Anesthesia for Valvular Heart Surgery

1. Anesthesia for Valvular Heart Surgery Charles E. Smith, MD Professor of Anesthesia Director, Cardiothoracic Anesthesia MetroHealth Medical Center Case Western Reserve University

2. Objectives • Pathophysiology • Aortic valve: AS, AI • Mitral valve: MS, MR • Tricuspid valve: TR • Hemodynamic Goals • Anesthetic management

3. Aortic Stenosis • May occur at 3 levels: • Valvular • Subvalvular • Supravalvular

4. Valvular Aortic Stenosis • Calcification + fibrosis of normal tricuspid valve- very common • Calcification + fibrosis of congenital bicuspid AV • Rheumatic- uncommon since antibiotics

6. Aortic Stenosis • Normal AVA: 2-4 cm2 • Severe AS: AVA < 1cm2 • If normal LV- mean PG > 50 mmHg • If poor LV function- mean PG may be low!

8. Pathophysiology of Aortic Stenosis • Chronic LV pressure overload • Concentric LVH to ↓ wall stress • LVH → ↓ diastolic compliance, ↓ coronary blood flow + imbalance of MVO2 supply-demand • ↓ diastolic compliance →↑LVEDP + LVEDV • Myocardial ischemia bc LVH, ↑ wall stress, ↓ diastolic coronary perfusion + ↓ coronary flow reserve

10. Hemodynamic Goals: AS • SR is crucial. Cardiovert SVTs promptly • Optimal HR 60-80. Tachycardia → ischemia + ectopy. Bradycardia → low CO due to fixed SV • Adequate preload essential but difficult to predict bc diastolic dysfunction [TEE useful] • Maintain contractility. Avoid myocardial depressants • Treat hypotension promptly- phenylephrine, volume, Trendelenburg

11. AS: Considerations • Drugs to maintain CPP: • Phenylephrine • Norepinephrine • Atrial kick – crucial. HR 60-80 preferred • Spinal + epidural anesthesia poorly tolerated if  preload or  HR

12. AS: Management • Premed: young+ anxious get benzos. Frail + elderly  dose (or avoid) • Intraop: std monitoring + preinduction art line. • Resting HR 60-80. Avoid myocardial depressants • CVP, PAC, TEE- routine for optimal management

13. AS: Weaning from Bypass • Thick, hypertrophied heart may be difficult to protect- stone heart still occurs (rare) • Noncompliant LV dependent on stable rhythm • Inotropes if preop LV dysfunction • Dynamic subaortic or cavitary obstruction after AVR if septal LVH • Tx w volume, β-blockers. Rarely need myomectomy [inotropes worsen obstruction]

14. Septal LVH with SAM. Tx= volume + beta-blockers

15. Aortic Regurgitation: Etiology • Aortic root dilatation- HTN, ascending aorta dissection, cystic medial necrosis, Marfans, syphilitic aortitis, ankylosing spondylitis, osteogenesis imperfecta • Deformed + thickened cusps- rheumatic, IE, bicuspid valve • Cusp prolapse- dissection

17. Horse kick to upper chest with severe AI. The RCC was torn from the STJ

18. Pathophysiology: Chronic AR • Asymptomatic for many years • LV volume + pressure overload occurs • LV maintains systolic fct by dilation + ↑ compliance • LV decompensates at later stages w ↑ LVEDP + LVEDV→ CHF, arrhythmias, sudden death

19. Pathophysiology: Acute AR • LV unable to dilate acutely • LV volume overload occurs • ↑ LVEDP + LVEDV→ acute pulmonary edema • Emergency surgery often needed

20. Hemodynamic Goals: AR • Optimal HR= 90. • Avoid bradycardia- ↑ regurg • Avoid high afterload • SNP preferred • Acute AR- often need inotropes + vasodilator [epi+ SNP/milrinone] • IABP- contraindicated

21. Anesthetic Management: AR • Premed w benzos • Routine monitoring: art line, CVP, PAC • TEE beneficial • Narcotic based technique if impaired LV • If acute AR: RSI w ketamine-succinylcholine • Inotropes if acute AR or preop LV dysfunction

22. Mitral Stenosis • Usually rheumatic- thickening, calcification + fusion of MV leaflets + commissures • May be combined w MR + AR • Surgery if MVA < 1 cm2 w NYHA class III or IV dyspnea [or embolus- LAA clot]

