Cyanosis is an abnormal bluish discoloration of the skin and mucous membranes due to the presence of reduced hemoglobin in the blood.

The blue color usually represents excessive amounts of deoxygenated hemoglobin, although, in some patients, it results from increased amounts of methemoglobin or sulfhemoglobin. Cyanosis may be central or peripheral. In central cyanosis, the blood leaving the heart appears bluish; in peripheral cyanosis, the blood leaving the heart is red but becomes bluish colored by the time it reaches the fingers and toes. Pseudocyesis, in contrast, refers to a permanent bluish discoloration caused by deposition of blue pigments in the skin.

Cyanosis was first described in 1761 by Morgagni, who attributed it to pulmonic stenosis.1 In 1869, Claude Bernard described the qualitative difference in blood gases between blue venous blood and red arterial blood. The first person to quantify how much-deoxygenated hemoglobin was necessary to produce the blue color was Lundsgaard in 1919.

hand of the patient with cyanosis


1. Central cyanosis:-

  • Due to imperfect oxygenation of blood – as in heart failure and some lung diseases, or
  • From admixture of de-saturated venous blood with arterial oxygenated blood due to right to left shunt.
  • Cyanosis is general and extremities are warm.
  • Characteristically affects the tongue and lips.

2. Peripheral cyanosis:-

  • Due to excessive reduction of oxyhemoglobin in the blood when the flow of blood is slowed.
  • May happen on exposure to cold or venous obstruction, or in heart failure.
  • Extremities are cold and the tongue is unaffected.


  • The occurrence of cyanosis depends upon the total amount of hemoglobin in blood, degree of hemoglobin unsaturation and the state of capillary circulation.
  • It is the absolute rather than the relative quantity of reduced Hb that is important in producing cyanosis.
  • Higher the total Hb concentration, the greater is the tendency towards cyanosis. e.g polycythemia.

Where to look for cyanosis?

  • Central cyanosis – Earlobes, lips, tongue, mucous membranes, tip of nose.
  • Peripheral cyanosis –  Nail beds, fingers and extremeties – where the skin is thin.

Cyanosis doesn’t occur in

  1. Anemic hypoxia – because total hemoglobin content is low.
  2. CO poisoning – because the color of reduced hemoglobin is obscured by the cherry-red color of carbonmonoxyHb.
  3. Histotoxic hypoxia – because blood gas content is normal.


  • Decreased level of oxygen in air / decreased oxygen delivery to alveoli.
  • Decreased oxygen diffusion from alveoli to blood.
  • Mixing of deoxygenated blood with oxygenated blood.
  • Increased extraction of oxygen from Hb.


1. Cardiac

Ductal-independent mixing lesions

  • Truncus arteriosus
  • Total anomalous pulmonary venous return without obstruction
  • Transposition of great arteries

Lesions with ductal-dependent pulmonary blood flow

  • TOF
  • Ebstein’s anomaly
  • TOF with pulmonary atresia
  • Pulmonary valve atresia with the intact ventricular septum

Lesion with ductal-dependent systemic blood flow

  • Hypoplastic left heart syndrome
  • Interrupted aortic arch
  • Critical coarctation of the aorta
  • Critical aortic stenosis
  • Tricuspid atresia with transposed great arteries

2. Pulmonary

Primary lung disease

  • RDS
  • Persistent pulmonary HTN of newborn
  • TTN, MAS
  • Pneumonia, bronchiolitis
  • Croup
  • Pulmonary hypoplasia
  • Pulmonary AV malformation

Airway obstruction

  • Choanal stenosis or atresia, FB
  • Macroglossia, Goiter
  • Cystic hygroma
  • Vocal cord paralysis
  • Laryngotracheomalacia, RAD
  • Laryngeal web, TEF
  • Mediastinal mass
  • Sleep apnea

3. Neurological

CNS dysfunction

  • Drug-induced depression of respiratory drive
  • Post-asphyxial cerebral dysfunction
  • Intraventricular hemorrhage
  • SAH
  • SDH
  • Meningitis
  • Encephalitis
  • Sepsis
  • Shock
  • Seizures
  • Hypoglycemia

