Transcript Pathophysiologic consideration in patients with congenital
Pathophysiologic Consideration In Patients With Congenital Heart Disease
SAMIA SHARAF .MD
Professor Of Anaesthesia .. Ain Shams University
Classification Of Congenital Heart Lesions
1) 1) 1) Obstructive lesions eg. Aortic stenosis – coarctation of aorta Increased pulmonary blood flow eg. ASD – VSD – PDA Decreased pulmonary blood flow lesions eg. Tetralogy of fallot – tricuspid atresia – pulmonary atresia
Classification Of Congenital Heart Lesions Left To Right Shunt Right To Left Shunt Left Heart Obstructive Lesions Right Side Obstructive Lesions
Atrial Level : ASD 5% , TAPVC Ventricular Level : VSD 33% Great Artery Level : PDA 10% Truncus Arteriosus : 1% Coronary Level : ALCAPA TOF : 9% TGA : 1% Mitral Stenosis Aortic Stenosis : 8% Coarctation : 5% Hypoplastic Left Heart Syndrome Pulmonary Stenosis / Atresia : 10% Tricuspid Stenosis Hypoplastic Right Heart
Single Ventricle Others
Vascular Rings Venous Anomalies Arteriovenous Fistula
Clinical Presentation Of Children With CHD
1) 2) 3) 4) Cyanosis ( due to hypoxia ) Respiratory system abnormalities Cardiac failure Arrhythmias
Cyanosis Pathophysiologic Effects of Hypoxia
(1) Growth (2) Heart
Exercise intolerance : myocardial dysfunction ventricular compliance and contractility Irreversible myocardial damage .
Increased sympathetic tone down regulation of beta receptors cardiomyopathy
(3) Hematology
A major adaptive response to chronic hypoxia Red cell mass Polycythemia Secondary Spherocytosis Blood viscosity Risk of thromboembolic events
Hemostasis :
Polycythemia Primary fibrinolysis Coagulation abnormalities
DIC
Mechanism of coagulation abnormalities
Increased blood viscosity DIC Hypercoag. blood & tendency to bleed Increase intravascular strains Thrombocyt openia & Low Fibrinogen & Other Factor Level Consumpution of platlets , fibrinogen , factor V , VIII Fibrin deposition & platlet aggreg.
(4) CNS
Chronic hypoxia causes impairment of neurologic development and increase risk of neurologic damage .
Brain abscess : Rt. – Lt. shunt Cerebrovascular thrombosis and hemorrhage .
Respiratiry System Abnormalities
Anatomical abnormalities of airway Pulmonary abnormalities associated with or pulmonary blood flow .
Anatomical Abnormalities Of Airway
1) 2) Short trachea eg. interrupted aortic arch large airway obstruction : ( trachea & bronchi ) Compression by enlarged aorta or pulmonary artery .
Upwards displacement and increase angle of bifurcation of trachea by enlarged LA .
• • 3) Small airway obstruction : Compression of lung parenchyma by enlarged heart and vessels .
Pulmonary hypertension .
Pulmonary Changes Associated With Pulmonary Blood Flow
Patients with chronic hypoxia 1) Slight of alveolar ventilation 2) pulmonary venous PO2 is high 3) 4) V/Q mismatch alveolar – pulmonary venous O2 gradient Physiological dead space end tidal CO2 is lower than arterial PaCO2
Pulmonary Changes Associated With Pulmonary Blood Flow
Obstruction of small airway Pulmonary congestion pulmonary compliance , lung water & Impaired gas exchange Progressive of pulmonary vascular resistance due to hypertrophy in muscular layer of pulmonary arteries reverse of left to right shunt
Cardiac Failure
Causes of limited cardiac reserve : (1) Increased cardiac workload
Pressure overload :
ventricular outflow tract obstruction SVR blood viscosity
Volume overload :
* Valvular insufficiency * Single ventricle * Left – right shunt
(2) Myocardial contractility:
Prolonged workload of myocardium Vascular supply to ventricles Blood hyperviscosity Chronic hypoxia
Compansatory Mechanism
Ventricular hypertrophy Adrenergic system changes Activation of B receptors Renal system compansation *Salt & water retention *Renin secretion
Arrhythmias
Types :
* Congenital * Acquired
Etiology :
Intrinsic electrophysiology abnormalities Damage from chronic hypoxia – hemodynamic stress Surgical injury eg. F4 , Fontan operation , atrial correction of TGA
Congenital Conduction System Abnormalities
Congenital complete atrioventricular block Wolf – Parkinson white syndrome Supraventricular tachycardia Arrhythmias associated with Ebstien anomaly
Acquired Conduction System Abnormalities
Non surgical : rare Surgical by : * cardioplegia * mechanical retraction * ischemia * metabolic abnormalities
Why we are conserned about the pathophysiology of CHD Provide Safe Anaesthetic Technique Decrease Anaesthetic Risk
Anaesthetic Risk factors affecting anaesthetic risk in congenital heart disease Pulmonary disease Cyanotic heart disease Myocardial dysfunction Arrhythmias Cardiovascular impairment Magnitude of surgery Anaesthetic risk
How To Reduce Anaesthetic Risk ??
