Post on 07-Apr-2015
transcript
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!