Risk Factors for Retained Instruments and Sponges after Surgery

n engl j med
348;3
www.nejm.org january
16, 2003
The
new england journal
of
medicine
229
special article
patient safety
Risk Factors for Retained Instruments
and Sponges after Surgery
Atul A. Gawande, M.D., M.P.H., David M. Studdert, LL.B., Sc.D., M.P.H.,
E. John Orav, Ph.D., Troyen A. Brennan, M.D., J.D., M.P.H.,
and Michael J. Zinner, M.D.
From the Departments of Surgery (A.A.G.,
M.J.Z.) and Medicine (E.J.O., T.A.B.),
Brigham and Women’s Hospital; and the
Department of Health Policy and Management,
Harvard School of Public Health
(A.A.G., D.M.S., T.A.B.) — both in Boston.
Address reprint requests to Dr. Gawande
at the Department of Surgery, Brigham
and Women’s Hospital, 75 Francis St.,
Boston, MA 02115.
N Engl J Med 2003;348:229-35.
Copyright © 2003 Massachusetts Medical Society.
background
Risk factors for medical errors remain poorly understood. We performed a case–control
study of retained foreign bodies in surgical patients in order to identify risk factors
for this type of error.
methods
We reviewed the medical records associated with all claims or incident reports of a retained
surgical sponge or instrument filed between 1985 and 2001 with a large malpractice
insurer representing one third of the physicians in Massachusetts. For each
case, we identified an average of four randomly selected controls who underwent the
same type of operation during the same six-month period.
results
Our study included 54 patients with a total of 61 retained foreign bodies (of which 69
percent were sponges and 31 percent instruments) and 235 control patients. Thirtyseven
of the patients with retained foreign bodies (69 percent) required reoperation,
and one died. Patients with retained foreign bodies were more likely than controls to
have had emergency surgery (33 percent vs. 7 percent, P<0.001) or an unexpected
change in surgical procedure (34 percent vs. 9 percent, P<0.001). Patients with retained
foreign bodies also had a higher mean body-mass index and were less likely to
have had counts of sponges and instruments performed. In multivariate analysis, factors
associated with a significantly increased risk of retention of a foreign body were
emergency surgery (risk ratio, 8.8 [95 percent confidence interval, 2.4 to 31.9]), unplanned
change in the operation (risk ratio, 4.1 [95 percent confidence interval, 1.4 to
12.4]), and body-mass index (risk ratio for each one-unit increment, 1.1 [95 percent
confidence interval, 1.0 to 1.2]).
conclusions
The risk of retention of a foreign body after surgery significantly increases in emergencies,
with unplanned changes in procedure, and with higher body-mass index. Case–
control analysis of medical-malpractice claims may identify and quantify risk factors
for specific types of errors.
abstract
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n engl j med
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rror in medicine is common and
may cause harm.
1
However, isolating the
factors underlying specific types of errors
has proved to be a formidable task. The types of errors
that occur vary widely because of the extreme
complexity and heterogeneity of the tasks involved
in medical care. Furthermore, many of the most devastating
errors happen too infrequently for observational
or single-institution studies to identify the
risk factors and patterns of causation. As a result,
studies of error to date have generally measured only
the frequency and outcomes of specific types of errors,
not the roles of particular contributing factors.
One persistent but poorly understood error is
leaving sponges or instruments inside patients who
undergo surgery. Such incidents may result in major
injury. In a report on 24 cases of foreign bodies retained
after intraabdominal surgery, complications
observed included perforation of the bowel, sepsis,
and in two patients, death.
2
The retention of sponges
and instruments is considered by many to be
avoidable, and when it occurs, it can attract wide,
critical press coverage.
3-5
Yet these errors persist.
Although the incidence has not been determined,
estimates suggest that such errors occur in 1 of every
1000 to 1500 intraabdominal operations.
6,7
There is great uncertainty about why these incidents
occur and how to prevent them. The standards
of the Association of Operating Room Nurses have
long required that only sponges detectable on radiography
be used and that they be counted once at
the start and twice at the conclusion of all surgical
procedures.
8
The standards also recommend that
instruments be counted in all cases involving an
open cavity. If a count is incorrect — that is, not all
materials are accounted for — then radiography or
manual reexploration is to be performed. In published
case series, some incidents appear to result
from a failure to adhere to these standards.
9,10
However,
in the majority of cases, foreign bodies go undetected
despite proper procedures. Previous descriptive
studies have been unable to establish the
human and systems-related factors involved.
