Describes coronary blood supply anatomy, myocardial oxygen demand and supply, and basic anesthesia consideration (history taking, special investigation, and optimization)

1. Introduction to Cardiac
anesthesia
Tenzin Yoezer
Moderator – Dr. Mustafa
3/11/2022 1

2. Background
Cardiac anesthesiologist:
 Normal and altered cardiac physiology
 Cardiovascular and anesthetic medications
pharmacology
 Physiologic alterations associated with cardiopulmonary
bypass (CPB)
 Surgical procedures.
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3. Coronary blood supply:
 RCA – RA, RV and variable
portion of LV( inferior wall)
 85% - gives PDA ( dominant)
 LCA – LA, Left
interventricular septum, LV
 After short course – LAD &
CX artery ( PDA – 15%)
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4.  SA node – RCA (60%), LAD(40%)
 AV node – RCA(85-90%), CX (10-
15%)
 Bundle of His – PDA & LAD
 Anterior papillary muscle –
diagonal branch of LAD
margincal branch of CX
 Posterior papillary mucle – only
PDA( more vulnerable to
ischaemia)
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5. Myocardial
oxygendemand
 Prevention/treatment of MI during CABG
surgery decreases the incidence of
perioperative myocardial infarction.
 Avoid factors that increase myocardial oxygen
demand (MV⋅O2)
 Vulnerable period - pre-CPB period
 It is well recognized that most ischemic events
occur with minimal or no change in MV⋅O2
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6. Myocardial O2
demand
The principal determinants of MV⋅O2
are:
 wall tension
 contractility.
Explained by Laplace Law
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MVO2 ~ wall
Tension

7. Myocardial O2
Supply
• Myocardial O2 demand only met by increasing
coronary blood flow
 Coronary Blood Flow
 The critical factors that modify coronary blood
flow are :
 Perfusion pressure
 vascular tone of the coronary circulation
 Time available for perfusion (determined mainly
by heart rate),
 Severity of intraluminal obstructions
 Presence of (any) collateral circulation.
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8. CoronaryBlood
Flow:
1)Perfusion
pressure
Most vulnerable area – subendocardium of
left ventricle
Directly exposed to intracavitory pressure
Greatest metobolic requirement
Greater systolic shortening time than other
areas of myocardium
LV perfusion – entirely during diastolic
RV – diastolic and systolic
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9. CoronaryBlood
Flow:
1)Perfusion
pressure
LV CPP = AoDP - LVDP
Low LVDP is ideal for improving
perfusion (higher pressure gradient)
and reducing MV⋅O2 (decreased LV
volume and wall tension).
Increasing perfusion pressure by
raising the aortic pressure will
increase MV⋅O2.
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10. CoronaryBlood
Flow:
2)Vasculartone
 Autoregulated
 Coronary vascular reserve = Basal flow
(autoregulated) - max flow
 normally 3-5 times higher than basal flow.
 Once perfusion pressure decreases to < 40 mmHg,
autoregulation of subendocardial coronary flow is
lost.
 Whenever MV⋅O2 increases above available
reserve, signs, symptoms, and metabolic evidence of
ischemia develop.
 Irreversible injury to the myocardium can occur if
coronary blood flow is occluded for longer than 20
minutes, leading to myocardial cell death and
necrosis.
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11. CoronaryBlood
Flow:
2)Vasculartone
 In reversible ischemia, the myocardium remains viable
:
• Stunning myocardium:
• to a state of abnormal function that occurs after an
acute, discrete episode of ischemia.
 No cell death occurs
 but it may take several days or longer for the myocardium
to recover, even though adequate blood flow has been
restored.
 Hibernating myocardium :
 to a chronic state of reduced coronary blood flow and
abnormal function
 usually secondary to a fixed stenosis.
 In response to decreased oxygen supply, hibernating
myocardial cells downregulate their metabolism and
oxygen demand to maintain viability.
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12. Haemodynamic
goals
Pry goal:
 prevention of myocardial ischemia
 prompt identification and
treatment of new ischemic episodes
The anesthetic interventions -
reducing and controlling the factors
that increase MV⋅O2 (heart rate,
contractility, and wall tension).
