A pharmacist is preparing a total parenteral nutrition admixture for a critically ill patient. Which pair of electrolytes must be added with caution to prevent precipitation of insoluble crystals in the bag?

• A Sodium and potassium
• B Calcium and bicarbonate
• C Magnesium and chloride
• D Calcium and phosphate ✓

Explanation

Calcium and phosphate can combine to form insoluble calcium phosphate crystals when concentrations are high or mixing order is incorrect. ASPEN guidelines recommend adding phosphate first, then calcium last, with adequate dilution and agitation. Precipitation can cause pulmonary embolism if infused. Bicarbonate can also cause calcium precipitation but is less commonly used. Sodium, potassium, and magnesium do not form insoluble precipitates with each other in TPN. Careful compounding is essential.

Reference: ASPEN Guidelines on Parenteral Nutrition, 2022 ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.