Study background: To identify important risk factors for subsequent amputation within one year after surgery in
patients with acute lower limb ischemia undergoing distal arterial bypass.
Methods: A chart review of patients undergoing distal vascular bypass for lower limb ischemia within the 5-year
period between 2006 and 2011 was done. All patients were followed for at least one year. The outcome of interest
was the need for amputation of the treated limb within one year after bypass surgery. Potential risk factors associated
with the need to perform amputations were abstracted from the medical charts. Logistic regression and chi-square
tests were used to identify significant associations between risk factors and amputation.
Results: Of 128 patients reviewed, only 18 (14%) had amputations within one year. Although there was a
trend for increased risk of amputation for patients with a history of smoking, DM, renal dysfunction, presenting
with rest pain, lower ABI, multilevel disease, circumferential thickening of the stenosis, and lower risk for patients
taking postoperative antiplatelets (but not anticoagulants), the only significant risk factor at the 5% level were poorly
controlled diabetes mellitus after operation and cerebrovascular disease.
Conclusion: A few well-known risk factors were associated with increased risk of early amputation after arterial
bypass surgery.
Limb salvage is the primary goal in management of peripheral
arterial occlusive disease (PAOD), especially in patient with critical limb
ischemia [1-3]. Tentative conclusions might be drawn by examination of
the outcome of surgery for PAOD as measured by the rate of amputation
[4]. Evaluation of therapeutic effectiveness of interventional procedures
used to treat peripheral arterial occlusive disease (PAOD) requires use
of several outcome measures that assess factors that affect patients
directly (e.g., survival, amputation-free survival, quality of life, and pain
relief), and clinical measures (e.g., laboratory test measurement) [5-7].
To evaluate the long-term outcome of revascularization procedures
for PAOD at the population level, survival and major amputation-free
survival rates should be used, because they provide more clinically
accepted estimates compared with the correlation between utilization
rates for revascularization and amputation procedures, which have
been used to describe outcome in previously published reports in the
literature [8].
Several population-based studies have decreased rate of amputation
in association with increased use of revascularization procedures
[1,2,4,5,8]. On the other hand some studies showed no changes in lower
extremities amputation rates [9-11]. The assumption in these studies is
that if revascularization procedures avert the need for amputation in
some patients, then a negative correlation should exist between rates of
amputation and revascularization procedures.
Risk of amputation following revascularization procedures was
positively associated with type of procedure, black race, uninsurance/
Medicaid, and diabetes status [12]. Risk of death was also higher
following bypass surgery while this might reflect underlying severity
of disease. Patient education, screening, and optimal care of lower
extremities should be emphasized to peripheral vascular disease (PVD)
patients at an early stage of the disease process [12].
For several risk factors, diabetes-related amputation rates exhibit
high regional variation, even after age, sex, and race adjustment [13].
Only patients receiving dialysis, and not patients with milder degrees
of renal insufficiency, appear to be at higher risk for limb loss after
revascularization, compared with patient with normal renal function
[14].
Materials and Methods
Study design
A retrospective hospital based cohort study utilizing administrative
database in Ramathibodi hospital was conducted from 1 January 2006-
31 December 2011.
Data source
The study was conducted at the Ramathibodi hospital. Case record
for bypass surgery from Ramathibodi hospital discharge was analysed.
The database record contains information on patient demographics,
underlying diseases of patients (diabetes mellitus, hypertension,
coronary artery diseases, congestive heart failure, cerebrovascular
accident, renal insufficiency), diagnosis and procedures. The diagnosis
codes were based on International Classification of Diseases (ICD) 10th
division while operations were based on ICD-9 CM.
Identification of cases
A procedure code for lower extremities arterial bypass surgery code
39.29, the code 39.25 were considered for aorto-ilio-femoral bypass.
Characteristics of patients such as presence of diabetes mellitus,
hypertension, coronary artery diseases, congestive heart failure,
cerebrovascular accident, renal insufficiency were abstracted from
medical records. History of smoking was recorded.
Patients were followed from date of surgery until the occurrence
of the outcome of interest (major amputation within 1 year) or until
last follow up, whichever comes first. Major amputation was defined
as through-ankle amputation, below knee amputation, or above knee
amputation.
Statistical analysis
Logistic regression and chi-square tests were used to identify
significant associations between risk factors and amputation. All P values reported were two-tailed and were considered significant at 0.05,
statistical analysis were perform with SPSS.
