Ruptured
abdominal aortic aneurysm: prognostic factors
Denise Rabelo da Silveira, Vanessa Prado dos Santos, Aline Faria Lamaita, Henrique Jorge Guedes Neto, Alvaro Razuk Filho, Valter Castelli Jr., Roberto Augusto Caffaro*
*
Department of Surgery, School of Medical Sciences, Santa Casa de São
Paulo, São Paulo, SP, Brazil.
Correspondence:
Denise Rabelo da Silveira
Rua São Vicente de Paula, 416/94
CEP 02350-002 - São Paulo, SP, Brazil
Phone: +55 (11) 3226.7273
Fax: +55 (11) 3226.7273
E-mail: suely.longui@fcmscsp.edu.br
ABSTRACT
Objective:
To analyze the prognostic factors related to the mortality of ruptured
abdominal aortic aneurysm.
Methods:
Seventy-two patients who suffered ruptured abdominal aortic aneurysm
and were operated in the period between 1976 and 2000 by the Vascular
Surgery Unit of the Santa Casa de São Paulo - School of Medical
Sciences were retrospectively analyzed.
Results: The descriptive analysis of the data shows a mean age
of 67.93 years, with a standard deviation of 11.58, 32% female and
68% male. Of the total number, 28% had a previous history of aneurysm
and 72% were not aware of the disease. Mean systolic blood pressure
during hospital admission was 96.53 mmHg. Pain was present in 100%
of the patients, as well as throbbing abdominal mass. In 93% of
the cases the location of the aneurysm rupture was the retroperitoneum,
4% in the duodenum, and 2% in the free peritoneum.
Conclusions: The prognostic factors related to mortality and
morbidity that demonstrated statistical significance were: age,
initial blood pressure at hospital admission, diuresis during surgery,
volume infused, and creatinine levels.
Key-words:
ruptured aneurysm, abdominal aortic aneurysm, morbidity.
J
Vasc Br 2005;4(4):321-6
The rate
of aortic aneurysms is estimated to be 2.5% in the male population between
65 and 74 years, possibly reaching up to 9% in patients over 75 years
of age.1 In the period between 1951 and 1980, a significant increase
was observed in the rate of abdominal aortic aneurysm (AAA) from 12.2/100,000
to 36.2/100,000 inhabitants.2,3
Ruptured
AAA is the most frequent and most serious complication, with 20-40/100,000
cases each year, and could be the first aneurysmal manifestation in
up to 50% of the cases, representing 1.1% of all deaths in the male
population over the age of 50.1,4 Its rate rises relative to age and
reaches its peak in the 80-89 male age group, with rates of 112.7/100,000
and rates of 67.7/100,000 in women older than 90 years.2
The mortality
of ruptured AAA varies between 15 and 68%, with mean of 50%, which demonstrates
a great contrast when compared to the mortality of 2.9% in patients
submitted to optional/elective surgery.2,5,6 Most authors speculated
a significant rise in the mortality of these patients, approximately
90%, if patients with home deaths are included, due to the fact that
only 50% of these arrive to the hospital alive.1,5,7
Due to
significant improvements of the survival rate of patients with this
affliction in the last decade attributed to the progress in all treatment
stages - from pre-hospital care to more developed surgical and anesthetic
techniques - a more detailed study was virtually mandatory to find out
why there is such elevated inferior prognostic rates in patients with
ruptured AAA.2,8
Hemorrhagic
shock and reperfusion/ischemic syndrome may lead to tissue lesions with
the liberation of free radicals, activating neutrophils and the release
of inflammatory mediators. Free radicals cause lipoprotein membrane
lesions causing changes in cellular function, contributing to post-surgery
multiple organ and system failure, which explains the higher difficulty
to treat these patients and may explain the poor prognostic, despite
all the advanced techniques mentioned in the literature.9
All patients
presented a diversity of factors that determined a greater predisposition
to aneurysm rupture, and a worse prognosis after surgical treatment
of ruptured AAA. Therefore, there is a need for understanding the contribution
for the prognosis of each of these factors individually.2,10 Other authors
in the last decade studied factors that could be used as early risk
factors predisposing to increased mortality.1,2,5,6,11
The factors
most frequently studied can be divided into preoperative (previous coronary
disease, chronic obstructive pulmonary disease, systolic blood pressure,
hematocrit, creatinine, gender and age) and intraoperative (aortic clamping
time, location of aortic clamping, surgery duration, diuresis, and infusion
volume).1,2,5,6,8,11
The goal
of this study was to analyze prognostic factors that determine premature
death in patients with ruptured AAA.
