Preparation for Cardiac Surgery

Seoul National University Hospital

Department of Thoracic & Cardiovascular Surgery

Evaluation for Congenital HD

• Signs of symptoms of hypoxia 1. Tachypnea & tachycardia

2. Clubbing of the nail bed

3. Small for age from poor feeding

4. Fatigue and poor exercise tolerance

5. Mental obtundation

• Signs & symptoms of congestive heart failure 1. Tachypnea & tachycardia

2. Frequent respiratory infections

3. Wheezing, diffuse rhonchi

4. Feeding difficulty & failure to thrive(small for age)

5. Evidence of peripheral vasoconstriction(pale, cool, mottled)

6. Hepatomegaly, ascites

Preoperative Considerations

Premature Infants• Lungs; bronchopulmonary dysplasia, meconiu

m aspiration, pneumothorax• Heart ; other associated congenital anomalies• G-I tract ; malrotation, intestinal atresia, necro

tizing enterocolitis• Hematologic ; Vk deficiency• Matabolic ; hypoglycemia, hypocalcemia

Preoperative Considerations

Infants under 1 year

• Otitis media

• Upper respiratory infections; RS virusToddlers & children

• URI(otitis media, tonsillitis) and G-I infection(parasites)

• Parental involvement in daily care

Preoperative Considerations

Adult (History)• Bleeding issues ; aspirin, warfarin, bleeding disorder• Smoking ; COPD, bronchospasm• Alcohol ; cirrhosis, delirium tremens• Diabetes ; protamine reaction, wound infection• Neurologic symptoms; TIA, stroke, carotid endart.• Vein stripping ; alternative conduits• Ulcer disease/ G-I bleeding• Active infections ; urinary tract• Current medications• Drug allergy

Preoperative Considerations

Adult (Physical Examination)• Skin infections/rash• Dental caries ; valve surgery• Presence of heart murmur• Vascular examination ; carotid bruits & periph

eral pulse(IABP)• Heart/lung ; congestive heart failure• Differential arm blood pressures • Abdominal aortic aneurysm• Varicose vein ; alternative conduit

Preoperative Diagnosis

• Hematologic• Chemistry• Urinalysis• Chest x-ray• Electrocardiogram• Two-dimensional echocardiography• Cardiac catheterization• CT scan , PET scan, MRI etc

Preoperative Bleeding Issues• Aspirin irreversibly acetylates platelet cyclooxygenase, i

mpairing thromboxane A2 formation and inhibiting platelet aggregation for 7 days, needs to stop for 5-7 days before surgery.

• Warfarin should be stopped 4 days before surgery. Consideration may be given to use IV heparin (low-molecular-weight heparin 3000u sc bid), when INR falls below therapeutic level, although the risk of thromboembolism is low.

• Bleeding disorders or coagulopathy needs evaluation.

Thrombolytic or antiplatelet medications (ticlopidine, clopidogrel, glycoprotein IIb/IIIa inhibitors , such as, abcximab (reopro) tirofiban(aggrastat), or eptifibatide(integrilin), specific measure is needed. Nonsteridal antiinflammatory drugs have a reversible effect on platelet function and need to be stopped only a few days.

Preparation for Heart Surgery

• Antibiotics; cefazolin 12.5mg/kg before surgical incision or vancomycin of same dose in allergic to cefazolin

• Blood bank• Most medications are withheld (digoxin, diuretics) th

e morning of surgery• Vk 0.25mg/kg before OHS• Premedication ; avoid to increase PVR• Kept NPO after midnight and fluids can be given abo

ut 3~4 hours before surgery to avoid dehydration

States of Congenital Heart Diseases

• Acute conditions of left and/or right ventricular volume or pressure overload or both may reduce myocardial reserve & high energy phosphate and impair recovery from periods of ischemia during cardiac surgery.