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13. Haemodynamic
goals
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14. Preoperative
preparation
Cardiovascular system
Recent MI
Previous cardiac surgery or
chest radiation
Hypertension
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15. Preoperative
preparation
Other systems:
 Pulmonary- COPD or infection, cigarette
smoking, pulmonary HTN
 Renal dysfunction – common in post op
 Hepatic dysfunction
 Neurologic- Cerebrovascular disease ,
carotid bruits, TIA
 Endocrine - diabetes
 Hematologic - Conditions predisposing to
bleed
 Electrolytes – arrythmia
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16. Preoperative
preparation
The depth and detail of the
explanation should be custom-
tailored to each patient
The anticipated events from
transport to the operating room
until emergence should be
discussed with the patient.
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17. Preoperative
preparation
The depth and detail of the
explanation should be custom-
tailored to each patient
The anticipated events from
transport to the operating room
until emergence should be
discussed with the patient.
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18. METS
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19. Current
medications
Almost all cardiovascular drugs are
continued until the time of surgery
Interactions between these drugs
and anesthetics are more often
beneficial than harmful in
maintaining hemodynamic control
during periods of surgical stress
and reducing morbidity and
mortality
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20. Current
medications
Regular medication:
 Beta blockers should be continued in same dosage
 Anti platelet medications - stopped at least 1 week prior to
surgery
 ACEI may be stopped 24 to 36 hours prior to surgery
(substituted with calcium channel blockers)
 For DM patients – conversion to short acting Insulin.
Anti aspiration prophylaxis:
 Pantoprazole 40mg, prokinetic -metoclopramide 10mg
Anti anxiety:
 Alprazolam 0.5 -1mg, midazolam 0.05 mg/kg
 Fentanyl 1mcg/kg IV
 30 minutes prior to surgery with supplemental oxygen.
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21. 3/11/2022 21
Physical
examination
Barash et al 8th edition

22. Preoperative
evaluation
Investigation:
FBC
Clotting screen
Creatinine and electrolytes
LFT
CXR
Echo
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23. Preparation
Preparation, organization, and attention
to detail permit one to deal more
efficiently with unexpected intraoperative
problems
The anesthesia machine, monitors,
infusion pumps, and blood warmer should
all be checked before the patient arrives.
Drugs —including anesthetic and
vasoactive agents—should be immediately
available.
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24. Preparation
 Many clinicians prepare one vasoconstrictor
and one vasodilator infusion before the start
of the procedure.
 2 anesthesiologist
 Premedication – good monitoring system
 In children – induction started at
premedication
 Trolley should have monitor together
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25. Monitoring
*** 2 monitors- 1 for surgeon & 1 for
anesthesiologist
Continous ECG monitoring for ST
segments
 II, V4 or V5
 V4R, V5R – risk of RV ischaemia
SpO2, ETCO2
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26. Monitoring
IBP – femoral or radial
CVP
UOP
Temperature
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27. Monitoring –
Pulmonary artery
catheter(PAC)
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28. Monitoring –
Pulmonary artery
catheter(PAC)
 Usually placed via the right internal jugular vein
 Differs from centers to centers
 2011 AHA/ACCF CABG practice guidelines -
hemodynamically compromised patient
 Sudden occlusion – LV dysfunction
 Use is controversial - ASA Practice Guidelines
 Indications:
 EF <0.4
 Significant abnormality of the left ventricular
wall motion
 LVEDP > 18 mm Hg at rest.
 Recent MI and unstable angina.
