Transcript Your Title Here

Case Presentation
Presented by
Assistant lecturer /
Rafik E. Doss
The Case
 A 71-year-old female was scheduled to
undergo an elective total hip arthroplasty.
 Her activity level is minimal due to arthritic
changes of her hips. She has a history of
hypertension and hypothyroidism, both
under good control with medications.
 Prior to her surgery, a systolic murmur was
appreciated prompting a full cardiac workup.
The Case
 A transthoracic echocardiogram revealed
aortic stenosis with a peak gradient across
the aortic valve of 48 mm Hg and a left
ventricular EF of 35% with concentric
hypertrophy.
 No evidence of stress-induced ischemia was
appreciated on a dobutamine stress test.
Objectives:
1) What
is
the
etiology
and
pathophysiology of aortic stenosis?
2) How should preload, afterload, heart
rate, and contractility be managed in a
patient with aortic stenosis?
3) How would you optimize this patient’s
condition preoperatively?
4) What intraoperative monitoring would
be appropriate?
5) How would you anesthetize this
patient?
Etiology of Aortic Stenosis
Aortic stenosis is usually an idiopathic disease
In patients older than 70 years,
the most common cause of aortic stenosis is
degenerative calcification of the valve
(Mönckeberg senile calcific aortic stenosis).
Etiology of Aortic Stenosis
• Calcific aortic stenosis also occurs in older
patients with congenital or acquired bicuspid
valves, but this is usually presented earlier in
life (30 – 40 yrs).
• Other causes include rheumatic fever–induced
aortic stenosis.
Pathophysiology
• The normal valve surface area
is 2.6–3.5 cm2. A valve area of
1 cm2 or less is likely to cause
clinically significant AS.
• AVA of < 0.8 cm2 with peak
gradient > 50 mmHg is
classified
as
critical
AS
[capable of causing sudden
death].
• Presenting symptoms include
angina, syncope, dyspnea and
congestive heart failure.
Stenotic aortic valve
(macroscopic appearance)
Hemodynamic Goals
• This patient is classified as having severe AS
according to her transvalvular peak gradient
(48 mmHg). However, being asymptomatic,
she is still compensated due to increased LV
mass.
• Our goal for preload is high filling pressures,
adequate
volume
administration,
and
avoidance of factors that decrease venous
return.
Hemodynamic Goals
• Heart rate must be maintained at low normal
levels [60 – 70 bpm] to allow for adequate
ventricular filling and ejection.
• Tachycardia should be avoided as  loss of
timed atrial stroke   CO   time for
coronary filling  angina. Bradycardia as well
  CO as a consequence of limited SV.
Hemodynamic Goals
• Maintaining sinus rhythm is optimally essential
as atrial fibrillation [AF] or junctional rhythm 
marked  ventricular filling.
• Systemic vascular resistance (Afterload)
should be maintained, or even augmented to
provide adequate coronary flow. Furthermore,
angina may require administration of an αagonist like phenylepherine rather than
nitroglycerin to increase coronary perfusion
pressure.
Hemodynamic Goals
• Inotropic support is not needed as long as
myocardial contractility is maintained by the
compensatory LVH.
Preoperative assessment
 History
and clinical examination:
 Careful history and examination
 AS:
• Drug therapy (β-blockers, diuretics, CCBs or
ACEIs).
•Other concomitant diseases: Hypertension and
Hypothyroidism that may cause difficult airway
management.
Preoperative assessment
•Oxygen-dependent exercise tolerance testing
(METs); couldn’t be assessed in this patients due
to her joint disease and was replaced by druginduced stress testing, revealing no ischemic
changes.
•Signs of congestive heart failure (dyspnea,
orthopnea, congested neck veins, LL edema,
gallop, fine basal crepitation) were not observed in
this case.
Vital data (HR, BP, RR, UOP, temp).
 Investigations:
 CBC: Hb, Hct.
 Coagulation profile: INR, PT and PTT.
 Renal and liver function tests.
 CXR: Cardiomegaly, pulmonary congestion, chest
infection.
 ECG :Rate , dysrhythmias, ischemic changes or
chamber enlargement.
 Cardiac catheterization and coronary angiography will
not be important in this case, as echocardiographic
results were conclusive enough.
Risk Assessment
According to new guidelines of ACC/AHA for preoperative
cardiac risk assessment:
Step 1: Evaluate urgency of noncardiac surgery
• Emergency requires surgery regardless of risk.
• Manage Cardiac Risk Factors postoperatively.
Step 2: Noninvasive cardiac testing not required
• No acute cardiovascular disease and able to perform 4 METS without
symptoms:
 Able to climb one flight of stairs holding a bag of groceries
 Able to walk on level ground at 4 miles per hour (1 mile in 15
minutes)
• Coronary revascularization in past 5 years:
Must be stable and no recurrent symptoms or signs.
• Coronary evaluation in last 2 years:
Evaluation must have been favorable and adequate.
No new symptoms or signs since evaluation.
Step 3: Indications for noninvasive cardiac testing
• Evaluation based on patient risk factors
– See Eagle's Cardiac Risk Assessment (typically used for
ACC-AHA Guideline)
– See Detsky's Modified Cardiac Risk Index
• Consider in patients with functional capacity < 4 METS or
unknown capacity
• Major patient risk:
– Indication: Three or more risk factors and cardiovascular
surgery.
– Cardiac evaluation needed in all cases.
• Intermediate Risk: Indications for cardiac evaluation
– See High Risk Surgery.
– Indication: Vascular Surgery or Intermediate Risk Surgery
and at least 1 risk factor.
• Minor risk: Indications for no cardiac evaluation
– Evaluate on individual basis.
– No symptoms at functional capacity >4 METS activity requires
no evaluation.
Our Patient’s assessment:
Evaluation of Patient factors:

