Transcript Slide 1

ANESTHETIC MANAGEMENT OF
PATIENTS WITH ISCHEMIC HEART DISEASE
UNDERGOING NONCARDIAC SURGERY
By
Ahmed Ibrahim ; M.D.
Prof.of Anesthesia
Ain Shams University
Cairo, Egypt
Regarding perioperative myocardial ischemia , two
mechanisms are important:
(i) imbalance in the O2 supply /demand
(ii) coronary plaque rupture
acute coronary syndrome (ACS)
The preoperative management of patients suffering from
or having risk factors for ischemic heart disease (IHD) is
directed toward :
(1) Determining the extent of IHD and any previous
interventions (CABG, PCI)
(2) Assessing the severity and stability of the disease
(3) Reviewing medical therapy e.g. antiplatelets or
anticoagulants

The first two goals are important in risk stratification

in patients at high risk, attention to these factors should
be given which may lead to adaptations in surgical plan
Cardiological evaluation may influence :
•the perioperative measures taken to reduce the cardiac risk
•the type of operation and guide the choice to less invasive
interventions
N.B. it will not influence the decision to perform the
intervention but in some situations , as it can reliably
predict perioperative cardiac complications and
estimate late survival, should be taken into
consideration even when deciding whether to perform
an intervention or not.
Risk Stratification
•Surgical risk
•Functional capacity (exercise tolerance)
•Risk indices
•Biomarkers
•Non-invasive testing
•Angiography
Surgical risk for cardiac events
•Any operation elicits a stress response which is mediated by
neuroendocrine factors
tachycardia and hypertension
•Fluid shifts in the perioperative period add to the surgical stress.
•Alterations in the balance between prothrombotic and fibrinolytic
factors
hypercoagulability and possible coronary
thrombosis
The
extent of such changes is proportionate to the
extent and duration of the intervention and may cause
myocardial ischemia and heart failure .
Boersma et al. Am J Med 2005
Functional capacity
•is considered to be a pivotal step in pre-operative cardiac risk
assessment.
•it can be estimated by the ability to perform the daily life activities
is measured in metabolic equivalents (METs):
• 1 MET = represents metabolic demand at
rest, (the basal metabolic rate).
• 4 METs = climbing two flights of stairs
• >10 METs = strenuous sports such as swimming
•The ability to climb two flights of stairs or run for a short distance
(≥ 4METs)
good functional capacity
•The inability to climb two flights of stairs or run a short distance
(<4 METs)
poor functional capacity with an increased
incidence of postoperative cardiac events
when functional capacity is poor or unknown, the presence and
number of risk factors in addition to the risk of surgery will determine
pre-operative risk stratification and perioperative management
Risk indices
Lee index (1999), the widely
used cardiac risk prediction index
in non-cardiac surgery.
Lee TH, Marcantonio ER, Mangione CM, et al.
Circulation. 1999;100:1043-1049
All factors contribute equally
to the index (1 point each)
incidence of major cardiac complications is estimated at
0.4, 0.9 , 7, and 11%
in patients with an index of
0 , 1, 2, and 3 points, respectively.
Biomarkers focusing on :
•Myocardial ischemia and damage
T & I (cTnT & cTnI)
•Inflammation
cardiac troponins
CRP
•LV function
Brain natriuretic peptide (BNP) and
N-terminal pro-BNP (NT-proBNP)
•cTnT & cTnI are the preferred markers for the diagnosis of MI
(demonstrate sensitivity and tissue specificity ).
Even small increases reflect clinically relevant myocardial injury with
worsened cardiac prognosis and outcome.
• CRP might identify patients with an increased risk of unstable coronary
plaque.
•BNP & NT-proBNP are produced in response to increases in myocardial
wall stress which may occur at any stage of heart failure, independently of
the presence or absence of myocardial ischemia. Their levels have
prognostic value for long-term mortality and for cardiac events after major
non-cardiac vascular surgery.
routine assessment of biomarkers for patients undergoing
non-cardiac surgery cannot be proposed for routine use
as an index of cell damage
Non-invasive testing
provides information on :
• LV dysfunction (radionuclide ventriculography, gated
single photon emission computed tomography (SPECT)
,echocardiography, MRI, or CT)
•Valve abnormalities
•Myocardial ischemia
Non-invasive testing for myocardial ischemia
•ECG(12-lead) may be normal or non-specific in a patient with either
ischemia or infarction.
•Physiological exercise( treadmill or bicycle ) is the preferred method for
detection of ischemia and provides an estimate of functional capacity.
•Pharmacological stress testing with either nuclear perfusion imaging or
echocardiography is more suitable in patients with limited physical abilities.
•MRI can be used for detection of ischemia; both perfusion and wall motion
can be detected during stress and at rest.
•CT can be used to detect coronary calcium and for non-invasive
angiography.