10
We performed a case–control study to identify
risk factors for the retention of foreign bodies during
surgery that might provide direction for ameliorative
efforts. Because these cases are avoidable
and frequently injurious, many lead to malpractice
claims; given the high likelihood of litigation after
such cases, most liability insurers also encourage
clinicians and hospitals to report them. Therefore,
we used malpractice-insurance files from several
institutions to identify cases.
cases and controls
We used a retrospective case–control design. Patients
with cases were those in whom instruments
or sponges had been left after a surgical procedure;
controls were patients who had undergone the same
type of procedure without this complication.
To obtain cases, we sought records from all malpractice
claims and incident reports involving retention
of a surgical instrument or sponge that were
filed between January 1, 1985, and January 1, 2001,
with the Controlled Risk Insurance Company
(CRICO), a malpractice insurer representing one
third of the physicians in Massachusetts and 22 hospitals.
We first performed a computerized search
of CRICO’s administrative data base to identify potential
cases. Then, a physician-reviewer screened
the legal and medical records associated with these
cases to select those in which records confirmed
that a surgical instrument or sponge was inadvertently
left in the patient after a surgical procedure and
in which operative records were available for review.
For each case, we identified a set of control patients
from among those who had undergone the
same procedure as a given patient with a retained
foreign body during the same period at, when feasible,
the same institution. Given an estimated 60
cases available for review, we determined that four
controls for each case would give the study sufficient
power to detect a risk factor present in 30 percent
of patients that produced a doubling of the
likelihood that a foreign body would be left behind.
Through a search of hospitals’ administrative data
bases, we identified at least 10 patients who had
undergone the same principal procedure, as defined
according to the procedure codes of the
International
Classification of Diseases, 9th Revision, Clinical Modification
11
during the six-month period preceding the
date of surgery in the corresponding case. We then
randomly selected five patients for a review of records
(one more than the minimum, because we anticipated
that some might not have complete records
available).
The cases came from 10 hospitals, with 4 hospitals
accounting for 83 percent of the cases. We were
able to obtain permission to sample controls from
these four principal hospitals only. For cases from
the remaining six hospitals, we selected matching
controls from the principal hospitals in proportion
to their share of cases. We obtained approval for
the review of records from the institutional review
board at each of the four hospitals, and we obtained
e methods
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n engl j med
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retained instruments and sponges after surgery
231
approval for the overall study from the institutional
review board at Brigham and Women’s Hospital,
Boston.
development of the data form
We developed a data form for recording information
about patients with a retained foreign body and
controls on the basis of a review of the literature
and interviews with individual surgeons. Possible
risk factors identified in the literature were a change
in nursing personnel during surgery, excessive loss
of blood, lack of a complete count of sponges and
instruments, fatigue in the surgical team due to the
lengthiness or lateness of the procedure, and urgency
of the surgery.
7,9,10
The surgeons we interviewed
cited the following additional factors, drawn
from anecdotal experience: obesity of the patient,
unexpected intraoperative developments, the involvement
in a procedure of multiple surgical teams,
and the performance of more than one major procedure
at a time.
The final form included the following information:
age; sex; weight and height; the cavity of operation;
the starting time; the duration of the operation;
the volume of blood lost; the volume of blood
transfused; whether the operation was performed
on an emergency basis; whether unexpected developments
led to a change in or addition to the procedure
that had been planned; whether more than
one surgical team, more than one major procedure,
or both were involved; whether there was a complete
count of sponges and instruments; whether
the nursing personnel changed between counts; and
whether the surgeon or another team member (a
resident or physician’s assistant) performed the closure.
Operations starting between 5 p.m. and 7 a.m.
or completed between 7 p.m. and 7 a.m. were categorized
as late procedures. The operation was classified
as an emergency (needed to be performed
within hours), urgent (needed to be performed within
hours to days), or elective. Emergency surgery
included repair of a symptomatic aortic aneurysm,
operation for trauma, unplanned cesarean section,
hysterectomy for uncontrolled postpartum bleeding,
and closure of vaginal or rectal tears after delivery.
