Cyanosis resident survival guide

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Cyanosis Resident Survival Guide Microchapters
Differential Diagnosis

Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-in-Chief: Sara Zand, M.D.[2] Chandrakala Yannam, MD [3]

Synonyms and keywords: Cyanosis approach, Cyanosis workup, Cyanosis management, Approach to blue discoloration of skin, Hypoxemia approach, Hypoxia approach


Cyanosis is defined as bluish discoloration of skin and mucous membrane due to decreased oxygenation of tissue. Approximately 2% of oxygen dissolved in plasma and 98% is carried by hemoglobin. In central cyanosis, there is decreased oxygen saturation (less than 85%) or abnormal or nonfunctional hemoglobin, depending on whether reduced hemoglobin or desaturated hemoglobin exceeds 5 g/dl. Common signs of central cyanosis include the tongue and conjunctiva appearing blue in color and the extremities becoming warm with rapid capillary filling. In peripheral cyanosis, the oxygen saturation is normal but there is inadequate delivery of oxygen to tissue or increased oxygen extraction by tissue due to peripheral vasoconstriction. In peripheral cyanosis extremities are cyanotic, pale, cool but tongue and conjunctiva are pinkish. All causes of central cyanosis may lead to peripheral cyanosis. In the presence of anemia and severe hypoxemia, cyanosis may not be apparent due to fewer levels of reduced hemoglobin. Conversely, in polycythemia and mild hypoxemia, cyanosis may be easily apparent due to an increased level of reduced hemoglobin.


Life Threatening Causes

Life-threatening causes include conditions that may result in death or permanent disability within 24 hours if left untreated.

Common Causes

Central cyanosis
Peripheral cyanosis
Hematologic abnormalities: [13]

Methemoglobinemia (congenital or acquired)
Sulfhemoglobinemia (acquired)
❑ Hemoglobin mutations with low oxygen affinity:

❑ Hb Kansas
❑ Hb Beth israel
❑ Hb Saint Mande
❑ Hb Bruxells

Polycythemia vera
Disseminated intravascular coagulation
Metabolic disorders:
❑ Severe hypoglycemia
Inborn errors of metabolism
Drugs and chemicals: [14][15]

Beta blockers
Nitrite or nitrate-containing compounds (eg, nitroglycerin)

❑ Venomous snakebites [16] ❑ Brief resolved unexplained events (BRUE) [17]
High altitude [18]
Congenital diaphragmatic hernia
Cirrhosis of liver
❑ Chocking
❑ Hanging

Upper airway obstruction: [19][3]

Foreign body aspiration
Pertussis / Croup
Bacterial tracheitis
❑ Traumatic disruption (thermal injury, fractures)
Acute chest syndrome [20] ❑ Congenital airway abnormalities:

Choanal atresia
Micrognathia or retrognathia (eg, Pierre-Robin syndrome)

Neurologic abnormalities: [21][22][23]
CNS depression
Birth asphyxia
❑ Severe head trauma
Apnea of prematurity
Obstructive sleep apnea
❑ Infections (eg, meningitis, encephalitis)
Intraventricular hemorrhage
❑ Cyanotic breath holding spells [24]
Neuromuscular disorders:
Myasthenia gravis
❑ Injury to the phrenic nerve
❑ Type 1 spinal muscular dystrophy (Wernig-Hoffman disease)
Intrinsic lung diseases:[25][26][27][28][29]
Respiratory distress syndrome (Hyaline membrane disease)
Pleural effusion
Cystic fibrosis
Bronchopulmonary dysplasia

Alveolar capillary dysplasia
Vascular causes:

Cardiac tamponade
Cyanotic congenital heart diseases (Right to left shunts): [30][31][8]

Decreased pulmonary flow:
Tetralogy of fallout [8]
❑ Tricuspid valve anomalies:
Tricuspid atresia
Tricuspid stenosis
Ebstein's anomaly
Pulmonary stenosis (critical valvular)
Pulmonary atresia with intact ventricular septum
Increased pulmonary flow:
TGA (Transposition of great arteries, most common dextro type)
Truncus arteriosus
TAPVC (Total anamalous pulmonary venous connection)
Heart failure: Condition that present with cyanosis and severe heart failure include:
❑ Left sided obstructive lesion (HLHS)
Coarctation of aorta
❑ Critical valvular aortic stenosis

Eisenmenger syndrome
Congestive heart failure
Atrial septal defect
Pulmonary hypertension
Pulmonary edema
Pulmonary hemorrhage
Pulmonary embolism
❑ Pulmonary arteriovenous malformations
❑ Multiple small intrapulmonary shunts

Amniotic fluid embolism [12]
Conditions associated with decreased concentration of inspired oxygen (FiO2): [32]

