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1. Anaesthesia for off pumpcoronary artery bypass grafting- the
current concepts Presented- DR. SACHIN BANSAL Moderator- DR.
ANJUM
2. DEFINITION Off-pump coronary artery bypass or "beating
heart" surgery is a form of coronary artery bypass graft
(CABG)surgery performed without cardiopulmonary bypass (heart-lung
machine) as a treatment for coronary heart disease During most
bypass surgeries, the heart is stopped and a heart-lung machine
takes over the work of the heart and lungs. When a cardiac surgeon
chooses to perform the CABG procedure off-pump, also known as OPCAB
(Off-pump Coronary Artery Bypass), the heart is still beating while
the graft attachments are made to bypass a blockage.
3. Historical aspects the first open heart surgery was
performed by John Gibbon in 1952 us-ing cardiopulmonary bypass
First successful OPCAB was per-formed in 1961 and Kolesov in 1964
performed the first successful anastomosis of left internal mammary
artery to left anterior descending artery In 1967 Favalaro and
Effler performed reversed saphenous vein grafting. In 1968 Green
performed anastomosis of the internal mammary artery to the
coronary artery .
4. Off pump coronary artery bypass grafting vs. onpump coronary
artery bypass grafting Systemic inflammatory response syndrome
(SIRS) -A combination of non pulsatile flow, myocardial ischaemia,
hypothermia and contact of the patient blood with the artificial
surface of the extra corporeal circuit is responsible for the
inflammatory process. Coagulopathy-disruption of the coagulation
system and haemodilution after cardiopulmonary by-pass is avoided
in OPCAB.
5. Off pump coronary artery bypass grafting vs. on pumpcoronary
artery bypass grafting Neurologic dysfunction-four major causes-
embolization, inflammation, hypoperfusion and hyperthermia. Two
type-1. death either due to stroke or hy-poxic
encephalopathy,stuper n coma. Risk factors are diabetes mellitus,
atherosclerosis in the proximal aorta and preexisting impairment of
cerebral blood flow. Type-2- intellectual dysfunction, memory
deficits, confusion or agitation are due to small micro emboli and
inadequate perfusion
6. The incidence of stroke after OPCAB is about 1% when
comparedto 9% after CABGMyocardial injury:- myocardial injury as
assessed by biochemical markers is much less after OPCAB when
compared to CABG. Pulmonary dysfunction: CABG pulmonary dysfunction
may be caused by alveolar atelectasis, inflammation, increased
shunting, and volume infu-sion. . The rate of renal failure is
lower in patients undergoing OPCAB.
7. The goals of anaestheticmanagement Provision of safe
anaesthesia using a technique that offers maximum cardiac
protection and stability Maintaining haemodynamics in the
intraoperative period by physical and pharmacological methods
Allowing early emergence, ambulation Providing adequate pain relief
in the postoperative period.
8. Preoperative anaestheticassessment Preoperative optimization
of diabetes, hypertension and reactive airway is essential.
Preoperative assessment of the carotid arteries is routinely
carried out. Preoperative transthoracic echocardiography, chest X
ray, and ECG serve as baseline investigations.
9. Preoperative anaestheticassessment Beta blockers should
continue to receive it in the same dose Anti plate-let medications
should be stopped atleast 1 week prior to surgery ACE inhibitors
should be stopped 24 to 36 hours prior to surgery. The last dose of
low molecular weight heparin should be 12 hours prior to surgery
& unfractionated heparin 6 hours prior to surgery. review the
coronary angiogram for a patient with poor left ventricular
function coupled with small caliber coronary arteries.
10. Premedication Benzodiazepines, opioids and anticholinergic
medications. 0.05mg.kg -1 of midazolam and 1g.kg -1 of fentanyl are
administered intramuscularly thirty minutes prior to surgery.
provide supplemental oxygen.Before insertion of intravenous and
arterial cannulae administer additional midazolam and
fentanyl.
