PERI OPERATIVE MANAGEMENT
FOR PERIPHERAL VASCULAR SURGERY
TILOTTAMA P MANGESHIKAR, S KARTHIK
Department of Cardiovascular and
Thoracic Surgery, Department of Anaesthesia, Bombay Hospital Institute of Medical
The incidence of peripheral vascular disease
(PVD) increases with age and affects 5.7% of the middle aged and elderly. There
is a clear association between smoking, PVD and coronary artery disease (CAD).
Patients with PVD are at high risk for developing complications after surgery
Active intervention is indicated for disabling symptoms. The intervention may
be as minimally invasive as a percutaneous transluminal angioplasty (PTA) or
a peripheral vascular reconstruction where the anaesthetist contributes significantly
to the safety of the patient during and after surgery and also to the graft
Pre Anaesthetic Assessment
The pre operative assessment of a patient subjected to peripheral vascular surgery
is difficult because these patients usually present as emergencies and elaborate
invasive diagnostic tests may not be feasible.
Patients with PVD present with numerous concurrent medical illnesses like diabetes
mellitus, hypertension, concurrent coronary, cerebro vascular and renovascular
disease and pulmonary dysfunction secondary to prolonged tobacco abuse.
Consequently, long term survival after surgery may be less than 65% at twelve
months. Myocardial ischaemia and infarction are the commonest causes of mortality
and morbidity. Myocardial ischaemia may be silent, especially in diabetics.
Hence, clinical evidence of CAD seems to be a better predictor of peri operative
cardiac events. But unfortunately, the usual clinical presentation of CAD i.e.
angina on walking is frequently masked in the patient with PVD.
Why are Surgeries for PVD High Risk?
Hence, a risk assessment is mandatory. In
the mid 1970s, Goldman and colleagues put forth a multifactorial risk index
for the prediction of cardiac risk in patients subjected to non-cardiac surgery.
Though it was effective for other surgical patients, it included a very small
population of vascular surgery patients, and hence its usefulness is limited
in the assessment of the PVD patients.
- PVD is generally associated with CAD
and/or carotid artery disease.
- Though exercise tolerance is a useful
indicator of the severity of CAD, it is almost always limited by intermittent
claudication, disability due to previous amputation or old age.
- Vascular reconstructions are of prolonged
duration and associated with hypovolaemia and hypothermia.
- Myocardial ischaemia is very common,
usually silent and often associated with infarction.
The American College of Cardiology and the American Heart Association task force
classified patients into three stratas of increasing risk as follows:
- Recent myocardial infarct (MI) - within
7 to 30 days
- Unstable angina
- Severe valvular disease
- Uncontrolled congestive cardiac failure
- Atrio ventricular block
- Previous MI - greater than 30 days
- Mild angina
- Diabetes mellitus
- Treated CCF
After stratifying patients according to
the above factors, it is suggested that high risk patient should undergo further
invasive assessment regardless of the surgical procedure.
- Age beyond 70 years
- Abnormal ECG findings
- Rhythm other than sinus
- Uncontrolled hypertension
- Previous stroke
Low risk patients require no special tests and one can proceed with surgery.
For those with intermediate risk, some amount of further assessment of functional
capacity is essential.
The patients to be focussed on are those with intermediate risk but a poor functional
capacity. They should undergo a coronary angiography and a cardiological assessment.
If there is associated left ventricular dysfunction in them, then peri operative
MI is a possibility. Hence, no further non invasive tests should be performed
and the patient should be subjected to coronary angiography and if permissible,
a coronary revascularisation also.
The following is a list of investigations:
Dipyridamole Thallium Imaging (DTI), the most widely used non invasive test
Radionuclide Ventriculography and
Dobutamine stress Echocardiography.
A rationale for the use of DTI was proposed by Eagle et al by combining the
test results with clinical variables such as Q waves on ECG, history of ventricular
ectopics, diabetes mellitus, age beyond 70 years and angina.
It was suggested that patients with three or more risk factors can be directly
subjected to coronary angiography rather than a DTI.
The technique of anaesthesia should be individualised in these patients due
to the presence of concurrent medical illnesses. Though some studies show that
the anaesthetic technique bears no influence on the outcome of surgery, many
other studies have put forth that the type of anaesthesia ‘is’ important in
overall outcome in terms of graft patency and lesser cardiac complications.
Pre operative evaluation and Preparation
The preoperative investigations reveal treatable medical conditions and the
severity of the cardiac, respiratory and renal dysfunction if associated. These
should be optimized before surgery.
Patients with coronary disease coming for surgery for PVD may be on anticoagulant
regimens. A full anti coagulant course is a near total contra indication to
regional anaesthesia. Patients in addition may be on anti platelets and thrombo-prophylaxis
with low molecular weight heparins and aspirin. Studies have shown that low
molecular weight heparins upto 5000 IU given prophylactic or intra operatively
are safe provided they are not given within 4 hours prior to or 1 hour after
the institution of a regional block. Hence, timing of heparin dosage, monitoring
of anti coagulation with an ACT and postponement of surgery or abandoning the
technique if a bloody tap is encountered are important factors that may influence
outcome. Trials like the CLASP trial (1994) have confirmed that epidural is
safe in patients taking aspirin.