PATIENTS
AND METHODS
A retrospective
analysis was done of all cases of ruptured AAA admitted to the Emergency
Service of the Santa Casa de Misericórdia Hospital de São
Paulo from January 1976 to December 2000 that were submitted to
surgical treatment by the Vascular Surgery Unit of this service. All
patients admitted with ruptured AAA in the emergency room were submitted
to surgical treatment, and all of them were included for analysis, even
the ones who died in the operating room.
Seventy-two
patients were analyzed and initially included in the protocol, divided
into subgroups according to the prognostic factors to be studied, and
morbidity rates of each group submitted to statistical analysis. Some
patients were excluded from a few subgroups because they did not have
all the information analyzed in this specific group factor.
Statistical
analysis was made using the chi-square and Fisher's exact test, admitting
a P < 0.005. The chi-square test was used for the factors
of age, gender, creatinine level, systolic blood pressure, aortic clamping
duration, volume transfused and surgery duration. The rest of the factors
were analyzed using Fisher's exact test depending on the size of the
group.
RESULTS
The sample
was comprised of 32% female patients and 68% male patients, with a general
mortality rate reaching 54%. Mean age was of 67.93 years, with a standard
deviation of 11.58 years. Previous history of AAA was present in 28%
of cases and 100% presented abdominal pain and throbbing abdominal mass
when admitted to the hospital.
The aneurysms
presented a mean diameter of 8.17 cm, with a standard deviation of 2.57
cm. The retroperitoneum was the most common location for rupture (93%),
followed by the duodenum (4%) and free peritoneum (2%).
Mean blood
pressure was 96.53 mmHg, with a standard deviation of 41.01 mmHg. Duration
of aortic clamping had a mean of 109.71 minutes, with a standard deviation
of 55.5 minutes; surgery duration had a mean time of 4.22 hours, with
a standard deviation of 1.37 hours. This subgroup was composed of: 17
cases with blood pressure lower than 70 mmHg; 27 cases higher than 119
mmHg and 28 cases in between.
When gender
was analyzed as a prognostic factor, the mean death rate was 57% for
male patients and 52% for female patients, but it presented no statistical
significance (P = 0.69), which demonstrates that gender is not
related to the mortality rate in our study.
Age proved
to be a significant (P = 0.002) prognostic factor, with a higher
death rate in the age groups between 61-70 years (90%) and 71-80 years
(83%), showing that age and morbidity are directly proportional factors
(Figure 1). Our group study was composed of: five patients with 40-50
years (one death); 11 patients with 51-60 years (three deaths); 24 patients
with 61-70 years (10 deaths); 18 patients 71-80 years (15 deaths); 14
patients 81-90 years (11 deaths).
 Figure
1 - Analysis of the prognostic factor of age vs. mortality
The prognostic
factor of creatinine during hospital admission shows a death rate of
60% in groups with creatinine levels over 1.3 mg/dl (n = 30 patients)
and of 12.5% with creatinine lower than 1.3 mg/dl (n = 16 patients),
with a statistically significant difference between groups (P = 0.002)
(Figure 2). Twenty-six patients were excluded because we did not have
all the information required.
Figure
2 - Analysis of the prognostic factor of creatinine vs. mortality
Blood pressure
during hospital admission proved to be inversely proportional to death
rate, with a higher rate (88%) in patients with pressure index less
than 70 mmHg (P = 0.003), (Figure 3).
