coronary artery bypass graft under cardiopulmonary bypass

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2. • Main cause of CAD is atherosclerotic narrowing of major
branches of coronary arteries resulting in luminal
obstruction and myocardial ischemia.
• Risk factors for increased morbidity and mortality are -
poor LV function
- h/o CHF or EF<30%
- h/o DM, HTN etc.
- obesity
- redo procedures
- emergency procedures
- advanced age

3. ardiac ischemia occurs when coronary blood flow does
not increase to an extent to meet increased myocardial
oxygen demand
V subendocardial blood flow is intermittent and occurs
only during diastole
oronary blood flow is directly proportional to coronary
perfusion pressure
CPP = Aor tic DP - LVEDP

4. oronary blood flow is inversely proportional to
coronary vascular resistance and thus coronary
stenosis increases resistance and decreases blood
flow
esistance to coronary blood flow depends on-
- length of stenosis
-degree of stenosis
-presence or absence of collaterals
-co-existing diseases like DM or HTN

5. • Patients may present with typical anginal pain,
atypical pain or discomfort, silent or asymptomatic
attack with evidence of ECG changes only.
• 50% decrease in diameter causes symptoms on
exertion and 75% decrease in diameter causes
angina at rest

6. • Myocardial oxygen demand is increased by
Increase in- heart rate
- contractility
-chamber pressure(afterload)
- chamber size(preload)
• Ways to increase myocardial oxygen supply are
maintaining DBP, Hb conc, oxygen saturation,
decreasing oxygen demand by decreasing HR and
ventricular wall tension

8. CABG is a surgical procedure in which one or more
blocked coronary vessels are bypassed by a blood vessel
graft to restore normal blood flow to myocardium and
most of these grafts come from patient’s own body.
ost common conduits used are
aphenous vein for bypassing right coronary artery and
circumflex coronary artery
nternal mammary artery for bypassing left anterior
descending coronary artery
f more conduits are needed upper extremity vessels can

11. According to AHA, indications of CABG are-
• Disease of the left main coronary artery
• Multi vessel disease
• Non-discrete or diffuse disease not amenable to
t/t with PCI

12. CABG CAN BE
PERFORMED EITHER
ONPUMP OR
OFFPUMP(BEATING
HEART CABG)

13. PREOPERATIVE EVALUATION-
• Histor y and physical examination to evaluate
LV dysfunction and LV/RV failure, respiratory
disease, prior cardiac surgery
• Chest radiograph to detect resp. disease, CHF,
abnormal cardiothoracic ratio etc.
• Resting ECG to detect rhythm disturbances,
conduction defects, decision of intra-op lead
selection

14. xercise ECG showing significant ST segment
changes in early stages, sustained changes,
abnormal changes in HR or BP, development of
angina or arrythmia indicate severe CAD
CHO shows segmental wall motion abnormality
tress ECHO with exercise or dobutamine and
contrast ECHO detect abnormal areas of perfusion

15. yocardial per fusion scans using thallium-201 or
Tc 99m locate and quantitate ischemic areas
ngiography defines location and degree of occlusion
and coronary artery spasm
ontrast ventriculography shows areas of
hypokinesia, akinesia and dyskinesia
F= EDV-ESV/EDV [N-50-75%]
25-50%- symptoms on exercise

16. INTRA-OP MONITORING-
BP- Dominant hand radial art preffered .
CG- ST segment changes or new T wave
changes are diagnostic of ischemia
imultaneous observation of an inferior lead [II,
III, aVF ] and anterior lead [V4,V5] detects
approximately 90% of events.
osterior heart ischemia is difficult to detect

17. •CVP – Internal juglar vein
• PA CATHETER- Appearance of new V wave in
pulmonary artery pressure waveform indicates
development of MVR due to ischemic papillary muscle
dysfunction
Imp in post-op period where TEE can not be used
Intra-op monitoring may require frequent balloon
inflations

18. TEE –
an assess regions supplied by all three major
coronary arteries
egional wall motion abnormality can precede ECG
and PA wave form changes
ntra op stress TEE with low dose dobutamine can
demonstrate myocardial contractile reserve and
helps revascularize myocardium that will be
benefited from increased blood supply

19. ARDIO-PULMONARY-BYPASS-It
provides both artificial ventilation and perfusion
by diverting blood away from vascular system and
performing the function of both lungs and heart
temporarily
The goal of this CPB is to provide a bloodless and
motionless surgical field

20. PREMEDICATION
arcotic or Anxiolytic agent or both to mitigate pain and
anxiety.
upplemental intra-venous drugs- commonly midazolam
and fentanyl- are often necessary during radial artery
cannulation before induction of anesthesia.
atients with low cardiac output secondary to CHF
sedation should be performed judiciously to avoid
myocardial depression and resultant hypotension.

