ANESTHESIA FOR CABG

PRESENTED BY

DR. KANCHAN SHARMA

Prior to 1930’s, heart surgery seen as impossible, with high morbidity and mortality “Surgery of the heart has probably reached the limits set by nature to all surgery”  

–Stephen Paget, 1896, Surgery of the Chest

1937: Dr. John Gibbon designs heart-lung machine, which enables cardiopulmonary bypass (CPB)

1955: Vineburg and Buller implant internal mammary artery into myocardium to treat cardiac ischemia and angina

1958: Longmire, Cannon and Kattus at UCLA perform first open coronary artery endarterectomy without CPB

During 1960’s and 1970’s, CPB and cardioplegic arrest are adopted, allowing Coronary Artery Bypass Graft (CABG) to emerge as a viable surgical treatment

SINUS OF VALSALVA

RCA LCA

Ant.Left Post.

PDA Posterolateral branches

LAD LCx PDA

4-6Septalperforators

1-3Diagonalvessels

4 Obtuse marginal

ANATOMY

Coronary Angiography

Epicardial vessels

Small intramural branches

Altering the resistance of circulation

Venous drainage Coronary sinus RA

Thebesian veins

CONTD…

PATHOPHSIOLOGY

MYOCARDIAL ISCHAEMIA

PATHOPHYSIOLOGY OF MI

Decrease Oxygen Supply

Coronary vasoconstriction

Intracoronary platelet aggregation

Thrombus formation

Vasodilation

Increase Oxygen Demand

Tachycardia

Exercise

Emotional stress

Increase in coronary blood flow

vasodilation paradoxical vasoconstriction

low flow ischaemia

myocardial dysfunction

compromise

tissue perfusion cellular aerobicmetabolism

RISK FACTORS-MI

Genetic susceptibility

Obesity

Diabetes Mellitus

Increased cholesterol & triglycerides

Smoking

Hypertension

Type A

AFFECTED ARTERIES

LAD or CircumflexMost commonly affected;

proximal areas

RCAProximal or distal areas

Chronic angina Unstable angina Acute myocardial infarction Acute failure of percutaneous transluminal

coronary angioplasty (PTCA) Severe coronary artery disease

TYPES OF CABG

CONVENTIONAL CABG BEATING HEART CABG MINIMALLY INVASIVE CABG:

1.BEATING HEART WITHOUT CPB

2.PORT ACCESS WITH VIDEO

ASSISTANCE AND CLOSED CHEST

CPB

Saphenous vein used for bypassing right coronary artery and circumflex coronary artery

Internal mammary artery (IMA) used for bypassing left anterior descending coronary artery

If more veins are needed, alternative sites such as upper extremity veins can be used.

RADIAL ARTERY

Coronary lesion must be > 70 % stenosed

No difference at 5 years for RCA disease compared to SVG

RADIAL HARVEST

RISK FACTOR AND CLASSIFICATION FOR POST OP MORTALITY AND MORBIDITY

Age > 75 years, Female gender Unstable angina or recent

MI Evidence of heart failure Severe obesity (BMI > 30) Emergency surgery Reoperation Other significant and

uncontrolled systemic disturbances.

1. Normal risk – patient with none of the above factors

2. Increased risk – patient with one of the above factors

3. High risk – patient with more than one of the above factors

CLASSIFICATION OF PATIENTS

Good LV function

CI > 2.5 L/min; EF > 55%

LVEDP < 12 mmHg

No chest pain

Poor LV function

CI < 2.0 L/min; EF < 40%

LVEDP > 18 mmHg

CHF symptoms

CARDIOPULMONARY BYPASS• CPB passively drains blood from venous

system into pump, forcing it through an oxygenator, and then back into patient’s arterial circulation.

• Drained by gravity.

• Bypass machine assumes functions of heart and lungs.

* GOAL: Normal organ perfusion while surgeon has optimal operating conditions .

PARTS OF EXTRACORPOREAL CIRCIUT

1. Circuit/Pumps

2. Heat Exchanger

3. Oxygenators

4. Filters

5. Pressure transducers

BYPASS SETUP

CARDIOPULMONARY BYPASS

BY PASS MACHINE

CARDIOPULMONARY BYPASS

1. Circuit/Pumps * Blood is drained from RA

* Travels through the extracorporeal circuit

* Returned to the ascending aorta

* Pump (generates the pressure required to

return the perfusate to patient)A. Roller (nonpulsatile)

B. Centrifugal

C. Pulsatile

CONTD…….

