AGREEMENT BETWEEN DIFFERENT EQUATIONS TO ESTIMATE OSMOLARITY OF PARENTERAL NUTRITION SOLUTIONS

Area of Science:

• Parenteral Nutrition
• Clinical Chemistry
• Formulation Science

Background:

• Parenteral nutrition (PN) formulas require accurate osmolality assessment.
• Literature equations for calculating osmolarity may not reliably predict osmolality across diverse experimental conditions.

Purpose of the Study:

• To measure the osmolality of various PN formulas at different concentrations.
• To evaluate the predictive accuracy of existing equations for PN osmolality.

Main Methods:

• Osmolality of 12 PN solutions (9 central, 3 peripheral) was measured using freezing point depression.
• Agreement and bias between measured osmolality and calculated osmolarity were assessed using three established equations (Pereira Da Silva, ASPEN Manual, ASPEN guidelines).

Main Results:

• Mean osmolality was 1789 ± 256 mOsm/kg for central and 751 ± 64 mOsm/kg for peripheral PN.
• Glucose and amino acids were the primary contributors to PN osmolality.
• All tested equations showed good correlation but tended to underestimate measured osmolality; the ASPEN guidelines equation overestimated peripheral PN osmolality.

Conclusions:

• Measuring peripheral PN osmolality is vital for reducing phlebitis risk.
• Existing PN osmolality calculation equations demonstrate good correlation but generally underestimate actual values.