Cases & Commentaries

Right? Left? Neither!

Spotlight Case
Commentary By Elizabeth A. Howell, MD, MPP; Mark R. Chassin, MD, MPP, MPH

Case Objectives

  • Appreciate the role of Reason's Swiss
    Cheese Model in medical errors
  • Understand the process of analyzing a
    single error
  • Provide suggestions for remediation

Case & Commentary

A 79-year-old woman presented to an after
hours clinic with a 1-week history of diarrhea and progressive
weakness. Due to signs of dehydration, the patient was directly
admitted to the hospital. Past medical history was notable for
stroke with residual left-sided hemiparesis, hypertension, coronary
artery disease with ischemic cardiomyopathy, peptic ulcer disease,
asthma, and obesity. Two weeks prior to this admission, she had
spontaneously developed right ankle and foot pain and had been
evaluated in the emergency department (ED) of another hospital. The
family was told of a possible fracture and a splint was applied.
She was instructed to follow up with an orthopedist as soon as
possible. Due to transportation difficulties, the patient was not
seen in follow up.

On physical examination, she was afebrile and
appeared weak. She had a left-sided hemiparesis. The right ankle
and foot were in the same splint that had been applied 2 weeks
earlier. When examined, the ankle had a normal range of motion with
no localized tenderness. A stool specimen collected in the ED was
subsequently positive for
Clostridium difficile toxin. At
the time of admission, a release of information was signed and
faxed to the other hospital to obtain records of the recent ED
visit for the ankle and foot injury. The family requested an
orthopedic consultation to expedite work-up. Outside records of the
previous ED visit did not arrive promptly, so another x-ray was
taken of the right foot and ankle. This x-ray was read by the
radiologist as showing a right ankle trimalleolar fracture and
dislocation. The consulting orthopedist reviewed the x-ray report
then briefly examined the patient. Surgery was recommended and
discussed with the family, and consent was obtained.

The next morning, the patient was taken to the
operating room (OR), and spinal anesthesia was administered. The
orthopedist was scrubbed and was preparing to operate. The ankle
x-ray was on the view box in the OR. Prior to making an incision,
the orthopedist reviewed the x-ray and was shocked to notice that
it was a left ankle x-ray showing a trimalleolar fracture. A prompt
examination of both of the patient's ankles under anesthesia did
not demonstrate any clinical evidence of fracture or dislocation.
The x-ray was clearly labeled as belonging to the patient. Stat
x-rays of both ankles were then done in the OR. The left ankle was
intact, and the right showed an intact ankle with a healing
fracture of the fifth metatarsal bone.

During the ensuing confusion, one of the OR
technicians recalled that another patient had undergone an
operative reduction-internal fixation (ORIF) of a left ankle
trimalleolar fracture 2 days prior. It was later confirmed that the
x-ray showing the left ankle trimalleolar fracture was mislabeled
by date and patient and belonged to this other patient who already
had surgery.

The spinal anesthesia was reversed, and the
patient was returned to her room and fortunately did not have any
consequences. Full disclosure and an apology were given to the

The patient continued to recover from the
dehydration and colitis and was able to be discharged from the
hospital. Treatment for the metatarsal fracture consisted of a
supportive boot. By the time of discharge, a faxed copy of the ED
records from the outside hospital had been received. Included in
these records was an x-ray report describing a non-displaced, fifth
metatarsal fracture of the right foot.

Performing an invasive procedure on the wrong
patient should never happen. Neither should operating on the wrong
side of the right patient. Reliable estimates of the frequency of
this kind of adverse event are not available. The data that do
exist suggest that events like these are underreported to the
voluntary sentinel events database of the Joint Commission on
Accreditation of Healthcare Organizations (JCAHO), as well as to
state programs that require adverse event reporting.(1-3) Wrong-patient or wrong-site invasive procedures may
be uncommon but “for patient and doctor it is the ultimate

Broadly speaking, adverse events in hospitals
occur through two different mechanisms. A single mistake, if it is
serious enough, may cause harm by itself. Alternatively, and more
commonly, many smaller errors may occur—not one of which
alone is severe enough to cause harm. In combination, however, as
seen in this case, they become toxic. James Reason has developed a
powerful explanatory model to understand adverse events that occur
by the second mechanism, which he has called “organizational
Synthesizing the work of many psychologists, accident experts, and
organizational sociologists, Reason provides a conceptual framework
that delineates how errors made by individuals interact with system
defects in complex organizations to cause harm.(5) Like other complex organizations, hospitals put
defenses into place to prevent errors from doing harm. Examples of
such defenses include training programs; safety protocols,
policies, and procedures; and computerized decision support tools.
Every layer of defense has weaknesses. If an error gets past one
defense, another layer of defense usually prevents harm from
occurring. Adverse events occur only when all the defenses around a
particular patient's situation have been circumvented by many
errors. Reason has referred to this framework for understanding
adverse events as the “Swiss Cheese Model.”(6)

Let us review this adverse event to determine (i)
which of the two causal pathways was involved (single error versus
Swiss cheese); (ii) whether the Swiss cheese pathway was causative
and which defenses failed to prevent harm; and (iii) what remedial
action might be called for. We will start by identifying the
primary errors made by individuals during the course of this
patient's care that contributed to causing the event.