2. Heat exchanger Allows production of hypothermia

3. Oxygenators Adds O2/removes CO2

A. Bubble (time-dependent trauma to blood)B. Membrane (less damage to blood)

4. Filters Traps bubbles/debris

5. Pressure transducers Monitor its function

SAFETY FEATURES

Air detectors : prevent pumping air into arterial

circulation Continuous measurement of MVO2:

detect inadequate tissue O2 delivery Continuous monitoring of hydrostatic

pressure within pump circuit : detect obstruction or prevent rupture of

circuit

EXTRACORPOREAL CIRCULATION AND CARDIOPULMONARY BYPASS

Reroutes unoxygenated blood from RA away from heart and lungs through circuit

Circuit oxygenates venous blood; acts as a heart-lung machine

Oxygen-enriched blood is returned to aorta for peripheral circulation

PREOP ASSESSMENT

HISTORY

PHYSICAL EXAMINATION

AIRWAY ASSESMENT

PRE OPERATIVE DRUG THERAPY

NTG

Ca channel blockers

-blockers

CONTD….

Aspirin

Aprotinin

Heparin

Thrombolytic agents

PRE OP LAB INVESTIGATIONS

NON INVASIVE:

CBC,RFT,BLOODSUGAR,CXR,ECHO,STRESTESTING,PFT,COAGULATION PROFILE CARDIAC ENZYMES

INVASIVE:

CORONARY ANGIOGRAPHY

ANESTHESIA CONSIDERATIONS

GOALS:- Precision of safe anesthesia using a

technique that offers maximum cardiac protection and stability.

Maintaining haemodynamics in the intraoprative period by physical and pharmacological methods.

Allowing early emergence, ambulation. Pain relief.

PREMEDICATIONS

Reduce fear, anxiety, analgesia, amnesia Drugs:

1. Diazepam – 0.1-0.15 mg/kg (oral)

2. Morphine – 0.1 mg/kg (i.m.)

3. Scopolamine – 0.2-0.4 mg (i.m.)

4. Glycopyrrolate – 0.005-0.01mg(i.m.)

HAEMODYNAMIC MONITORING

LARGE BORE IV CANNULA

PULSE OXIMETRY

ECG :

ARTERIAL PRESSURE Invasive

Avoid harvest arm if arm vessel used

Place right radial if Left IMA used Non-invasive

.

CVP

CORE TEMPERATURE

PULMONARY ARTERY CATHETER

ASA practice guidelines:EF < 40%

Significant abnormality of left ventricular wall motion

LVDEP > 18 mmHg at rest

Recent MI or unstable angina

Post MI complications

Emergency surgery

Reoperation

TRANSOESOPHAGEAL ECHOCARDIOGRAPHY

Used to assess ventricular/valvular kinetics.Allows continuous monitoring:

a. Heart chambersb. Aortac. Valvular functiond. Chamber fillinge. Wall contractility and motionf. Ischemia: Regional wall motion

INDUCTION AGENTS

1. Morphine

2. Fentanyl

3. Sufentanyl

4. Alfentanyl

Disadvantages: Histamine Prolonged respiratory depression Lack of amnesia

Advantages: Lack of any direct effect on the heart Pain free post operative period Bradycardia

HYPNOTICS:

Thiopentone

Propofol

Benzodiazepines:

Diazepam 0.5 mg/kg IV

Midazolam 0.2 mg/kg IV

CONTD….

MUSCLE RELAXANT

Succinylcholine 1-1.5 mg/kg IV

Pancuronium 0.08-0.15 mg/kg IV widely used

Vecuronium 0.08-0.2 mg/kg IV cautiously used

Atracurium 0.5-1.0 mg/kg IV histamine release

Rocuronium 0.6 mg/kg IV

Mivacurium 0.15 mg/kg

0.2 mg/kg histamine release

PERIODS OF STIMULATON

Incision

Sternotomy

Rib disarticulation

Change in position of rib retractor

Excision of pericardium

HEPARINISATION

DOSE OF 300-400U/KG BOLUS IV

SUBSEQUENT DOSING TARGETED AT

ACT>400 SECONDS

NEUTRALISATION

PROTAMINE

Dose: 1-1.3mg /100U of heparin

CALCULATION BASED ON:

1)Total amount of heparin

2)Calculated heparin concentration :

automatically : heparin concentration

monitoring system

Graphically: plotting ACT values creating

heparin dose response curve

SIDE EFFECTS OF PROTAMINE

A. HISTAMINE RELEASEAnaphylaxis (ST & B/P)Pulmonary HTN/ bronchoconstriction

B. ALLERGIC REACTIONS Received protamine-containing insulin Vasectomy in past

R/T anti-protein antibodies in serum of males who have had a vasectomy or in infertile males

