1. Anesthesia for Cardiovascular Surgery
Part I…after Part II…whatever
Anesthesia for Cardiovascular Surgery

2. What to look forward to…
Overview of Cardiopulmonary Bypass
Overview of On-Pump CABG
TEE will not be covered.

3. Cardiopulmonary Bypass

4. General Functions include: Non-physiologic
Diverting venous blood away from the heart
Adding oxygen
Removing CO2
Returning blood to arterial side
Non-physiologic
Requires steps to minimize organ damage

5. CPB Circuit Patient Venous Reservoir Oxygenator Heat exchanger
Main Pump
Arterial Filter

6. CPB Circuit Additional parts
Accessory pump for Cardiotomy suction
Accessory pump for left ventricular vent
Cardioplegia line
Circuit primed with mL for adults
Balanced salt solution
Colloid
Heparin
Dilutes hematocrit to 22-25%

7. CPB Circuit Patient Venous Reservoir Oxygenator Heat exchanger
Main Pump
Arterial Filter

8. Reservoir Receives blood from the patient via Driving force is GRAVITY
One cannula in right atrium
Two cannulas in superior and inferior vena cava
Driving force is GRAVITY
Reservoir on the floor
Flow proportional to difference in height
Must monitor fluid level
If reservoir empties air can enter pump and cause air embolism
Frowned upon

9. CPB Circuit Patient Venous Reservoir Oxygenator Heat exchanger
Main Pump
Arterial Filter

10. Oxygenator Blood drained from bottom of reservoir
Blood-gas interface allows blood to equilibrate with gas mixture
Oxygen
Volatile anesthetic
Thin gas-permeable membrane
Oxygenation inversely related to thickness of blood film over the membrane
CO2 tension dependent on gas flow

11. CPB Circuit Patient Venous Reservoir Oxygenator Heat exchanger
Main Pump
Arterial Filter

12. Heat Exchanger Water (heated or cooled) runs through exchanger
Heat transfer by conduction
As temperature rises, gas solubility decreases
Bubbles created
Caught by filter

13. CPB Circuit Patient Venous Reservoir Oxygenator Heat exchanger
Main Pump
Arterial Filter

14. Main Pump Roller Pump Centrifugal Pump
Rotating pump produces flue by compressing tubing
Flow directly related to revolutions per minute
Centrifugal Pump
Series of cones spin causing centrifugal force
Flow is pressure sensivitve: Increase in distal pressure requires an increase in the pump speed to maintain flow
Nonocclusive: Less daming to RBCs
Often placed between reservoir and oxygenator
Organs accustomed to pulsatile flow
Not possible with centrifugal pumps, some roller pumps
Possibly improves perfusion, oxygen extraction

15. CPB Circuit Patient Venous Reservoir Oxygenator Heat exchanger
Main Pump
Arterial Filter

16. Arterial Filter Particulate matter common with CPB circuit
Thrombi
Fat globules
Debris
Filter placed to prevent systemic embolism
Filter contructed with bypass limb in case of clogging and to extract air

17. Accessory Devices Cardiotomy Suction Left Ventricular Vent
Suctions blood from surgical field
Left Ventricular Vent
Blood reaccumulates in LV due to residual pulmonary flow
Aortic regurgitation
Distention of LV increases wall tension thereby compromising myocardial preservation
Cardioplegia pump
Ultrafilter
Ultrafiltration to increase hematocrit
Hydrostatic pressures force water and electrolytes across membrane

19. Hypothermia Core body temperature to 20-32°C.
Metabolic oxygen requirements are CUT IN HALF FOR EVERY 10°C reduction
Profound hypotension for total circulatory arrest: 15-18°
Adverse effects
Platelet dysfunction
Potentiation of citrate toxicty
Coagulopathy
Depression of contractility

20. Myocardial Preservation
Cardiac Surgery is tough on the heart
Goal is to accomplish surgery efficiently while minimizing damage to the organ
Damage results from imbalance between myocardial oxygen demand and supply
Reperfusion injury
Oxygen-derived free radicals
Intracellular calcium overload
Abnormal endothelial-leukocyte interactions
Myocardial cellular edema
Symptoms post-bypass
Low Cardiac Output
ECG signs of ischemia
Arrythmias

21. Myocardial preservation
At aortic cross-clamp, clock starts ticking
CPB times longer than 120 minutes undesirable
Ischemia causes depletion of ATP and accumulation of intracellular calcium
Preventing ischemic damage requires maintaining normal cellular integrity
Reducing energy expenditure
Preserving availability of high-energy phosphate compounds

22. Myocardial Preservation
Reduce Basal metabolic oxygen consumption
Hypothermia
Reduce energy expenditure
Cardioplegia
Prevent ventricular fibrillation

23. Cardioplegia Potassium-rich solution Additional components
K: mEq/L
Additional components
Sodium (<140)
Calcium to maintain cellular integrity
Magnesium to prevent excessive calcium influx
Buffer to prevent buildup of acidic metabolits
Bicarbonate
THAM (histidine and tromethamine)
Energy substrate (glucose, glutamine, aspartate)

24. Cardioplegia
Increased extracellular potassium reduces transmembrane potential
Interferes with normal sodium current during depolarization
Decreases rate of rise, amplitude and conduction velocity of action potential
With time sodium channel is inactived, action potentials cease, heart arrests in diastole
Washout necessitates redosing after 30 minutes
Where is cardioplegia given?
Anterograde cardioplegia (through aortic root) may not reach areas distal to occlusion
Retrograde cardioplegia given through coronary sinus
Excessive cardioplegia result in absence of eletrical activity, AV block, poor contractility

25. Effects of CPB Non-physciologic Increase in stress hormones
Inflammatory response similar to sepsis or trauma
Complement system by contact with circuit
Coagulation
Platelet dysfunction
Fibrinolysis
kallikrein
Elevated levels of
Catecholamines
Cortisol
Arginine vasopressin
Angiotensin
Plasma concentration of drugs acutely decrease with CPB

26. CABG
We are going to make this interactive…hopefully won’t crash and burn.
Let’s talk through a CABG
65 year-old man with remote history of right knee history presents for 3-vessel CABG. History significant for 3 months worsening chest pain during Saturday morning walks at the mall.