Results
This study was undertaken to determine the outcome of
revascularization procedures of PAOD on a hospital basis by reviewed
data in Ramathibodi hospital between 2006 and 2011. The overall
amputation rate in one year was 18 patients in 128 patients (14 %)
after revasucularization procedure. Mean of ABI in affected limb
in amputation group and non-amputation group were 0.46 and 0.53
respectively. Mean of ABI in contralateral side in amputation group and
no- amputation group were 0.82 and 0.86 respectively. Patient baseline
characteristics are summarized in table 1.
Table 1: Patient baseline characteristics.
For many parameters in these 128 patients reviewed in Ramathibodi
Hospital in between 1994-2004, there was a trend for increase risk of
amputation for patients with history of smoking, diabetes mellitus, renal
dysfunction, presenting with rest pain, lower ABI, multilevel disease,
circumferential thickening of the stenosis, and lower risk for patients
taking postoperative antiplatelets (but not in anticoagulant group),
the only significant factors were poorly controlled diabetes mellitus
and cerebrovascular diseases. There was no correlation between risk of amputation in one year and coronary artery diseases, congestive heart
failure (during hospital period).
For surgical procedures, there was no significance in comparing by
type of inflow, outflow and types of graft in both groups.
Discussion
Although there was a trend for increased risk of amputation for
patients with a history of smoking, DM, renal dysfunction, presenting
with rest pain, lower ABI, multilevel disease, circumferential thickening
of the stenosis, and lower risk for patients taking postoperative
antiplatelets (but not anticoagulants), the only significant risk factor at
the 5% level were poorly controlled diabetes mellitus after operation
and cerebrovascular disease.
Dormandy et al. [15] showed a 5-year survival rate of 70% in
patients with intermittent claudication while other studies reported a
5-year survival rate of 38 to 48% for patients with critical leg ischemia
treated surgically [16]. Al-Omran et al. [8] showed 5-year cumulative
survival rate of 61.5% and major amputation-free survival rate of 83.4%,
compared with 69% and 92.2% in patients who underwent angioplasty.
Male sex, older age, diabetes, and heart disease were associated with
increased risk for death after revascularization procedure [8]. Increased
risk of major amputation after revascularization procedures was
associated with male sex, older age, and diabetes where as hypertension
was linked to decreased risk. However, because of absence of clinical
indications (intermittent claudicating or ischemia) for intervention in
the databases, comparison between survival rates for these procedure
reports is not possible [17,18].
Ages [19-21], male sex [20-22], coronary artery disease [19,21,23],
diabetes [5,18], and hypertension [23-26] have all been reported as
predictors for increased mortality in patients with PAOD. The most
significant factor in our study was poorly controlled diabetes mellitus
when compared to other factors such as patients with history of
smoking, diabetes mellitus, renal dysfunction, presenting with rest
pain, lower ABI, multilevel disease, circumferential thickening of the
stenosis. The risk was lower in patients who were taking postoperative
antiplatelets (but not in anticoagulant group).
PAOD in diabetic patient (DM) progress more rapidly and
more severely than non-diabetic patient [27]. DM compromises
endothelial function by several mechanisms i.e., hyperglycemia, excess
circulation of free fatty acid, increased oxidative stress, decreased
nitric oxide synthesis and prostacyclin [27]. DM also augments the
unstable atheroma formation due to secretion of cytokine by diabetic
endothelial cell that inhibits collagen production of smooth muscle cell
[28]. Fibrinolytic activity is impaired in DM which favors a tendency
to coagulate and persistent thrombin formation [29]. All these
pathophysiological mechanisms are important reasons that explain the
significance of poorly controlled DM in lower limb amputation after
bypass surgery.
Limitation of this retrospective study was that we couldn’t control
many parameters because of small volume of patients, making many
well known risk factors not significant for amputation. However
this study provides more clinically accepted estimates of outcome of
revascularization procedures at the population level, which may be of
great interest to patients undergoing revascularization to treat PAOD.
Physicians could use survival and amputation-free survival rate and
factors that influence them to explain to patient the long term outcome
of revascularization procedures.
In future we will extend this study to increase the number of
patients enrolled that impact on factors affecting the outcome of
revascularization procedures and searching for other factors influencing
amputation free survival rate or significant parameters that may predict
outcome of revascularization procedures.
Acknowledgements
Study concept and design: Chumpon Wilasrusmee
Acquisition of data: Piya Lebkhao, Napaphat Proprom
Analysis and interpretation of data: Chumpon Wilasrusmee, Panuwat
Lertsittichai
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