Patients with Diabetes mellitus should be closely monitored for glucose levels.
A sliding scale insulin regimen should be started intra operatively and followed
strictly due to the prolonged nature of these surgeries.
Hypertensive patients should take their anti hypertensive medication until the
morning of surgery. Pre operative beta blockade may help in diminishing peri
operative tachycardia, surges in blood pressure and ischaemic events that are
otherwise frequently seen.
In addition to drugs for concurrent medical disorders, analgesics and anxiolytics
are essential. This could include a dose of benzodiazepine and opioids for pain
and sedation too.
There may be opioid tolerance as the patient may already be on these drugs for
INDUCTION - This should include a combination of oxygen, nitrous oxide,
opioids and inhalational agents. Neuromuscular blockade to facilitate endotracheal
intubation is necessary. This drug should be cardiostable and free of histamine
release. Hence, Vecuronium would be the ideal choice with fentanyl or alfentanyl
as the opioid. Propofol or Thiopentone may be used judiciously as induction
should be smooth without Haemodynamic fluctuations. It should include manoeuvres
to diminish the pressor.
MAINTENANCE - A balanced anaesthetic technique with endotracheal intubation
and controlled ventilation is preferred. Isoflurane as the inhalational agent
may be disadvantageous due to its properties of producing a coronary steal.
Halothane being a myocardial depressant should be used with caution. A total
intra venous technique has no added benefits. In fact it may be hazardous in
the patient with severe respiratory disease, most of the drugs used being respiratory
depressants. Our preference is for controlled ventilation with air and oxygen
and a continuous Propofol and vecuronium infusion which keeps the patient asleep
and immobile. We also almost always use an Epidural or a Spino-dural block along
with the general anaesthetic. The epidural is used for intra and post operative
analgesia, this being provided with a continuous infusion of 0.125% Bupivacaine
and I mcg/ml of Fentanyl solution.
An important aspect during the maintenance of general anaesthesia is the maintenance
of a normal body temperature due to the prolonged nature of these surgeries
and cold theatre environments. Lower body temperatures are harmful. Firstly,
they cause shivering and vasoconstriction increasing the myocardial oxygen demand.
Secondly, vasoconstriction results in poor peripheral perfusion with thrombosis
and graft failure ultimately. Therefore, active heat conserving measures are
a must. At our Institution we use the Biotherm circulating mattress and an intravenous
Intraoperative hypertension due to clamping of the artery needs to be anticipated
and controlled with a vasodilator. Similarly the hypotension on release of the
clamps can be extreme. Volume preloading as well as careful use of vaso pressors
such as mephentermine can be helpful. Revascularisation causes some degree of
acid metabolites entering the circulation and this needs to be assessed and
corrected if severe. We use Allopurinol, Mannitol and Vitamins C and E to prevent
injury due to the free radicals released after revascularisation.
Fluids and Monitoring
Good hydration should be maintained intra operatively with replacement of blood
losses. The peripheral nature of these surgeries implies a minimal third space
loss. Our patients are routinely started on fluids such as Lomodex which prevents
roleaux formation of the red blood corpuscles which would hamper graft patency.
Monitoring should include all the routine monitoring equipment. In addition,
a multi-lead ECG with ST segment analysis is superior to a routine ECG as myocardial
ischaemia is a frequent complication intraoperatively. Invasive arterial blood
pressure monitoring is essential. A central venous pressure monitor helps in
administration of fluids, inotropes and vaso-active drugs. A pulmonary artery
pressure trace may be useful in the patient with a poor LV function.
Recovery from GA should be smooth taking care not to cause tachycardia and hypertension.
This is the period when chances of MI are high. Patients should continue to
remain pain free, normothermic and normovolaemic.
An infra inguinal arterial reconstruction can be effectively managed by regional
anaesthesia with sedation or light general anaesthesia.
A continuous epidural technique is the preferred technique of choice. It has
the added advantage that it can cater to a long duration of surgery and at the
same time can be prolonged into the post operative period for analgesia. Drugs
like lignocaine or bupivacaine or a combination of both is used. A small dose
of an opioid may also be added.
Dose Regional Blockade Alter Outcome?
Theoretically speaking, regional anaesthesia has several advantages over general
anaesthesia. It modifies the cardiovascular and metabolic responses to the stress
of surgery. This helps to diminish myocardial ischaemic episodes. Tachycardia
and hypertension caused by endotracheal intubation are avoided by regional techniques.
The sympathetic blockade caused decreases both preload and afterload. The vasodilatation
produced improves the graft perfusion, decreases chances of graft failure.
With regional blockade it is seen that the levels of catecholamines are also
diminished which decreases the probability of vasoconstriction. There is increased
fibrinolysis too due to decrease in procoagulant factors. All these factors
put together definitely improve the graft survival.
Post Operative Care
These patients are best looked after in an Intensive care unit that will continue
the monitoring of the patients’ organ systems as well as the graft, regularly
anticipating and correcting trends. A vigilant ICU nurse has many a time prevented
loss of a limb or life by getting the patient back to theatre on time in case
of bleeding or graft revision being needed.
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