11. MonitoringElectrocardiogram (ECG)-well visualized P wave
and QRS complex prior to commencing the surgery.Non invasive
monitors- include pulse oximetry and capnography.Invasive blood
pressure monitoring-By radial or femoral artery. The cannula-tion
of the femoral artery not only permits access to the central
arterial tree but provides access to quick insertion of an intra
aortic balloon pump. If radial artery cannulation is planned the
Allens test must be performed prior to performing cannulation.
12. Pulmonary artery catheter (PAC)-PAC is usually via the
right internal jugular vein.Indication- Ejection fraction less than
0.4. Significant abnormality of the left ventricular wall motion.
LVEDP greater than 18 mm Hg at rest. Recent MI and unstable
angina.
13. pulmonary artery catheter(PAC)- Post MI complications VSD
LV aneurysm Mitral regurgitation Congestive cardiac failure
Emergency surgery Combined procedures Reoperations
14. Transesophageal echocardiography(TEE)Advantages- Identify
myocardial ischaemia early by detecting regional wall motion
abnormalities. assess left ventricular dysfunction intra
operatively. assessing the improvement in myocardial function after
the completion of revascularization.Dissadvantage- Inability to
image the required part of the heart during grafting .Monitoring of
urine output, oropharyngeal and rectal tem-perature is
essential.
15. INDUCTION induction should be slow. induce general
anaesthesia by inhalational technique by either sevoflurane or
isoflurane in 1-2 minimal alveolar concentration. Neuromuscular
blockade is achieved by injecting 0.7 mg.kg -1 of rocuronium
intra-venously prior to intubation. Maintenance of is achieved with
an infusion of fentanyl, atracurium and isoflurane.
16. Intraoperative management Hypotension- treated with volume
loading. adequate heart rate in sinus rhythm. increasing afterload
to maintain systemic perfusion pressures. Inotrope therapy should
,like dopamine, epinephrin & dobutamine by infusion. informing
to surgeon for cotton packs under heart and the epicardial
stabilizers should be repositioned. resting the heart in the
pericardial cavity. If there is no improvement, an intra aortic
balloon pump support can be instituted.
17. Intraoperative management Arrhythmia- Use lidocaine
(without preservative) infusion if patient has arrhythmia caused by
myocardial ischaemia. If arrhythmias caused by electrolyte
imbalance then start an infusion of potassium chloride and
magnesium chloride.
18. Intraoperative management Intraoperative heparinisation and
neutralization- The dose of heparin is 2mg.kg -1 (200 units.kg -1 )
in-travenously.Activated clotting time( ACT) should be per-formed 3
minutes after administration. The goal is to keep the ACT between
250 - 300 seconds.
19. Intraoperative managementACT should be repeated hourly and
repeat bolus of 5000 units intrave-nously is essential if the ACT
value is less than 250 sec-onds.Heparin is reversed with protamine
sulfate with dose 1 mg/1mg of heparin. Accept-able ACT is in the
range of 130 to 140 seconds after protamine administration.A high
ACT will require additional protamine in a dose of 25 to 50
mg.
20. Prevention of hypothermiaWarm blanket covers in the pre
operative Period.Keep the operating theatre warm till induction and
there after the temperature can be decreased gradually.The time
taken for sterile preparation by painting and drap-ing by sterile
sheets should be kept to the minimum.
21. Prevention of hypothermia Spillage of cold fluids on the
patient is avoided by draping the patient with water-proof sheets.
intravenous fluids intended for use are warmed by fluid warmers.Low
fresh gas flows with carbon di oxide reabsorp-tion circuits.
22. Prevention of Myocardialischaemia Maintaining systemic
blood pressure by keeeping mean arterial pressure of at least 70 mm
Hg all times by administration of boluses intravenous fluid and
Trendelenburg position. Reduction in myocardial oxygen consumption
by avoiding tachycardia , using intraoperative beta- blockers or
calcium channel blockers. Ischaemia during distal anastomosis can
be prevented by using intraluminal coronary shunts .
23. IntracoronaryshuntsThese are doublelimb shunts that fitinto
the proximaland distal ends ofthe open coronaryartery
24. Intracoronary shuntsBenefits:-Native coronary arterial
blood flow is maintained preventing intraoperative ischaemia.Blood
loss during coronary anastomosis is avoided or decreased.The
coronary stent prevents embolization of carbon dioxide into the
coronary arteries.