1 2 3 • Consultation • Surgical Status • How To Look To The Data
Consultation
Role Of Surgeon
Case discussion :
Pts. with CHD may not tolerate :
Abdominal laparoscopic procedures ( eg. stenotic valvular lesions , single ventricle ) Absorption of CO2 ( C.O.P dependant low PVR) .
One lung ventilation Prone position ( Fontan pt. )
Role Of Pediatric Cardiologist
Preoperative consultation sometimes add a little benefit to anesthiologist !!!!!
Pediatric cardiologist consultation History data exact anatomy Previous cardiac operation Myocardial function status Murmurs Gallops Pulse in extremities Base line O2 saturation Vital data Planned followup as needed 2-3 months interval New echo Unstable pt.
Major operation
Surgical Status Of The Patient Untreated Cured
*Normal life expectancy *Normal CV reserve *No further medical ttt
Corrected
*Markedly prolonged life expectancy *Some limitation of cardiac reserve *May require further medical ttt
Palliated
*Prolonged life expectancy *Definitly abnormal CV physiology *Certainly require medical or surgical ttt
Efficacy Of Repairs For CHD Lesions
PDA ASD
CURED CORRECTION
VSD TFO Coarctation of aorta Pulmonary or aortic stenosis AV Canal repair
PALLIATION
Conduits PA banding Modified Glenn shunt
How To Look To Patient Data DATA
History Taking
o o o o o Growth Exercise Intolerance Recurrent Chest Infection Syncopal Attacks Squatting
ECG , Echo & Cardiac Cath.
Systolic & Diastolic Dysfunction Systolic Dysfunction
Reduced Fractional Shortening
Diastolic Dysfunction
Before Repair e.g
valvular & outflow obst.
Obstructive Ventricular Hypertrophy Concentric Eccentric Volume
After Repair e.g
Homograft conduit Before Repair e.g
Lt . to Rt. shunt After Repair e.g
• Pulmonary valve regurge ( F4 ) • MV repair
Anaesthetic considerations :
Consider determinants of coronary perfusion & myocardial oxygen balance • • • Heart rate changes Hypotension Myocardial contractility
Anaesthetic considerations Cardiomyopathy RV increase wall thickness LV anaesthetic myocardial depression coronary filling becomes diastolic Decrease driving filling pressure of coronary arteries Maintain heart rate to decrease regurgitant fraction coronary perfusion depends on bl. p. & hr Coronary ischemia Syst. Dysfunction In Dialted type Diast. Dysfunction In Hypertrophic & restrictive type
Residual Shunts :
o o Occasionally present after repair of ASD , VSD & F4 Small patch leaks are hemodynamically benign
Dysrhythmias :
Atrial & ventricular types increase mortality and morbidity
Arrhythmias Associated With Specific Surgical Procedures
• • Ostium secondum ASD : P-R interval is prolonged in 20-30% of patients AF , atrial flutter with advancing age
VSD : • RBBB • Atrial ectopic , junctional beats , premature ventricular beat • Late onset of complete heart block or ventricular arrhythmias are rare Repair of F4 : • RBBB & complete heart block Mustard or Senning operation : • Sinus nodal dysfunction • Bradycardia • A-V block , AF
Pulmonary hypertension
Severity of hypertension of base line PAH correlated with the incidence of major complications ( pulmonary hypertensive crisis or cardiac arrest )
Cardiovascular risk of PAH
Major perioperative hemodynamic deterioration mainly pulmonary hypertensive crisis and acute right ventricular failure and cardiac arrest .
Data to look for :
o Mean pulmonary artery pressure > 25 mmHg o Severity of base line PH : Subsystemic PAP < 70% of syst. bl. pressure Systemic PAP = 70 – 100 of syst. bl. pressure Suprasystemic PAP > 70 of syst. bl. pressure (
based on mean pressures
)
ANAESTHETIC CONSIDERATIONS Avoid Factors Rapidly Increasing PVR
Laboratory data Hematocrit value
HCT.
Decompansated Erythrocytosis Increase Red Cell Mass Increase Erythropoitin Level Increase More Blood Viscocity Hyperviscosity symptoms Decreased oxygen delivery
Blood Indicies : Iron Deficiency Anaemia Low Hemoglobin Concentration Microspherocytosis Rigid Cell Membrane Increase Blood Viscosity Hyperviscosity Symptoms At Lower Hematocrit Value
Phlebotomy
Done to relieve hyperviscosity symptoms with hematocrit > 65 % in absence of iron deficiency anaemia or signs of dehydration
Hemostatic values
• Prolonged PT , PTT , APTT values most frequently seen in cyanotic patients • Thrombocytopenia is related to degree of polycythemia .
Summary
General associated risk factors in CHD
Severe form of isolated lesion Complex lesions Concurrent infectious disease Congestive heart failure Acute hemodynamic deterioration Previous palliative or corrective procedures
Summary
Risk criteria of hemodynamic critical impairment in perioperative period in CHD
• • • • • • Arterial saturation < 75 % Hematocrit > 65 % Qp / Qs > 2 : 1 LV outflow tract gradient > 50 mmHg RVOT gradient > 50 mmHg PVR > 6 wood units