This patient lies within class II (6 – 12 points)
according to modified Goldman cardiac risk index,
with complications incidence of 1 – 10%.

While according to Eagle’s risk index, She will be at
the major cardiovascular risk category owing to her
severe AS.

According to Detsky’s cardiac risk index, this patient
is class 1 (0-15 points) which carries the lowest risk.
Evaluation of her functional Capacity: [METs]
Evaluation of this patient was non-conclusive due
to her limited physical activity attributed to her hip
problems. Anaerobic threshold (AT) can be used
instead to estimate for her cardiopulmonary exercise
tolerance.
Considering Surgery-Specific risk:
This patient is having elective orthopedic surgery
which is considered an intermediate risk surgery with
cardiac risk 1 – 5%.
Preoperative Optimization
A. Optimize Medical Therapy

Regarding this patient's hypothyroidism which is
adequately controlled by medications, it will be optimal
to keep her in the euthyroid (normal thyroid function
tests especially TSH) or even mild hypothyroid states to
maintain good coronary perfusion.
 ACEIs or angiotensin-receptor blockers should be
used as the LV EF is less than 40%. She should also be
taking ß-blockers for tight control of her hypertension.
Care must be taken to avoid hypotension and coronary
hypoperfusion.
Preoperative Optimization
A. Optimize Medical Therapy
Medications for treatment of AS-induced CHF and
consequent pulmonary congestion should be adequately
adjusted, these include: Digitalis and diuretics.
 All preoperative medications must be tailored to
minimize the likelihood of decreases in systemic
vascular resistance.
B. Surgical therapy
• Indeed, the only effective treatment is relief of the
mechanical obstruction to left ventricular ejection by
surgical replacement of the diseased aortic valve.
• This patient showed no evidence of stress-induced
ischemia on dobutamine test. So, in this controversially
asymptomatic patient with severe aortic stenosis (48
mmHg pressure gradient), it appears to be relatively safe
to delay valve replacement surgery until symptoms
develop (i.e. no need to postpone her elective hip
arthroplasty).
B. Surgical therapy
• Mortality approaches 75% within 3 years after aortic
stenosis becomes symptomatic unless the valve is
surgically replaced.
• The prognosis with surgery even in this age group is
acceptable.
• She would benefit from balloon aortic valvotomy only if
decompensating symptoms occurred just before her
elective hip surgery.
C. Antibiotic prophylaxis
• NYHA recently updated its guidelines regarding
which patients should take a precautionary antibiotic
to prevent infective endocarditis (IE).
• They show that taking preventive antibiotics is not
necessary for most people and, in fact could cause
allergic
reactions
and
dangerous
antibiotic
resistance.
• According to these, our patient in is not endangered
from IE.
• So, antibiotic prophylaxis will be omitted.
D. Premedications
• Sedatives are cautiously administered or
even totally omitted to avoid respiratory or
vasomotor center depression. Besides, this
patient will be calm owing to her hypothyroid
and age factors.
• Anticholinergics are given with care to avoid
tachycardia; glycopyrrolate is preferred to
atropine.
O’Keefe has suggested that aggressive
intraoperative monitoring and prompt
recognition of haemodynamic abnormalities
can allow for safe anaesthesia in patients
with severe, symptomatic AS undergoing
non-cardiac surgery.
This patient
should be
monitored
intraoperati-vely by
Defibrillator
Anesthetic Management
Management of anesthesia for this patient with
severe aortic stenosis includes avoidance of events
that may further decrease the cardiac output.
There is no evidence that elective orthopedic
surgery is associated with increased morbidity and
mortality in this patient.
General anesthesia is often prefered to epidural
or spinal anesthesia because peripheral sympathetic
nervous system blockade produced by regional
anesthesia can lead to undesirable decreases in
systemic vascular resistance.
1) Anesthetic considerations
• Maintain normal sinus rhythm.
• Avoid bradycardia.
• Avoid sudden increases or decreases in
systemic vascular resistance.
• Optimize intravascular fluid volume to
maintain venous return and left ventricular
filling.
• Arrhythmias should be treated promptly by
cardioversion in the event of haemodynamic
compromise.
2) Induction of Anesthesia
• Induction of anesthesia can be achieved by intravenous
etomidate (of choice), thiopentone in a small dose can
be used but ketamine is avoided.
• Tracheal intubation is facilitated by administration of
muscle relaxants [vecuronium or atracurium are of
choice] with avoidance of stress response by combination
of i.v. lidocaine + alfentanyl + deep plane of anesthesia.
• Pancuronium is avoided as it produces tachycardia.
• The reverse is better with glycopyrrolate (than atropine).

