Art imitates life! Error portrayal
From the December 13, 2000 issue
PROBLEM: The opening general session at the recent
ASHP Midyear Clinical Meeting in Las Vegas featured a dramatic
production that focused on a medication error and its wide-ranging
effects on the patient, his family, and the involved healthcare
professionals. In "Anatomy of an Error," a pediatric patient
received an overdose of IV calcium gluconate. The drug was
ordered as "calcium gluconate 1,200 mg." However, a seasoned
pharmacist prepared 1,200 mg of elemental calcium (nearly
130 mL using 10% calcium gluconate injection). Some in the
ASHP audience probably wondered how anyone could overlook
such a large dose of calcium for a pediatric patient. Coincidentally,
just a few days prior to the meeting, an actual medication
error report reached us that closely resembled the dramatic
presentation. In the actual incident, a 2-day-old infant with
a serum calcium of 6.7 was ordered "calcium gluconate 400
mg IV." Package labeling on the vial is a set-up for confusion.
One label we recently examined stated "0.465 mEq Ca++/mL"
in bold print on the front of the label but also stated, "each
mL contains calcium gluconate 94 mg" in the fine print on
the back. The label further mentioned "9.3 mg Ca++/mL"
in bold in another spot on the label. The nurse confused this
statement about the mg amount of elemental calcium with the
mg amount of the salt, calcium gluconate. For the 400 mg dose
of calcium gluconate that was ordered, she divided it by 9.3
and calculated that she needed 43 mL. A 50 mL vial of calcium
gluconate (approximately 1 g/10 mL) was removed from a crash
cart and 43 mL (approximately 4 g of calcium gluconate or
20 mEq of calcium ion) was administered to the infant instead
of around 4 mL or 400 mg. There was an immediate deterioration
of the infant's condition, but fortunately, as in the ASHP
drama, the infant survived the error.
It is easier than you may think for staff to become confused
by product labeling. Variations in the way prescribers express
the dose of calcium gluconate can also lead to dosing errors.
Some prescribe the drug as mg of elemental calcium while others
express the dose in mEq of elemental calcium. Still others
prescribe the drug in terms of calcium gluconate and others
in terms of volume and percent concentration (e.g., 10 mL
of a 10% solution). The lack of a standardized method for
expressing doses of calcium gluconate (and calcium chloride),
and the lack of a standard dose expression in labeling, increases
potential for serious medication errors.
SAFE PRACTICE RECOMMENDATION: The dosage of parenteral
calcium should be standardized at each practice site and based
on the amount of elemental calcium rather than the mg strength
of the salt. Develop protocols for the use of electrolyte
solutions, including calcium gluconate, to address proper
dose expression in mEq of elemental calcium, dose limits,
labeling methods, infusion rates, and necessary monitoring
parameters. Require independent double checks of all calculations
and dose preparations for concentrated electrolytes or electrolyte
solutions. Minimize the vial size (no 50 mL vials) and quantity
of calcium gluconate available in patient care areas, including
storage in crash carts and automated dispensing cabinets.
Whenever possible, have all IV infusions prepared in the pharmacy.
If calcium supplements must be a part of floor stock, use
auxiliary labels that clearly state the total contents of
calcium (in mEq). In hospitals without 24-hour pharmacy service,
a "night formulary" should be created which allows minimal
amounts and volumes of medications to be available for use
after hours. Specific directions for preparation of electrolyte
solutions should be provided. On-call pharmacists should be
contacted for any medication-related questions. Each morning,
pharmacy staff should immediately reconcile all drugs removed
from the night cabinet via comparison against the physician's
orders. Educate the staff about the proper dosing of calcium
during orientation and through continuing education.