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Cyanosis

Definedas bluish discoloration of tissues caused by excessive concentrationof reduced Hgb in capillary blood.

Bluish color of fingers and toes occurswith peripheral cyanosis, whereas bluish color of skin, lips, andmucous membranes occurs with central cyanosis.

Factors that determine cyanosis includedegree of oxygen saturation, total amount of Hgb in blood, stateof circulation, and presence of abnormal Hgb in blood.

Arterial oxygen saturation must be <85% inindividuals with a normal blood Hgb for cyanosis to be visible.Arterial oxygen saturation must decrease to ≤60% withsevere anemia (<8 g/dL Hgb) before cyanosis isvisible.

Poor perfusion of circulation leadsto release of oxygen into tissues and more reduced Hgb in capillaries.

Presence of abnormal Hgb (e.g., methemoglobin),which cannot bind oxygen, produces reddish-brown color of blood.

Focus here is on cyanosis as sign ofheart disease, primarily in neonate or young infant.

Principal Causes of Cyanosis

1. Peripheralcyanosis
2. Central cyanosis
   1. Respiratorydisorders
      1. Respiratorydistress syndrome (hyaline membrane disease)
      2. Pneumonia
      3. Bronchiolitis
      4. Asthma
      5. Pneumothorax
      6. Bronchopulmonary dysplasia
      7. Pulmonary malformations
      8. Airway obstruction
      9. Cystic fibrosis
   2. Cardiovascular disorders
      1. Congenitalheart lesions with decreased pulmonary blood flow
         1. Tricuspidatresia with intact ventricular septum and normal origin of thegreat arteries
         2. Ebstein malformation of the tricuspidvalve
         3. Pulmonic atresia with intact ventricularseptum
         4. Ventricular septal defect and pulmonicstenosis or pulmonary atresia (tetralogy of Fallot)
         5. Critical pulmonic stenosis with patentforamen ovale
         6. Complex lesions
      2. Congenital heart lesions with normalor increased pulmonary blood flow
         1. Transposition of the great arteries withintact ventricular septum
         2. Tricuspid atresia with ventricularseptal defect and normal origin of the great arteries
         3. Tricuspid atresia with transpositionof the great arteries
         4. Hypoplastic left heart syndrome
         5. Transposition of the great arterieswith large patent ductus arteriosus or ventricular septal defector both
         6. Double-outlet right ventricle
         7. Truncus arteriosus
         8. Univentricular heart
         9. Total anomalous pulmonary venous return
      3. Persistent pulmonary artery hypertensionof the newborn (persistent fetal circulation)
      4. Pulmonary vascular disease
      5. Pulmonary arteriovenous malformation
   3. Abnormal hemoglobin: methemoglobinemia

Clinical Features and Diagnosis

Peripheral Cyanosis

When peripheralvasoconstriction results in decreased peripheral perfusion, moreoxygen is extracted from peripheral blood. Decrease in oxygen contentof venous blood produces bluish discoloration.

Cold temperature, fever, hypovolemia,septicemia, and cardiac failure may cause peripheral vasoconstriction.

Polycythemia is another cause of peripheralcyanosis. Increase in blood viscosity impairs capillary blood flow,producing excessive amount of reduced Hgb. Venous Hct of >65–70% isdiagnostic.

Common cause of polycythemia is delayedcord clamping at birth.

Central Cyanosis

Respiratory Disorders

See Chap.56, Respiratory Distress and Apnea.

Cardiovascular Disorders

3 mechanismsor their combination can produce central cyanosis: right-to-leftshunts at atrial, ventricular, or ductal levels (congenital heartdisease, persistent pulmonary artery hypertension of the newborn,pulmonary vascular disease); alveolar hypoventilation (cardiac failure);and V/Q inequality (pulmonary arteriovenous malformation).

The congenital heart lesions can bedivided into 2 groups: lesions with either decreased or increasedpulmonary blood flow.

Chest radiography can show decreaseor increase in pulmonary vascular markings, which indicates amountof pulmonary blood flow.

Congenital Heart Lesions with Decreased Pulmonary Blood Flow

Tricuspid Atresia with Intact Ventricular Septum and NormalOrigin of Great Arteries

RV is hypoplastic,and pulmonary arteries may be small.