Bradycardia that may be associated with
the administration of succinylcholine is
undesirable.

Interventions to prevent this rare response
(increased heart rate is the more common
response) may be considered, including prior
administration of anticholinergics.
3) Maintenance of Anesthesia
 Maintenance of anesthesia in this patient with
poor LV function (EF = 35 %) is best
accomplished with nitrous oxide (cautiously as it
increases
PVR
leading
to
pulmonary
hypertension) plus opioids.
 Opioids can be used alone in high doses;
fentanyl 50 to 100 μg/kg IV or equivalent doses of
other potent opioids except pethidine.
 That's to avoid the disadvantage of volatile
agents (especially halothane), which depress
SAN automaticity  junctional rhythm and loss of
properly timed atrial contractions.
 Furthermore, it is useful to avoid any additional
depression of myocardial contractility with volatile
anesthetics.
• Decreased systemic vascular resistance produced by
high concentrations of isoflurane, desflurane, or
sevoflurane would be undesirable; in contrast, clinical
experience has shown that low concentrations of these
drugs are unlikely to be associated with undesirable
responses.
• Non-depolarizing neuromuscular blocking drugs
(mentioned in induction) with minimal effects on the
circulation are useful.
• Intravascular fluid volume is maintained by prompt
replacement of blood loss and liberal administration (5
ml/kg/hr) of intravenous fluids.
4) Regional Anesthesia
• Spinal or epidural anesthesia and the associated
sympathetic nervous system blockade have been
considered undesirable in patients with aortic
stenosis.
• Owing to the concentric LVH this patient’s
myocardium is susceptible to ischemia even in
absence of coronary artery disease.
• Large drop in systemic vascular resistance could
initiate a cycle of hypotension-induced myocardial
ischemia, subsequent ventricular dysfunction, and
worsening hypotension.
 If a regional anesthetic is selected in this patient, it
may be useful to consider continuous spinal
anesthesia.
 Increasingly combined nerve blocks are invading the
regional anesthetic field, particularly for prolonging
the postoperative analgesic period.
 Combined lumbar plexus and sciatic nerve blocks will
be very adequate for this elderly patient with severe
aortic stenosis undergoing hip replacement surgery.
Due to its great hemodynamic and cardiovascular
stability.
5) Intraoperative complications
• The onset of junctional rhythm or bradycardia
requires prompt treatment with intravenous atropine.
• Persistent tachycardia can be treated with opioids,
i.v. digitalis (if with AF) 0.25 - 0.5 mg over 10 min, or
βB such as esmolol, keeping in mind that this patient
may be dependent on endogenous β-adrenergic
activity to maintain LV stroke volume especially in the
presence of increased SVR that occurs in response to
surgical stimulation.
• SVT should be promptly terminated with electrical
cardioversion.
• Lidocaine is kept available, as this patient have a
propensity to develop ventricular dysrhythmias.
• Hypotension is treated by phenylephrine (pure α
agonist) better than ephedrine or dopamine (α and β
agonist) as both have β action so; they affect heart
contractility & increase HR.
• P++ & RVF treated by inotropic support e.g. dopamine,
pulmonary VD e.g. nitroprusside.
• Hypertension is treated by potent vasodilators with full
hemodynarnic monitoring.
6) Postoperative Risks
There is increased risk of pulmonary
edema and RVF due to sympathetic
overactivity caused by pain, hypoventilation
(with subsequent respiratory acidosis) and
hypoxemia  pulmonary VC.
Careful monitoring, O2 supplementation
and adequate postoperative analgesia would
be essential.
Thank
You