Figure
3 - Analysis of the prognostic factor of systolic blood pressure vs.
mortality
Intraoperative
diuresis was related to death rates of 100% in patients with less than
199 ml (P = 0.008) (Figure 4). This group study was composed by: 38
patients with over 200 ml of diuresis (15 deaths) and 06 patients less
than 199 ml (six deaths). Twenty-eight patients were excluded because
we did not have all the information required.
Figure
4 - Analysis of the prognostic factor of intraoperative diuresis vs.
mortality
Aortic
clamping time did not prove to be related to prognosis (P = 0.29).
Mean clamping time was 109 minutes, with a standard deviation of 55.51
minutes.
An improved
prognosis was observed in patients who received between 4 and 8 l of
transfused volume (41%) compared with patients who received over 8 l
or under 4 l (P = 0.002), showing a statistically significant
difference between volume transfused and death rate (Figure 5).
Figure
5 - Analysis of the prognostic factor of volume transfused vs. mortality
The variables
of surgical time, hematocrit, and aneurysm size are not related to a
better or worse prognosis. Our group study was comprised of 23 patients
with hematocrit lower than 29 mg/dl and 10 patients above it. We did
not have the hematocrit value for 39 cases.
DISCUSSION
The signs
and symptoms that accompany ruptured AAA are usually dramatic. Sudden
abdominal pain that radiates to the back seems to be present in nearly
70% according to the literature, and is associated to a throbbing abdominal
mass during physical examination in 80% of cases.8 In our study, the
presence of abdominal pain and abdominal mass and mortality was 100
and 54%, respectively, which is consistent with the literature.
There was
a predominance of 68% in males, results that are similar to most studies
that evidence gender incidence, which varies in the ratio of 4:1 for
men.2,5 As in the literature, the gender factor alone does not seem
to have a strong correlation with the prognosis.
Regarding
the location of the ruptured aneurysm, 93% of cases were in the retroperitoneum,
with only 2% occurring in the free peritoneum. In general, a higher
incidence of rupture in the free peritoneum is described with a higher
mortality rate, even though this is not a consensus in the literature.
Gloviczki et al. and Wakefield et al. claim that a lower incidence of
ruptures in the free peritoneum reflects an inferior prognosis for patients
who would have a faster evolution and thus represents the group of home
deaths, being therefore a repercussion of the pre-hospital care.6,8
Age has
been cited as an important variable for the prognosis, even though it
is mainly considered a contributive factor and not an independent one.2,8
Crawford et al. and Johansson & Swedenborg showed a higher morbidity
rate in octogenarians, but agree that the age factor alone should never
contraindicate surgical treatment.6,12,13 Furthermore, there are authors
who believe age has no association with morbidity.5,11 In our study,
we observed that the age group is a factor that presents a strong connection
with morbidity, being directly proportional variables.
The hypovolemic
shock is the most common factor associated to ruptured AAA. It is in
general agreement that low-pressure levels during hospital admission
are strong predictors of morbidity. In our unit, the place where preoperative
pressure levels were determined was inversely proportional to morbidity,
with higher rates with levels under 70 mmHg (80%). Crawford et al.12
advocate that preoperative resuscitation should be performed with little
volume maintaining pressure levels between 50 and 70 mmHg until aortic
clamping is performed, due to the fact that higher pressure levels are
related to the detachment of thrombus and subsequent hemodynamic instability.