Allergy to fish Protamine is a compound isolated from fish

sperm

SURGICAL ASPECTS

Most common arteries bypassed: Right coronary artery Left anterior descending

coronary artery Circumflex coronary artery

Conduit removed Median sternotomy

Sternum divided using electric saw

Cold potassium cardioplegia Cardiopulmonary bypass

Cannulation of: Ascending aorta Femoral artery Right atrium

Heparin administered to minimize clotting

Bypass of arteries: Incision in target artery:

Anastamosis of graft with artery:

MAINTENCE OF ANESTHESIA

Opioids:

Fentanyl : 0.1-0.5 µg/kg/min infusion

Low dose inhalational agents isofurane,sevoflurane

Benzodiazepine

Propofol

PATIENTS WITH POOR LV FUNCTION

Aim : Minimize oxygen demand and maximize oxygen supply Premedication:

dose should be reduced / omitted if patient is in CHF or is orthopnoeic

Mechanized circulatory support (IABP)

Drug infusion (inotropes and dilators) should be continued

Propped up position

Oxygen supplement

Preparation of anesthesia : Availability of resuscitation drugs

ANESTHETIC DRUGS

Dose : Benzodiazepine to be omitted Drugs to suppress the intubation reflux – avoided During induction circulation decrease inotropes started Propofol – avoided Pancuronium – muscle relaxant Commencement of PPV – CO and BP decreases

Myocardial preservation: Blood cardioplegia – warm / cold Retrograde cardioplegia Ischaemic preconditioning

MAINTAINENCE OF ANESTHESIA

CARDIOVASCULAR SUPORT MOST IMPORTANT

PROVIDED BY: Arrhythmia management Volume Myocardial contractibility Afterload control Inotropes Mechanical assistance

FAST TRACK CABG

FAST TRACK CABG Reason behind development:

Cost containment Efficient resource utilization Pressure on ICU beds

Definition: Extubation on the operating table 2-4 hrs stay in the recovery room

OR Extubation within 12 hrs ICU stay as long as 24 hrs

Hallmark: Reducing the total amount of opioids administered Precautions

Patient should not be actively cooled during CPB High risk patient with poor EF, low CO, CHF are less optimal

candidate for early extubation

ANESTHESIA TECHNIQUES

Extubation at the end of surgery prolong the OT time

Better option move the patient to ICU Extubate

Technique to shorter the time to extubation Use of inhalational agents Reducing the dose of opioids in conjunction with

propofol Epidural / Intrathecal technique

MINIMAL INVASIVE SURGERY

RISKS

Profound hemodynamic and ischemic

changes due to: Slowed HR

Mechanical tamponade by stabilizers

Poorly tolerated in a patient with: Multiple vessel disease

Concurrent disease processes

IDEAL PATIENT

LAD lesion not amenable to treatment with

interventional cardiology procedures

High risk for death if CABG: Poor LV function

CRF

Aortic calcification

EXCLUSION CRITERIA

Aortic valvular insufficiency

Aortoiliac disease

Inaccessibility to coronary artery

Decompensated heart failure

Pulmonary insufficiency

Lack of suitable conduit

CONTRAINDICATIONS

Intramyocardial LAD Diffuse, calcified LAD < 1.5 mm Rightward displacement of LAD Severe HTN Morbid obesity Severe COPD Atrial fibrillation IABP

ADVANTAGES

Smaller incision/no sternotomy Less operative time Less invasive/Less surgical bleeding No CPB and its associated risks No cardioplegia & topical cooling Less pain Shorter extubation/recovery times Earlier discharge/Less expensive Decreased risk of infection

DISADVANTAGES

Limited number of graft sites If other lesions present,

incomplete revascularization Smaller surgical field

more technically difficult Resuscitation limited

due to exposure of great vessels

Small incisions for video-assisted LIMA harvest

Thoracotomy incision (~10 cm)

Small portion of front of 4th rib removed LIMA clipped and dissected

MIDCAB retractor and LIMA stabilizer facilitates grafting

LAD exposed Anastamosis preformed with assistance of mechanical stabilizer

Completed graft

ANESTHESIA MANAGEMENT

MONITORING PREVENTION OF ISCHAEMIA MAINTAINCE OF DEPTH HAEMODYNAMIC STABILITY POST OPERATIVE CARE

Uses CPB Balloon catheter system for aortic occlusion

and cardioplegic arrest 5-8 cm left anterior thoracotomy incision

No sternotomy!!!

LIMA harvested using specialized retractor

Aorta drawn into operating field

Aorta clamped, anastamosis performed

REQUIREMENTS

TRANS OESOPHAGEAL ECHOCARDIOGRAPHY

COLOUR DOPPLER FLOW THROUGH FLUOROSCOPY

DOUBLE LUMEN TUBE

ANESTHESIA MANAGEMENT

Additional expertise

Insertion : endopulmonary vent

& endocoronary sinus catheter.