Coronary angiography
is
rarely indicated to assess the risk of non-cardiac
surgery.
indications
for pre-operative coronary angiography
and revascularization are similar to angiography
indications in the non-surgical setting.
The history of co-existing noncardiac disease :
•patients with ischemic heart disease are likely to have
peripheral vascular disease.
•A history of syncope may reflect cerebrovascular disease,
a seizure disorder, or cardiac dysrhythmias.
•Cough is often pulmonary rather than cardiac in origin.
•Chronic obstructive pulmonary disease is likely in patients
with a long history of cigarette smoking.
•Diabetes mellitus often co-exists with ischemic heart disease.
.
•Renal insufficiency (creatinine level of >2.0 mg/dL) .
Risk reduction strategies
control of ischemia before surgery, either medically or with
intervention, is recommended whenever noncardiac surgery
procedures can be delayed
•Pharmacological
-β-Blockers
-Statins
-Nitrates
-Angiotensin-converting enzyme inhibitors
-Calcium channel blockers
-Ivabradine
-α2 Receptor agonists
-Diuretics
-Aspirin
-Anticoagulant therapy
•Revascularization
β-Blockers (β.B)
•decrease myocardial oxygen consumption by reducing heart rate
•lengthening of the diastolic filling period
•decrease myocardial contractility
•redistribution of coronary blood flow to the subendocardium
•plaque stabilization
•antihypertensive
•antidysrhythmic
•Perioperative use of β.B had been shown to be efficacious in reducing cardiac
morbidity and mortality in high-risk patients undergoing vascular surgery.
•However, acute administration of high-dose β-blockers is not recommended
as recent trials have not shown its efficacy in reducing overall mortality in
patients undergoing noncardiac surgery.
If to be used for prophylactic purposes , “they should be initiated at least a
week before elective surgery”.
•Currently the only class I recommendation (action that should be taken) for
perioperative administration of β-blocker is to continue its use in patients who
are already receiving it i.e. therapy should be continued throughout the
perioperative period specially the postoperative period as inadvertent
withdrawal may occur and results in rebound hypertension and tachycardia.
•Isoproterenol is the specific pharmacologic antagonist for excessive β-blocker
activity. Atropine or glycopyrrolate can be used to treat excessive bradycardia
caused by β-blockers .
Statins (3-Hydroxy-3-methylglutaryl co-enzyme A reductase inhibitors )
•lipid-lowering effect
•Induce coronary plaque stabilization (non-lipid or pleiotropic effects)
that may prevent plaque rupture and subsequent MI .
•Clinical trials have demonstrated a beneficial effect of perioperative
statin use. European guidelines recommend starting therapy 1 to 4
weeks before high-risk surgery.
•It is recommended that statins be continued perioperatively as their
discontinuation may cause a rebound effect that may be harmful.
Nitrates
•well known to reverse myocardial ischemia.
However, prophylactic use of nitroglycerin has not been shown to
be efficacious in reducing perioperative morbidity and mortality.
•may pose significant hemodynamic risk (decreased preload may
lead to tachycardia, and hypotension).
Calcium channel blockers
Their effect on the balance between myocardial oxygen supply
and demand makes them theoretically suitable for risk reduction
strategies.
Angiotensin-converting enzyme inhibitors (ACEi) :
•May have beneficial effects on postoperative outcome: blood pressurelowering effect ,preserve organ function and may prevent events related to
myocardial ischemia and LV dysfunction.
•Perioperative use of ACEi (or ARBs) carries a risk of severe hypotension
under anesthesia, specially with induction and concomitant b-blocker use.
Although this remains debated, many recommend withholding ACEi for 24
hours before surgery involving significant fluid shifts or blood loss.
They should be resumed after surgery as soon as volume is stable.
•In patients with clinically stable LV systolic function, it seems reasonable to
continue ACEi during the perioperative period under close monitoring.
•Hypotension attributable to ACEi is usually responsive to fluids or
sympathomimetic drugs. If hypotension is refractory to these measures,
treatment with vasopressin or one of its analogues may be required.
Ivabradine
Is a specific inhibitor of the pacemaker in the S-A node reducing
heart rate independently of sympathetic activation. It does not
affect blood pressure or myocardial contractility. It might be
considered for patients with strict contra-indications to b-blockers.
α2 Receptor agonists
•Have analgesic, sedative, and sympatholytic effects( might
reduce catecholamine surge during surgery)
•Perioperative use of α2-agonists may be considered in patients
who cannot tolerate β-blockers.
Diuretics
•Frequent treatment for hypertension or heart failure.
•If for hypertension ,they can be discontinued on the day of
surgery, and resumed orally when possible.
•If necessary to control heart failure, they should be continued up
to the day of surgery, and resumed orally when possible.