Respiratory Neuromuscular Dysfunction

  • Myasthenia gravis
  • Botulism
  • Phrenic nerve paralysis

4. Hematologic

  • Methemoglobinemia

– Methemoglobin reductase deficiency
– Oxidant stress (benzocaine, hydralazine, NG, Nitroprusside, prilocaine, sulphonamides)

  • Polycythemia



  • Birth history- perinatal and postnatal complications
  • Prematurity
  • Age of onset of cyanosis
  • 0 to 6 days – TGA, HLHS, TOF, coarctation, VSD
  • 7 to 13 days – coarctation, VSD, HLHS, TGA, TOF
  • 14 to 28 days – VSD, TOF, coarctation, TGA, PDA.

Older children

  • H/o trauma, possible ingestion or choking
  • Respiratory depressants.

Any evaluation in the past / positive findings and conclusion.
Associated signs/symptoms – edema, breathlessness, chest pain.

Chest pain –

  • Trauma, pneumonia, RAD, FB, embolism
  • Pericarditis, endocarditis.
  • Cardiomyopathy

Feeding problems – the volume of each feed, time spent in each breast.
Weight gain/loss

Physical activity

  • Tiring easily
  • H/o squatting
  • Cyanotic spells
  • Exercise intolerance

Maternal complications

  • GDM
  • Medications
  • SLE
  • Substance abuse

H/o orthopnea /PND- the severity of the disease.
Inciting factors, length of episodes and whether the tongue and mucous membranes appear cyanotic.
Family history

  • Early coronary artery disease/stroke – familial hypercholesterolemia or thrombophilia.
  • Generalized muscle disease – muscular dystrophy, dermatomyositis, familial or metabolic cardiomyopathy.
  • Relatives with congenital heart disease.

General Examination

  • Comfortable/distressed – grunting, nasal flaring, stridor.

Pallor/ polycythemia

  • Severe pallor with anemia – high output cardiac failure.
  • Polycythemia – pulmonary pathology, cyanotic congenital heart disease.


  • Hepatic congestion.
  • Cardiac cirrhosis.

Cyanosis – central/peripheral

  • Differential cyanosis – blue lower extremities and pink upper extremities are seen when deoxygenated blood from pulmonary circulation enters the descending aorta through PDA. Seen in persistent pulmonary HTN of a newborn, and in lesions with left ventricular outflow tract obstruction (aortic arch hypoplasia, interrupted aortic arch, coarctation of the aorta).
  • Reverse differential cyanosis – is seen in transposition of great arteries with coarctation of the aorta or interrupted aortic arch and in transposition of great arteries and pulmonary HTN. In this, the upper extremities appear blue and the lower extremities appear pink as the descending aorta is filled with oxygenated blood from the pulmonary circulation.
  • Acrocyanosis – especially in infants on exposure to cold.


  • Suggests chronic/persistent cyanosis.
  • Is not usually manifested until late 1st year of life.


  • Dependent/ pitting in cardiac disease.
  • In pre-walking child – may be appreciated along the back and may be prominent in the periorbital area.

Nose and throat examination

  • Choanal atresia/stenosis
  • Size of the tongue – macroglossia.
  • Tonsillar /adenoid enlargement
  • Posterior pharyngeal wall
  • Vocal cords

Pulse rate and rhythm

  • Tachycardia, irregular/ regular, volume, radio-femoral delay.
  • Normal heart rates – age variation
Age Rate/min
Newborn 80 – 180
1wk – 1mth 80 – 160
1mth – 2yr 80 – 150
2 – 10yr 75 – 110
10yr – adult 50 – 100

Blood pressure

  • Age wise variation.
  • Neonate=40-80/20-5 mmHg.
Age (yrs) 50th centile 95th centile
2 96/60 112/78
6 98/64 116/80
9 106/68 126/84
12 114/74 136/88

Respiratory rate

  • Tachypnea
  • Grunting
  • Wheezing
Age Rate/min
Neonate 30-50
1-6mths 20-40
6mths-2yrs 20-30
2-12yrs 16-24
Adolescent 12-20


– signifies infective/inflammatory pathology of lung/ heart (IE).


  • To be seen in older children.
  • Raised in CCF and Cor-pulmonale.