Systemic perfusion: endo-aortic catheter

Antegrade cardioplegia and aortic root vent

Venous return: catheter advanced through IVC-

RA junction through femoral veins

Retrograde cardioplegia- endocoronary sinus

IMPORTANT CONSIDERATIONS

ARRHYTHMIA HAEMOSTASIS MYOCARDIAL PROTECTION DE-AIRING

Benefits: Bloodless field Heart arrested

allows more accurate anastomoses than MIDCAB Smaller incision than CABG No sternotomy

Drawbacks Uses CPB Technically very difficult

OFF PUMP VS ON PUMP CABG

FACTORS Off Pump coronary

artery bypass grafting

On pumps coronary

artery bypass

SIRS decrease increase

Coagulopathy decrease increase

Neurological

dysfunction (stroke)

1% 9%

Myocardial injury less more

Rate or Renal failure less more

INTRA OPERATIVE EVENTS

GOALS TO MANAGE HYPOTENSION

PRELOAD

SINUS RHYTHM

INCREASING THE AFTERLOAD

PRELOAD

Enough to support CO but avoid distention

Volume may be administered from CPB machine

INCREASE THE AFTERLOAD

VASODILATORS: Coronary vasodilation decrease

ischemia increase compliance and contractility

Decrease in RV preload decrease RV pressure increase compliance of LV

INOTROPES SUPPORT

1. Improved myocardial contractility 2. Minimize cardiac distension 3. Coronary perfusion is optimized 4. DRUGS: Epinephrine,Nor epinephrine Dobutamine Dopamine Isoprenaline Milrinone,Amainone,Enoximone

RHYTHM

VENTRICULAR DYSRHYTHMIAS

Cause must be identified rapidly and treatment instituted

V tach and V fib treated with internal defibrillation

V tachydysrhythmias treated with:Lidocaine Procainamide

Bretylium Esmolol

Magnesium

SUPRAVENTRICULAR DYSRHYTHMIAS

Atrial fib and tachycardia treated with synchronized internal cardioversion

Need to look at blood gases, acid-base status, and electrolytes

Assume ischemia - use NTG

Other treatments;Digoxin , Esmolol,Verapamil , Adenosine

Procainamide

HYPOTHERMIA

Warn Blankets - preoperatively. Keep the theatre warm till induction thereafter

the temperature can be decreased gradually Time taken for sterile preparation of the patient

be kept to the minimum. Warm blankets under the patient. Warm IV fluids. Low fresh gas flow with CO2 resorption circuit.

MYOCARDIAL ISCHAEMIA

MAP > 70 mm Hg. Mixed venous oxygen saturation 60%. Wedge pressure - low. Reduction in myocardial oxygen

consumption. Avoidance of Bradycardia.

CONTD….

Intraluminal Coronary Shunts:- Fits into the proximal and distal end.

Benefits:- Maintain native coronary arterial blood flow.

Decrease blood loss.

Prevents embolization of CO2.

CONTD….

Prevents taking the suture on the posterior wall of coronary artery.

Proper coronary anastomosis.

Reverses the changes produced by ischaemia

HYPERTENSION

Deepening anesthesia

Administration of vasodilator NTG infusion

With tachycardia - -blockers

RISKS AND COMPLICATIONS

RISKS AND COMPLICATIONS

A. PULMONARY: - Postoperative atelectasis

- Acute lung injury (congestion, edema)

- 3rd spacing/fluid shifts during CPB & several days post-bypass

B. RENAL: - Impaired function R/t length of surgery, CO,

infection

CONTD….C. CNS:

Major CNS complication: CVA (1-5%)

During CPB, arterial pressure reflects CPP if superior

vena cava outflow not obstructed

D. COAGULOPATHY :-Hypothermia

-Dilutional thrombocytopenia (50% in CPB)

-Can lead to abnormal ACT, PT, PTT, platelets

-Platelets become nonfunctional at 28C

CONTD….E. HYPOKALEMIA

-Increased uptake by cells

-Due to hypothermia

F. ANEMIA-About 3-5 % receive > 10 units of blood

G. EMBOLI-Air, oxygen, nitrous oxide, thrombus

-Can lead to PE, CVA

CONTD…..

H. HYPOPERFUSION

I. PHRENIC NERVE DAMAGE -Due to hypothermia

J. RECALLAwareness during CPB, especially with

rewarming

Give versed PRN

Avoid agents at this time due to myocardial depression

CONTD…

K. ARRYTHMIAS-Hemorrhage/Irritation/Low K+

L. HYPOTHERMIA

- Common after rewarming

M. HTN

Common after rewarming

Due to light, pump flows too high

POST OPERATIVE PAIN

EPIDURAL ANALGESIA INTRAVENOUS OPOIDS

THANKS!