21. NDUCTION-
oal is to avoid undue hypotension and to attenuate
hemodynamic response to laryngoscopy and
intubation
ypotension may be due to hypovolemic state and
reduction in sympathetic tone in response to
inducing agents particularly in patients with poor LV
function. Fall in BP >20% of baseline needs use of
inotropes.

22. ypertension may be due to pre-induction
anxiety and sympathetic stimulation
ll anesthetic agents except ketamine cause
decreased blood pressure by decreasing
sympathetic tone , systemic vascular
resistance , inducing bradycardia or directly
depressing myocardial function.

23. elected agent should be given in small incremental
doses and titrated first against loss of
consciousness then to an acceptable fall in BP.
uscle relaxation and controlled ventilation ensures
adequate oxygenation and prevents hypercapnia.

24. IGH DOSE NARCOTICS-
entanyl 50-100 mcg/kg or sufentanil 15-25mcg/kg
roduces prolonged post-op respiratory depression,
high incidence of awareness, rigidity, fail to control
hypertensive response to stimulation

25. OTAL INTRAVENOUS ANESTHESIA-
nfusion of propofol,0.5-1.5 mg/kg f/b 25-100
mcg/kg/min and remifentanil 1 mcg/kg bolus f/b
0.25-1 mcg/kg infusion.
otal dose of fentanyl should be 5-7 mcg/kg
se of short acting agents results in early extubation
and lesser hospital stay
rugs are costlier and remifentanil should be

26. MIXED INTRAVENOUS/INHALATION
ANESTHESIA-
• Propofol 0.5-1.5 mg/kg or thiopentone 2-3 mg/kg and
midazolam 0.05 mg/kg
• Opioids are given intermittently and total dose of
fentanyl and remifentanil should not exceed 15 and 5
mcg/kg respectively.

27. • Iso, sevo or desflurane are used for maintenance
• It results in easy control of depth of anesthesia and
hemodynamic stability and early extubation
OTHERS-
• In frail patients, combination of ketamine and
midazolam provides hemodynamic stability, good
amnesia, analgesia and minimal respiratory
depression.

28. RE CARDIO-PULMONARY BYPASS PERIOD-
heck bilateral breath sounds
djust fresh gas flow
heck pressure points
rotect eyes
heck all monitors and tubings after final position
dminister antibiotics

29. kin incision can cause sympathetic stimulation, so
adequate depth of anesthesia is necessary
ternal incision and splitting accompanies high level of
sympathetic stimulation
ternal splitting can cause awareness and recall, so
amnesic agents like benzodiazepines or propofol is to
be used

30. achycardia and raised BP can be treated by
nitroglycerine boluses or by esmolol
igh doses of fentanyl can reduce response to pain
ungs are to be deflated during sternal splitting to
avoid damage

31. ternal spread can cause kinking or malpositioning of
PA cath.
issection of post ganglionic sympathetic fibres from
aorta to cannulate it can cause intense stimulation

32. HEMODYNAMIC CHANGES ASSOCIATED IN THIS
PERIOD
HYPOTENSION-may be due to
Hypovolemia
Decreased venous return due to increased airway
pressure , tension pneumothorax , handling of heart
and great vessels
Impaired myocardial contractility
Ischemia
Dysarrythmia
Measurement error due to kinked catheter, wrist
positioning error etc.