Cases involving unexpected changes in procedure
included those with unanticipated findings
of a perforated diverticulitis, ectopic pregnancy,
duodenal mass, or other new diagnoses, as well as
technical complications including bladder laceration
requiring repair, shoulder dystocia at delivery,
and intraoperative respiratory failure. For patients
with a retained foreign body, we also recorded the
type of foreign body retained, the way in which it
was detected and when it was detected, the corrective
procedure (if any), and the patient’s health
outcome.
record review
Four senior surgical residents who were trained to
use the data form conducted reviews of records
during the fall of 2001. In addition, we extracted
data on indemnity payments and legal-defense expenses
for the cases from the insurer’s administrative
data base.
statistical analysis
We generated descriptive statistics and performed
a matched case–control analysis using univariate
conditional logistic regression. Variables found to
be associated with an increased likelihood of retention
of a foreign body in univariate analysis at a level
of statistical significance of P<0.20 were then included
in a multivariate conditional logistic-regression
model. Because retention of objects occurs
relatively rarely, odds ratios were considered to
approximate risk ratios. We performed all analyses
using the SAS statistical package, version 8 (SAS
Institute).
characteristics of the cases
We identified 60 potential cases in CRICO’s administrative
data base. Fifty-four were confirmed to
involve a retained foreign body after surgery and to
have the required medical records available. Fortyseven
of these cases were identified on the basis of
malpractice claims and seven on the basis of incident
reports.
These cases involved 61 retained foreign bodies.
A total of 69 percent of cases involved sponges; 31
percent involved instruments (Table 1). No major
bodily cavity was spared. Over half (54 percent) of
the foreign bodies were left in the abdomen or pelvis,
22 percent in the vagina, 7.4 percent in the thorax,
and 17 percent elsewhere, including the spinal
canal, face, brain, and extremities. No surgeon was
responsible for more than one case.
The median date of detection was the 21st day
after surgery (range, day of surgery to 6.5 years after
surgery). In only 3 of 54 cases (6 percent) was the retained
object detected by the first day after surgery.
In 14 cases (26 percent), the retained object was not
results
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detected until 60 days or more after surgery. The
objects were most often detected by radiography or
computed tomography (67 percent). Other retained
objects (24 percent) were detected on physical examination
or self-examination (particularly for objects
left behind after vaginal procedures) or on reoperation
(9 percent).
Overall, the retention of a foreign body was a
rare event. The incidence varied from 1 in 8801 to
1 in 18,760 inpatient operations at the nonspecialty
acute care hospitals (the four principal hospitals
and one other) insured by CRICO for which complete
data on inpatient operations and claims and
incident reports on retained foreign bodies were
available throughout the period from 1990 through
2000. However, the consequences were serious.
Thirty-seven patients with a retained foreign body
(69 percent) required reoperation for removal of
the object and management of complications. In
the remainder, the foreign body was expelled, could
be removed at the bedside, or was discovered incidentally
and removed at the time of another operation.
In 12 cases (22 percent), the retained foreign
bodies resulted in small-bowel fistulae, obstruction,
or visceral perforations; and in 1 case, the retained
object resulted in death.
In all 47 of the cases that had prompted litigation,
the claims were closed by the time of our review.
These claims resulted in an average of $52,581 in
costs for compensation and legal-defense expenses.
case–control analysis
We obtained complete medical records for 235 controls
(a mean of 4.4 per case). According to univariate
analyses, cases were more likely to involve an
emergency surgical procedure, an unexpected
change in procedure, a procedure involving more
than one surgical team, or the lack of a count of
sponges and instruments (Table 2). Of the patients
with a retained foreign body, 33 percent had undergone
an emergency operation, whereas only 7 percent
of the control patients had undergone such an
operation. A total of 34 percent of patients with a
retained foreign body had undergone an operation
with an unexpected change in procedure, as compared
with 9 percent of control patients (Table 2).
Patients with retained foreign bodies also had a significantly
higher body-mass index than control
patients. The age of the patient, the duration or
lateness of the operation, and the involvement of
multiple procedures were not significantly associated
with a risk of retention of a foreign body.
Among the instances in which counts were performed,
the count was reported as correct for 88 percent
of patients with retained objects and 92 percent
of controls; the difference between groups was not
significant.
In multivariate analysis (Table 3), three factors
remained significantly associated with an increased
risk of retention of a foreign body: emergency procedure
(risk ratio, 8.8; P<0.001); unplanned change
in the procedure performed (risk ratio, 4.1; P=0.01);
and body-mass index (risk ratio for each one-unit
increment, 1.1; P=0.01). The sex of the patient, the
involvement of multiple teams, the estimated volume
of blood lost, and changes in nursing personnel
were not significantly associated with the risk
of retention of a foreign body. Failure to perform a
count of the sponges and instruments, which had
shown a strong relation to the retention of foreign
bodies in univariate analysis, was no longer a significant
predictor in the multivariate model. Further
testing showed that omission of counts was
strongly related to the emergency status of the
procedure.
