Cardioanaesthesia

Coronary artery disease O 2 delivery Coronary 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 O 2 delivery Coronary 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 O 2 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 < 3/1230 % 3-6/1215% 6/125 %  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 O 2 supply –NO hypoxia, anaemia, hypotension –Obstruction due to ahteroma unrelieved by vasodilators  O 2 requirement – NO sympathetic activity &  LVEDV (  preload – GTN) –Hr & BP =  20% of awake values

Monitoring Pulse BP ECG –II lead to detects inferior ischaemia –V 5 lead to detects anterior ischaemia CVP/ PAWP – in selected case Rate Pressure Product (RPP) = HR x Sys.BP maintain value <

Pharmacological manipulations  BPlighten anaesthesia; give fluids; inotrope or vasopressor  BPdeepen anaesthesia; vasodilator ( arteriolar)  HRdeepen 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 maintained BP = 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 -  O 2 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