The first error (or series of errors) occurred 2
weeks prior to admission when the staff in the ED who diagnosed the
non-displaced metatarsal fracture failed to communicate this
diagnosis clearly and unambiguously to the patient and her family.
If the patient and family had known the correct diagnosis of her
foot pain and reported that history at the time of admission, this
mishap might have been prevented, particularly if that information
had been supplemented by confirmatory documentation from the ED.
The next group of errors occurred when the patient was admitted.
The physician in the ED who examined the patient and found a normal
right ankle failed to communicate his or her findings to the
physician responsible for admitting the patient or to the
consulting orthopedic surgeon. The case summary does not identify
the admitting physician, but since the patient was admitted
primarily to treat dehydration, it is unlikely that she was
admitted directly to the service of the orthopedic surgeon. It is
not clear from the case narrative whether the ED physician ordered
the repeat foot and ankle radiographs while the patient was in the
ED or the consulting orthopedic surgeon ordered them after the
patient had been admitted. If the ED physician ordered them, he or
she erred further in not personally reviewing the films. If the
patient was admitted to an internist or other primary care
physician, that physician also erred in not examining the patient
and her x-rays.

The case summary does not reveal how the
patient's foot and ankle radiographs were mislabeled in radiology,
but it is very likely that several errors were involved. Initially,
an erroneous report on the patient was generated showing a right
trimalleolar fracture with dislocation. It is highly implausible
that the patient's actual films were misread by the radiologist. A
non-displaced fifth metatarsal fracture can hardly be mistaken for
a trimalleolar fracture with dislocation. As we learn later, it is
far more likely that a different patient's films were somehow
mislabeled with the current patient's identifying information and
current date. Why the initial erroneous report identified the side
of the trimalleolar fracture as right is also unclear. Did the
radiologist misread the side of the trimalleolar fracture because
the order for the current patient called for right foot and ankle

By any reasonable standard of judgment, the
orthopedic surgeon committed by far the most serious errors in this
case. The orthopedist failed to elicit or to discover the history
of the patient's previous diagnosis or treatment. The history
reported by the patient's family was not consistent with the x-ray
findings. It is very unlikely that any hospital would let a patient
with a displaced trimalleolar fracture (at risk for vascular
compromise) leave the ED in a splint without an orthopedic consult.
Had the orthopedist obtained this history, he or she might have
been led to question the x-ray findings. Compounding this error,
the orthopedist “briefly examined the patient.” It is
difficult to comprehend how even a brief physical examination of
this patient's foot and ankle could not have caused this physician
to question the radiographic diagnosis. One is forced to suspect
that the surgeon may not have removed the bed covers and visualized
the right ankle. This single error is serious enough, but the
surgeon made it even worse by recommending surgery on the basis of
this incomplete evaluation, obtaining “consent” (which
could hardly be called informed) and scheduling the operation.

The final set of errors occurred prior to the
patient receiving spinal anesthesia. Surgical site verification was
not conducted prior to the patient going to the OR or prior to
administering spinal anesthesia. JCAHO has recommended a series of
steps to prevent wrong-site, wrong-side, and wrong-person
procedures.(7) The
Universal Protocol clearly delineates these steps, which include
(i) a preoperative verification process to ensure that all studies
and records are available, have been reviewed, and are consistent;
(ii) marking the operative site; and (iii) a “time out”
to conduct a final verification of the correct patient, procedure,
and site prior to starting the procedure.(7) There is no indication in this case that any of these
procedures were undertaken. While a recent study notes the fact
that the effectiveness of preoperative verification protocols has
not been evaluated (8),
there is every reason to believe that in this case the patient
would have been spared an unnecessary spinal anesthesia if the
Universal Protocol had been properly applied. The patient was
spared unnecessary surgery at the last moment when the orthopedist
discovered that the presumptive diagnosis was wrong. We suspect
that the orthopedic surgeon was prompted to review the x-rays in
the OR after finally recognizing that the ankle he or she was
“preparing to operate” on looked nothing like an ankle
with a trimalleolar fracture/dislocation.