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29. Monitoring –
Transeophageal
echocardiography
(TEE)
 Provides real time
information about cardiac
anatomy & function
 Can detect:
 regional & venricular
abnormalities
 Chamber dimensions
 Vulvular anatomy
 Intracardiac air
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30. Monitoring –
Transeophageal
echocardiography
(TEE)
 Helpful in confirming
cannulation of coronary sinus
for cardioplegia
 Most commonly used 2 views:
 4 chamber view
 Transgastric view(short axis)
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31. TEE-4chamber
view
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32. TEE-short
axis/transgastric
view
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33. Electroencephal
-ography(EEG)
For Anesthetic depth
Not useful for neurological
insult
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34. Transcranial
doppler
 TCD- nonivasive measurement of blood flow
velocity in middle cerbral artery
 useful for detecting cerebral emboli
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35. Near-infrared
cerebral
oximetery (NIRS)
 Measures cerebral oximetry
 Baseline value – measured before preoxygenation
 Decreased cerebral oxygen saturation may be seen
when oxygen delivery is impaired secondary to:
 decreased PaCO2 tension
 anemia
 decreased arterial oxygen saturation
 diminished cardiac output
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36. Near-infrared
cerebral
oximetery (NIRS)
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37. Monitoring–
Labparameter
Lab testing is mandatory in cardiac
surgery
ABG, Hb, K+, ionized Ca+, Glu
report should be immediately
available
ACT / TEG
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38. Selectionof
anesthesia
No ideal anesthesia
The choice of anesthetic should be based
on:
 known hemodynamic, pharmacologic, and
pharmacokinetic effects of each drug
 Experience of the anesthesiologist
 relative cost–benefit of each agent
 extent of pre- existing myocardial dysfunction.
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39. Selectionof
anesthesia
Titrated to desired effect
For mild and moderate – some
degree of myocardial depression
is beneficial
Reduces episodes of ischemia by
decreasing oxygen demand
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40. Selectionof
anesthesia
Volatile anesthetic with low dose
narcotic
TIVA with short acting narcotics
Fast track cardiac surgery
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41. Selectionof
anesthesia–
Opioids
The primary advantages of opioids are:
 lack of myocardial depression
 maintenance of a stable hemodynamic
state
 reduction of heart rate.
 Current practice – supplementation of
opioids with benzodiazepine & volatile
agents
Morphine – cardioprotective and anit-
inflammatory
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42. Selection of
anesthesia-
volatile anesthesia
 Desirable features:
 dose-dependent hemodynamic changes
 easy reversibility
 titratable myocardial depression
 amnesia
 suppression of sympathetic responses to surgical
stress and CPB.
 Volatile anesthetics protect the myocardium from
ischemia and reperfusion injury and reduce
myocardial infarct size
 “anesthetic preconditioning”
 “anesthetic postconditioning”
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43. Selection of
anesthesia-
volatile anesthesia
Only volatile based – systemic
hypotension
Balanced technique with opioids
Isoflurane is a coronary vasodilator
other volatile anesthetics - lesser degree
< 1 MAC – no clinical significant
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44. Selection of
anesthesia-
volatile anesthesia
Desflurane –
 cardiac profile = isoflurane.
 rapid uptake and distribution
 useful in cases in which hemodynamic changes
mandate rapid changes in anesthetic depth
Desflurane vs Sufentanil – Sympathetic
activity as outcome
 Helman et al – Desflurane has increase
sympathetic activity
Isoflurane + Fenta vs Sevo + Fenta
 Similar outcome
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45. IVsedative
hypontics
Shorting acting - Mida, Propofol,
dexmedetomine
Alternative adjunct
Can be continued postop in the ICU
Volatile vs propofol
Propofol:
 Less favourable for cardiac function
 Higher need for inotropes
 elevated plasma troponins after cardiac
surgery in elderly patients
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46. Treatmentof
ischeamia
 The use of anesthetics or vasoactive drugs is aimed
at decreasing heart size, decreasing heart rate, and
improving myocardial perfusion pressure.
 The principal vasoactive drugs are:
 nitrates,
 β-blockers,
 peripheral vasoconstrictors
 calcium entry blockers.
 Volatile anesthetics can also be used to control
blood pressure and reduce contractility.
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47. Treatmentof
ischeamia-
Nitrates
Nitroglycerin(TNG) –
 Drug of choice in acute MI
 Dose - 0.5 to 3 μg/kg/min
( reduced in hepatic & renal failure)
 Higer dose – hypotension
 Methemoglobin
 Role of prophylaxis in intra or post ?