Right-to-left shunting occurs at atriallevel, and cyanosis often occurs during first 24 hrs of life.

Usual findings include prominent apicalimpulse and loud single S2. Continuous murmur of patent ductus maybe heard at upper left sternal border, but sometimes no murmursare heard.

Chest radiograph shows normal-sizedheart, decreased pulmonary vascular markings, and absent pulmonaryartery segment.

ECG usually shows right atrial hypertrophy,LV hypertrophy, and left axis deviation.

2-D echocardiography is diagnostic.

Cardiac catheterization and angiographyare usually performed prior to surgery.

Ebstein Malformation of Tricuspid Valve

Septal andinferior leaflets of tricuspid valve are displaced into RV. Dependingon specific anatomy, wide spectrum of clinical presentations canoccur. Severe RV dysfunction and increased pulmonary vascular resistancecan produce intense cyanosis and cardiac failure in neonates.

Usual physical findings are wide splittingof S1 and S2, prominent S3 and S4, murmur of tricuspid incompetence,and hepatomegaly.

Chest radiograph shows marked cardiomegalyand decreased pulmonary vascular markings.

ECG commonly shows right atrial hypertrophy,prolonged PR interval, right bundle branch block, and evidence ofWolff-Parkinson-White syndrome.

2-D echocardiography is diagnostic.

Cardiac catheterization and angiographyare performed when specific anatomic details need to be evaluated.

Pulmonary Atresia with Intact Ventricular Septum

Consistsof atresia of pulmonary valve and, occasionally, infundibulum of RV.

Tricuspid valve and RV are usuallysmall.

Right-to-left shunting occurs at atriallevel.

Blood flow to lungs depends on patentductus arteriosus and bronchial circulation.

Cyanosis usually appears during first24 hrs of life. As ductus closes, cyanosis becomes more severe.

Palpable apical impulse, absence ofRV impulse, and single S2 are usual physical findings. Murmurs ofpatent ductus arteriosus and tricuspid incompetence may or may notbe heard.

Chest radiograph shows variable heartsize, diminished pulmonary vascular markings, and flat or concavepulmonary artery segment.

ECG usually shows absence of RV predominancepattern of newborns, but normal R waves occasionally are seen inright precordial leads. Tall P waves indicative of right atrialenlargement develop within first month of life.

2-D echocardiography shows small RVwith absence of pulmonary valve.

Cardiac catheterization and angiographyare performed to demonstrate coronary artery anatomy and prior toany procedure.

Ventricular Septal Defect with Pulmonic Stenosis or PulmonaryAtresia (Tetralogy of Fallot)

VSD withpulmonic stenosis usually presents with cyanosis but depends onseverity of RV obstruction. Pulmonary valvar stenosis, infundibularstenosis, or both may occur.

With VSD and severe pulmonary valvarstenosis, cyanosis usually occurs in newborns.

With infundibular stenosis alone, cyanosisusually occurs later in infancy.

Some children with mild stenosis have left-to-rightshunt at rest and no cyanosis, but as infundibular narrowing becomesmore severe, cyanosis appears.

Usual physical findings are prominentRV impulse, narrowly split or single S2, and grade II–III/VIsystolic ejection murmur heard with maximum intensity in secondand third left intercostal spaces.

The more severe the outflow tract obstruction,the less intense the murmur.

With VSD and pulmonary atresia, cyanosisoccurs during first week of life and becomes more severe as ductusbegins to close.

Ifductus stays open or large collateral vessels supply pulmonary vascularbed, cyanosis is less pronounced.

Usual findings are single S2 and continuousmurmur from patent ductus or large collateral circulation.

Chest radiograph shows typical boot-shapedheart of normal size, diminished pulmonary vascular markings, absentpulmonary artery segment, and sometimes right aortic arch.

ECG shows RV hypertrophy.

2-D echocardiography confirms diagnosis.

Cardiac catheterization and angiographyare performed to demonstrate levels of stenosis in pulmonary outflowtract and pulmonary arteries, presence of multiple VSDs, and anycoronary artery anomalies.

Critical Pulmonary Stenosis with Patent Foramen Ovale

Neonateswith critical pulmonary valvar stenosis develop severe cyanosisand cardiac failure during first few days of life.

