Transcript Measurement the risk of morbidity and mortality. Appropriate patient

Preoperative Assestment
of Vascular Patients
Sussan Soltani Mohammadi,M.D.
Vascular surgical patients
have a high incidence of
morbidity
and
mortality
following surgery due to
coexisting disease associated
with advanced age, cigarette
smoking,
DM,
and
hypertension, affecting CVS ,
respiratory and renal system.
The preoperative period presents
an opportunity to optimize
pharmacologic management ,
perform
diagnostic and
therapeutic interventions , and
adjust care to ↓peri operative
risk and the long term risks from
cardiovascular events.
Purpose of preoperative
assessment:
Measurement the risk of morbidity
and mortality.
Appropriate patient selection.
Appropriate pre, peri , and postop
management.
Ensure that patient is fully informed
of the risk
Cardiovascular system
Most of the perioperative mortality
associated with vascular surgery is due to
cardiovascular complications.
The body’s oxygen demand increases by
up to 40% following major surgery, such
as aortic aneurysm repair.
This extra oxygen demand lasts for
several days postoperatively→↑ CO.
The history and physical examination are
not very reliable for detecting CAD.
An estimate of the patient’s cardio
respiratory
reserve is important, but
can be difficult, because of the high
incidence of claudication , previous
strokes and amputations.
The symptoms of IHD are often not
manifested in diabetic patients, and silent
myocardial ischemia goes unrecognized.
Despite these limitations, important
risk predictors can be obtained from
the History and PH.Exam:
Age >70 years
 DM
 Angina
 CHF
 Prior MI or CABG
 Exercise tolerance, or functional
capacity.
Exercise tolerance, or functional
capacity, is valuable information
that may eliminate the need for
preoperative cardiac testing.
Perioperative risk ↑in patients with
poor exercise tolerance.
Functional capacity, expressed by
metabolic equivalents (METs).
Guidelines published AHA and ACC use the
concept of metabolic equivalents
MET(metabolic aquvalant of task)is the
basal metabolic oxygen consumption at rest
(3 ml/kg/min) and can be measured.
Various activities can be assigned
approximate MET values and an estimate of
the patient’s exercise capacity made.
An inability to increase oxygen consumption
more than 4 METS identifies a high-risk
patient.
Other scoring systems have
been devised to assess cardiac
risk most of which can be
established from a history,
examination and simple
investigations,
such as the ECG.
Investigations for cardiac
risk
1)ECG:A preoperative ECG
should be obtained for all
patients undergoing vascular
surgery for comparison if MI or
ischemia
is
suspected
postoperatively.
If Q waves or other evidence of prior
MI is present →to determine the
timing of the infarct for the purpose
of risk stratification.
 Dysrhythmias should be evaluated
preoperatively to optimize peri
operative management (rate control
for AF).
The presence of a cardiac
rhythm
other
than
sinus
indicates risk for perioperative
cardiac.
 Approximately 50% of patients
with CAD have a normal resting
ECG, demonstrating that the
ECG lacks sensitivity for predict
 24-hour ECG: preoperative ST
segment analysis of a 24-hour ECG
recording gives an indication of the
frequency and severity of ischemic
episodes, it can detect ‘silent’
ischaemia if there is no sign of
silent ischemia on a 24-hour ECG,
the risk of perioperative cardiac
complications is very low.
2) Exercise ECG testing: If vascular surgery
patients are able to exercise and achieve
85%
of their predicted maximal HR, they are low
risk for perioperative cardiac.
3) Dobutamine stress echo :has a ↑sensitivity
compared with resting echo.
4) Dipyridamole–thallium imaging(DTI):This test
will identify ischaemic myocardium accurately,
but has a poor predictive value for progression
of perioperative MI.
5)Cardiopulmonary exercise testing: The
level of oxygen consumption (ml/kg/min)
at the anaerobic threshold has been used
to risk-stratify patients for high-risk
surgery.
6)Coronary angiography: is the gold
standard for the assessment of CAD ,
allows the measurement of intra
ventricular
pressures,
ventricular
function and the gradients across valves.
A meta-analysis found DSE
to be the best predictor of
cardiac morbidity (relative
risk [RR] = 6.2), followed
by DTI (RR= 4.6), and
AECG (RR = 2.7)
Specific conditions
a)Coronary artery disease
 only 10% of vascular patients have
normal coronary arteries with more than
50% having severe coronary disease
demonstrated on angiography.
 This correlates with a perioperative MI
rate of approximately 5%.
b) Previous myocardial infarction
Patients who have had a previous MI
have a 5–6% chance of reinfarction in
the perioperative period.
Surgery within 3 months of an MI
carried up to a 36% chance of
reinfarction.
Traditional
anesthetic
practice
dictated post poning elective surgery
until a 6month interval passed.
Much of the risk after a prior MI is
related to the functional status of the
ventricles and the presence of ongoing
ischemia, rather than to the actual age of
the infarction.
Current guidelines recommend waiting 6
weeks after an uncomplicated MI before
proceeding with an elective surgical
procedure.
Vascular surgery, however, is often
not elective and urgent surgery is
often necessary.
 For this reason, each patient with a
prior or recent MI must be assessed
carefully from the risk-benefit
standpoint.
3) Cardiac failure
symptomatic CHF has a poor prognosis.
In severe failure → ‘non-operative’
approach if possible, or a less invasive.
The patient’s medical condition should
be preoptimized, with appropriate use of
diuretics, vasodilators, or ACEIs.
Invasive monitoring, inotropes and
postoperative critical-care facilities may
be needed.
4)Aortic stenosis
The most frequent causes
congenital
abnormalities
degenerative calcific stenosis.
are
and
 Severe AS is defined by a mean
pressure gradient of more than 50 mm
Hg across a valve or a cross-sectional
area of less than 0.8 cm2.