1. Acute hypoxia and acidosis

2. Chronic ischemia ; decreased EF, drop high energy phosphate

3. Volume overload ; effects the distensibility of the other,

unfavorable structural & metabolic changes in myocardium

4. Pressure overload ; inefficient O2 use, lower level of high

energy phosphates

5. Noncoronary collateral flow ; washout cardioplegia

Structural Abnormalities of Great Arterial Wall in Congenital Heart Disease

• Etiology Inherent, one or more genetic defects? Independent variables Pregnancy, age, systemic hypertension influence aortic media

• Grading of Medial Change Normal ; normal aortic media with closely packed long parallel arrays of intact elastic fiber Grade I ; mild elastic fiber fragmentation, patch pale zone in continuity, & mild increase in collagen Grade II ; widespread elastic fiber fragmentation & loss of smooth muscle, further increase in ground substance Grade III ; large areas of complete loss of elastic fiber & smooth muscle & abundant collagen

Features of Pediatric Cardiac Management

• Variable pathology

• Compensatory mechanism

• Monitoring limitations

• Assessment of LCO states

• Special studies

Early reinvestigation is indicated

• Acceptable parameters

Neonatal Physiology of Normal Myocardium

• Decreased compliance of fetal & neonatal

right and left ventricle

• Decreased capacity for peripheral vasodilation

• Decreased capacity for response to volume

loading (diminished preload reservoir)

Predisposition to Postoperative RV Failure

• Underdevelopment of RV structure• Chronic high pressure loading (hypertrophy)• Chronic volume overload (dilatation)• Less effective myocardial protection• Right ventriculotomy incision• Interruption of right coronary artery branches• Residual pulmonary stenosis or insufficiency or t

ricuspid insufficiency

Factors Affecting Myocardial Protection of Infant Heart

• Cardiac size ; large surface area to mass ratio

• Collateral circulation ; increased collateral circulation

• Microcirculation ; increased permeability of capillary membr

ane to albumin & large molecules --- edema formation

• Traumatic myocardial injury ; excision, cardiotomy

• Pathologic states of myocardium ; cyanosis, congestive hea

rt failure, hypertrophy,

Assessment of RV Function

• Clinical signs of RV failure Jugular venous distention Hepatomegaly Peripheral e4dema Ascites Periorbital, flank, and generalized edema Rising BUN

• Elevated RA pressure with low LA pressure Volume loading, often to an RA pressure of 15mmHg or greater, may be necessary to ensure adequate left-sided filling

Fluid & Electrolyte Requirement

• Fluid volume a. Daily fluid requirement is 4ml/kg/h for the first 10kg, 2ml/kg/h for the next 10kg, and 1ml/kg/h for each subsequent kg. b. Intubated patients are given two-thirds of maintenance of level (due to water gain)

• Eletrolytes a. Sodium; 3mEq/100ml/d b. Potassium; 2-3mEq/100ml/d

Physiology of Coronary Artery

• Proximal epicardial vessel Richly innervated by sympathetic alpha & beta

fiber(alpha; proximal, beta; distal) -- cause spasm

• Distal intramyocardial vessel Little autonomic innervation, less smooth muscle, do

not constrict markedly, but do dilate to the metabolic demand -- cause little spasm

• Spasm is common in RCA & LAD, especially in underlying obstruction

Arterial Blood Pressure

• Determinants of systolic blood pressure 1. Volume of blood ejected

2. Compliance of arterial wall

3. Rate of run-off (resistance)

• Determinants of diastolic blood pressure

1. Volume of blood remained

2. Compliance of arterial wall

3. Peripheral resistance

Venous Blood Pressure

• Determinants of venous pressure 1. Blood volume

2. Pressure-volume characteristics of venous bed

(compliance)

3. Size of venous bed (capacitance)

4. Ability of heart to eject venous return

• Location of venous blood volume 1. Peripheral vein ; 65%

2. Pulmonary venous system ; 5%

Cardiac Receptors

• Atrial receptors Located mainly pulmonary venous and caval-atrial junction, others

on the body of left & right atrium, appendage connected to the myeli

nated fiber of Vagus nerve.

Not related BT, PVR, myocardial contractility

1. Type A ; atrial contraction for pressure ( a wave )

2. Type B ; stretch receptor for volume ( v wave )

• Ventricular receptors Myelinated & unmyelinated, but uncertain function

Ventricular reflexes – LV distention cause reflex vasodepression

Arterial Baroreceptors

1. Anatomic location

Carotid sinus ; segmental enlargement of internal carotid

artery at it’s origin, (stimulation; drop BP in 23% & 14% of SVR, low carotid sinus pressure; vasoconstriction, increase CO in 30%)

