Anesthesia in the Cardiac Patient

1. Anesthesia in the Cardiac Patient

2. Monitoring Routine Pulse Oximetry PNS Capnography Temperature Core and peripheral ECG Leads V5 and II

3. Monitors of Cardiac Performance Arterial Line Standard of Care Site selection Pulmonary Artery Catheter Provides means for assessing filling pressures Reliable site for drug administration Transesophageal Echocardiography

4. Anesthetic Technique Goals of Anesthesia loss of conciousness amnesia analgesia suppression of reflexes (endocrine and autonomic) muscle relaxation

5. Inhalation Agents Advantages Myocardial oxygen balance altered favorably by reductions in contractility and afterload Easily titratable Can be administered via CPB machine Rapidly eliminated

6. Inhalation Agents Disadvantages Significant hemodynamic variability May cause tachycardia or alter sinus node function Possibility of “coronary steal syndrome”

7. Coronary Steal Arteriolar dilation of normal vessels diverts blood away from stenotic areas Commonly associated with adenosine, dipyridamole, and SNP Forane causes steal and new ST-T segment depression May not be important since Forane reduces SVR, depresses the myocardium yet maintains CO

8. Opioids Advantages Excellent analgesia Hemodynamic stability Blunt reflexes Can use 100% oxygen

9. Opioids Disadvantages May not block hemodynamic and hormonal responses in patients with good LV function Do not ensure amnesia Chest wall rigidity Respiratory depression

10. Induction Drugs Barbiturates Benzodiazepines Ketamine Etomidate

11. Nitrous Oxide Rarely used due to: increased PVR depression of myocardial contractility mild increase in SVR air expansion

12. Muscle Relaxants Used to: Facilitate intubation Prevent shivering Attenuate skeletal muscle contraction during defibrillation

13. Cardiopulmonary Bypass Basic Components Arterial and venous cannula Reservoir Pump Oxygenator Heat exchanger

14. Cardiopulmonary Bypass Oxygenators Bubble - most common Direct contact between blood and fresh gas The smaller the bubbles the greater the rate of transfer Perfusate must be de-foamed Associated with platelet destruction, microemboli, and decreased leukocyte counts

15. Cardiopulmonary Bypass Oxygenators Membrane Blood gas interface separated by semipermeable membrane No direct mixing of gas and blood Less trauma to blood

16. Cardiopulmonary Bypass Cannulation Venous cannula placed into RA, IVC, or SVC Arterial cannula into proximal aorta or femoral artery Aorta cannulated first Systolic BP reduced to 100 - 110 mm Hg.

17. Cardiopulmonary Bypass Complications of Cannulation Arterial Hypertension Venous Supraventricular dysrhythmias Atrial fibrillation

18. Cardiopulmonary Bypass Pumps Roller positive displacement pump that maintains constant flow when increased resistance is encountered Impeller with increased resistance forward flow is reduced

19. Cardiopulmonary Bypass Heat Exchanger Adjusts temperature of perfusate to provide hypothermia Metabolic requirements are decreased about 8% per degree of decrease in body temperature Provides protection during periods of hypoperfusion and potential tissue ischemia

20. Cardiopulmonary Bypass Heparinization 300 u/kg ACT determines adequacy of anticoagulation ACT value greater than 400 sec.

21. Cardiopulmonary Bypass Preparation of Machine Crystalloid solution used to “prime pump” Causes a dilution of plasma drug concentration Hgb and HCT are reduced Blood viscosity decreases MAP drops to 30 -40 mm Hg.