 No evidence
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48. Treatmentof
ischeamia-
Nitrates
Sodium Nitroprusside (SNP)–
 Decreases peripheral vascular resistance
 Improves ventricular compliance in the ischemic
myocardium.
 Dose - 0.5 to 3 μg/kg/min
( reduced in hepatic & renal failure)
 cyanide and thiocyanate toxicity,
 Triad - elevated mixed venous O2 (SVO2),
tachyphylaxis and metabolic acidosis
 Other drugs should not be infused in the same
solution as SNP.
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49. Treatmentof
ischeamia-
Vasoconstrictor
Phenylephrine, norepinephrine, Vasopressin
 Adjuncts in the prevention and treatment of
ischemia :
 increase systemic blood pressure
 Improves coronary perfusion pressure,
 (at the expense of increasing afterload and perhaps MV⋅O2 )
 Venoconstriction – increases preload
 (TNG added to counteract)
 No one vasoconstrictor is superior
 Combination may be needed
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50. Treatment of
ischeamia -β-
Blockers
Metoprolol, Labetalol, Esmolol,
propranolol(rarely)
 Improves myocardial oxygen balance by
decreasing the chronotropic and inotropic state
 Propranolol - nonselective β-blocker, t1/2 4 to 6
hours
 Metoprolol - β1- selectivity, less likely to trigger
bronchospasm
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51. Treatment of
ischeamia -β-
Blockers
Labetalol – β and α- blockade, useful in
treating hyperdynamic and hypertensive
situations
Esmolol –
 Short-acting β1-blocker (half-life of - 9.5
minutes)
 Cardio selective
 Useful in treating transient increases in heart
rate owing to episodic sympathetic stimulation.
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52. Treatment of
ischeamia -Calcium
channel blockers
 Depresses contractility
 Reduces coronary and systemic vascular tone
 Decreases SA firing rate
 Impede AV conduction at a remarkably variable
degree.
 CCB have been found to have cardioprotective
effects during reperfusion
 Negative inotropic effect:
 Verapamil > nifedipine > diltiazem >nicardipine
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53. Treatment of
ischeamia -Calcium
channel blockers
Verapamil – Atrial fibrillation/flutter
Diltiazem- preferred in myocardial function
Nicardipine - coronary antispasmodic and
vasodilatory effects more than systemic arterial
vasodilatory effects.
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54. Treatment of
ischeamia -Calcium
channel blockers
Nifedipine & Nicardipine - postoperative
hypertension in cardiac surgical patients
(prominent systemic arterial dilators )
 Clevidipine was a better antihypertensive agent
than SNP or TNG and was equivalent to nicardipine
Aronson S et al. The ECLIPSE trials (2008)
3/11/2022 54

55. Treatment of
ischeamia -
Magnesium
Coronary arterial dilating properties
Reduces the size of myocardial infarction
in the setting of acute ischemia
Decreases mortality associated with
infarction
Antiarrhythmic
minimizes myocardial reperfusion injury
Garcia LA et al. Magnesium reduces free radicals in an in
vivo coronary occlusion-reperfusion model. J Am Coll
Cardiol. 1998;32:536–539.
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56. Treatment of
ischeamia -
Magnesium
Although magnesium was found to
prevent atrial fibrillation in
coronary artery surgery, in patients
treated with β-blockers, the
addition of prophylactic IV
magnesium did not reduce the
incidence of atrial arrhythmias
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57. Summary
 Blood supply of the heart
 Avoid factors that increase myocardial oxygen demand
(MV⋅O2)
 Anesthetic goal - reducing and controlling the factors
that increase MV⋅O2 (heart rate, contractility, and wall
tension).
 Meticulous preparation, organization & monioting
 No ideal anesthesia in cardiac surgery
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58. Thank you
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59. Refeences
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Barash et al. 8th edition
Morgan 6th edition
2011 AHA/ACCF practice guideline
(https://www.ahajournals.org/doi/pdf/10.1161/CIR.0b013
e31823c074e)