Aortic arch ; located in the adventitia adjacent to media

between brachiocephalic trunk and ligament arteriosum

2. Transmission Afferent impulse ; generated by stretch of arterial walls and

transmitted myelinated & nonmyelinated sensory fiber of carotid sinus nerve travel glossopharyngeal nerve No distant pathway of aortic arch stretch receptor

Efferent impulse ; consist of sympathetic adrenergic nerves

to heart, vessel

Low Cardiac Output Syndrome• Diagnosis

a. Suspicion of LCO by evidence of peripheral vasoconstriction

( cool, pale extremities, mottling, absence of pedal pulses, and

capillary refill exceeding 3 seconds), oliguria, metabolic acidosis,

and hyperthermia.

b. Narrow arterial pulse, elevated filling pressure, low RA oxygen

saturation, development of atrial or ventricular arrhythmias,

should draw attention to a LCO

• Treatment

a. Assessment and manipulation of heart rate, and rhythm, volume

state, contractility, and afterload.

b. Additional contributory factors should be identified

Cardiac temponade, ventilator problems, metabolic problems

Cardiac Surgery during Pregnancy

Measures to reduce maternal & fetal mortality • Avoid functional deterioration during pregnancy• Prescribe earlier surgery to prevent these patients from re

quiring an emergency procedure • Perform surgery as fast as possible, with minimal ECC • Provide adequate fetal monitoring (cardiotachometer & in

traoperative fetal echocardiography)• Perform surgery in the second trimester of pregnancy pref

erably

Preparation for Cardiac Surgery

Seoul National University Hospital

Department of Thoracic & Cardiovascular Surgery

Evaluation for Congenital HD

• Signs of symptoms of hypoxia 1. Tachypnea & tachycardia

2. Clubbing of the nail bed

3. Small for age from poor feeding

4. Fatigue and poor exercise tolerance

5. Mental obtundation

• Signs & symptoms of congestive heart failure 1. Tachypnea & tachycardia

2. Frequent respiratory infections

3. Wheezing, diffuse rhonchi

4. Feeding difficulty & failure to thrive(small for age)

5. Evidence of peripheral vasoconstriction(pale, cool, mottled)

6. Hepatomegaly, ascites

Preoperative Considerations in Premature Infants

• Lungs; bronchopulmonary dysplasia, meconium aspiration, pneumothorax

• Heart ; other associated congenital anomalies

• G-I tract ; malrotation, intestinal atresia, necrotizing enterocolitis

• Hematologic ; Vk deficiency• Matabolic ; hypoglycemia, hypocalcemia

Preoperative Considerations in Infants & Child

Infants under 1 year

• Otitis media

• Upper respiratory infections; RS virusToddlers & children

• URI(otitis media, tonsillitis) and G-I infection(parasites)

• Parental involvement in daily care

Preoperative Considerations in Adult (History)

• Bleeding issues ; aspirin, warfarin, bleeding disorder

• Smoking ; COPD, bronchospasm

• Alcohol ; cirrhosis, delirium tremens

• Diabetes ; protamine reaction, wound infection

• Neurologic symptoms; TIA, remote stroke, carotid endart.

• Vein stripping ; alternative conduits

• Ulcer disease/ G-I bleeding

• Active infections ; urinary tract

• Current medications & drug allergy

Preoperative Considerations in Adult (Physical Examination)

• Skin infections/rash• Dental caries ; valve surgery• Presence of heart murmur• Vascular examination ; carotid bruits & periph

eral pulse(IABP)• Heart/lung ; congestive heart failure• Differential arm blood pressures • Abdominal aortic aneurysm• Varicose vein ; alternative conduit

Preoperative Diagnostic Studies

• Hematologic• Chemistry• Urinalysis• Chest x-ray• Electrocardiogram• Two-dimensional echocardiography• Cardiac catheterization• CT scan , PET scan, MRI etc

Preoperative Bleeding Issues• Aspirin irreversibly acetylates platelet cyclooxygenase, i

mpairing thromboxane A2 formation and inhibiting platelet aggregation for 7 days, needs to stop for 5-7 days before surgery.

• Warfarin should be stopped 4 days before surgery. Consideration may be given to use IV heparin (low-molecular-weight heparin 3000u sc bid), when INR falls below therapeutic level, although the risk of thromboembolism is low.

• Bleeding disorders or coagulopathy needs evaluation.