•In heart failure, diuretics are often used at high dose.
Dosage should be increased if signs of fluid retention are present
or reduced if there is a risk of hypovolemia, hypotension or
electrolyte disturbances (increase renal excretion of K and Mg).
Aspirin
•Aspirin should only be discontinued if the bleeding risk
outweighs the potential cardiac benefit.
•In principle and based on individualized ‘risk to benefit’
assessments, there is often no need for stopping the antiplatelet treatment prior to minor surgical or endoscopic
procedures in patients who are taking antiplatelet therapy.
•For patients receiving antiplatelet therapy, i.e. aspirin,
clopidogrel, or both, with excessive or life-threatening
perioperative bleeding, transfusion of platelets or
administration of other prohemostatic agents is recommended.
Anticoagulant
Therapy
Poldermans et .European Journal of Anaesthesiology 2010, 27:92–137
Interventions that can modulate triggers of
perioperative myocardial injury
Revascularization
•Patients who are clinically stable in the years after CABG have a
diminished risk of cardiac complications after a non-cardiac surgery.
•The indications for preoperative surgical coronary revascularization
are the same as those in the nonoperative setting.
•It was thought that PCI before elective noncardiac surgery could
improve perioperative outcomes. However, PCI, which is now often
accompanied by stenting and dual antiplatelet therapy, poses its
own unique set of problems that need to be considered in patients
who are scheduled to undergo elective noncardiac surgery.
“There is no value in preoperative coronary intervention in a patient
with stable ischemic heart disease.”
Preoperative Management
Strategies aimed at reducing the risk of perioperative cardiac
complications should involve cardiac evaluation prior to the
surgical procedure, for two main reasons:
•First, patients with an anticipated low cardiac risk can be
operated on safely without further delay. It is unlikely that risk
reduction strategies can reduce the perioperative risk further.
•Secondly, risk reduction by pharmacological treatment is
most cost-effective in patients with a suspected increased
cardiac risk.
The ACC/AHA guidelines provide a multistep algorithm for determining
the need for preoperative cardiac evaluation.
The principal theme of the guidelines is “An intervention is
indicated or not indicated irrespective of the need for surgery ”
Clinical risk factors:
(1) Major : unstable coronary syndrome, decompensated heart
failure, significant dysrhythmias, severe valvular heart disease
(2) Moderate : stable angina pectoris, previous MI identified by
history or pathologic Q waves, compensated or previous heart
failure, insulin-dependent diabetes mellitus, renal insufficiency.
(3) Minor : hypertension, left bundle branch block, nonspecific
ST-T wave changes, history of stroke
•BMS, Bare metal stent
•CABG, coronary artery
bypass graft
•DES,drug-eluting stent
•PCI, percutaneous
coronary intervention
noninvasive test =stress testing
Previous MI
•Incidence of myocardial reinfarction during the perioperative
period is influenced by the time elapsed since the previous MI.
•Acute MI (1 to 7 days previously), recent MI (8 to 30 days
previously), and unstable angina are associated with the
highest risk of perioperative myocardial ischemia, MI, and
cardiac death.
•It is common practice to delay elective surgery for some time
(at least 30 days) following MI.
•Controlling hyperglycemia in patients undergoing cardiac
surgery and in patients in intensive care units has been
associated with improved outcomes. It is prudent to actively
manage hyperglycemia with insulin. This is especially
important in patients who are at high risk of cardiac injury.
•Preoperative anxiety reduction can be achieved by both
conversational and pharmacologic means.
The goal of drug-induced sedation and anxiolysis is maximum
sedation and/or amnesia without significant circulatory or
ventilatory depression.
Intraoperative Management
•The basic challenge is to prevent (optimize O2 supply/ demand)
, monitor and treat myocardial ischemia if it develops.
•Hyperventilation must be avoided, because hypocapnia may
cause coronary artery vasoconstriction.
•Keep the heart rate and blood pressure within 20% of the normal
awake value .
Anesthetic technique (regional versus general)
•the incidence of perioperative cardiac morbidity and mortality
does not appear to be significantly different for general and
regional anesthesia.
•Regional anesthesia is an acceptable technique in patients
with ischemic heart disease. However, the decrease in blood
pressure associated with epidural or spinal anesthesia must
be controlled. Prompt treatment of hypotension that exceeds
20% of the preblock blood pressure is necessary.
INDUCTION OF ANESTHESIA
•Can be accomplished with an intravenous induction drug.
•Ketamine is not a likely choice
and blood pressure
increase in heart rate
•Tracheal intubation is facilitated by administration of a muscle
relaxant.
•Myocardial ischemia may accompany the sympathetic
stimulation that results from direct laryngoscopy and
endotracheal intubation.
