anesthesia for valvular heart surgery charles e. smith, md professor of anesthesia director,...
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Anesthesia for Valvular Heart Surgery
Charles E. Smith, MD
Professor of Anesthesia
Director, Cardiothoracic Anesthesia
MetroHealth Medical Center
Case Western Reserve University
Objectives
• Pathophysiology– Aortic valve: AS, AI– Mitral valve: MS, MR– Tricuspid valve: TR
• Hemodynamic Goals
• Anesthetic management
Aortic Stenosis
• May occur at 3 levels:1. Valvular
2. Subvalvular
3. Supravalvular
Valvular Aortic Stenosis
1. Calcification + fibrosis of normal tricuspid valve- very common
2. Calcification + fibrosis of congenital bicuspid AV
3. Rheumatic- uncommon since antibiotics
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!
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
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
AS: Considerations
• Drugs to maintain CPP:
– Phenylephrine
– Norepinephrine
• Atrial kick – crucial. HR 60-80 preferred
• Spinal + epidural anesthesia poorly tolerated if preload or HR
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
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]
Septal LVH with SAM. Tx= volume + beta-blockers
Aortic Regurgitation: Etiology
1. Aortic root dilatation- HTN, ascending aorta dissection, cystic medial necrosis, Marfans, syphilitic aortitis, ankylosing spondylitis, osteogenesis imperfecta
2. Deformed + thickened cusps- rheumatic, IE, bicuspid valve
3. Cusp prolapse- dissection
Horse kick to upper chest with severe AI.
The RCC was torn from the STJ
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
Pathophysiology: Acute AR
• LV unable to dilate acutely
• LV volume overload occurs
• ↑ LVEDP + LVEDV→ acute pulmonary edema
• Emergency surgery often needed
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
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
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]
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
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
Anesthetic Management: MS
• Premed: benzos to avoid tachycardia
• If pulm HTN- supplemental O2
• Control of HR- β blockers, digoxin, CEB, amiodarone
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
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
Mitral Regurgitation: Etiology
1. Myxomatous degeneration (most common)
2. Ischemic (functional)- papillary muscle dysfunction, annular dilatation, LV dysfct + tethering
3. Infective endocarditis
4. Trauma
Papillary muscle rupture after blunt trauma
MR- Pathophysiology
• Volume overload of LV→ LVE, LAE
• LA can massively dilate
• Atrial arrhythmias with LAE
• Dilated LV decompensates at later stages w LVEDV
Chronic MR. Dilated LA w normal LAP
Chronic MR. Dilated LA w normal LAP
Acute MR. Small LA with ↑ ↑ LAP+ pulmonary edema
Severity of MR
1. Pressure gradient between LA + LV
2. Size of regurgitant orifice (ERO)
3. Duration of ventricular systole
Hemodynamic Goals- MR:
• Vasodilators: NTG, SNP - ↓ afterload + regurgitant fraction + ↑ forward flow
• High normal HR to ↑ time of ventricular systole
• Maintain contractility
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
Tricuspid Regurgitation
• Primary: rheumatic, IE, carcinoid, Ebstein’s, trauma
• Secondary: chronic RV dilatation, often w MV disease
Flail TV after blunt trauma
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
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
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
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
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.