Thrombolytic or antiplatelet medications (ticlopidine, clopidogrel, glycoprotein IIb/IIIa inhibitors , such as, abcximab (reopro) tirofiban(aggrastat), or eptifibatide(integrilin), specific measure is needed. Nonsteridal antiinflammatory drugs have a reversible effect on platelet function and need to be stopped only a few days.

Preparation for Heart Surgery

• Antibiotics; cefazolin 12.5mg/kg before surgical incision or vancomycin of same dose in allergic to cefazolin

• Blood bank• Most medications are withheld (digoxin, diuretics)

the morning of surgery• Vk 0.25mg/kg before OHS• Premedication ; avoid to increase PVR• Kept NPO after midnight and fluids can be given

about 3~4 hours before surgery to avoid dehydration

States of Congenital Heart D.

• Acute conditions of left and/or right ventricular volume or pressure overload or both may reduce myocardial reserve & high energy phosphate and impair recovery from periods of ischemia during cardiac surgery.

1. Acute hypoxia and acidosis

2. Chronic ischemia ; decreased EF, drop high energy phosphate

3. Volume overload ; effects the distensibility of the other,

unfavorable structural & metabolic changes in myocardium

4. Pressure overload ; inefficient O2 use, lower level of high

energy phosphates

5. Noncoronary collateral flow ; washout cardioplegia

Abnormalities of Great Arterial Wall in Congenital Heart Disease

• Etiology Inherent, one or more genetic defects? Independent variables Pregnancy, age, systemic hypertension influence aortic media

• Grading of Medial Change Normal ; normal aortic media with closely packed long parallel arrays of intact elastic fiber Grade I ; mild elastic fiber fragmentation, patch pale zone in continuity, & mild increase in collagen Grade II ; widespread elastic fiber fragmentation & loss of smooth muscle, further increase in ground substance Grade III ; large areas of complete loss of elastic fiber & smooth muscle & abundant collagen

Features of Pediatric Cardiac Management

• Variable pathology

• Compensatory mechanism

• Monitoring limitations

• Assessment of LCO states

• Special studies

Early reinvestigation is indicated

• Acceptable parameters

Neonatal Physiology of Normal Myocardium

• Decreased compliance of fetal & neonatal

right and left ventricle

• Decreased capacity for peripheral vasodilation

• Decreased capacity for response to volume

loading (diminished preload reservoir)

Predisposition to Postoperative RV Failure

• Underdevelopment of RV structure• Chronic high pressure loading (hypertrophy)• Chronic volume overload (dilatation)• Less effective myocardial protection• Right ventriculotomy incision• Interruption of right coronary artery branches• Residual pulmonary stenosis or insufficiency or t

ricuspid insufficiency

Factors Affecting Myocardial Protection of Infant Heart

• Cardiac size ; large surface area to mass ratio

• Collateral circulation ; increased collateral circulation

• Microcirculation ; increased permeability of capillary membr

ane to albumin & large molecules --- edema formation

• Traumatic myocardial injury ; excision, cardiotomy

• Pathologic states of myocardium ; cyanosis, congestive hea

rt failure, hypertrophy,

Assessment of RV Function

• Clinical signs of RV failure Jugular venous distention Hepatomegaly Peripheral e4dema Ascites Periorbital, flank, and generalized edema Rising BUN

• Elevated RA pressure with low LA pressure Volume loading, often to an RA pressure of 15mmHg or greater, may be necessary to ensure adequate left-sided filling

Fluid & Electrolyte Requirement

• Fluid volume a. Daily fluid requirement is 4ml/kg/h for the first 10kg, 2ml/kg/h for the next 10kg, and 1ml/kg/h for each subsequent kg. b. Intubated patients are given two-thirds of maintenance of level (due to water gain)

• Eletrolytes a. Sodium; 3mEq/100ml/d b. Potassium; 2-3mEq/100ml/d

Physiology of Coronary Artery

• Proximal epicardial vessel Richly innervated by sympathetic alpha & beta

fiber(alpha; proximal, beta; distal) -- cause spasm

• Distal intramyocardial vessel Little autonomic innervation, less smooth muscle, do

not constrict markedly, but do dilate to the metabolic demand -- cause little spasm