Smoke inhalation most commonly from house fires
Carbon monoxide poisoning
❑ Hydrogen cyanide poisoning
❑ Intentional or unintensional exposure to asphyxiating gases (eg, Propane, methane, butane, hydrogen sulphide)
Impairment of chest wall or lung expansion:
❑ External compression
Pneumothorax [33]

Flail chest
Causes: [34][35]

Cold exposure
Raynaud's phenomenon
Raynaud's disease
❑ Arterial obstruction:

Peripheral vascular disease
Buergers disease

❑ Venous obstruction:

Deep vein thrombosis
Superior vena cava syndrome

❑ Decreased cardiac output:

Left sided heart failure
❑ Redistribution of blood flow from extremities
Extensive tattoos
Pigmentary lesions
Consumption of dyed food


Abbreviations: TGA: Transposition of great arteries; COPD: Chronic obstructive pulmonary disease; PDA: Patent ductus arteriosus  ; ASD: Atrial septal defect; VSD: Ventricular septal defect; TAPVR: Total anomalous pulmonary venous return; TOF: Tetralogy of fallot; ILD: Interstitial lung disease; ARDS: Acute respiratory distress syndrome;

Mechanism of hypoxemia
V/Q mismatch:

❑ Common cause of hypoxemia[36]
❑ High proportion in apex of the lung due to higher ventilation compared with perfusion
❑ Easily corrected by supplemental oxygen therapy
❑ widened (A-a )oxygen gradient
❑ High V/Q mismatch such as pulmonary embolism that ventilation is higher than perfusion[37]
Cystic fibrosis
Interstitial lung disease (ILD)
Pulmonary hypertension due to lung disease

Diffusion limitation:
❑ Normal PCO2 level[38]
❑ Good response to oxygen therapy
❑ widened P(A-a)O2 level
❑ Alveolocapillary impairment

Right to left shunt:

❑ Poor response to oxygen therapy
❑ Normal PCO2 level
❑ Widened P(A-a) O2 gradient
❑ Presence of Small physiologic pulmonary shunt about 2-3% of cardiac output due to deraining of bronchial veins into pulmonary veins and deraining coronary veins into left ventricle[39]
❑ If the shunt fraction reaches 50%, hypercapnia may be present
❑ Shunt fraction<20% if PaO2/FIO2>200
❑ Shunt fraction>20% if PaO2/FIO2<200
❑ Cyanotic congenital heart disease with right to left shunt
Pulmonary edema
Acute respiratory distress syndrome(ARDS)
Alveolar collapse

Pulmonar arterionenous connection

❑ High PCO2 level
❑ Low ventilation leading to Low PAO2, PaO2 level[37]
❑ Normal P(A-a)O2 gradient due to normal alveolar capillary memberane
❑ longstanding hypoventilation leading to atelectasia and widened P(A-a)O2 gradient
❑ Corrected by supplemental oxygen therapy
❑ One Cause of respiratory failure in COPD, Asthma,ILD
Disorders leading to hypoventilation include:
Impaired central drive:

Opiom overdose, benzodiazepine, alcohol
Brain stem infarct, hemorrhage
❑ Primary alveolar hyperventilation

Spinal cord level:

Amiotrophic lateral sclerosis
Cervical spinal cord injury

nerve supplying respiratory muscle:

Guillain-Barre syndrome

Neuromascular junction:

Lambert-eaton syndrome

Respiratory muscle:


Defect in chest wall:


PAO2 is the mean alveolar oxygen pressure. PH2O is the water vapor pressure (47 mmHg at 37°C). PaCO2 is the alveolar carbon dioxide tension and is equal to arterial PCO2. R is the respiratory quotient and is 0.8 on the standard diet. FiO2 is the fractional concentration of inspired oxygen. It is 0.21 at room air. PAO2 = FiO2× (Pb − PH2O) − (PACO2/R)=0.21× (760 − 47) − (40/0.8)=100 mmHg.

