**4.4 Hypophosphatemia**

	- 1.Shifting phosphate into cells: Diabetic ketoacidosis, refeeding syndrome, respiratory alkalosis, hungry bone syndrome

2.Reduced GI uptake: Inadequate oral intake, chronic diarrhea, drugs (chronic use of antacids containing calcium, magnesium or aluminum).

• Most patients are asymptomatic until concentration is <1.2 mg/dl however presentation can overlap with other abnormalities. Patients can present with nausea/vomiting, loss of appetite, neuromuscular irritability, tremors/tetany,

hypocalcemia, hypokalemia, seizures, psychosis and arrythmias [48].

1.Medications: - Diuretics (except potassium sparing diuretics), antibiotics such as aminoglycoside, amphotericin and pentamidine, cyclosporine and tacrolimus, platinum based chemotherapy and proton

3.Renal disease: - Post-ATN diuresis, osmotic diuresis, renal tubular acidosis

5.Chronic alcoholism, diabetes, large volume transfusion of citrated blood

• Magnesium repletion is generally safe except for myasthenia gravis (due to

used. Oral formulations are magnesium oxide 400 mg twice a day or

• For patients with mild hypomagnesemia (1.5-2 mg/dl), oral magnesium can be

magnesium hydroxide milk of magnesia) 15 ml once daily. If unable to take PO

• For moderate hypomagnesemia (1.2-1.5 mg/dl), intermittent infusions of 2-4 g magnesium sulphate IV can be given. To improve intracellular absorption, the

• For severe hypomagnesemia (<1.2 mg/dl), multiple doses of IV magnesium can be given or a continuous infusion of IV magnesium (4-8 g IV magnesium

• 1 g magnesium sulphate is equivalent to 100 mg of elemental magnesium.

• In Torsade de Pointes or seizures secondary to hypomagnesemia, patients can be loaded with 2 g magnesium sulphate over 5-15 min followed by 2 g additionally over 30-60 min. These are followed by a continuous infusion of magnesium sulphate 1 g/hour. If the magnesium level is 5-7 mg/dl, the infusion should be reduced by 50%. If magnesium is >7 mg/dl then the infusion should

2.Hypercalcemia, hyperphosphatemia, metabolic acidosis

4.GI Losses: - Malabsorption, diarrhea/vomiting, pancreatitis

increased risk of muscle weakness) and renal failure.

medication, 2 g of IV magnesium sulphate can be given.

dose can be infused for a longer period of time.

sulphate over 24 hours) (see **Figure 10**).

be stopped.

**157**

• Hypomagnesemia induced EKG changes include:

2.Prolonged QT interval and widened QRS complex

1.Flattened T wave and U waves

3.Prolonged QT interval

*DOI: http://dx.doi.org/10.5772/intechopen.96957*

*Electrolytes in the ICU*

• Causes of hypomagnesemia are:

pump inhibitors

products, sepsis

	- Phosphate <sup>≤</sup>1.5 mg/dl:- Orally, 16 mM phosphate every 6 hours. Intravenously, initial dose can be 30 mM infused over 4 hours
	- Phosphate <sup>&</sup>gt;1.5 mg/dl:- Orally, 8 mM phosphate every 8 hours. Intravenously, initial dose of 15 mM phosphate can be infused over 2 hours.