Which adverse event pathway did this case follow?
This is clearly an example of the Swiss cheese pathway (Figure). There was no single, critical error. Many
individuals made many errors. Many defenses failed to protect this
patient. Communication failed in several instances (eg, between the
first ED and the patient, between the second ED physician and the
orthopedist, between the admitting physician and the orthopedist).
Policies and procedures were inadequate (eg, mislabeling of the
x-ray, failure to implement the universal protocol). Teamwork
failed in the OR when no one—nurses, OR technicians, the
anesthesiologist—observed that the patient's ankle appeared
normal, and no one questioned whether the procedure should
continue. The failure of the orthopedist to perform an adequate
history and physical examination on the patient prior to surgery
stands out as the most serious individual error. But even that
error combined with the second-most serious error (the mislabeling
of the ankle x-ray) was not sufficient to cause this adverse event.
Many other individuals, including the staff in the first ED, the
second ED physician, the admitting physician, and the OR staff, had
the opportunity to stop this sequence of errors before the patient
was harmed. Only when all the defenses surrounding this patient
failed did she experience the harm of unnecessary spinal

While some might call this case a “near miss” or
close call—a situation that could have led to an adverse
event but did not—we would call this case an adverse event. This
patient was subjected to spinal anesthesia for no reason. Although
the risks are low, spinal anesthesia is occasionally associated
with severe risks, such as cardiac arrest and neurological

The institution at which this adverse event
occurred should consider several remedial actions to strengthen its
defenses. The process of identifying and labeling radiographs
should be reviewed to discover exactly how the errors occurred in
this case and improved to avoid them in the future. The Universal
Protocol should be implemented in all ORs and procedure areas. The
multiple communication failures suggest the need for a formal
protocol to delineate precisely how responsibility for care is
handed off from the ED to admitting physicians and consultants.
Finally, the actions of the orthopedist should be examined by the
appropriate peer review committee.

Take-Home Points

  • Reason's Swiss Cheese Model, in which
    multiple errors combine to create major adverse events because of
    inadequate defenses, explains many adverse patient events in health
  • Analysis of adverse patient events
    should focus on discovering which defenses failed and bolstering
  • To strengthen defenses against
    wrong-site and wrong-patient invasive procedures, hospitals should
    implement the principles of the Universal Protocol.

Elizabeth A. Howell, MD, MPP
Assistant Professor
Departments of Health Policy and Obstetrics, Gynecology, and
Reproductive Science
Mount Sinai School of Medicine

Mark R. Chassin, MD, MPP, MPH
Edmond A. Guggenheim Professor of Health Policy
Chairman, Department of Health Policy
Mount Sinai School of Medicine

Faculty Disclosure: Dr. Howell and Dr.
Chassin have declared that neither they, nor any immediate member
of their family, have a financial arrangement or other relationship
with the manufacturers of any commercial products discussed in this
continuing medical education activity. In addition, their
commentary does not include information regarding investigational
or off-label use of pharmaceutical products or medical


1. Sentinel Event Alert: A follow-up review of
wrong site surgery. Oakbrook Terrace, IL: Joint Commission on
Accreditation of Healthcare Organizations; December 5, 2001.
Available at:
Accessed April 3, 2006.

2. Chassin MR, Becher EC. The wrong patient. Ann
Intern Med. 2002;136:826-833. [go to PubMed]

3. NYPORTS—New York Patient Occurrence and
Tracking System—Annual Report 1999. Albany, NY: New York
State Department of Health; February 2001. Available at:
Accessed April 3, 2006.

4. Bakalar N. Before first incision, checking for
an X to mark the spot. The New York Times. April 18,

5. Reason J. Managing the risk of organizational
accidents. Aldershot, United Kingdom: Ashgate Publishing Ltd;

6. Reason J. Human error: models and management.
BMJ. 2000;320:768-770. [go to PubMed]

7. Universal Protocol for Preventing Wrong Site,
Wrong Procedure, Wrong Person Surgery. Oakbrook Terrace, IL: Joint
Commission on Accreditation of Healthcare Organizations. Available
Accessed April 3, 2006.

8. Kwaan MR, Studdert DM, Zinner, MJ, Gawande AA.
Incidence, patterns, and prevention of wrong-site surgery. Arch
Surg. 2006;141:353-358. [go to PubMed]

9. Horlocker TT. Complications of spinal and
epidural anesthesia. Anesthesiol Clin North America.
2000;18:461-485. [go to PubMed]


Figure. Swiss Cheese Model