33. T/T of hypotension-
• Rule out technical and mechanical factors
• Check for dysarrythmia
• Use of inotropes
• Fluid loading
• Decrease inhalational agents

34. HYPERTENSION-may be due to
 Light anesthesia
 Hypercapnia
 Hypoxia
 Hypervolemia
T/T of hypertension-
• Increasing anesthetic depth
• Vasodilator agents like nitroglycerine,
nitroprusside
• Using b-blockers

35. SINUS BRADYCARDIA- may be due to
 Vagotonic effects of narcotics
 Use of b-blockers
 Hypoxia
 Ischemia
• T/t of bradycardia is indicated if there is fall in BP
or HR<40 even with no fall in BP
• Atropine 0.4-0.6 mg i.v is indicated

36. SINUS TACHYCARDIA- may be due to
Light anesthesia
Hypovolemia, anemia
Inotropic drugs , pancuronium , isoflurane
Hypoxia
Hypercapnia
Ischemia
Management of tachycardia includes
• Checking ventilation abnormalities
• Increasing depth of anesthesia
• Volume loading
• Using b-blockers

37. DYSRYTHMIAS may be due to-
 Mechanical stimulation of heart
 Preexisting dysrythmia
 Electrolyte imbalance
 Increased catecholamines
 Ischemia
These can be treated by treating underlying causes,
using lidocaine,b-blockers and by synchronized
cardioversion.

38. RIMING of circuit is to be done by balanced salt
solution(1200-1800ml for adults)
ther components like albumin or hetastarch,
mannitol, heparin and bicarbonate are added
t decreases hematocrit to 22-25%
n patients who are severely anemic or pediatric
patients blood is used as prime

39. ENEFITS OF HEMODILUTION-
ecreased viscosity improves microcirculation
and compensates for increased viscosity
due to hypothermia
RISKS-
ecreased SVR decreases BP
ilution of drugs and coagulation factors

40. HEPARINIZATION-
• Heparin 300-400u/kg is administered through a
central vein targeting ACT level min of 480s
• ACT is the time from adding whole blood to a tube
containing a contact phase activator (celite or kaolin)
up to the time when first clot appears.
• Repeat ACT is measured after 5 mins and if it is less,
100u/kg is to be administered again

41. • Whole blood heparin conc. of about 3-4u/ml is
sufficient for CPB.
• Heparin resistance is seen in cases of AT-III
deficiency which can be treated with infusion of 2-3
units of FFP , AT-III concentrates , recombinant AT-III
etc.

42. ANNULATION-
or tic cannula is inser ted first to allow rapid
volume infusion in cases of hemorrhage during
venous cannulation
BP is lowered to avoid risk of dissection and PEEP
applied to avoid air entrainment by increasing
intracardiac pressure

43. omplications during aortic cannulation can be
ortic dissection
leeding
mbolisation of atheromatous plaque
ysrythmia
ypotension

44. REBYPASS CHECKLIST-
nticoagulation (min ACT of 480sec) is needed
osition of cannulae is to be checked by checking
waveforms
rine noted and urobag is to be emptied
quality of carotid pulse is to be checked
upplemental doses of anesthetic agents are to be
administered to compensate for dilution

45. NITIAL BYPASS CHECKLIST-
ace is to be checked for colour , edema , conjunctival
chemosis
A pressure should be less than 15 mm Hg
rterial blood pressure should be mean 30-40 mm Hg
VP should be<5 mm hg
ardiac contractility and distensibility is to be checked

46. MAINTENANCE OF BYPASS-
• ACT repeated every 30-60 mins, if less supplemental
heparin is added
• Blood gas values to be evaluated every 30-60 mins
• PaO2 maintained between 100-300 mm Hg & PaCO2
between 35-40 mm Hg.
• Blood glucose and hematocrit is measured every 30-
60 min

47. ufficient anesthetic depth is maintained to prevent
awareness, spontaneous movement, hypertensive and
tachycardic responses
epth maintained by adding anesthetic agents and
muscle relaxants directly into the circuit and adding
volatile agents by connecting vapouriser to oxygenator

48. • INTRA OPERATIVE AWARENESS may be due to
underdosing , dilution or absorption of drugs and
increased requirement during rewarming .
• It can be prevented monitoring BIS and
supplementing drug.
• Ventilation should cease when total bypass begins.