• Spasm is common in RCA & LAD, especially in underlying obstruction

Arterial Blood Pressure

• Determinants of systolic blood pressure 1. Volume of blood ejected

2. Compliance of arterial wall

3. Rate of run-off (resistance)

• Determinants of diastolic blood pressure

1. Volume of blood remained

2. Compliance of arterial wall

3. Peripheral resistance

Venous Blood Pressure

• Determinants of venous pressure 1. Blood volume

2. Pressure-volume characteristics of venous bed

(compliance)

3. Size of venous bed (capacitance)

4. Ability of heart to eject venous return

• Location of venous blood volume 1. Peripheral vein ; 65%

2. Pulmonary venous system ; 5%

Cardiac Receptors

• Atrial receptors Located mainly pulmonary venous and caval-atrial junction, others

on the body of left & right atrium, appendage connected to the myeli

nated fiber of Vagus nerve.

Not related BT, PVR, myocardial contractility

1. Type A ; atrial contraction for pressure ( a wave )

2. Type B ; stretch receptor for volume ( v wave )

• Ventricular receptors Myelinated & unmyelinated, but uncertain function

Ventricular reflexes – LV distention cause reflex vasodepression

Arterial Baroreceptors

1. Anatomic location

Carotid sinus ; segmental enlargement of internal carotid

artery at it’s origin, (stimulation; drop BP in 23% & 14% of SVR, low carotid sinus pressure; vasoconstriction, increase CO in 30%)

Aortic arch ; located in the adventitia adjacent to media

between brachiocephalic trunk and ligament arteriosum

2. Transmission Afferent impulse ; generated by stretch of arterial walls and

transmitted myelinated & nonmyelinated sensory fiber of carotid sinus nerve travel glossopharyngeal nerve No distant pathway of aortic arch stretch receptor

Efferent impulse ; consist of sympathetic adrenergic nerves

to heart, vessel

Low Cardiac Output Syndrome• Diagnosis

a. Suspicion of LCO by evidence of peripheral vasoconstriction

( cool, pale extremities, mottling, absence of pedal pulses, and

capillary refill exceeding 3 seconds), oliguria, metabolic acidosis,

and hyperthermia.

b. Narrow arterial pulse, elevated filling pressure, low RA oxygen

saturation, development of atrial or ventricular arrhythmias,

should draw attention to a LCO

• Treatment

a. Assessment and manipulation of heart rate, and rhythm, volume

state, contractility, and afterload.

b. Additional contributory factors should be identified

Cardiac temponade, ventilator problems, metabolic problems

Re-Operative Surgery in Pediatric Patients

• Re-do sternotomy Anatomic considerations Planning Technique

• Alternative cannulation sites • Pericardial substitutes Infection Tamponade Epicardial reaction

• Aprotinin Hypersensitivity (or adverse reaction ; 3%) Histamin blocker

Anatomic considerations in Re-do Sternotomy

• Substernal homografts or conduit

• Degenerated homografts

• Enlarged right ventricle due to PR or TR

• Dilated right atrium due to TR or Ebstein’s anomaly or atrio-pulmonary connection

• Presence of pseudoaneurysm

Planning & Techniques in Re-Do

• Techniques of re-do sternotomy 1. Head facing to the left 2. Provide gentle cervical extension 3. Cutaneous defibrillation patches 4. Incision rather than excise the previous incision 5. Incision carried inferiorly 1-3cm below previous incision 6. Division of the adhesions immediately below the sternum• Alternative cannulation sites ; femoral vessels are often of an in

adequate, particularly in pre-toddler patients, consequently cervical (common carotid a, internal jugular vein) cannulation is prefered

• Pericardial substitutes PTFE membrane, bovine pericardium, polyglycolic acid mesh, hyalu

ronic acid, poly-beta-hydroxybutyrate(PHB), glutaldehyde-chitosan treated porcine pericardium, epoxy fixed porcine pericardium

Cardiac Surgery during Pregnancy

Measures to reduce maternal & fetal mortality • Avoid functional deterioration during pregnancy• Prescribe earlier surgery to prevent these patients from re

quiring an emergency procedure • Perform surgery as fast as possible, with minimal ECC • Provide adequate fetal monitoring (cardiotachometer & in

traoperative fetal echocardiography)• Perform surgery in the second trimester of pregnancy pref

erably

Cardiac Surgery during Pregnancy

Measures to reduce maternal & fetal risks• Extracorporeal circulation with high flow, high

pressures (mean blood pressure of 60 mm Hg), and normothermia should be used

• Hyperoxygenation should be maintained and hematocrit should be kept higher than 25%