22. Cardiopulmonary Bypass Management of Gas Exchange pH stat Alpha-Stat

23. Cardiopulmonary Bypass Adequacy of Perfusion MAP Hematocrit Mixed venous oxygen saturation Blood lactate levels Central and peripheral temperature Urine output

24. Cardiopulmonary Bypass Central Nervous System Protection Injury thought to be a consequence of emboli Contributing factors inadequate cerebral perfusion duration of bypass age

25. Cardiopulmonary Bypass Rewarming 10 degree gradient maintained to reduce gas bubble formation Awareness may be a problem

26. Separation from Bypass Accomplished in three stages Preparation Partial Bypass Off Bypass

27. Separation from Bypass Preparation Release of aortic cross clamp reestablishes myocardial perfusion and cardiac rhythm Often requires electrical defibrillation

28. Separation from Bypass Problems encountered during preparation phase Recurrent or resistant ventricular fibrillation Persistent left ventricular distention Persistent asystole

29. Separation from Bypass Partial Bypass Venous return partially restricted Venous blood enters the right ventricle Lungs inflated and right ventricle ejects blood into pulmonary artery Modest PA pressure and good systemic pressure indicate successful separation

30. Separation from Bypass Factors contributing to problems during partial bypass unusually low hematocrit excessive vasodilation marked respiratory or metabolic acidosis

31. Separation from Bypass Off Bypass Complete occlusion of venous return to machine Continuous assessment of filling pressures important venous blood remaining in reservoir used to transfuse as necessary

32. Reversal of Anticoagulation Protamine administration Most common method to use standard dose calculated on original dose of Heparin 1 mg Protamine per 100 u Heparin

33. Protamine Reactions Three Types Hypotensive (Type I) - Transient hypotension occuring with rapid administration of Protamine Anaphylactic/ Anaphylactoid (Type II) - True allergic reaction or response to release of vasoactive mediators Catastrophic Pulmonary Vasoconstriction (Type III) - systemic hypotension and elevated PAP

34. Hemodynamic Goals Post-Bypass Heart Rate Must provide adequate cardiac output 70 -90 bpm Rhythm should be sinus Ventricular dysrhythmias Supraventricular dysrhythmias

35. 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

36. 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 Edrophonium Procainamide

37. Hemodynamic Goals Post-Bypass Preload Enough to support CO but avoid distention Volume may be administered from CPB machine Excessive preload may be relieved with NTG or diuretic

38. Hemodynamic Goals Post-Bypass Afterload Reduction advantageous to the post-bypass patient Decreased wall stress lowers MVO2 Favors forward flow

39. Hemodynamic Goals Post-Bypass Contractility Optimize to maintain CO May be augmented with inotropic support Choice of agent depends on: severity of ventricular dysfunction heart rate afterload personal preference

40. Inotropic Drugs

41. Common Problems Post-Bypass Left Ventricular Failure Causes Ischemia Valve failure Hypoxemia Inadequate Preload Volume Overload Decreased contractility

42. Common Problems Post-Bypass Left Ventricular Failure Treatment Nitroglycerine Inotropes Transfusion Treat any acid-base/electrolyte abnormalities

43. Common Problems Post-Bypass Right Ventricular Failure Causes Same as LV failure RV ischemia or infarction Pulmonary HTN COPD Mechanical ventilation Protamine reaction Pulmonary embolus

44. Common Problems Post-Bypass Right Ventricular Failure Treatment Ischemia treated with NTG to decrease preload and improve coronary flow Control Preload Pulmonary vascular resistance

45. Mechanical Assist Devices Intraaortic Balloon Pump (IABP) Indications for use Intractable cardiac failure Preop stabilization of angina or LV failure Complications of MI refractory to pharmacologic support

46. Mechanical Assist Devices IABP Placed percutaneously or via cutdown through femoral artery Balloon inflates at beginning of diastole augmenting coronary blood flow Balloon deflates at beginning of systole reducing afterload Triggered by ECG or arterial pressure waveform

47. Mechanical Assist Devices Ventricular Assist Devices Designed to augment either R or L ventricular function Goal is to decrease MVO2 Three types available Roller pumps Centrifugal pumps Pneumatic pulsatile pumps

48. Common Problems Post-Bypass Coagulopathy Pulmonary Complications Pump lung Broncho spasm

49. Postoperative predictors Ischemia does occur most commonly in the postoperative period Persists for 48 hours or longer following non-cardiac surgery Predictor value is unknown Goldman, L., (1983) Cardiac Risk and Complications of noncardiac surgery, Annals of Internal Medicine. 98:504-513

50. Nonadrenergic Cardiovascular Drugs