Cyanosis is a bluish discoloration of the skin, mucous membranes, tongue, lips, or nail beds and is due to an increased concentration of reduced hemoglobin (Hb) in the circulation.1 Clinically evident cyanosis typically occurs at an oxygen saturation of 85% or less.2 It is easier to identify under natural lighting and is typically more difficult to detect in patients with mild cyanosis, dark skin pigmentation, or anemia. Long-term complications of chronic cyanosis include clubbing, polycythemia, stroke, brain abscess, platelet abnormalities, lower-than-expected IQ, scoliosis, and hyperuricemia.1
Normally, there is ~ 2 g/dL of reduced (or deoxygenated) Hb in the circulation, and clinically evident cyanosis occurs when the concentration of reduced Hb reaches 5 g/dL. Therefore, the total amount of Hb is critical to the development of cyanosis. For instance, a hypoxic child with severe anemia may not have enough reduced Hb in the circulation to produce clinical cyanosis. In contrast, a hypoxic child with polycythemia may have enough reduced Hb to produce clinical cyanosis at a higher oxygen saturation level.3
Hypoxia results from one or a combination of the following mechanisms:
Decreased inspired oxygen content (FIO2)
Decreased respiratory rate or apnea
Increased right-to-left shunt
Increased ventilation–perfusion mismatch
Diffusion abnormality
Decreased affinity of hemoglobin for oxygen
Methemoglobin is formed when the iron in Hb is oxidized to the ferric state (Fe3+).4 Methemoglobin is unable to carry oxygen and normally constitutes less than 2% of circulating Hb. With congenital or acquired causes of methemoglobinemia, as well as with certain abnormal Hb variants, such as the Hb M group, elevated levels of methemoglobin cause central cyanosis and give the blood a chocolate brown appearance.5
DEFINITIONS
Cyanosis: Bluish discoloration of the skin or mucus membranes due to reduced fraction of oxygenated hemoglobin.
Hypoxemia: A relative or absolute deficiency of oxygen in the blood.
Hypoxia: A relative or absolute deficiency of oxygen.
A careful and complete history and physical examination are essential in the evaluation of cyanosis (Tables 21-1 and 21-2). The history should focus on a detailed description of the cyanosis including areas of the body involved, timing, and severity, as well as associated symptoms. Changes in cyanosis with crying, choking, vomiting, or postural changes may help identify the underlying cause.
| Description of cyanosis |
| Timing of first observation |
| Involved body parts |
| Severity |
| Persistent or episodic |
| Exacerbating and alleviating factors |
| Timing of episodes (e.g. cyanotic spells of tetralogy of Fallot in the morning) |
| Duration |
| Worsening, stable, or improving |
| Description of typical cyanotic event |
| Associated symptoms or behaviors |
| Effect of crying (e.g. crying may worsen cyanosis with cardiac causes, improve cyanosis with respiratory or neurologic causes)1 |
| Inciting event (e.g. choking with foreign body aspiration) |
| Postural changes, such as squatting, with the episodes (e.g. cyanotic spells with tetralogy of Fallot) |
| Effect of feedings (e.g. cyanosis after feedings with gastroesophageal reflux) |
| Sweating or tachypnea with feeding (e.g. congenital heart disease) |
| Occurrence primarily when the child is angry or hurt (e.g. breath holding) |
| Focused review of systems |
| Respiratory status |
| Recent fever |
| Easy fatigability |
| Alertness |
| Difficulty growing or gaining weight |
| Difficulty or choking during feeding |
| Developmental milestones |
| Feeding history |
| Recurrent respiratory infections or chronic cough |
| Unusual movements, such as seizures |
| Birth history (especially important in neonates and infants) |
| Gestational age, birth weight, maternal medical history and screening tests, maternal medications or sedatives, delivery complications such as fetal distress or meconium |
| Apgar score |
| Prenatal ultrasonography results |
| Mode of delivery (e.g. scheduled cesarean section with no labor and transient tachypnea of the newborn) |
| Past medical history |
| Known cardiac, pulmonary, or neurologic disease |
| Chronic illnesses |
| Medications, including over the counter, herbal remedies, teething gel, topical anesthetics, recent anesthesia |
| Prior surgeries or hospitalizations |
| Other history |
| Family history of cyanosis, congenital cardiac disease, pulmonary disease, neuromuscular disease, or early childhood death |
| Social history, including potential exposures at home and school |
| Vital signs, including temperature and blood pressures in the right arm and right leg |
| Right lower extremity systolic blood pressure 10 mmHg lower than that in right upper extremity suggests coarctation of the aorta or interrupted aortic arch |
| General |
| Dysmorphic features may indicate syndrome with other congenital anomalies |
| Poor growth indicates chronic underlying pathology |
| Cyanotic changes with crying or feeding |
| Skin |
| Degree and location of cyanosis; evaluate nail beds; jaundice may indicate underlying liver disease |
| Head, eyes, ears, nose, and throat |
| Foreign body or anatomic anomaly causing upper airway obstruction |
| Plethoric sclera with CHD |
| Cyanosis of oral mucosa, tongue, and lips with central cyanosis |
| Neck |
| Meningismus suggests meningitis |
| Mass causing possible obstruction |
| Respiratory |
| Rales, wheezing, grunting, or flaring suggests pulmonary pathology |
| Unequal air entry (e.g. pneumothorax or foreign body aspiration) |
| Stridor with upper airway obstruction or laryngeal irritation due to severe gastroesophageal reflux |
| Significant retractions and labored breathing indicate pulmonary pathology |
| Shallow, irregular respirations or apnea may indicate CNS depression |
| Tachypnea is common with CHD2 |
| Breathing is often minimally affected with CHD unless congestive heart failure, acidosis, or pulmonary edema is present2 |
| Cardiovascular |
| Hyperactive precordium with CHD |
| Arrhythmia may cause congestive heart failure with pulmonary edema and cyanosis |
| Murmur is suggestive of CHD, although the absence of murmur does not rule it out (e.g. transposition of the great arteries may have no murmur or only a soft murmur) |
| Single, loud S2 may indicate CHD |
| Gallop |
| Unequal peripheral pulses or pulse lag suggests coarctation of the aorta or interrupted aortic arch |
| Poor peripheral perfusion may indicate sepsis, shock, or low cardiac output |
| Gastrointestinal |
| Hepatosplenomegaly or ascites may indicate congestive heart failure or underlying hepatic disease |
| Extremities and musculoskeletal |
| Clubbing signifies long-standing hypoxemia and cyanosis |
| Peripheral edema may indicate heart failure |
| Scoliosis is seen with chronic cyanosis and CHD, notably tetralogy of Fallot |
| Restrictive chest deformities |
| Neurologic |
| Abnormal head circumference may indicate hypoxic injury or other CNS pathology |
| Weakness may suggest neuromuscular disease |
| Hypotonia and lethargy may indicate CNS depression |
| Inconsolability may indicate meningitis |
| Unusual movements or seizures |
Stay updated, free articles. Join our Telegram channel
Full access? Get Clinical Tree