• Myocardial protection using intermittent clamping allows, during normothermia, short perfusion times with pulsatile flow, which favors the fetus

Ideal Gestational Age for Operation

• Period between the 13th and 28th weeks as ideal• Higher trend towards fetal malformations in the

first trimester.• Higher trend towards preterm delivery, materna

l hemodynamic alterations, and mortality in the third

• There was no relationship between maternal and fetal outcome and surgical indication according to gestational age

• Fetal mortality is described as higher than 50% in patients in functional class III and IV

Preparation for Cardiac Surgery

Seoul National University Hospital

Department of Thoracic & Cardiovascular Surgery

Evaluation for Congenital HD

• Signs of symptoms of hypoxia 1. Tachypnea & tachycardia

2. Clubbing of the nail bed

3. Small for age from poor feeding

4. Fatigue and poor exercise tolerance

5. Mental obtundation

• Signs & symptoms of congestive heart failure 1. Tachypnea & tachycardia

2. Frequent respiratory infections

3. Wheezing, diffuse rhonchi

4. Feeding difficulty & failure to thrive(small for age)

5. Evidence of peripheral vasoconstriction(pale, cool, mottled)

6. Hepatomegaly, ascites

Preoperative Considerations in Premature Infants

• Lungs; bronchopulmonary dysplasia, meconium aspiration, pneumothorax

• Heart ; other associated congenital anomalies

• G-I tract ; malrotation, intestinal atresia, necrotizing enterocolitis

• Hematologic ; Vk deficiency• Matabolic ; hypoglycemia, hypocalcemia

Preoperative Considerations in Infants & Child

Infants under 1 year

• Otitis media

• Upper respiratory infections; RS virusToddlers & children

• URI(otitis media, tonsillitis) and G-I infection(parasites)

• Parental involvement in daily care

Preoperative Considerations in Adult (History)

• Bleeding issues ; aspirin, warfarin, bleeding disorder

• Smoking ; COPD, bronchospasm

• Alcohol ; cirrhosis, delirium tremens

• Diabetes ; protamine reaction, wound infection

• Neurologic symptoms; TIA, remote stroke, carotid endart.

• Vein stripping ; alternative conduits

• Ulcer disease/ G-I bleeding

• Active infections ; urinary tract

• Current medications & drug allergy

Preoperative Considerations in Adult (Physical Examination)

• Skin infections/rash• Dental caries ; valve surgery• Presence of heart murmur• Vascular examination ; carotid bruits & periph

eral pulse(IABP)• Heart/lung ; congestive heart failure• Differential arm blood pressures • Abdominal aortic aneurysm• Varicose vein ; alternative conduit

Preoperative Diagnostic Studies

• Hematologic• Chemistry• Urinalysis• Chest x-ray• Electrocardiogram• Two-dimensional echocardiography• Cardiac catheterization• CT scan , PET scan, MRI etc

Preoperative Bleeding Issues• Aspirin irreversibly acetylates platelet cyclooxygenase, i

mpairing thromboxane A2 formation and inhibiting platelet aggregation for 7 days, needs to stop for 5-7 days before surgery.

• Warfarin should be stopped 4 days before surgery. Consideration may be given to use IV heparin (low-molecular-weight heparin 3000u sc bid), when INR falls below therapeutic level, although the risk of thromboembolism is low.

• Bleeding disorders or coagulopathy needs evaluation.

Thrombolytic or antiplatelet medications (ticlopidine, clopidogrel, glycoprotein IIb/IIIa inhibitors , such as, abcximab (reopro) tirofiban(aggrastat), or eptifibatide(integrilin), specific measure is needed. Nonsteridal antiinflammatory drugs have a reversible effect on platelet function and need to be stopped only a few days.

Preparation for Heart Surgery

• Antibiotics; cefazolin 12.5mg/kg before surgical incision or vancomycin of same dose in allergic to cefazolin

• Blood bank• Most medications are withheld (digoxin, diuretics)

the morning of surgery• Vk 0.25mg/kg before OHS• Premedication ; avoid to increase PVR• Kept NPO after midnight and fluids can be given

about 3~4 hours before surgery to avoid dehydration

States of Congenital Heart D.

