkins; 2013: 356.

Question 10

What are the neurologic symptoms of

hypophosphatemia?

Answer 10

Paresthesias, myopathy and, encephalopathy.
Butterworth JF, Mackey DC, Wasnick JD. Morgan & Mikhail’s
Clinical Anesthesiology. 5th ed. New York, NY: McGraw-Hill;
2013: 1134-1135.

Question 11

How is hyperphosphatemia treated in patients with

renal failure?

Answer 11

Limited phosphate intake and aluminum hydroxide ingestion
can help ameliorate hyperphosphatemia, but dialysis is the
most effective method for treating it quickly.
Barash PG, Cullen BF, Stoelting RK, Cahalan MK, Stock MC,
Ortega R. Clinical Anesthesia. 7th ed. Philadelphia, PA:
Lippincott Williams and Wilkins; 2013: 356.

Question 12

How is hyperphosphatemia treated in patients

without renal failure?

Answer 12

The cause of the elevated phosphate level should be eliminated
(if possible) and any associated hypocalcemia should be
corrected. Phosphate excretion in the urine should be
encouraged with saline and acetazolamide. Gastrointestinal
losses of phosphate can be increased by administering
aluminum hydroxide.
Barash PG, Cullen BF, Stoelting RK, Cahalan MK, Stock MC,
Ortega R. Clinical Anesthesia. 7th ed. Philadelphia, PA:
Lippincott Williams and Wilkins; 2013: 356.

Question 13

What is the most common cause of

hyperphosphatemia?

Answer 13

Renal failure
Barash PG, Cullen BF, Stoelting RK, Cahalan MK, Stock MC,
Ortega R. Clinical Anesthesia. 7th ed. Philadelphia, PA:
Lippincott Williams and Wilkins; 2013: 356.

Question 14

What are the three basic mechanisms by which

hyperphosphatemia occurs?

Answer 14

1. Inadequate renal excretion of phosphate, 2. the movement of
   phosphate from inside the cells to outside the cell, and 3.
   increased phosphate or vitamin D intake.
   Barash PG, Cullen BF, Stoelting RK, Cahalan MK, Stock MC,
   Ortega R. Clinical Anesthesia. 7th ed. Philadelphia, PA:
   Lippincott Williams and Wilkins; 2013: 356.