Several services believe that such low pressure levels result in a higher
morbidity rate with a higher incidence of multiple organ failure.1,2,5,8,11
With regard
to necessary volume restitution, we observed that patients who received
more than 8,000 ml and less than 4,000 ml had a better prognosis than
the patients who received intermediary levels. In general, estimated
volume loss was a determinant factor in inferior prognosis in most cases
and aggressive volume restitution followed such results. A better prognosis
was observed in services that advocate quick control of volume loss
through aortic clamping or placement of an intra-aortic balloon, thus
causing a reduction in volume loss and consequent volume restitution.8,14
Lindsay
et al.2 found a lower survival rate in patients who presented creatinine
levels higher than 1.3 mg/dl, showing that creatinine levels are factors
strongly associated with morbidity. In our study, there was a morbidity
rate of 60% in patients with creatinine higher than 1.3 mg/ml, with
statistical analysis showing that this factor is strongly associated
with lethality. When renal function is altered before the surgical procedure,
there is a higher risk of postoperative deterioration, and if this complication
is present, a high morbidity rate is observed.14
As well
as creatinine levels, intraoperative diuresis proved to be an independent
indicator of morbidity with a higher lethality rate in patients with
diuresis less than 199 ml (100% lethality), consistent with other studies
in the literature, which show a strong correlation between diuresis
and morbidity.2
There is
an agreement that the duration of aortic clamping is a determinant factor
of worse prognosis and is related to postoperative renal insufficiency,
as well as sepsis and pulmonary complications; lack of such complications
in our study may be explained by the size of our sample and could be
better studied with an increase in the number of patients in a future
study.2,5,14 The Brazilian literature has some descriptions of different
forms of aortic clamping that can help in surgery, such as the aortic
compressor, which can be done with a smaller incision, a quicker one,
stopping the bleeding while the rest of the incision is made. Another
form of aortic clamping time is the use of a catheter with a balloon
implanted through the brachial artery, which is insufflated in the aorta.15
Unfortunately, we did not have access to those techniques and in all
our cases the aortic clamping was made by clamping the infrarenal aorta
in the surgery.
Similarly
to clamping time, surgical duration seems to have a strong relation
with an inferior prognosis, although it has not been evidenced in our
study. Surgical duration of more than 300 minutes reveals a higher lethality,
with rates of 100% in a period greater than 400 minutes.8
Aneurysm
size is classically related to aneurysm rupture. Sterpetti et al.16
report that rupture occurs in 9.5% of aneurysms smaller than 4 cm, 24.5%
between 4 and 7 cm, and 59.4% in patients with aneurysms larger than
7 cm. However, there is no scientific evidence that aneurysm size has
any correlation with a better or worse prognosis after rupture.
Hemoglobin
values under 11 g/dl are related to a morbidity of 67%, while morbidity
rates of 27% were observed with higher values of hemoglobin.8 Preoperative
hematocrit values were assessed in our study and statistical analysis
did not match the previously reported findings.
A great
unknown fact that motivated our study of prognostic factors related
to lethality of ruptured AAA was the belief that an associated factor
or associated factors could characterize inferior prognosis and, by
correcting such factors could improve the evolution of these patients.
In this way, several authors in the last decade investigated the relationship
of isolated and associated factors.
Some authors
such as Crawford et al.12,17 and Gloviczki et al.6 believe that no factor
or association of factors should contraindicate surgical treatment,
even finding mortality rates of 90% in some subgroups, such as female
patients over the age of 80 with admission hematocrit levels lower than
25% and with mortality of 100% in patients with previous serious coronary
complications.
On the
other hand, Johansson & Swedenborg13 believe that in some situations
surgery should not be performed, in accordance with Hardman et al.18,
who propose in their study that age over 76 years, loss of conscience
after arrival, hemoglobin inferior to 9%, ischemia identified in the
electrocardiogram and creatinine levels higher than 0.19 mmol/l to be
used as criteria, in which the presence of three or more of such factors
should be considered as a contraindication to surgical treatment, since
these patients present mortality rate of 100%.13
In general
it is believed that these criteria should be extremely necessary postsurgically
as an additional factor to indicate or not a more aggressive clinical
treatment for patients with lower chances of evolution. The endovascular
treatment has been advocated as an alternative to open surgery for patients
with ruptured AAA with low mortality rates, but with a high percentage
of secondary interventions.19 However, it is limited by morphologic
aneurysm characteristics (including neck length and diameter) and by
the patient's hemodynamic conditions.
In summary,
we demonstrated in this study that the prognostic factors of age, creatinine
levels, systolic blood pressure, intraoperative diuresis, and volume
transfused have strong association as indicators of premature mortality
in ruptured AAA.
Acknowledgments
We are
grateful to the Support Center for Scientific Publications of Santa
Casa de São Paulo - School of Medical Sciences for the editorial
assistance.
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