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Tricks but no treats: Illusions and
medication errors
From the October 30, 2002 issue
Various "tricks of the mind," including cognitive
and visual illusions, affect accurate performance. Illusions
are generally defined as systematic distortions between our
thoughts, perceptions, and reality. Like a mirage in the desert,
they lead us astray by creating incorrect assumptions about
how to think, see, hear, or otherwise interpret events.
Physicians' prescribing patterns illustrate the problem of
potential cognitive illusions well because their orders often
are predictable. The doctor's name on an order for a common
anti-infective, for example, may easily trigger automatic
mental processes for what to dispense. If the physician usually
orders 250 mg of the medication, a pharmacist or nurse may
assume that 250 mg is required and miss cases in which the
physician actually has ordered 500 mg. A misguided reliance
upon memory of the physician's prescribing pattern produces
this self-deception.
Visual and auditory illusions, on the other hand, arise from
perceptual rules that misinterpret or fail to organize the
information properly. Thus, we may see or hear things that
are not actually present. Some medications, for example, are
confused because their names and packaging have look-alike
and sound-alike qualities (e.g., Serzone-Seroquel; Zyrtec-Zyprexa,
Celebrex-Cerebyx). In this case, the names are blended visually
or acoustically and one product is mentally transformed into
the other. Such illusions resist correction, and thus persist
throughout the medication use process, resulting in an error.
Are some illusions more likely to occur than others? A recent
study examined how susceptible 51 pharmacists were to six
situations that normally created misperceptions.1 Outcomes
showed that pharmacists were more prone to: a.) misreading
drug names or strengths on prescriptions and medication containers;
b.) misjudging the spatial location of a product stored in
a pharmacy; and c.) mistaking the size of a medication for
a smaller look-alike counterpart. Participants were more successful
in resisting problems with miscalculating quantity and miscopying
prescription information.
While "tricks of the mind" do not affect everyone
to the same degree (indeed, some people are able to resist
their influence), interventions are needed for those that
are most problematic. Outcomes of the study reinforce the
need for barcode technology and electronic transmission of
prescriptions to counter the misreading of drug names and
strengths. While nurses and pharmacists still may be prone
to spatial illusions that distort correct location when selecting
products from storage areas, some errors can be averted by
avoiding the practice of just "reaching and grabbing"
the product when busy without careful examination that the
correct product has been selected.
Finally, the study showed that size might not be a reliable
cue to differentiate two medications that otherwise look alike
or have names that are similar. Thus other ways to set items
apart, including packaging, color, shape, and the use of auxiliary
labels, may be needed. Rotating placement of fast moving medications
also can help staff avoid the habit of "reaching and
grabbing" for products based on their usual position
on the shelf.
Reference: 1. Tranum D, Grasha A. Susceptibility to
illusions and cognitive style: Implications for pharmacy dispensing.
Perceptual and Motor Skills, 2002, In Press. For more information,
contact Dr. Grasha at tony.grasha@uc.edu
ISMP thanks Anthony F. Grasha, PhD, Professor of Psychology,
University of Cincinnati, for contributing this article.
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