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| Journal of the New Zealand Medical Association,
10-September-2004, Vol 117 No 1201
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Co-morbidities in trauma patients: common and
significant
Chuan-Ping Tan, Alex Ng, Ian Civil
Trauma is a heterogeneous ‘disease’ that affects
all age groups with varying degrees of severity. Factors that affect trauma
outcome include the severity of the injury, pre-existing health status, time to
definitive care, and the quality of care.
While injury severity, time to definitive care, and the
quality of care in trauma patients can be easily quantified, it has been a lot
more difficult to quantify pre-existing health status (or ‘host
factors’) in trauma patients and relate these to trauma outcome.
The trauma literature gives little credence to
co-morbidities seen in trauma patients. In most trauma outcome analyses, the
surrogate of age is used to represent co-morbidity. In the most commonly used
trauma outcome analyses, age >551 is used as
a single co-morbid surrogate.
In an earlier analysis of co-morbidity in trauma patients
admitted to Auckland Hospital,2 co-morbidities
were seen in patients aged as young as 40 years of age.
As part of a larger study designed to establish a single
abbreviated injury scale (AIS)-like’ grade for co-morbidity (where the
clinical severity of the patient’s co-morbidity is graded like the
AIS),3 the authors evaluated the incidence of
all major and minor co-morbidity in a cohort of trauma patients aged ≥40
years admitted to Auckland Hospital.
MethodsStudy
type—A prospective study of the incidence of co-morbidities in
trauma patients aged ≥40 years who were admitted to the Auckland hospital
was undertaken.
Study population and
period—Between 1 January 2003 and 3 March 2003, data was collected
on all trauma patients admitted to Auckland Hospital. The primary inclusion
criterion for the study were patients who had suffered a significant traumatic
event that required a period of hospitalisation under the trauma team. The
second inclusion criterion was that the population to be studied had to be 40
years of age or greater.
Data
collected—The data was collected using a customised trauma registry
available to the Auckland Hospital trauma
team.4 We also recorded major and minor
co-morbidities from these patients. The APACHE 2
PIC (pre-injury
conditions)
system 6 was used to define our criteria
for major co-morbidities, whereas minor co-morbidity was any other ongoing
condition recorded in the patient clinical record or noted by the first
author.
Data collection
method—Patients were identified by checking Auckland
Hospital’s Trauma Registry daily. The first author then reviewed the case
notes; and if the case notes were unclear, the patient would then be
interviewed. A simple questionnaire with the data points stated above was used
to facilitate data collection. Data was also collected from the Auckland
Hospital Discharge Database.
ResultsDuring the study period (1 January
2003 to 3 March 2003), 105 patients who fitted the above study criteria were
reviewed. Of these 105 patients, 57 were males and 48 were females. Their
demographics, co-morbidities, ISS
(injury severity score), and outcome data are broken down into the
various age groups as seen in Table 1.
Table 1. Demographics table
ISS=injury
severity score; SNF=specialised nursing facility; LOS=length of
stay
Co-morbidities were seen in all age groups in both genders.
Overall, 71% of the population had pre-existing co-morbid conditions; 23% of the
study population had major co-morbidity described in the APACHE 2
PIC6 system (Table 2).
Table 2. APACHE 2 Pre-injury criteria (PIC)
CAPD=chronic ambulatory
peritoneal dialysis.
Examples of the minor co-morbidities are shown in Table 3.
Table 3. Minor co-morbidities
An ISS of >15 is classified as major trauma. Injury
severity in patients admitted to Auckland Hospital was found to decrease as age
increases.
The mortality rate in this study population was 4.7%. All
deaths were due to unsurvivable head injury.
The mean length of stay for the cohort of study patients was
8 days (range 1–61 days), and there was an association between major
co-morbidities and the length of stay.
When we compared the length of stay between those with and
without co-morbidities, their length of stay in hospital was 11 days (range
1–61 days) vs 6.8 days (range 2–35 days).
Twenty-one percent of the patients were discharged to a
specialised nursing facility (ie, other hospitals, nursing homes, or
rehabilitation facility). Of these 21% who were discharged to a specialised
nursing facility, 33% had an ISS of >15.
DiscussionThe results of this study showed
that co-morbidities are very common in trauma patients admitted to Auckland
Hospital. The prevalence of co-morbidities in the various age groups seen in
this study is similar to that seen by Mittal et al in their
study.2 They noted that 53.3% of patients aged
≥60 years had co-morbidities compared with our study where we found that
58% of patients aged ≥65 years had co-morbidities.