Usual physical findings are prominentRV impulse; normal, diminished, or inaudible pulmonary componentof S2; grade II–IV/VI systolic ejection murmurwith maximum intensity at upper left sternal border; and hepatomegaly.Occasionally, continuous murmur of patent ductus arteriosus or pansystolicmurmur of tricuspid incompetence is heard.

Chest radiography shows cardiomegalyand decreased pulmonary vascular markings.

ECG usually shows RV hypertrophy, unlessRV is hypoplastic. T-wave inversion sometimes is seen in right precordialleads.

2-D echocardiography confirms diagnosis.

Cardiac catheterization and angiographyare performed prior to any procedure.

Complex Lesions

Transpositionof great arteries and pulmonic stenosis ± VSD, double-outletright ventricle with pulmonic stenosis, and univentricular heartwith pulmonic stenosis are complex lesions that may present withcyanosis.

Degree of cyanosis depends on degreeof intracardiac mixing and severity of pulmonic stenosis. With severestenosis, usually S2 is single and grade II–III/VIsystolic ejection murmur is heard at left second intercostal space.With pulmonary atresia, S2 is always single, and continuous murmurfrom patent ductus or large collateral circulation may be heard.

These lesions cannot be distinguishedfrom each other by physical exam.

Chest radiograph shows normal or mildlyenlarged heart with decreased pulmonary vascular markings.

2-D echocardiography is usually diagnostic.

Cardiac catheterization with angiographyis performed prior to surgery.

Congenital Heart Lesions with Normal or Increased PulmonaryBlood Flow

Transposition of Great Arteries with Intact Ventricular Septum

Aorta arisesfrom RV, pulmonary artery arises from LV, and ventricular septumis intact. Mixing of blood occurs at atrial or ductal level or atboth levels.

Severe cyanosis and respiratory distressusually appear within 24 hrs of birth.

Prominent RV impulse, narrowly splitor single S2, and either no murmur or grade I–II/VI systolicejection murmur along left sternal border are usual physical findings.

Chest radiograph shows oval or egg-shaped,mildly enlarged heart, mild increase in pulmonary vascular markings,and absent pulmonary artery segment.

ECG shows normal RV predominance ofnewborn.

2-D echocardiography is diagnostic.

Balloon septostomy can be performedto increase atrial mixing and improve oxygenation as temporizingmeasure.

Cardiac catheterization and angiographyare performed before surgical intervention.

Tricuspid Atresia with Ventricular Septal Defect and NormalOrigin of Great Arteries

Most childrenwith tricuspid atresia and normal origin of great arteries have VSD.

Commonly presents with cyanosis andcardiac failure at 2–3 wks of age.

Prominent LV impulse, normally splitS2, and typical murmur of VSD are usual physical findings.

Chest radiograph shows enlarged heartwith increased pulmonary vascular markings.

ECG usually shows right atrial andLV hypertrophy as well as left axis deviation.

2-D echocardiography confirms diagnosis.

Tricuspid Atresia with Transposition of Great Arteries

Usuallypresents during first month of life with mild cyanosis and cardiacfailure.

Usual physical findings are grade II–III/VIsystolic ejection murmur along left sternal border and narrowlysplit S2.

Chest radiograph shows enlarged heart,increased pulmonary vascular markings, and narrow vascular pedicle.

ECG shows right atrial enlargement,LV hypertrophy, and left axis deviation.

2-D echocardiography is diagnostic.

Other Lesions

Hypoplasticleft-heart syndrome, transposition of great arteries with ventriculardefect or large patent ductus arteriosus, double-outlet right ventricle,truncus arteriosus, univentricular heart, total anomalous venousreturn ± obstruction, and other pulmonary venous obstructivelesions may produce cyanosis.

Cardiac failure is common manifestation.

See Chap.7, Cardiac Failure.

Persistent Pulmonary Artery Hypertension of Newborn (PersistentFetal Circulation)

Can be dueto pulmonary vasoconstriction, prenatal increase in pulmonary vascular smoothmuscle development, or decrease in cross-sectional area of pulmonaryvascular bed.

Right-to-left shunting occurs at atrialor ductal levels or both.

Clinical spectrum depends on amountof pulmonary blood flow.