Surgery in patients with AS is
hazardous due vasodilatation and
myocardial depression caused by
induction of anaesthesia.
Patients with associated angina or
syncope have severe disease, and
consideration
should be given to
surgical correction of the valve if
possible.
5) Hypertension
Is a risk factor for IHD.
Patients are prone to BP lability both
intra- and postoperatively
 Uncontrolled hypertension is only a
minor risk factor in the ACC and AHA
guidelines
 There is little evidence to support
cancelling hypertensive patients, who
are undergoing elective surgery, on the
day of surgery.
Patients with a diastolic blood pressure> 110
mm Hg, which fails to settle, should be
referred for further investigation and
treatment.
Current guidelines suggest a target blood
pressure of 140/90 mm Hg.
 Patients taking antihypertensive medication
should continue in the perioperative period,
but omit ACEIs as they may cause
perioperative hypotension.
6)Atrial fibrilation
patients in atrial fibrillation should
have their HR controlled to <90 beats
per min.
 These patients are frequently
anticoagulated to reduce the risk of
thromboembolic events.
 Ideally, patients should remain
without anticoagulation for as little
time as the surgical procedure allows.
Modifying cardiac risk
Coronary artery intervention:
patients with severe CAD should be
investigated and treated along standard
medical,
surgical
or
radiological
guidelines.
Cardiac surgery should be undertaken
only if the disease makes it necessary.
Correcting severe CAD before elective
surgery does not reduce short term
mortality.
Focus is correction of CAD by
pharmacological optimization with βblockers and statins.
Vascular surgery immediately following
percutaneous coronary stenting is
hazardous, despite adequate antiplatelet
treatment.
Surgery should be delayed at least 6
weeks in these patients.
B-blockers:
β-blockade reduced arrhythmias and
myocardial ischaemia but had no effect
on mortality, MI rate or length of
hospital stay.
prescribe β-blockers to patients with a
history or evidence of myocardial
ischaemia on testing, but not to all
patients→ will cause an excess of side
effects.
Statins
They↓inflammation,stabilize
atherosclerotic plaques and may reduce peri
operative cardiovascular complications.
Because one of the proposed mechanisms
of perioperative MI is rupture of a
coronary artery plaque, All vascular
patients should be prescribed a statin to
reduce vascular events.
Preoptimization:
maximizing oxygen delivery by using
incremental fluid boluses and inotropes.
SV monitoring is optimized with a PAC
or an oesophageal Doppler probe.
The younger, fitter patient undergoing
aortic aneurysm surgery may benefit
from preoptimization,
In the older patient with significant
cardiac disease the use of β-blockade and
the avoidance of tachycardia would seem
logical.
Perioperative medical therapy
Antiplatelet/anticoagulant agents:
Aspirin
should
be
continued
throughout the perioperative period.
Clopidogrel,
an
ADP/platelet
binding inhibitor, should be stopped
for at least 5 days before surgery.
Warfarin should also be stopped 5–7
days before surgery and the patient
started on either LMW heparin or
unfractionated heparin.
A risk/benefit analysis should be
made for each patient,Patients with
coronary artery stents should not be
left without antiplatelet cover.
Respiratory system
Because the number of vascular patients
who smoke is high, COPD is very
common and functional assessment of
the severity of the condition is useful.
Much of the damage to the alveoli will be
permanent, but there is usually an
element of reversible airway disease, and
this should be optimized preoperatively.
If functional ability is seasonal, schedule
elective surgery for the best time of year.
Stop smoking 6–8 weeks before
surgery
to
allow
ciliary
function to return, failing that,
get the patient to stop on the
day of surgery to decrease
carboxyhaemoglobin
and
improve oxygen carriage.
Admit the patient several days in
advance to allow time for chest
physiotherapy.
Bronchodilators, and steroids
will help treat any reversible
element.
Exclude active infection.
Encourage the patient to lose
weight.
Investigations:
PFT → assess the severity of respiratory
disease.
FEV1 is a good measure of ventilatory
capacity ,FEV1 <1 liter indicates
extremely poor function and predicts a
high risk of postoperative ventilation.
FVC indicates the severity of diffuse
parenchymal disease, FVC<50% of that
expected for height, weight and sex
indicates a high likelihood of needing
postoperative support.
PFT
before
and
after
the
administration of bronchodilators
give an indication of the reversibility
of the disease.
ABG should be done if PFT are below
50% of the predicted value.
CXR rarely adds to the assessment
after history, examination and
respiratory function testing.
Renal system
Preoperative
renal
impairment
and
postoperative renal failure ↑perioperative
mortality.
Avoid:
Hypovolaemia
Hypotension
Nephrotoxic drugs (NSAIDs)
Sepsis
Hypoxaemia
Prolonged periods of oliguria.
Angiographic contrast media are
potentially nephrotoxic.
Pre-angiographic
intravenous
hydration, the use of low-osmolar
dyes, and minimizing the dose
used help reduce the renal insult.
Aminophylline
and
N-acetyl
cysteine have been used to
counteract the toxicity.
Diabetes Mellitus
The anaesthetist should seek the presence
of IHD, renal impairment and peripheral or
autonomic neuropathies.
The management of patients involves either
omitting the morning dose of oral hypoglycaemics on the day of surgery or a
glucose-potassium-insulin infusion through
the perioperative period.
Patients with autonomic neuropathy
may not tolerate the vasodilatation
associated with the induction of
anaesthesia or the fall in venous return
on commencing PPV.
Preoperative standing/sitting blood
pressure, tachycardia during a
Valsalva maneuver can assess the
autonomic nervous system.
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