Height and weight

  • FTT- cardiac failure and chronic cyanosis.
  • If length or HC is also affected then congenital malformations or metabolic disorder may be present.

Congenital malformation syndromes

  • Down syndrome – ASD, VSD, endocardial cushion defect.
  • Cat- eye syndrome- TAPVR.
  • Turner syndrome- bicuspid aortic valve, coarctation of the aorta.
  • CHARGE association- VSD, ASD, PDA.
  • Congenital rubella – PDA
  • Fetal alcohol syndrome – ASD, VSD.

System Examination

Respiratory System


  • Intercostal / subcostal indrawing.
  • Spinal Deformity.
  • Apical impulse
  • Expansion of the chest.


  • Crepitus (Subcutaneous emphysema).
  • Friction Rub
  • Apex beat
  • Position of trachea


  • Hyper-resonant – pneumothorax.
  • Dullness


  • B/L air entry.
  • Bronchial / vesicular breath sounds
  • Added sounds – crackles, wheeze.

Cardiovascular System


  • Precordial bulge
  • Pulsations over the precordium (hyperdynamic/ quiet)
  • Neck vessels


  • Site and character (normal/tapping/heaving) of apex beat.
  • Parasternal heave
  • Thrill (site and timing in relation to cardiac cycle)


  • Heart sounds – intensity
  • Split of S2
  • Third heart sound
  • Gallop rhythm and S4
  • Murmurs – site of maximum intensity, grade, timing (systolic, diastolic, continuous), character (ejection, pansystolic, crescendo or decrescendo) and conduction.


  • Distension, umbilicus-position
  • Engorged veins, epigastric pulsations


  • Flow or blood in engorged veins
  • Tender hepatomegaly – CCF.


  • Free fluid
  • Upper margin of liver dullness


  • Bruit over the hepatic area and renal vessels.


  • Level of consciousness, GCS
  • Signs of meningeal irritation.
  • Pupillary size and reaction to light.
  • Focal neurological deficit – UMN/LMN.
  • Gag reflex



  • Hb – polycythemia, abnormal hemoglobin.
  • TC,DC- for e/o infection.

Pulse Oximetry

  • To see O2 saturation of Hb in bedside.
  • Documented at preductal and postductal sites to assess for differential or reverse differential cyanosis.
  • If preductal saturation > postductal saturation, the differential cyanosis exists.


  • Rate, rhythm, axis, conduction defects, ventricular hypertrophy.


  • Estimation of partial pressures of O2 and CO2 in blood along with blood PH is used for making a diagnosis of acute or compensated respiratory failure.


  • To see for e/o
    • Cardiomegaly, pulmonary edema, infiltration.
    • Plethoric/ oligemic lung fields.
    • Collapse-consolidation.


  • To evaluate the structural and functional status of the heart.

– congenital heart diseases, valvular heart diseases, CCF, myocarditis, pericardial effusion/ tamponade.

Radionuclide lung scan

  • V/Q scan
  • Congenital cardiovascular and pulmonary defects.


  • To see the movement of the diaphragm with respiration – Dx of diaphragmatic palsy.

Hyperoxia test

  • Should be carried out in neonates with a resting pulse oximetry reading < 95%, visible cyanosis or circulatory collapse.
  • Consists of obtaining a baseline right radial (preductal) ABG measurement with the child breathing room air (FiO2=0.21), and then repeating the measurement with the child inspiring 100% O2.
  • A PaO2>200mmHg on 100% O2 excludes CHD from the D/D.
  • A PaO2 < 150mmHg on 100% O2 – a cardiac lesion characterized by complete mixing without restricted pulmonary blood flow.
  • A PaO2 < 50mmHg on 100% O2 – indicates a cardiac lesion a mixing lesion with restricted pulmonary blood flow.


  • Multislice CT scanner – 3D-reconstruction of images (especially in complex congenital heart diseases), important for a cardiac surgeon for planning the surgery.

Cardiac catheterization

  • Diagnostic as well as therapeutic.
  • Measures pressure gradients across the lesions.

Pulmonary Function Tests

  • Useful in chronic respiratory illnesses.


Ganesh Kr Shah. Institute of Medicine, TU.