Severe cyanosis and respiratory distressusually develop soon after birth.

Usual physical findings are prominentRV impulse and narrowly split S2 with loud pulmonary component.Grade I–II/VI systolic ejection murmur sometimesis heard along middle and upper left sternal borders. Liver alsomay be enlarged.

Chest radiography shows enlarged heartwith decreased, normal, or increased pulmonary vascular markings.

ECG shows RV hypertrophy.

Partial pressure of arterial oxygen (P_aO₂)is slightly higher in right arm than in umbilical artery becauseof right-to-left ductal shunting. Placing infant in 100% oxygenusually increases this difference.

2-D echocardiography that demonstratesright-to-left or bidirectional shunting at atrial or ductal levelsin structurally normal heart confirms diagnosis.

Sometimes difficult to distinguishthis lesion from total anomalous pulmonary venous return with obstruction.In this circumstance, cardiac catheterization and angiography shouldbe performed.

Pulmonary Vascular Disease

Pulmonaryvascular resistance is greater than systemic vascular resistance.

Common causes include

Cardiac lesionswith high pulmonary blood flow or pressure or both (e.g., VSD, patentductus arteriosus, AV canal, transposition of great arteries withVSD, truncus arteriosus)

Cardiac lesions with decreased pulmonaryflow requiring systemic-pulmonary artery shunting procedures, resultingin pulmonary artery hypertension

Primary pulmonary hypertension

Physical findings include increasedRV impulse, loud single or narrowly split S2, often murmur of pulmonaryregurgitation, and clubbing of digits.

Chest radiograph usually shows normalheart size, but in advanced cases heart may be enlarged.

Main pulmonary artery and branchesare prominent with tapering of more distal branches.

ECG shows RV hypertrophy.

2-D echocardiography can demonstrateright-to-left shunting at atrial, ventricular, or ductal levels.

Cardiac catheterization evaluates pulmonaryvascular resistance and reactivity.

Pulmonary Arteriovenous Malformation

Pulmonaryarteries communicate directly with variable number of pulmonaryveins to produce pulmonary arteriovenous fistula. Bypass of pulmonarycapillary bed produces mixing of oxygenated and unoxygenated blood,arterial desaturation, and cyanosis.

Usual presentation in childhood oradolescence is cyanosis, clubbing of fingers and toes, and exerciseintolerance. Grade II–III/VI systolic or continuousmurmur may be heard on chest wall over the fistula.

Chest radiograph shows ≥1 opacitiesof variable size in 1 or both lung fields. Vascular nature of lesioncan be demonstrated by contrast-enhanced CT or MRI.

Pulmonary angiography is definitive.

Abnormal Hemoglobin: Methemoglobinemia

Decreasescapacity of blood to deliver oxygen to tissues.

Color of blood is reddish-brown ratherthan bright red; however, P_aO₂ isnormal.

When measured by blood oximetry, oxygensaturation is low, but when measured by pulse oximetry, oxygen saturationis normal. Blood oximetry measures oxyhemoglobin as percentage oftotal Hgb, whereas pulse oximetry measures oxygen saturation ofonly the Hgb available for saturation.

Congenital causes are NADH-dependentmethemoglobin reductase deficiency (autosomal-recessive trait) andhemoglobin M disease (autosomal-dominant trait). Intense cyanosismay occur soon after birth in both disorders.

Mass spectrometry of blood sample confirmspresence of methemoglobinemia, whereas Hgb electrophoresis confirmsdiagnosis of hemoglobin M disease.

Acquired methemoglobinemia may be dueto ingestion of specific drugs (sulfonamides, phenytoin) or chemicals(naphthalene, nitrates, cyanides, benzene, aniline).

Usual presentation is intense cyanosis1–2 hrs after ingestion. In mild cases, no other distress occurs.In severe cases, respiratory distress and shock may occur.

Diagnostic Approach

First taskis to decide whether cyanosis is peripheral or central. This isusually accomplished by history and physical exam.

Presence of central cyanosis must beinvestigated immediately because of possibility of life-threateningheart or lung disease.

Certain findings favor diagnosis oflung disease: respiratory distress or apnea in extreme prematureinfants in whom most common cause of lung disease is respiratorydistress syndrome; significant increase in P_aO₂ afteradministration of 100% oxygen (usually >150 mmHg); and elevated partial pressure of carbon dioxide (PCO₂).

