Which of the following information is/are TRUE about preparing TPN formulation? [Select ALL THAT APPLY].
a. A lipid emulsion in a three-in-one admixture obscures the presence of calcium phosphate precipitates.
b. The solubility of the added calcium should be calculated from the volume at the time the calcium is added and should NOT be based upon the final volume.
c. If the amount of calcium or phosphate which must be added is likely to cause a precipitate, some or all of the calcium should be administered separately.
d. If a three-in-one admixture is medically necessary, then add the calcium before the lipid emulsion.
e. When adding calcium and phosphate to an admixture, the calcium should be added first.
Answer: (a,b,c,d). TPN solutions are made according to a variety of formulations and compounding protocols. Thus, there are possibilities of calcium phosphate precipitates and many other chemical incompatibilities. Precipitates could develop because of a number of factors such as: the concentration, pH, and phosphate content of the amino acid solutions; the calcium and phosphorous additives; the order of mixing; the mixing process; or the compounder. The presence of a lipid emulsion in the TPN admixture would obscure the presence of any precipitate.
Because of the potential for life threatening events, caution should be taken to ensure that precipitates have not formed in any parenteral nutrition admixtures.
1. The amounts of phosphorous and of calcium added to the admixture are critical. The solubility of the added calcium should be calculated from the volume at the time the calcium is added. It should not be based upon the final volume.
Some amino acid injections for TPN admixtures contain phosphate ions (as a phosphoric acid buffer). These phosphate ions and the volume at the time the phosphate is added should be considered when calculating the concentration of phosphate additives. Also, when adding calcium and phosphate to an admixture, the phosphate should be added first.
2. The line should be flushed between the addition of any potentially incompatible components.
3. A lipid emulsion in a three-in-one admixture obscures the presence of a precipitate. Therefore, if a lipid emulsion is needed, either:
(1). use a two-in-one admixture with the lipid infused separately, or
(2). if a three-in-one admixture is medically necessary, then add the calcium before the lipid emulsion and according to the recommendations in number 1 above.
If the amount of calcium or phosphate which must be added is likely to cause a precipitate, some or all of the calcium should be administered separately. Such separate infusions must be properly diluted and slowly infused to avoid serious adverse events related to the calcium.
4. A filter should be used when infusing either central or peripheral parenteral nutrition admixtures. Standards of practice vary, but the following is suggested: a 1.2 micron air eliminating filter for lipid containing admixtures, and a 0.22 micron air eliminating filter for nonlipid containing admixtures.
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