49. • Pump flow rate is to be maintained at 50-70
ml/kg/min or 2.2-3.1 l/min/square mt
• Urine output should be at least 0.5ml/kg/hr
• Core temp. is to be monitored at nasopharynx or
tympanic membrane( jugular bulb temp is gold
standard)
• De-airing of heart is to be done before weaning
from CPB by increasing venous pressure by inflating
lungs

50. MYOCARDIAL PROTECTION-
• To provide a motionless field for surgery,
heart is stopped in diastole by administering
a potassium rich cardioplegia soln.
• It interrupts myocardial electromechanical
activity, reduces oxygen consumption by 90%
and cold cardioplegia soln. reduces it by 97%.

51. • For most complete cardioplegia , both antegrde
(through aortic root) and retrograde(through coronary
sinus) approach is used
• Arrest can be reversed by reperfusing heart by warm
normokalemic blood(hot shot)

52. PREPARATION FOR WEANING-
(Elements of Romanoff and Royster’s)
Pneumonic is CVP
• COLD- patient’s temp. should be 36-37 degrees,
hyperthermia is deleterious
• CONDUCTION- HR of 80-100 bpm is optimal,
bradycardia may need epicardial pacing wire for AV
pacing or inotropes, tachycardia needs t/t of cause,
AV block may need AV pacing and supraventricular
tachycardia needs pharmacotherapy and
cardioversion

53. • CONTRACTILITY is estimated by TEE and CO by PA
catheter
• CELLS-Hb should be at least 7-8g%
• COAGULATION- long bypass period and extreme
hypothermia increase risk, PT,PTT,PC should be
normal
• VENTILATION OF LUNGS- must be established after
PA blood flow is restored

54. ISUALISATION of heart and TEE for regional and
global contractility
OLUME EXPANSION-if necessary
ACER AND PRESSOR AGENTS should be readily
available
OTASSIUM must be corrected as hypokalemia can
cause dysrythmias and hyperkalemia can cause
conduction blocks

55. WEANING FROM BYPASS-
• Before termination, patient should be rewarmed,
heart is de-aired, regular cardiac electrical activity
confirmed or supported by pacemaker, lab values
confirmed and corrected
• Ventilation of lungs is established, venous drainage
is slowly reduced and cardiac filling volume is
gradually increased
• Vasopressors or inotropic support may be needed

56. • When patient becomes hemodynamically stable,
protamine is administered to reverse
anticoagulation
• 1-1.3mg of protamine per 100 units of heparin is
administered slowly over 10-15 mins
• ACT should be brought to baseline values
• When pre-loading is optimal and contractility is
adequate, aortic inflow line is clamped to separate
from bypass

57. • Elevated BP should be avoided to prevent stress on
suture lines
• If CO is not optimal, preload can be increased in
100ml increments as rewarming is associated with
vasodilation
• Increase in hemodynamic instability and use of
inotropes may need reinstitution of CPB

58. EVENTS IN POST BYPASS PERIOD-
1.Cardiovascular decompensation-
Ischemia and infarction may be due to
• Thrombosis or particulate or air emboli in graft
• Kinking or spasm of graft
• Incomplete revascularization due to distal disease
• Inoperable vessels

59. LV dysfunction is amenable to combination of inotropes and
vasodilators to increase CO
RV dysfunction may be due to inadequate protection,
ischemia, infarction, pulmonary air emboli, preexisting
pulmonary HTN
RV failure needs inotropic support as well as pulmonary
vasodilation nitroglycerin, nitroprusside, prostaglandin E1
(PGE1), B-type natriuretic peptide (e.g., nesiritide),
sildenafil, or inhaled agents such as nitric oxide and
prostacyclin (prostaglandin I2 [PGI2, epoprostenol]).

60. YPOTENSION may be due to low SVR, severe
anemia, low viscosity, acid-base disturbances and is
treated with vasoconstrictors
YSRYTHMIAS - AF is most common and converted
to sinus rhythm by synchronized cardioversion,
amiodarone etc.
VF or flutter needs defibrillation and drugs like
amiodarone and lidocaine
Bradycardia and heart block need AV sequential

61. 2.Bleeding and coagulopathy-
• Inadequate surgical hemostasis is most common
cause
• Platelet dysfunction due to hemodilution,
hypothermia, contact activation, adhesion and
sequestration