24. MS- Pathophysiology • Pressure gradient between LA + LV- prevents LV filling • Pulmonary HTN w ↑ LAP • ↑ LAP → LAE, atrial arrhythmias (Afib) • Pulm HTN → RV dysfct, RVE, TR [may need TV repair] • LV dysfct uncommon unless CAD

27. MS: Hemodynamic Goals • Preserve SR, if present • Avoid tachycardia which ↓ diastolic filling of LV + worsens MS • Avoid factors which worsen pulmonary HTN- hypercarbia, acidosis, hypothermia, sympathetic nervous system activation, hypoxia

28. Anesthetic Management: MS • Premed: benzos to avoid tachycardia • If pulm HTN- supplemental O2 • Control of HR- β blockers, digoxin, CEB, amiodarone

29. Intraop Management: MS • Std monitors + CVP, PAC, TEE • PAP underestimates LVEDP + LVEDV • Esmolol: • single most useful drug with severe MS, even if CHF + pulmonary edema • 10-20 mg bolus; 50-100 mcg/kg/min • N2O avoided bc effects on pulm HTN • Panc avoided bc tachycardia

30. Weaning from Bypass: MS • MV replacement- hemodynamics usually improved bc obstruction to LV filling resolved • If preop pulm HTN + RV dysfct- may need milrinone or nitric oxide

31. Mitral Regurgitation: Etiology • Myxomatous degeneration (most common) • Ischemic (functional)- papillary muscle dysfunction, annular dilatation, LV dysfct + tethering • Infective endocarditis • Trauma

32. Papillary muscle rupture after blunt trauma

33. MR- Pathophysiology • Volume overload of LV→ LVE, LAE • LA can massively dilate • Atrial arrhythmias with LAE • Dilated LV decompensates at later stages w  LVEDV

34. Chronic MR. Dilated LA w normal LAP

35. Chronic MR. Dilated LA w normal LAP Acute MR. Small LA with ↑ ↑ LAP+ pulmonary edema

36. Severity of MR • Pressure gradient between LA + LV • Size of regurgitant orifice (ERO) • Duration of ventricular systole

37. Hemodynamic Goals- MR: • Vasodilators: NTG, SNP - ↓ afterload + regurgitant fraction + ↑ forward flow • High normal HR to ↑ time of ventricular systole • Maintain contractility

38. Anesthetic Management MR: • MV repair (v. replacement) • preserved papillary muscle + chordae • enhanced LV function • requires TEE to assess repair • LV dysfct unmasked after MV surgery bc LV cannot offload into LA • May need inotropes + vasodilators

39. Tricuspid Regurgitation • Primary: rheumatic, IE, carcinoid, Ebstein’s, trauma • Secondary: chronic RV dilatation, often w MV disease

40. Flail TV after blunt trauma

41. TR- Pathophysiology • RV + RA overloaded + dilated • RA v compliant so RAP rises only w end stage disease • Pulm HTN due to MV disease- ↑ RV afterload + worsens TR • RVE → paradoxical motion LV septum w imapired LV filling + compliance • Right heart failure: hepatomegaly, ascites

42. TR- Hemodynamic Goals • If secondary to MV- treat left heart lesion • Avoid pulm HTN + high PVR • Normal to high preload for RV stroke volume • Hypotension treated w inotropes + volume bc vasoconstrictors may worsen pulm HTN

43. TR- Anesthetic Management • Premed- benzos • Std monitors + art line, CVP, TEE • PAC if pulm HTN + MV pathology; but CO overestimated w severe TR. May be impossible to float Swan • Weaning from CPB: if preop RV dysfunction/ dilation- inotropes, inodilators, vasodilators, nitric oxide

44. Summary- I • Knowledge of patient + extent of valvular heart disease • Functional + hemodynamic status • Co-morbidities • Planned surgery: cannulation sites, repair vs replacement, minimally invasive vs full bypass. • Inotropes, vasodilators, vasopressors, infusion pumps

45. Summary- II • Understand pathophysiology of lesions + hemodynamic goals: AS, AR, MS, MR, TR • Monitoring: standard + invasive +TEE • Anesthetic technique: most can be used safely. • Adjustment of dosages more important than adhering to a rigid anesthetic technique.