Differential Diagnosis of Peripheral and Central Cyanosis

Eisenmenger disease
Increased pulmonary vascular resistant leading to right to left shunt, systemic arterial desaturation, central cyanosis
low cardiac output, low stroke volume, elevated cardiac filling pressures, increased sympathetic tone( tachycardia, peripheral vasoconstriction, peripheral cyanosis)[40]
Pulmonary thromboembolism
Pulmonary artery vasoconstriction, hypoxia, right ventricle pressure overload, right to left shunt via patent foramen ovale,central cyanosis[41]
Cardiogenic shock
Decreased myocardial perfusion, muscle hypoxia,necrosis, impaired myocardial contraction., decreased cardiac out put, Increased vasoconstrictor,peripheral cyanosis[42]
Tetralogy of fallot
Episods of Tet spell between 2-4 months of age, aggravated with crying ,feeding stooling,dehydration,in patients with severe pulmonary stenosis and large VSD, central cyanosis[43]
Differential diagnosis of peripheral and central cyanosis
Increased level of reduced hemoglobin, congenital or due to medication, central cyanosis[44]
Chronic obstructive pulmonary disease
Central cyanosis, respiratory failure, PO2<60 mmHg, PCO2>45mmHg while breathing at sea level, peripheral edema due to right heart failure
Pulmonary edema
Decreased arterial oxygen saturation, central cyanosis
High altitude
Hypoxia, peripheral cyanosis due to ischemia and occlusion small peripheral vessels, central cyanosis due to pulmonary edema in acute mountain sickness, pulmonary hypertension in chronic mountain sickness[45]
Central cyanosis due to impaired gas exchange and intrapulmonary shunt
Acute pulmonary parenchimal disease other than cardiac origin or volume overload, alveolar filling with exudates or alveolar collapse, central cyanosis due to decreased oxygen saturation and intrapulmonary shunting[46]

Approach to Cyanosis at Birth

Differentiating cardiac and pulmonary causes of cyanosis at birth:

History and physical exam
Blood pressure measurement in four limbs
Oxygen saturation measurement
Cardiac cause:

Cardiomegaly in CXR
❑ Relatively comfortable at rest
❑ Cyanosis may worsen with crying
❑ Cardiac murmur
❑ Abnormal rhythm or axis in ECG
❑ Normal PCO2 level
❑ NO response to O2 therapy
Pulmonary cause:

Respiratory distress,tachypnea at rest
Rale, crackle, wheezing in chest auscultation
❑ Normal cardiac margine in CXR
Ground glass appearance, pneumonia, atelectasia,pneumothorax in CXR
❑ Normal ECG finding
❑ Elevated PCO2 level
❑ Corrected with oxygen therapy

Cyanosis in Congenital heart disease
Cyanosis + pulmonary edema at the time of birth:

TGA (Transposition of great vessel) without associated PDA,VSD,ASD: two great arteries are misplaced, oxygenated pulmonary blood re-enter the pulmonary circulation via morphologic left ventricle and deoxygenated aorta blood re-enter the systemic circulation via morphologic right ventricle
Total anomalous pulmonary venous connection(TAPVR):connection between pulmonary veins and right system and mixing the oxygenated and deoxygenated blood
Truncus arteriosus: one great vessel arise from both ventricle then the gives rise to the aorta and pulmonary artery

Cyanosis +shock and collapse within hours or days after birth:

Tetralogy of fallot: pulmonary stenosis (valvular, subvalvular) with ventricular septum defect and overridding aorta[43]
❑ Severe pulmonary stenosis with intact ventricular septum
Ebstein anomaly: small functional right ventricle, huge right atrium, severe tricuspid regurgitation, right to left shunt via ASD or PFO

Cyanosis +shock and collapse in the first week of birth:

Hypoplastic left heart syndrome
❑ Severe coarctation of aorta
❑ Severe aortic stenosis
Tachycardia induced cardiomyopathy due to atrial flutter or PSVT
Dilated cardiomyopathy
Other differential diagnosis: neonate sepsis, menangitis or hypoglycemia

Differencial cyanosis ( upper limbs O2 saturation > lower limbs O2 saturation):

❑ Severe pulmonary hypertension with PDA[47]
❑ Severe aortic coactation or interruption

Differencial cyanosis ( lower limbs O2 saturation> upper limbs O2 saturation):

TGA + severe pulmonary hypertension + PDA[48]
TGA + severe aortic arch interruption + PDA
❑ Connection right subclavian artery to right pulmonary artery Right upper limb oxygen saturation is lower than left upper and left lower limbs oxygen saturation


Shown below is an algorithm summarizing the treatment of cyanosis.

TGA, TAPVR ,Truncus arteriosus
Infusion of Prostaglandin, Diuretic therapy,surgery [49]
Hydration, modified blalock taussing shunt, insertion stent in PDA and right ventricular outflow tract, total repair [43]
Ebstein anomaly
Tricuspid valve repair[50]
Treatment of Cyanosis
Hypoplastic left heart syndrome
Infusion of Prostaglandin for keeping patency of ductus arteriosus, infusion of vasodilator for reduced systemic resistance, mechanical ventilation in shock state and imposing hypercapnia and alveolar hypoxia for increased pulmonary resistance
Sepsis, shock, low cardiac output state, cold exposure, metabolic disorder, polycythemia
Treatment of underlying disorder
Eisenmenger syndrome with pulmonary hypertension,
Phosphodiesterase-5 inhibitor (sildenafil, tadalafil), Endothelin receptor antagonist (bosentan,macitentan, ambrisentan)[51]
Infusion of Methylenblue,dextrose,N-acetyl cystein,cimethidin,ketoconazole




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