Certain findings suggest heart disease:significant murmur, cardiomegaly, hepatomegaly, chest radiographwith decreased or increased pulmonary vascular markings, abnormalECG, marked generalized cyanosis with P_aO₂ thatdoes not improve significantly with 100% oxygen (usually <100mm Hg), and normal or decreased P_aCO₂.

Absence of murmur does not rule outpossibility of heart disease.

Examples of life-threatening cardiaclesions that may not be associated with murmurs include transpositionof great arteries with intact ventricular septum, pulmonary atresiawith intact ventricular septum, and total anomalous pulmonary venousreturn with obstruction.

Infants with cyanotic heart diseasedo not usually have increased P_aCO₂,unless severe cardiac failure exists.

Cardiac lesions causing decrease inblood flow or lack of adequate mixing (transposition of great arteriesand intact ventricular septum) present with severe cyanosis ± mildrespiratory distress. Cardiac lesions causing increase in pulmonaryblood flow present with respiratory distress, cardiac failure, andmild cyanosis.

Chest radiographic findings of decreaseor increase in pulmonary vascular markings provide evidence of decreaseor increase in pulmonary blood flow, respectively, except in transpositionof great arteries with intact ventricular septum. In this lesion,pulmonary vascular markings may be mildly increased, but severecyanosis occurs because of parallel systemic and pulmonary circulationswith inadequate mixing of oxygenated blood.

Degree of cyanosis, presence of respiratorydistress, and chest radiographic findings (increase or decreasein pulmonary vascular markings) can be used to categorize lesionsto help make a diagnosis.

With suspected persistent pulmonaryartery hypertension in newborn, measurement of simultaneous P_aO₂ orarterial oxygen saturation (S_aO₂)at pre- and postductal sites (right radial and umbilical arteryor right finger and toe, respectively) may reveal right-to-leftductal shunt if preductal P_aO₂ or S_aO₂ ishigher. This finding also may be seen with severe coarctation ofaorta and interruption of aortic arch, but 2-D echocardiographycan usually confirm these diagnoses.

When severe generalized cyanosis occursin infants who do not appear to have septicemia, certain tests shouldbe performed: CBC with differential, chest radiography, ECG, pulseoximetry in room air and in 100% oxygen, and 2-D echocardiography.In most cases, diagnosis can be made based on test results.

If diagnosis is still uncertain andlife-threatening cyanotic congenital heart disease is possible,cardiac catheterization and angiography should be performed.

References

1. Driscoll DJ. Evaluation of the cyanoticnewborn. Pediatr Clin North Am 1990;37:1–23.
2. Garson A Jr, et al., eds. The science and practiceof pediatric cardiology, 2nd ed. Baltimore: Williams & Wilkins,1998.
3. Kirklin JW, Barratt-Boyes BG. Cardiac surgery. NewYork: John Wiley & Sons, 1986.
4. Kirks DR, ed. Practical pediatric imaging: diagnosticradiology of infants and children, 3rd ed. Philadelphia: Lippincott-Raven,1998.
5. Kitterman JA. Cyanosis in the newborn infant. PediatrRev 1982;4:13–23.
6. Rudolph AM. Congenital diseases of the heart. Chicago:Year Book Medical, 1974.
7. Rudolph AM, ed. Rudolph's pediatrics, 20thed. Stamford, CT: Appleton & Lange, 1996.
8. Stack AM. Cyanosis. In: Fleisher GR, Ludwig S, eds.Textbook of pediatric emergency medicine, 4th ed. Philadelphia:Lippincott Williams & Wilkins, 2000:187–191.

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Book Source Details

• Book Title: The Diagnostic Approach to Symptoms and Signs in Pediatrics
• Author(s): Paul S. Bellet
• Year of Publication: 2006
• Copyright Details: The Diagnostic Approach to Symptoms and Signs in Pediatrics, Copyright © 2006 Lippincott Williams & Wilkins.

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More About This Book: Title: The Diagnostic Approach to Symptoms and Signs in Pediatrics Authors: Paul S. Bellet Publisher: Lippincott Williams & Wilkins Copyright: 2006 ISBN: 0-78172-899-1

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