One of the limitations in our study was the small number of
patients so we cannot draw any statistically significant conclusions—but
when we analysed the data, we found that those patients with major
co-morbidities tended to have a longer hospital stay [11 days (range 1–61
days)] compared to those without co-morbidities [6.8 days (range 2–35
days)].
Morris et al5 (in their
study of the effect of pre-existing conditions on mortality in trauma patients)
showed that 8.8% of all trauma patients admitted into all acute care hospitals
in California in 1983 had co-morbidities. When they analysed their data by
breaking the patients up into various age groups they found that 25% of all
patients aged ≥65 years had co-morbidities compared to our study which is
about 58%. One of the limitations of the study by Morris et al is that they
depended on the discharge medical records for their study data, which could have
grossly under-reported the incidence of co-morbidities in these
patients.
A similar study by Milzman et
al6 prospectively evaluated the effect of pre
existing disease on the mortality of trauma patients, and found that 16% of
their study population of 7798 patients had one or more co-morbidities. On
further analysis of their results, they found that the mean age of patients with
co-morbidities was 49.2 years, whereas the mean age for those without
co-morbidities was 30.6 years. When they reanalysed their results according to
age groups, they found that 48.8% of all co-morbidities occurred in the age
group ≥65 years.
In Table 1, we also note that, as age progresses, the number
of major co-morbidities increases—whereas that of the minor co-morbidities
decreases. This trend is surprising as we would expect the number of minor
co-morbidities to increase as well. This could be due to the fact that younger
patients may have had fewer medical records to go through, hence data collection
of co-morbidities would be easy.
In contrast, the older age group may have had extensive
medical records and minor co-morbidities in this group might have been
overlooked. The minor co-morbidities seen in this older age group are shown in
Table 3. Some of the minor co-morbidities (such as atrial fibrillation and
peripheral vascular disease) although not life threatening on their own, could
contribute significantly to the patient’s morbidity and mortality when
included in the trauma scenario.
Undoubtedly, severe co-morbidity in a young patient (<40)
is likely to affect outcome, but the likelihood of such co-morbidities in this
age group is low. Existing trauma scales (using age as a surrogate) effectively
draws a line at 55 years of age and suggest that co-morbidity above 55 will
affect the outcome of the patient—whereas below 55, co-morbidity is
relatively uncommon.
Similarly we drew a line at the age of 40 (based on our
previous pilot study), however we believe that analysis of specific
co-morbidities, rather than age, will allow us to apply a ‘severity
factor’ to any injured patient, regardless of age.
Some studies have investigated the effect of co-morbidities
on a trauma patient outcome.5–7 All of
these studies found that the presence of co-morbidities worsens the outcome of
the trauma patient, but unfortunately they suffered from methodological
problems, such as flaws in the classification of minor vs major co-morbidities
(studies using ICD 9 classification versus the APACHE system) and over-reliance
on medical records in collecting study data which could have significantly
under-reported the incidence of co-morbidities in the study
populations.
Richmond et al8 found that
pre-existing medical conditions did not contribute to mortality risk but the
authors noted that their finding was inconsistent with the current literature
and they believed the reason for their study finding was due to their inability
stratify the medical condition by severity (which may have led to the above
finding). However these methodological flaws were implicated in the study by
Morris et al4 which found that the presence of
co-morbidities worsens the outcome of the trauma patient.
The same study by Richmond et
al8 showed that whilst co-morbidities did not
influence mortality they increase the odds of experiencing a complication, and
these complications significantly increased the odds of death.
Because of the modest numbers patients in our study, we were
unable to observe any statistically significant association between
‘pre-existing co-morbidities’ and ‘mortality and final
destination at discharge’. Indeed, co-morbidities in trauma patients are
complex and not well addressed by any of the existing injury scales.
Our study shows that co-morbidities are surprisingly common
in trauma patients and likely to impact on the outcomes—both in terms of
survival and complications/length of stay. The results also suggest that it is
feasible to perform a larger scale study at Auckland Hospital to further
evaluate the effect of co-morbidities on the outcome of trauma patients. An
appealing possibility would be the development of a modifier to the current ISS
system that incorporates a single ‘AIS–like’ co-morbidity
score.
Author information:
Chuan-Ping Tan, Surgical Registrar; Alex Ng, Trauma Surgeon and Associate
Director; Ian Civil, Trauma Surgeon and Director, Trauma Services, Auckland
City Hospital, Auckland
Correspondence: Dr
C-P Tan, Room 43.105, Level 4, Auckland City Hospital, Park Road, Private Bag
92024, Grafton, Auckland. Fax: (09) 375 4357; email: chuant@adhb.govt.nz
References:
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