25. Intracoronary shunts shunt prevents the surgeon from taking
a suture on the posterior wall of the coronary artery.Presence of
the shunt assures a proper coro-nary anastomosis. insertion of
intraluminal coronary shunts will reverse the changes caused by
ischaemia like myocardial oedema, endothelial and contractile
dysfunction.
26. Haemodynamic changes related toheart positionLifting and
rotating the heart during OPCAB can alter the haemodynamics such as
cardiac output, stroke work, left ventricular end diastolic
pressure and right atrial pressure. During grafting of right
coronary artery bradycardia can occure due to reduction in blood
supply to the sinus and AV nodes, so if required use atropine and
atrial pacing .
27. Haemodynamic changes related toheart position During
grafting of the right coronary artery and obtuse marginal branches
"verticalization" of the heart is required, so posterior
pericardial stitches and a gentle retracting socket will greatly
facilitate haemodynamic . Reduction in the dose of intravenous
vasodilators can increase the haemodynamic changes. During such
times it may be essential to reduce the dose of the vasodilator and
add a vasoconstrictor.
28. Post operative management Get a 12 lead electrocardiogram
for any fresh changes like ischaemia or myocardial infarction &
treated with low molecular weight heparin, anti platelet
medications, insertion of an intra aortic balloon pump or revision
of grafting. During transfer of the patient continuous monitoring
of ECG , pulse oximetery and invasive blood pressure is essential.
Always carry prefilled syringes of diluted 1:200,000 adrenaline,
1.2mg of atropine and 100mg of lidocaine (preservative free) to
treat a crisis during the transfer phase. cardiac index and partial
pressure of oxygen is decreased and took almost 15 to 20 minutes to
return to baseline.
29. I.C.U. managementPatients are connected to the ventilator:-
parameters are as follows:- FiO2 of 0.8 tidal volume- 7-10 ml.kg -1
frequency -12- 15/min I:E ratio of 1:2, and controlled mode of
ventilation.Arterial blood gas analysis is performed after thirty
minutes. FiO2 is reduced to 0.4 if oxygenation, carbon dioxide
elimination and tissue perfusion.
30. I.C.U. managementThirty minutes later a reassessment of-
blood loss (not more than 10% of blood volume) fluid balance (not
more than 10-15 ml.kg- 1 body weight) core tem-perature ( not less
than 35 deg Celsius ), arrhythmias urine output (at least 1-2 ml.kg
-1 .hr -1 ) are done.If the residual neuro-muscular blockade is
present then reversed by injecting a combination of neostigmine and
glycopyrrolate.
31. I.C.U. managementAfter confirming adequacy of reversal
ventilatory mode is switched to the spontaneous modes of
ventilation, such as pressure support, or continuous positive
airway pressure.Thirty minutes after supported ventilation arterial
blood gas analysis is repeated and If the analysis shows
satisfactory values of oxygenation, carbon dioxide elimination and
metabolism, the patients are extubated.
32. Fast track anesthesia Defined:- as tracheal extubation
within 8 hours after cardiac surgery, early mobilization of patient
and early discharge from the hospital. availability of short acting
opioid medications have made it possible to subject the patients
after cardiac surgery to fast track anaesthesia..
33. Fast track anesthesia Early extubation resulted in
regaining the cough reflex and thus a lower incidence of
atelectasis and pneumonia. All patients may not be suitable for
fast tracking; presence of bleeding, dysrryhtmias and haemodynamic
instability warrant ventilation till stability is achieved. Long
acting sedatives should be avoided
34. Management of postoperativepain Epidural analgesia:- begin
an epidural fentanyl infusion with Fentanyl 3000 mcg (60 ml), 0.5%
bupivacaine 55ml and saline 155ml are added to make a final total
volume 265 ml & start at a rate of 2ml.hour -1 Intravenous
opioids:- Fentanyl 3000mcg and saline 215ml are added to make a
final con-centration 11 mcg.ml -1 of fentanyl.