Pediatric emergency medicine trisk 126

Polycythemia, as in newborns with twin–twin transfusion, infants of diabetic
mothers, or children with high erythropoietin states may cause cyanosis. This can
occur even with normal pulse oximetry because the absolute amount of
deoxygenated Hb is above 5 g/dL, but with a normal proportion of oxygenated to
deoxygenated Hb.
The degree of Hb saturation is affected by many factors, which can be grouped
conveniently by systems. First is the significant contribution from respiratory
conditions. Any circumstance leading to a decrease in the concentration of
inspired oxygen, such as a house fire, confinement to a small unventilated space,
or high altitude, can lead to diminished PaO2 and cyanosis. Upper airway
obstruction, as with a foreign body, croup, epiglottitis, bacterial tracheitis,
tracheal/bronchial disruption, or congenital airway abnormalities, if severe, can
cause hypoxemia and consequent cyanosis. Age, events leading to presentation,
and examination features, such as barking cough, can help distinguish among
these diagnoses. Cyanosis ensues rapidly when chest wall movement or lung
inflation is impeded. This condition is often a result of trauma and includes
external chest compression, flail chest, or hemothorax. Tension pneumothorax,
whether traumatic or as a result of pre-existing lung disease such as asthma or
cystic fibrosis, is diagnosed by dyspnea, deviated trachea, and possibly distended
neck veins with diminished breath sounds on the affected side. Empyema or
pleural effusion caused by infection, malignancy, or large chylothorax may be
associated with fever, respiratory distress, dullness to percussion, and asymmetric
breath sounds on auscultation. Importantly, any lung dysfunction that directly
affects pulmonary gas exchange can lead to cyanosis. The most common
conditions in children are asthma, bronchiolitis, pneumonia, cystic fibrosis,
foreign-body aspiration, and pulmonary edema.


TABLE 21.1
CAUSES OF CYANOSIS

I. Respiratory
A. Decrease in inspired O2 concentration
B. Severe upper airway obstruction
1. Foreign body
2. Croup
3. Epiglottitis
4. Bacterial tracheitis
5. Traumatic disruption
6. Congenital anomalies (e.g., vascular malformation, hypoplastic
mandible, laryngotracheomalacia)
C. Chest wall
1. External compression
2. Flail chest
D. Pleura
1. Pneumothorax
2. Hemothorax
3. Empyema/effusion
4. Diaphragmatic hernia
E. Lower airway
1. Asthma
2. Bronchiolitis
3. Cystic fibrosis
4. Pneumonia
5. Acute respiratory distress syndrome
6. Foreign body/aspiration
7. Congenital hypoplasia
II. Vascular
A. Cardiac
1. Cyanotic congenital defects

a. Tetralogy of Fallot
b. Transposition of the great vessels
c. Truncus arteriosus
d. Pulmonary atresia
e. Severe pulmonary stenosis with patent foramen
f. Tricuspid atresia
g. Ebstein anomaly
h. Total anomalous pulmonary venous drainage
i. Atrioventricular canal defect
2. Congestive cardiac failure
3. Cardiogenic shock


B. Pulmonary
1. Pulmonary edema
2. Primary pulmonary hypertension of the newborn
3. Pulmonary hypertension
4. Pulmonary embolism
5. Pulmonary hemorrhage
C. Peripheral
1. Moderate cold exposure
2. Shock: septic/cardiogenic
3. Acrocyanosis of the newborn
4. Complex regional pain syndrome
III. Neurologic
A. Drug or toxin-induced respiratory depression (e.g., morphine, barbiturates)
B. Central nervous system lesions (e.g., intracranial hemorrhage, contusion)
C. Seizure
D. Breath holding
E. Brief resolved unexplained event (BRUE)

F. Neuromuscular disease (e.g., Guillain–Barré, spinal muscular atrophy)
IV. Hematologic
A. Polycythemia
B. Methemoglobinemia
V. Dermatologic
A. Blue dye
B. Pigmentary lesions
C. Tattoos
D. Amiodarone therapy
TABLE 21.2
COMMON CAUSES OF CYANOSIS
I. Peripheral cyanosis
A. Acrocyanosis of the newborn
B. Moderate cold exposure
II. Central cyanosis
A. Respiratory dysfunction
B. Congenital heart disease
Circulatory or vascular conditions leading to diminished PaO2 are also
associated with cyanosis. One of the most common causes of cyanosis in children