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June 2002
Volume 66 |
Number 6
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| Changing Trends
in Anesthesia-Related Death and Permanent Brain Damage |
Frederick W. Cheney, M.D., Director
ASA Closed Claims Project
Analysis of the most recent data from the ASA Committee on Professional
Liability Closed Claims Project indicates that severe anesthesia-related
injuries such as death and permanent brain damage are becoming
less frequent among injuries reported to insurance carriers. This
standardized collection of case summaries of adverse anesthesia-related
outcomes has been ongoing since 1985 and now contains 5,480 claims
or potential claims from 35 insurance organizations that insure
approximately 14,500 anesthesiologists. This analysis consists
of 1,870 claims for death or permanent brain damage occurring
in the 1980s and 1990s.
In the 1980s, 42 percent of claims involved death or permanent
brain damage compared to 32 percent in the 1990s (p<0.05) [Figure
1]. This decrease was predominately due to a decrease in claims
for death (32 percent versus 22 percent) in the 1980s versus the
1990s. In the 1980s, respiratory-related damaging events were
more common (48 percent) than cardiovascular-related damaging
events (23 percent) [Figure 2]. In the 1990s,
cardiovascular and respiratory damaging events were responsible
for the same percent of claims involving death or brain damage
[Figure 2]. The third most common damaging
event, equipment failure or misuse, showed little change between
the decades.
Trends in Respiratory Events
The most common respiratory damaging events causing death or permanent
brain damage in the 1980s and 1990s were inadequate ventilation,
esophageal intubation and difficult intubation [Figure
3]. Claims for inadequate ventilation and esophageal intubation decreased significantly in the 1990s as compared to the 1980s. These two events combined accounted for 25 percent of claims for death and brain damage in the 1980s, decreasing to 9 percent in the 1990s. As Figure 3 shows, reductions in these two events account for nearly the entire decrease in respiratory-related death and brain damage claims between the 1980s and 1990s. The proportion of claims for difficult intubation and other respiratory events leading to death or brain damage stayed relatively stable between the 1980s and 1990s [Figure
3].
The question arises as to the cause of the reduction in the relative
proportion of anesthesia-related deaths or permanent brain damage
as compared to other anesthesia-related injuries. The use of pulse
oximetry (SPO2) and end-tidal carbon dioxide (ETCO2) monitors,
which came into use in the mid- to late-1980s and became ASA standards
in the early 1990s, would seem to be the most likely cause. When
the claims are grouped by monitors used (or not used) during anesthesia,
a clearer picture emerges. Figure 4 shows
the most common respiratory events leading to death or brain damage
as a proportion of respiratory events (rather than all claims).
Inadequate ventilation decreased significantly when either SPO2
alone or ETCO2 also was monitored. On the other hand, SPO2 monitoring
did not affect the proportion of claims for esophageal intubation
unless ETCO2 also was monitored [Figure 4].
SPO2 only gives information about an end-stage symptom (hypoxemia)
of an esophageal intubation and does not make a primary diagnosis
of this condition as does ETCO2. The proportion of respiratory-related
claims for difficult intubation was unaffected by the presence
of SPO2 and ETCO2 monitoring [Figure 4]. If
anything, the proportion of respiratory-related claims for death
or permanent brain damage due to difficult intubation was greater
when SPO2 and ETCO2 were utilized. This is not surprising, as
placement of an endotracheal tube is a technical act whose success
may not be influenced by monitoring. Thus the overall reduction
in respiratory-related damaging events seems to be related to
two injuries (inadequate ventilation and esophageal intubation)
most affected by SPO2 and ETCO2 monitoring.
Trends in Cardiovascular Events
The cause of the increase in the proportion of cardiovascular-related
damaging events as a mechanism of death or permanent brain damage
in the 1990s is not readily apparent [Figure 2].
When the specific cardiovascular damaging events are analyzed
according to decade, no significant pattern emerges. The largest
cardiovascular-related category is the "unexplained/other," which
includes pulmonary embolism, stroke, myocardial infarction, arrhythmia
and undiagnosed (preoperative) conditions such as myocardial fibrosis
or cardiomyopathy identified post mortem. These events account
for 11 percent of death and brain damage claims in the 1980s and
17 percent in the 1990s (p<0.05). Likewise, the occurrence of
death or permanent brain damage due to cardiac arrest associated
with neuraxial block (4 percent in the 1980s and 1990s), inadequate
fluid replacement (2 percent in the 1980s; 3 percent in the 1990s)
and excessive blood loss (3 percent in the 1980s; 2 percent in
the 1990s) did not show any change with time. When the cardiovascular
damaging event data are analyzed by monitoring group, no clear
picture emerges.
Implications for Further Reductions in Death and Brain Damage
Do the current findings have any implications for further improvement
in decreasing the occurrence of anesthesia-related death or permanent
brain damage? Any interpretation of closed claims data for predictive
purposes has to be done with an understanding of its drawbacks,
including lack of denominator data and a three- to five-year time
lag between the date of injury and closure of a claim. The database
represents claims, not all patient injuries, so it is possible
(but unlikely) that plaintiff attorneys are not pursuing claims
for anesthesia-related death and permanent brain damage as frequently
in the 1990s as in the 1980s.
With the aforementioned in mind, the data seem to indicate that
there is a decrease in the proportion of anesthesia-related claims
for death and permanent brain damage in the 1990s. This seems
to be related to the use of SPO2 and ETCO2 monitoring, as evidenced
by the fact that the damaging events most affected are inadequate
ventilation and esophageal intubation. Within the respiratory
damaging events group, further opportunities for a reduction in
severe injury would seem to lie in utilization of the ASA "Practice
Guidelines for Management of the Difficult Airway."1
The Closed Claims Project Subcommittee has been collecting data
evaluating the role of this guideline (first published in 1993)
in claims where the injury was due to difficult intubation. Analysis
of these data should, in time, give information as to the impact
of the guideline on the occurrence of the injury due to difficult
intubation.
The relative increase in the proportion of cardiovascular damaging
events in the 1990s deserves comment. This increase may be due
to the fact that injuries related to the onset of bradycardia
and hypotension, which were previously attributed to inadequate
ventilation/oxygenation in the absence of SPO2/ETCO2 monitoring,
are now more appropriately attributed to primary cardiovascular
damaging events. There is no clear pattern of injury in the more
frequently occurring cardiovascular damaging events category (unexplained/other).
The only cardiovascular category where there is a recurring pattern
is that of cardiac arrest associated with neuraxial block. In
this case, early recognition of the phenomenon with prompt pharmacologic
therapy and thump-pacing or chest compression offer the most opportunity
for prevention of the injury.
In summary, Closed Claims Project data indicate a downward trend
in the occurrence of claims for severe patient injury. This seems
to be primarily due to injuries that are amenable to prevention
by SPO2 and ETCO2 such as inadequate ventilation/oxygenation and
esophageal intubation. If the downward trend is entirely due to
injuries preventable by monitoring, then future strategies to
prevent severe injuries should be directed to cardiovascular events
and respiratory-related damaging events not amenable to prevention
by SPO2 and ETCO2 monitoring.
Reference:
1. Caplan RA, Benumof JL, Berry FA, et al. Practice
guidelines for management of the difficult airway: A report by
the American Society of Anesthesiologists Task Force on Management
of the Difficult Airway. Anesthesiology. 1993; 78:597-602.
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Frederick
W. Cheney, M.D., is Professor and Chair, Department of Anesthesiology,
University of Washington School of Medicine, Seattle, Washington. |
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