Cyanosis corresponds to a bluish staining of the skin and mucous membranes caused by an increase in the level of decreased hemoglobin in arterial blood (congenital heart disease) or a buildup of aberrant hemoglobin (methemoglobinemia).
It is crucial to recognize if the cyanosis is central or peripheral in a particular patient. Inadequate blood oxygenation (congestive heart failure, certain lung disorders) or a combination of arterial and venous blood causes central cyanosis (right to left shunt, venous-arterial shunt). The involvement of the tongue is common in this kind of cyanosis. When blood flow is sluggish, a substantial decrease of oxyhemoglobin occurs in capillaries, causing peripheral cyanosis (cold injury, heart failure, venous obstruction). The tongue is unaffected, but the leg feels frigid in this case. It is vital to know that cyanosis caused by heart failure might be mixed.
It is significant to mention that, while cyanosis is diagnosed when there’s at least 5 g/dL of decreased (unsaturated) hemoglobin in the systemic arterial circulation, it is possible to miss it in those with severe anemia. Polycythemia patients, on the other hand, are more likely to show symptoms. The color and thickness of the skin, as well as blood flow, impact the diagnosis of cyanosis.
When looking for cyanosis in a patient, it is important to do it in bright light (ideally daytime) and with a normal control to compare. Once it is been determined that the person has central cyanosis, it’s time to determine if it’s caused by a heart or respiratory condition.
Cyanosis of Respiratory Disease
Upper Airway Obstruction
Congenital malformations of the larynx, trachea, and vascular ring, as well as aspiration/inhalation of amniotic fluid, mucus, or foreign material, can cause arterial blood oxygenation to be insufficient. Inspiratory stridor, as well as suprasternal and intercostal retraction, are all common symptoms.
Defect in Diffusion
The most common cause of cyanosis in newborns is acute respiratory distress syndrome, which includes hyaline membrane disease.
At any age, cyanosis can be caused by a diffusion defect caused by pneumonia.
A week or two after childbirth, Wilson-Mikity syndrome produces cyanosis and respiratory difficulty.
Cyanosis of Heart Disease
Congenital Heart Disease
The most common congenital cardiac condition, transposition of the great arteries (TGA), produces severe cyanosis at or shortly after childbirth. Later symptoms such as dyspnea, congestive heart failure, and failure to thrive appear. In a few months, clubbing develops as well.
It is more common in male newborns (male-female ratio 4:1). These newborns have a rather substantial birth weight, but they gain weight slowly after that. Diabetes mellitus has a high prevalence among grandparents.
An unusually enlarged heart is discovered during the examination. Auscultation reveals no characteristic pattern of murmurs, which are normally associated with the sort of simultaneous communication required for TGV to function.
Radiology reveals an enlarged heart that may seem “egg-shaped” and plethoric lung fields (not on the first day, but at the end of the first week).
Right ventricular hypertrophy (RVH), right axis deviation, and P-pulmonale are all seen on the ECG. In the presence of pulmonary hypertension or a ventricular septal defect(VSD), signs of left ventricular hypertrophy (LVH) may be seen.
To confirm the diagnosis of the particular kind of transposition, cardiac catheterization, and selective angiography are required.
Tetralogy of Fallot (pulmonary stenosis, ventricular septal defect, right ventricular hypertrophy, Dextro position, and aortic overriding) is the most prevalent cause of chronic cyanosis, which generally appears during the third month of birth. The infant also experiences dyspnea in addition to cyanosis. As he gets older, he only feels comfortable squatting or laying down. Cerebral anoxia can lead to anoxic, hypoxic, or cyanotic episodes. Dyspnea and cyanosis, with or without unconsciousness, are symptoms of these episodes. Some clubbing is apparent by the age of two years.
Auscultation indicates a strong brief systolic murmur in the third space, best detected near the left sternal boundary. The condition is less severe when the murmur is louder or harsher. Usually, the murmur is not preceded by a thrill. P2 is almost always single.
Polycythemia is discovered through blood tests.
X-ray chest reveals oligemic (poorly vascularized due to reduced pulmonary blood flow) lung fields, a tiny boot-shaped heart with the tip of the boot turned up over the diaphragm (due to right ventricular hypertrophy), and concavity of the pulmonary artery section (small pulmonary conus). In 20 to 25% of instances, the aortic arch is on the right side.
Right ventricular hypertrophy (RVH) and beaked P waves can be seen on an ECG.
The outflow ventricular septum is anterior-superiorly displaced on two-dimensional echocardiography, resulting in constriction of the subpulmonic right ventricular outflow.
In questionable instances, cardiac catheterization and selective angiocardiography are essential for elucidating anatomic abnormalities.
Tricuspid atresia is characterized by severe cyanosis, dyspnea, and hypoxic episodes that develop immediately after delivery.
Due to an atrial or ventricular septal defect, auscultation displays a systolic or continuous murmur at the base or apex.
P waves left ventricular hypertrophy with left axis deviation, and A-V block is all seen on the ECG.
An X-ray of the chest reveals oligemic lung areas. The left heart has a significant preponderance. Because the right ventricle is non-existent or hypoplastic, the base of the heart is small and the right border is straight, as long as the right atrium is not dilated.
The appearance of significant cyanosis at birth is a defining feature of Truncus. A strong systolic murmur can be heard during auscultation.
If there is no accompanying pulmonary atresia, an X-ray will reveal cardiomegaly and oligemic lung fields.
TAPVR (total anomalous pulmonary venous return) is characterized by severe cyanosis caused by a right-to-left shunt. An ECG demonstrates right ventricular hypertrophy. There may or may not be an incomplete bundle branch block.
The Eisenmenger complex is defined by the reversal of the shunt from left to right to right-to-left in the presence of abnormalities such as ventricular septal or patent ductus arteriosus, resulting in severe cyanosis. The prognosis for this illness is poor.
Congestive Heart Failure
As a result of the delayed venous return, cyanosis is mostly peripheral. Right-sided elevated JVP, hepatomegaly, splenomegaly in newborns, edema, basal crepitations; left-sided tachypnea, orthopnea, chest retraction, cough, perspiration overhead in infants are the remaining signs of heart failure.
Cyanosis Related to Abnormal Hemoglobin
Methemoglobinemia can cause a blue tinge that is less vivid and more leaden than cyanosis, which is common in respiratory and cardiac diseases. Poisoning from nitrite aniline dyes or medicines that produce methemoglobinemia, such as phenacetin, sulfonamides, and dapsone, are among the causes in newborns. Nitrobenzene-based medications may be harmful to older children.
A defective hemoglobin M causes a disorder known as familial congenital methemoglobinemia. The inheritance pattern is autosomal dominant.
Diaphorase deficiency is an autosomal recessive cyanosis illness caused by a lack of NADH-methemoglobin reductase (diaphorase).
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