Our study confirms previous findings that the
leaving behind of foreign bodies in a patient after
surgery is an uncommon but dangerous error. The
incidence we found of 1 in 8801 to 1 in 18,760 inpatient
operations corresponds to one case or more
discussion
Table 1. Characteristics of 54 Cases of a Retained
Foreign Body after Surgery.
Characteristic No. of Cases (%)
Type of foreign body retained
Sponge
>1 Sponge
Clamp
Other (e.g., retractor or electrode)
37 (69)
4 (7)
4 (7)
13 (24)
Cavity in which foreign body was left
Abdomen or pelvis
Vagina
Thorax
Other
29 (54)
12 (22)
4 (7)
9 (17)
Outcomes
Death
Readmission to hospital
or prolonged hospital stay
Sepsis or infection
Reoperation
Fistula or small-bowel obstruction
Visceral perforation
1 (2)
32 (59)
23 (43)
37 (69)
8 (15)
4 (7)
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retained instruments and sponges after surgery
233
each year for a typical large hospital. Because these
rates are calculated only on the basis of malpractice
claims, they are most likely underestimates. Also,
because of the lack of procedure-specific data, the
operations that form the denominator for our calculation
of incidence include large numbers of laparoscopic,
endoscopic, or catheterization procedures
— interventions that are unlikely to result in
a forgotten instrument or sponge. (We found no
cases involving such procedures.) The rates are
most likely substantially higher for operations involving
an open cavity. Overall, our results suggest
that, given the 28.4 million inpatient operations
performed nationwide in 1999,
12
more than 1500
cases of a retained foreign body occur annually in
the United States.
The case–control method we applied identified
several risk factors for these complications. We
found that the retention of a foreign object was
nine times as likely when an operation was performed
on an emergency basis and four times as
likely when an operation involved an unexpected
change in procedure. Each of these factors marks
situations in which disorganization is increased so
that it becomes more difficult to keep track of materials.
One indication of this relation is our finding
that emergency operations were significantly
more likely to involve a failure to perform a count
of sponges and instruments. The increased risk associated
with increased body-mass index probably
reflects the amount of room there is in a patient in
which to lose a sponge or instrument.
Certain limitations must be considered in interpreting
the findings of our study and the value of its
methodology for research on other domains of patient
safety. Malpractice claims and reports are an
imperfect representation of the true incidence and
nature of any complication.
13-15
Some cases of retained
foreign bodies undoubtedly did not result in
either a claim by a patient or a report by the physi-
* Plus–minus values are means ±SD. Denominators are the number of patients with data on the given variable. P values were determined
by matched univariate logistic regression.
† The body-mass index is the weight in kilograms divided by the square of the height in meters. Data were missing for seven patients
with retained foreign bodies and five control patients.
‡ Data were missing for four patients with retained foreign bodies and one control patient.
§ Data were missing for 9 patients with retained foreign bodies and 31 control patients.
¶Data are for operations that were started between 5 p.m. and 7 a.m. or completed between 7 p.m. and 7 a.m.
Table 2. Characteristics of Patients with a Retained Foreign Body, Control Patients, and Procedures.*
Characteristic
Patients
with a Retained
Foreign Body
(N=54)
Control
Patients
(N=235) P Value
Age — yr 46.3±17.6 48.3±18.5 0.39
Female sex — no./total no. (%) 34/54 (63.0) 161/235 (68.5) 0.19
Body-mass index† 28.2±6.3 26.4±5.2 0.04
Counts of sponges and instruments performed — no./total no. (%)
Count considered correct
36/54 (66.7)
30/34 (88.2)
181/228 (79.4)
167/181 (92.3)
0.01
0.44
Duration of operation — min‡ 181.9±152.7 173.8±152.1 0.20
Estimated volume of blood lost — ml§ 771.9±1646.5 503.8±982.6 0.06
Blood loss of >500 ml or transfusion given — no./total no. (%) 21/53 (39.6) 72/212 (34.0) 0.43
Operation performed on emergency basis — no./total no. (%) 18/54 (33.3) 16/235 (6.8) < 0.001
Operation performed after hours — no./total no. (%)¶ 15/46 (32.6) 57/232 (24.6) 0.26
Unexpected change in operation — no./total no. (%) 18/53 (34.0) 21/235 (8.9) < 0.001
>1 Surgical team involved — no./total no. (%) 8/54 (14.8) 17/235 (7.2) 0.05
>1 Major procedure performed — no./total no. (%) 9/54 (16.7) 27/235 (11.5) 0.31
Change in nursing staff during procedure — no./total no. (%) 19/33 (57.6) 76/177 (42.9) 0.16
Surgeon present at closure — no./total no.(%) 30/44 (68.2) 112/181 (61.9) 0.80
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cian to the insurer. The factors involved in such cases
may differ from those in the cases we studied.