• Acute conditions of left and/or right ventricular volume or pressure overload or both may reduce myocardial reserve & high energy phosphate and impair recovery from periods of ischemia during cardiac surgery.

1. Acute hypoxia and acidosis

2. Chronic ischemia ; decreased EF, drop high energy phosphate

3. Volume overload ; effects the distensibility of the other,

unfavorable structural & metabolic changes in myocardium

4. Pressure overload ; inefficient O2 use, lower level of high

energy phosphates

5. Noncoronary collateral flow ; washout cardioplegia

Abnormalities of Great Arterial Wall in Congenital Heart Disease

• Etiology Inherent, one or more genetic defects? Independent variables Pregnancy, age, systemic hypertension influence aortic media

• Grading of Medial Change Normal ; normal aortic media with closely packed long parallel arrays of intact elastic fiber Grade I ; mild elastic fiber fragmentation, patch pale zone in continuity, & mild increase in collagen Grade II ; widespread elastic fiber fragmentation & loss of smooth muscle, further increase in ground substance Grade III ; large areas of complete loss of elastic fiber & smooth muscle & abundant collagen

Features of Pediatric Cardiac Management

• Variable pathology

• Compensatory mechanism

• Monitoring limitations

• Assessment of LCO states

• Special studies

Early reinvestigation is indicated

• Acceptable parameters

Neonatal Physiology of Normal Myocardium

• Decreased compliance of fetal & neonatal

right and left ventricle

• Decreased capacity for peripheral vasodilation

• Decreased capacity for response to volume

loading (diminished preload reservoir)

Predisposition to Postoperative RV Failure

• Underdevelopment of RV structure• Chronic high pressure loading (hypertrophy)• Chronic volume overload (dilatation)• Less effective myocardial protection• Right ventriculotomy incision• Interruption of right coronary artery branches• Residual pulmonary stenosis or insufficiency or t

ricuspid insufficiency

Factors Affecting Myocardial Protection of Infant Heart

• Cardiac size ; large surface area to mass ratio

• Collateral circulation ; increased collateral circulation

• Microcirculation ; increased permeability of capillary membr

ane to albumin & large molecules --- edema formation

• Traumatic myocardial injury ; excision, cardiotomy

• Pathologic states of myocardium ; cyanosis, congestive hea

rt failure, hypertrophy,

Assessment of RV Function

• Clinical signs of RV failure Jugular venous distention Hepatomegaly Peripheral e4dema Ascites Periorbital, flank, and generalized edema Rising BUN

• Elevated RA pressure with low LA pressure Volume loading, often to an RA pressure of 15mmHg or greater, may be necessary to ensure adequate left-sided filling

Fluid & Electrolyte Requirement

• Fluid volume a. Daily fluid requirement is 4ml/kg/h for the first 10kg, 2ml/kg/h for the next 10kg, and 1ml/kg/h for each subsequent kg. b. Intubated patients are given two-thirds of maintenance of level (due to water gain)

• Eletrolytes a. Sodium; 3mEq/100ml/d b. Potassium; 2-3mEq/100ml/d

Physiology of Coronary Artery

• Proximal epicardial vessel Richly innervated by sympathetic alpha & beta

fiber(alpha; proximal, beta; distal) -- cause spasm

• Distal intramyocardial vessel Little autonomic innervation, less smooth muscle, do

not constrict markedly, but do dilate to the metabolic demand -- cause little spasm

• Spasm is common in RCA & LAD, especially in underlying obstruction

Arterial Blood Pressure

• Determinants of systolic blood pressure 1. Volume of blood ejected

2. Compliance of arterial wall

3. Rate of run-off (resistance)

• Determinants of diastolic blood pressure

1. Volume of blood remained

2. Compliance of arterial wall

3. Peripheral resistance

Venous Blood Pressure

• Determinants of venous pressure 1. Blood volume

2. Pressure-volume characteristics of venous bed

(compliance)

3. Size of venous bed (capacitance)

4. Ability of heart to eject venous return

• Location of venous blood volume 1. Peripheral vein ; 65%

2. Pulmonary venous system ; 5%

Cardiac Receptors

• Atrial receptors Located mainly pulmonary venous and caval-atrial junction, others

on the body of left & right atrium, appendage connected to the myeli

nated fiber of Vagus nerve.

