Glycerophosphate Compatibility

One of the internes was asking about diluent compatibility of glycerophosphate and for fluid restricted patients what is the minimum amount of fluid to be use for dilution!?

I am not aware of any studies or guidelines on how much organic phosphates we should add to PN or LVP in case of fluid restriction. The acceptable published ratio is 120 mMol of organic Phosphates per liter of Amino Acids and 48 mMol of Calcium per liter of Amino Acids although I am not satisfied with the study as we believe that the final concentration of Amino Acids should be taken in consideration and not the total volume (the higher the concentration, the higher the solubility of Ca and PO4) due to the solving effect of acidic proteins.

Example: if the dose of amino acids is 75 gm and you are using 15% concentration of any brand of amino acids this give a volume of 500 ml of amino acids; then the acceptable dose for phosphate is up 60 mMol of Organic Phosphates and up to 24 mMol of calcium that can be added to any PN volume. The stability is the same as applied to any PN storage.

The general guidelines as stated in the leaflet is as follow:

40mmol/L of calcium Chloride+100mmol of PO4/L = Safe in PN

60mmol PO4/L + Calcium Chloride 24mmol/L = Safe in D5W

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However, with the frequent shortage of Organic Phosphates, we might be obliged to use Sodium Acid Phosphates. We recommend to, CONSERVATIVELY, use below solubility curve with PN until we have Organic Phosphate (glycophos) in stock.

The key to success is not to exceed 2 mMol/L of Calcium in PN in case of more than 25 mMol/L of PO4 is required in PN. I highly recommend that:

1. We don’t allow less than 2% Amino Acids in PN (final concentration) in case more than 15 mMol /L of PO4 is added
2. We don’t add more than 4.6 mMol/L  of calcium in adult PN bag that is a general recommendation unless if true Hypocalcaemia (confirmed through ionized calcium level) exists.

Below curve is pertinent to Primine but can be used conservatively with other Amino Acids.