Cardioanaesthesia

Coronary artery disease

O2 deliveryCoronary blood flow = directly related to coronary

perfusion pressure (CPP)CPP = aortic diastolic pressure – LVEDP

= inversely related to HR= inversely related to coronary vascular resistance

• Blood viscosity• Sympathetic tone• Fixed resistance due to athermanous narrowing

Coronary artery disease

O2 deliveryCoronary blood flow = directly related to coronary

perfusion pressure (CPP)CPP = aortic diastolic pressure – LVEDP

= inversely related to HR= inversely related to coronary vascular resistance

• Blood viscosity• Sympathetic tone• Fixed resistance due to athermanous narrowing

Anaesthesia following MI

• O2 demand– HR– Systolic BP ( afterload )– Ventricular volume ( preload )– Myocardial contractility

• Induction of ischaemia– Tachycardia & LVEDP - demand & supply– Hypertension - demand, CPP, supply

Multifactorial index of cardiac risk by Goldman

Time since MI / risk of recurrent MI or cardiac death< 3/12 30 %3-6/12 15% 6/12 5 %

Heart failure Dysrhythmia Age > 70 years Emergency procedure Severe aortic stenosis Poor general condition Intraperitoneal or intrathoracic procedure

Further important factors

• Operation length

• Hypertension

• Intraoperative hypotension and hypertension

Anaesthetic Management

• O2 supply

– NO hypoxia, anaemia, hypotension– Obstruction due to ahteroma unrelieved by

vasodilators

O2 requirement

– NO sympathetic activity & LVEDV ( preload – GTN)

– Hr & BP = 20% of awake values

Monitoring

• Pulse• BP• ECG

– II lead to detects inferior ischaemia

– V5 lead to detects anterior ischaemia

• CVP/ PAWP – in selected case• Rate Pressure Product (RPP) = HR x Sys.BP

maintain value < 12 000

Pharmacological manipulations

BP lighten anaesthesia; give fluids;

inotrope or vasopressor

BP deepen anaesthesia; vasodilator ( arteriolar)

HR deepen anaesthesia; beta-blocker

CVP/PAWP

vasodilator (venous); restrict fluid;

diuretic; inotrope agent

Mitral Stenosis

• AF• Systemic embolus• Haemoptysis - PVP & pulmonary hypertension• C Left Atrial Pressure – pulmonary oedema pulmonary compliance

Anaesthetic considerations

• Fixed CO – SVR must be maintainedBP = HR x SVR

• Ventricular filling depends on high Atrial Pressure HR – reduced diastolic time for ventricular

filling & CO• Hypoxia - pulmonary vascular resistance

Mitral regurgitation

• Left ventricular dilatation & hypertrophy LV Stroke volume + LA fluid overload• In chronic case: dilation of the atrium limits

pressure rise• In acute case : PCWP is high + severe pulmonary

oedema

Anaesthetic considerations

• Fraction of blood regurgitating– Size of MV orifice during systole– HR (slow = more regurgitation)– Pressure gradient across the valve– Relative resistance of flow ( low SVR favours flow to

aorta)

• Mild HR, SVR• NO excessive myocardial depression• Antibiotic prophylaxis

Aortic stenosis

• Angina - O2 demand (muscle mass, wall tension), supply ( diastolic pressure, LVEDP)

• Left ventricular hypertrophy• Reduction AV area by 25 % results in symptoms• Gradient of 50 mm Hg = significant stenosis

Anaesthetic considerations

• Thick ventricle = reduced compliance – Atrial contraction is important for optimal ventricular filing –

SINUS RYTHM

– Higher PAWP to maintain CO

• NO tachycardia – less time for ejection & filling

– Likelihood ischaemia

• Fixed CO so SVR must not be reduced to maintain BP;high SVR – high LVP – ischaemia

• Coronary blood flow depends on aortic diastolic pressure

Aortic regurgitation

• Left ventricular hypertrophy• Magnitude of regurgitation depends on:

– HR – longer diastole grater regurgitation

– Diastolic aortic pressure

– Size of orifice during diastole

• Ischaemia is not a prominent finding (pressure work is low)

Anaesthetic considerations

• Slight tachycardia SVR• Antibiotic prophylaxis