March 24, 2016
The way electrolyte concentrations are expressed on IV bags in volumes less than or greater than 1 liter has tripped up many practitioners over the years. Concentrations are listed per liter, not per container volume. For example, a 250 mL 0.9% sodium chloride injection container label lists the sodium chloride content as 154 mEq/1,000 mL, rather than 38.5 mEq/250 mL. Commercially available parenteral nutrition (PN) products available in containers greater than 1 liter also express the electrolyte ingredients “per liter.”
The Institute for Safe Medication Practices recently described an error that occurred while a pharmacist was preparing a bag of 3% sodium chloride after the pharmacy unexpectedly ran out of the commercially available bags. The pharmacist mistakenly set the proportion up as 154 mEq/0.9% = x/3% and calculated that he needed 513 mEq of sodium chloride, when he actually only needed 256-257 mEq of sodium chloride for a 500 mL bag (77 mEq/0.9% = x/3%).
Clearly, it’s time for the U.S. Food and Drug Administration (FDA) and the U.S. Pharmacopeial Convention (USP) to rethink this electrolyte presentation with large volume parenterals (LVPs) in volumes less than or greater than 1 liter. For single- and multiple-dose injectables, USP requires the strength per total volume as the primary, prominent display on the label, followed in close proximity by the strength per mL enclosed in parentheses. This should apply to LVPs as well. Until it does, pharmacists who calculate electrolyte quantities should seek out an independent double check. Sufficient quantities of commercially available products should be used whenever possible. For products that routinely require admixture, an instruction sheet should be available to guide the process.
Has your pharmacy discovered errors that originated with the expressions of electrolyte content? What steps have you put into place to identify and prevent this type of error?
Matthew Grissinger, RPh, FISMP, FASCP, is the Director of Error Reporting Programs at the Institute for Safe Medication Practices.