27. Preoperative evaluation
What do you want to know?

28. Anesthetic Management
Premedication
Anesthetic Plan?
Lines?

29. Note on Pulmonary Artery Catheters
In general, utilized in patients:
Compromised ventricular function
Pulmonary hypertension
Complicated procedures
Information provided
PA pressures
Wedge pressures
Cardiac output
TEE provides opportunity to assess function

30. Prebypass Periods of intense stimulation
Skin incision
Sternotomy
Sternal retraction
Aortic dissection
Vagal response during sternal retraction or opening of pericardium
Fluid management goal to keep under 1000cc

31. Anticoagulation Heparin 3000-4000 U/kg Resistance to heparin
Acts upon Antithrombin III to enhance activity 1000-fold
Should be given via central line
Monitored by ACT, confirm >375 before cannulation
Resistance to heparin
Antithrombin III deficiency
Give FFP or antithrombin III
Patient with Heparin-induced Thrombocytopenia
Heparin-dependent antibodies agglutinate platelets
Remote history, no antibodies  heparin
Antibodies present  alternative anticoagulation, usually hirudin

32. Pre-bypass checklist Anticoagulation? Anesthesia adequate?
Cannulation correcct?
Infusions off?
Monitors in place?

33. Cannulation Anticoagulation confirmed
Blood pressure decreases to systolic of 100 for aortic cannulation
Closed heart procedures utilize one cannula in RA
Open heart procedures use two cannula: SVC, IVC
Malpositioning manifested by poor venous return or edema of head and neck
Initiation of CPB
Unclamp venous line first
Flow starts slow to ensure venous return, then increased
Failure of heart to empty signifies malpositioning

34. On Bypass Initial arterial pressure falls
Prolonged decrease pressure may indicate aortic dissection
If dissection, must cannulate aorta distally
On CPB, arterial mean pressure = pump flow x SVR
At Tulane, perfusionist controls hemodynamics during CPB
Muscle relaxant may be required
Light anesthesia may result in awareness, especially during rewarming

35. Weaning from Bypass Core body temperature at least 37°C
Stable rhythm, atrioventricular pacing may be required
Adequate heart rate between
Labs within limits, treat acidosis, hypocalcemia, hyperkalemia
Adequate ventilation with 100% oxygen

36. Weaning from bypass
Venous return line progressively clamped allowing blood to fill heart
Ventricular ejection resumes
Pump flow decreased
Once venous line is occluded and arterial pressure adequate, pump flow is stopped
Patient’s hemodynamics are evaluated

37. Weaning Group I: Vigorous Group II: Hypo-volemic Group IIIA LV Failure
Group IIIB
RV Failure
Group IV
Hyper-dynamic BP
Normal
Low
CVP
Normal or high
High
Normal or low
PA pressure
Wedge CO
SVR Tx
None (yay)
Volume (duh)
Inotrope; reduce afterload; IABP; LVAD
Pulmonary vasodilator; RVAD
Increase hematocrit

38. So… Patients flying off bypass or hyperdynamic can be weaned quickly
If patient is hypovolemic, coordinated bolus from bypass pump in 100cc doses (This is what’s going on when you are standing there and the attending keeps on asking, “What do you have for me? Ok, give me Give 100 more. Etc.”)
Pump failure is more difficult
For LV, inotropes +/- vasodilator if SVR is high
Evaluate TEE
Intraaortic balloon pump
Timing is vital: Inflation just afte dicrotic notch  augments diastolic BP and coronary flow
Deflation just prior to LV ejection

39. Reversal of anticoagulation
Protamine (1.3mg per 100 units of heparin)
Highly positive charged protein that inactivates heparing
Heparin-protamine complexes removed by reticuloendothelial system
Infuse slowly over 5-10 minutes
Allergic reactions
Men with previous vasectomies
Diabetics who received NPH insulin
Allergy to fish
Prior reaction
Type I Hypersensitivity reaction

40. Catastrophes Aortic dissection due to malposition of aortic cannula
Cannula within wall, not in true lumen
Clues
Occlusion of true lumen cause profound decrease in arterial pressure
High pressure on pump
Organ hypoperfusion
Management
Discontinue CPB
Reposition arterial cannula
Place arterial cannula distally

41. Reversed Cannulation
Blood drained from aorta, return under pressure to venous
Great risk for air entrapment in in aorta causing air embolism upon correction
Clues
Arterial hypotension
Severe facial edema
High CVP
Flaccid aorta
Management
Discontinue CPB
Steep head down
De-air the aorta and pump line
Exchange cannulas

42. Gas embolism High risk of MI, stroke, or death
Common causes include emptied reservoir, clotted oxygenator, opening a beating heart, disconnection of lines during CPB
Management
Head down
Vent
Retrograde CPB through SVC line
Carotid compression
Hypothermia
Ventilate with 100% oxygen