Not related BT, PVR, myocardial contractility

1. Type A ; atrial contraction for pressure ( a wave )

2. Type B ; stretch receptor for volume ( v wave )

• Ventricular receptors Myelinated & unmyelinated, but uncertain function

Ventricular reflexes – LV distention cause reflex vasodepression

Arterial Baroreceptors

1. Anatomic location

Carotid sinus ; segmental enlargement of internal carotid

artery at it’s origin, (stimulation; drop BP in 23% & 14% of SVR, low carotid sinus pressure; vasoconstriction, increase CO in 30%)

Aortic arch ; located in the adventitia adjacent to media

between brachiocephalic trunk and ligament arteriosum

2. Transmission Afferent impulse ; generated by stretch of arterial walls and

transmitted myelinated & nonmyelinated sensory fiber of carotid sinus nerve travel glossopharyngeal nerve No distant pathway of aortic arch stretch receptor

Efferent impulse ; consist of sympathetic adrenergic nerves

to heart, vessel

Low Cardiac Output Syndrome• Diagnosis

a. Suspicion of LCO by evidence of peripheral vasoconstriction

( cool, pale extremities, mottling, absence of pedal pulses, and

capillary refill exceeding 3 seconds), oliguria, metabolic acidosis,

and hyperthermia.

b. Narrow arterial pulse, elevated filling pressure, low RA oxygen

saturation, development of atrial or ventricular arrhythmias,

should draw attention to a LCO

• Treatment

a. Assessment and manipulation of heart rate, and rhythm, volume

state, contractility, and afterload.

b. Additional contributory factors should be identified

Cardiac temponade, ventilator problems, metabolic problems

Re-Operative Surgery in Pediatric Patients

• Re-do sternotomy Anatomic considerations Planning Technique

• Alternative cannulation sites • Pericardial substitutes Infection Tamponade Epicardial reaction

• Aprotinin Hypersensitivity (or adverse reaction ; 3%) Histamin blocker

Anatomic considerations in Re-do Sternotomy

• Substernal homografts or conduit

• Degenerated homografts

• Enlarged right ventricle due to PR or TR

• Dilated right atrium due to TR or Ebstein’s anomaly or atrio-pulmonary connection

• Presence of pseudoaneurysm

Planning & Techniques in Re-Do

• Techniques of re-do sternotomy 1. Head facing to the left 2. Provide gentle cervical extension 3. Cutaneous defibrillation patches 4. Incision rather than excise the previous incision 5. Incision carried inferiorly 1-3cm below previous incision 6. Division of the adhesions immediately below the sternum• Alternative cannulation sites ; femoral vessels are often of an in

adequate, particularly in pre-toddler patients, consequently cervical (common carotid a, internal jugular vein) cannulation is prefered

• Pericardial substitutes PTFE membrane, bovine pericardium, polyglycolic acid mesh, hyalu

ronic acid, poly-beta-hydroxybutyrate(PHB), glutaldehyde-chitosan treated porcine pericardium, epoxy fixed porcine pericardium

Cardiac Surgery during Pregnancy

Measures to reduce maternal & fetal mortality • Avoid functional deterioration during pregnancy• Prescribe earlier surgery to prevent these patients from re

quiring an emergency procedure • Perform surgery as fast as possible, with minimal ECC • Provide adequate fetal monitoring (cardiotachometer & in

traoperative fetal echocardiography)• Perform surgery in the second trimester of pregnancy pref

erably

Cardiac Surgery during Pregnancy

Measures to reduce maternal & fetal risks• Extracorporeal circulation with high flow, high

pressures (mean blood pressure of 60 mm Hg), and normothermia should be used

• Hyperoxygenation should be maintained and hematocrit should be kept higher than 25%

• Myocardial protection using intermittent clamping allows, during normothermia, short perfusion times with pulsatile flow, which favors the fetus

Ideal Gestational Age for Operation

• Period between the 13th and 28th weeks as ideal• Higher trend towards fetal malformations in the

first trimester.• Higher trend towards preterm delivery, materna

l hemodynamic alterations, and mortality in the third

• There was no relationship between maternal and fetal outcome and surgical indication according to gestational age

• Fetal mortality is described as higher than 50% in patients in functional class III and IV