However, we know of no reason why they would differ
in terms of the mechanism of causation. In addition,
these mishaps appear to have a high likelihood
of leading to litigation, given how injurious
and potentially avoidable they are.
Our results suggest at least two possible measures
to reduce the occurrence of retention of foreign
bodies. Although counts of sponges and instruments
were performed in most cases, there was no
documentation of such a count one third of the
time. The observation that the failure to perform
these counts was not a significant risk factor according
to multivariate analysis does not imply that such
counts are not important. Rather, the emergency
nature of an operation or the involvement of an unexpected
change in procedure was a marker of increased
risk from potentially several mechanisms,
of which failure to perform counts was apparently
just one. We found that counts of sponges were universally
omitted after the closure of an episiotomy
or vaginal tears after delivery; 11 such procedures
involved retained sponges. We strongly recommend
that hospitals actively monitor compliance with the
existing standard of counting sponges in every
operation, including obstetrical procedures, and
of counting instruments in every operation involving
an open cavity.
Counts are clearly not always sufficient, however.
Of the many cases of retained foreign bodies in
which counts were performed, 88 percent involved
a final count that was erroneously thought to be correct.
These findings suggest that screening of highrisk
patients at the end of operations should be
considered even when counts are documented as
correct. The primary method currently available is
radiographic screening, ideally performed before
the patient leaves the operating room. The current
use of radiographic screening varies widely. A few
institutions obtain radiographs in every patient who
undergoes an open-cavity operation; most use radiography
only in those with a count that is recorded
as incorrect; some appear to have no policy regarding
radiography at all.
16
Our findings imply that routine intraoperative
radiographic screening in selected, high-risk categories
of operations could prove to be a useful measure
for detecting foreign bodies that have been inadvertently
left behind. On the basis of previous
estimates that such incidents occur in 1 in 1500 operations
involving an open abdomen or chest
6
and
our findings that emergency status applied to one
third of patients with retained objects and just 7 percent
of controls, we estimate that 300 radiographs
would be needed to detect 1 retained foreign body.
A prospective study would be needed to test such
an estimate. However, given costs of more than
$50,000 per case for malpractice-claims expenses
alone, a $100 plain film could prove a cost-effective
intervention.
Policymakers have advocated establishing reporting
systems for errors to obtain information
on the patterns underlying specific types of errors.
1
Our study presents an effective method for identifying
and quantifying risk factors for medical errors
from such data, even for types of errors that are relatively
rare.
Supported by a grant (U18HS11886) from the Agency for Healthcare
Research and Quality and by the Risk Management Foundation
of the Harvard Medical Institutions. Dr. Studdert was also supported
in part by a grant (KO2HS11285) from the Agency for Healthcare
Research and Quality.
We are indebted to Kathy Dwyer and Anthony Chamberas for assistance
with data acquisition; to the hospitals and staff members
who provided access to the medical records required for this study;
and to Elisabeth Burdick for assistance with data management.
* Characteristics with P values of less than 0.05 according to matched multivariate logistic
regression were considered to be associated with a significantly increased
risk of retention of a foreign body. CI denotes confidence interval.
Table 3. Risk Factors for Retention of a Foreign Body after Surgery.*
Characteristic Risk Ratio (95% CI) P Value
Operation performed on an emergency basis 8.8 (2.4–31.9) <0.001
Unexpected change in operation 4.1 (1.4–12.4) 0.01
>1 Surgical team involved 3.4 (0.8–14.1) 0.10
Change in nursing staff during procedure 1.9 (0.7–5.4) 0.24
Body-mass index (per 1-unit increment) 1.1 (1.0–1.2) 0.01
Estimated volume of blood lost (per 100-ml
increment)
1.0 (1.0–1.0) 0.19
Counts of sponges and instruments performed 0.6 (0.03–13.9) 0.76
Female sex 0.4 (0.1–1.3) 0.13
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retained instruments and sponges after surgery
235
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