62. • Activation of coagulation cascade by contact factors
• Fibrinolysis by release of t-PA from damaged
endothelium
• Consumption of factors
• Treated by FFP and platelet concentrates

63. 3.pulmonar y complications-
• Atelectasis causing decreased oxygenation, lungs
are to be reinflated by hand before machine
ventilation
• Hemothorax, pneumothorax may need chest tube
insertion

64. • Cardiogenic pulmonary edema due to fluid overload
in patients with preexisting HF
• Noncardiogenic pulmonary edema due to
inflammatory response, multiple emboli, increased
permeability, transfusion reaction

65. .Metabolic disturbances-
ypokalemia due to diuretics, mannitol, hyperglycemia
treated with insulin :- treated with KCl @ 10-20 meq/hr
yperkalemia due to cardioplegia, blood products,
impaired renal function: - treated with hyperventilation,
calcium, diuretics, glucose and insulin infusion

66. ypocalcemia due to citrate in blood products,
hemodilution, alkalosis:- treated with 10% calcium
chloride 5-10mg/kg
ypomagnesemia due to hemodilution:- treated
with 2-4 g of magnesium
yperglycemia is deleterious and is due to stress of
surgery and inflammatory response, glucose level >
200mg/dl:- should be treated with insulin

67. 6.Ef fect on CNS-
• MC complication is transient neuropsychiatric
dysfunction, strokes are uncommon
• Causes are micro and macro emboli, global
hypoperfusion, cerebral hyperthermia, cerebral
edema, inflammation, BBB disruption
• Intra-op awareness should be avoided

68. Temperature regulation-
• Hypothermia causes increase in SVR, shivering
increasing oxygen consumption and coagulopathy
• So normothermia should be achieved at end of
bypass
• Rewarming should be gradual
• Hyperthermia should be avoided as it delays
neuronal metabolic recovery, increases excitotoxic
neurotransmitter release, oxygen free radical
production, intracellular acidosis, increased BBB
permeability.

69. enal ef fects-
luid loss, myocardial depression and vasodilation by
anesthetic agents, long term use of ACEIs,
inflammatory response, loss of pulsatile flow decrease
renal perfusion
luid replacement, vasoconstrictors, frusemide 10-20
mg or mannitol 0.5-1mg/kg can be used

70. RANSPORT TO ICU-
ortable monitoring equipment, infusion pumps, full
oxygen cylinder with a self-inflating bag for ventilation
should be ready
pon arrival to icu patient is attached to ventilator,
breath sounds checked, orderly transfer of monitors
and infusions should follow

71. OFF PUMP CABG
ANDIDATES-
pts with anterior lesions,single /double vessel ds.
ts with high risk of stroke, renal failure ,pulmonary
dysfunction, severe valvular ds.
urgeon employed
nstitute

72. Major differences from onpump
ollowing sternotomy , goal of heparin anticoagulation
achived is – > 2 times of baseline ACT or > 300 sec or
same as onpump(>400 secs).
Only focal area of heart is stablized via epicardial
stablizers. Distal anastmosisis done then aorta is
partially clamped to perform proximal anastmosis .(BP
kept <100 mmHg).
emodynamic disturbances & arrhythmias more
frequent and need to be adderssed.

73. Transport from OT
omplications during transpor t-
nadvertent extubation
ull off of monitors
oss of i.v lines
njury to body parts
isconnection of pacemaker wires

74. ARE IN ICU-
ost patients require mechanical ventilation for 2-12
hrs, sedation and analgesia should be continued
ypertension unresponsive to sedation and analgesics
should be aggressively treated with vasodilators
xtubation is considered when patient becomes
conscious, muscle paralysis has worn off, blood gas
values are acceptable, surgical hemostasis is
adequate and the patient is hemodynamically stable

75. ABG procedures relieve chest pain and angina, enable
patients to resume a healthy life style, lower the risk of
further heart attack and its consequences
hey do not prevent coronary disease from recurring,
hence medications along with appropriate lifestyle
changes are strongly recommended to reduce the risk
of recurrence.

76. UTCOMES OF CONVENTIONAL CABG-P
OSITIVE-
elief of angina in 90%
0% angina free after 5 years
5% survival after 1 year
ow chance of restenosis
EGATIVE-

77. TTHHAANNKK YYOOUU