MAINTENANCE OF ANESTHESIA
•Good analgesia
•Overall, volatile anesthetics may be beneficial in patients with IHD as they
decrease myocardial O2 requirements and precondition the myocardium to
tolerate ischemia, or they may be detrimental as they lead to a decrease in
blood pressure with associated reduction in coronary perfusion pressure.
Controlled myocardial depression induced by a volatile anesthetic may be
useful to minimize the increase in sympathetic activity likely to develop in
response to intense stimulation e.g. direct laryngoscopy ,surgical stimulation
•The AHA guidelines state that “it can be beneficial to use volatile anesthetic
agents during noncardiac surgery for the maintenance of general anesthesia
in patients in hemodynamically stable condition at risk for myocardial
ischemia”.
•Although isoflurane may decrease coronary vascular resistance,
predisposing to coronary steal syndrome, there is no evidence that it
increases the incidence of intraoperative myocardial ischemia.
•The use of nitrous oxide in patients with a history of coronary
artery disease has been questioned as animal and human
studies showed an increase in pulmonary vascular resistance,
diastolic dysfunction, and subsequent myocardial ischemia with
its use.
•Opioids may be selected as the principal anesthetic in patients
with severely impaired left ventricular function who may not
tolerate anesthesia-induced myocardial depression.
The addition of nitrous oxide, a benzodiazepine, or a low-dose
volatile anesthetic may be needed.
•Muscle relaxants with minimal or no effect on heart rate and
systemic blood pressure (vecuronium, rocuronium,
cisatracurium) are attractive choices for patients with IHD .
•The histamine release and resulting decrease in blood
pressure caused by atracurium make it less desirable.
•However, the circulatory changes produced by pancuronium
may be useful in offsetting the negative inotropic and
chronotropic effects of some anesthetic drugs.
•Glycopyrrolate , which has much less chronotropic effect than
atropine , is preferred in these patients for reversal of
neuromuscular blockade .
Perioperative monitoring
•Select methods that allow early detection of myocardial
ischemia.
- Electrocardiography (ECG)
- Transesophageal echocardiography (TEE)
- Right heart catheterization
•The simplest, most cost-effective method is ECG
ST
changes (elevation or depression of at least 1 mm) and T-wave
inversions.
•Because visual detection of ST-segment changes is unreliable,
continuous automated ST trending monitors are preferred.
•In patients with known or suspected coronary artery disease, it is
reasonable to assume that intraoperative ST-segment changes
represent myocardial ischemia although they can be caused by
other events e.g. dysrhythmias, cardiac conduction disturbances,
digitalis therapy, electrolyte abnormalities, and hypothermia.
Transesophageal echocardiography
The development of “new” regional ventricular wall
motion abnormalities – that occur before ECG
changes - is an accepted standard for the
intraoperative diagnosis of myocardial ischemia.
Right heart catheterization
•Intraoperative myocardial ischemia can manifest as an acute
increase in PAWP due to changes in LV compliance and systolic
performance.
If only small regions of LV become ischemic, overall ventricular
compliance and PAWP will remain unchanged, so the
“pulmonary artery catheter is a relatively insensitive method of
monitoring for myocardial ischemia”.
•Pulmonary artery catheter is more useful to guide the
treatment of myocardial dysfunction e.g. fluid replacement,
measure cardiac output, and SVR and thereby evaluate the
effectiveness of therapy.
•Right heart catheterization is not recommended routinely for
monitoring patients with intraoperative ischemia.
INTRAOPERATIVE MANAGEMENT OF MYOCARDIAL ISCHEMIA
should be instituted when there are ST-segment changes on the ECG.
•Nitroglycerin is an appropriate choice when myocardial ischemia is
associated with a normal or modestly elevated blood pressure.
•Prompt treatment of changes in heart rate and/or blood pressure .
•A persistent increase in heart rate can be treated by a β-blocker such
as esmolol.
•Hypotension is treated with sympathomimetic drugs to restore
coronary perfusion pressure. In addition , fluid infusion can be useful.
•In an unstable hemodynamic situation, circulatory support with
inotropes or an intra aortic balloon pump may be necessary.
•Plan for early postoperative cardiac catheterization.
Postoperative Management
•Again the goals : prevent ,monitor, and treat ischemia or infarction.
•Continuous ECG monitoring is useful for detecting myocardial ischemia as
most adverse cardiac events occur within the first 48 hours postoperatively.
•Avoid events that increase myocardial oxygen demand e.g. hypothermia
,pain, hypoxemia, hypercarbia, sepsis, and hemorrhage
•Avoid events that decrease myocardial oxygen supply e.g. hypovolemia ,
hypotension and inadequate hemoglobin concentration
•Patients taking β-blockers should continue to receive these drugs throughout
the perioperative period.
•Patients with IHD can become ischemic during emergence from anesthesia
and/or weaning from mechanical ventilation. Early extubation is desirable
whenever possible
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