Cyanosis in newborns

Cyanosis in newborns Microchapters
Overview
Historical Perspective
Classification
Pathophysiology
Causes
Epidemiology and Demographics
Risk factors
Natural History, Complications, and Prognosis
Diagnosis
Treatment
Prevention

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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1] Associate Editor(s)-in-Chief: Ifeoma Anaya, M.D.[2]

Synonyms and keywords: Acrocyanosis; central cyanosis

Overview

Cyanosis is derived from the word kuaneos which is Greek for dark blue. It is categorized into two major types: peripheral and central cyanosis. Cyanosis is observed with an increase in the absolute concentration of deoxygenated hemoglobin to a level of 3-5g/dl. A structured way of grouping the common causes of cyanosis in newborns is by using the ABC which stands for Airway, Breathing, and Circulation. Persistent pulmonary hypertension of the newborn and congenital heart diseases (CHD) are the common causes of newborn cyanosis. Common risk factors in the development of cyanosis in newborns are evident in the pregnancy and labor period. Prompt recognition, and administration of treatment modalities, with appropriate referral to the ideal hospital setting equipped to manage the diagnosis, can improve the prognosis. The primary symptom is the bluish/dark colored lips, mucous membrane, and/or hands and feet. Patients can have breathing difficulties which can be seen as nasal flaring and chest retractions. Findings from exam include lethargy, conjunctival injection, features of shock, and tachypnea. Laboratory findings include a complete blood count, and differentials showing packed cell volume (PCV) suggesting polycythemia, and white cell count (septicemia). ECG is used seldomly, however, it may aid in the diagnosis of arrhythmias and dextrocardia. X-rays can show pulmonary causes such as pulmonary hypoplasia and increased lung vascular markings in pulmonary edema, and bronchopneumonia. Echocardiography can be used when the diagnosis is equivocal or when physical exam findings and/or failed hyperoxia test suggests the presence of congenital heart disease. There are other imaging techniques used as adjuncts to making diagnoses. The immediate priority is to optimize the neonate, especially in severe cyanosis. Surgery is employed for more definitive treatment. The preventive measures that can be adopted include pre-conceptual counseling for expectant mothers especially women who are above the age of 35 years, routine prenatal and postnatal care for early detection of congenital anomalies, and adequate preparedness for its management during pregnancy, labor, and delivery.

Historical Perspective

• Cyanosis is derived from the word kuaneos which is Greek for dark blue. This is a result of the bluish discoloration of the skin or mucous membranes depending on the etiology.

Classification

• Cyanosis is classified into two major types:
  • Peripheral Cyanosis (acrocyanosis) seen on the hands and feet and mostly physiological.
  • Central cyanosis, considered to be pathological requiring prompt evaluation.

Pathophysiology

• Central cyanosis occurs as a result of an increase in the absolute concentration of deoxygenated hemoglobin to 3-5 g/dl. Deoxygenated hemoglobin is dusky blue or purple, which causes the discoloration seen in skin and mucous membranes as compared to the bright red oxyhemoglobin.
• Oxygen is transported in blood predominantly attached to hemoglobin while an insignificant amount is transported dissolved in plasma. Sufficient tissue perfusion relies on the concentration of saturated hemoglobin.
• With high hemoglobin concentrations (normal relative polycythemia,14-20 g/dl) seen in normal infants, cyanosis becomes apparent at higher PaO2 (partial pressure of oxygen) compared to the setting of severe anemia, whereas a far lower PaO2 leads to clinically recognizable cyanosis due to very low hemoglobin concentration. Therefore, cyanosis depends on the concentration of deoxygenated hemoglobin and not merely oxygen saturation. As an example, a neonate with a hemoglobin concentration of 24 g/dl exhibits signs of central cyanosis at 88% arterial saturation (SaO2) while cyanosis isn't clinically obvious in an anemic infant until SaO2 falls to about 62%.
• Oxygen binding capacities differ between fetal and adult hemoglobin. If a newborn has mostly adult hemoglobin, cyanosis would be observed at an elevated PaO2 of 42-53 mmHg which is comparable to SaO2 of 75%-85% as opposed to the predominantly fetal hemoglobin (PaO2 of 32-42 mmHg); infants have varied proportions of adult and fetal hemoglobin. Therefore, a major reduction in PaO2 would have set in before cyanosis becomes apparent in a newborn with elevated fetal hemoglobin, a setting that shifts the oxygen-hemoglobin dissociation curve to the left.
• Several changes occur in the newborn from the first breath. Blood flow resistance decreases within the pulmonary vasculature as a result of a rise in oxygen tension; this increase in oxygen tension and pulmonary circulation causes functional closure of the patent ductus arteriosus (PDA). Raised left atrial pressures closes the foramen ovale. The events resulting in the closures of these shunts invariably abolishes the right-to-left shunts of the precedent fetal circulation. The first breath also causes a net absorption of the fluid from the lungs, causing its expansion and successfully initiates the gaseous exchange. Furthermore, removal of the low-pressure placental bed causes a rise in blood flow resistance of the systemic vasculature. These are the traditional physiological changes observed in a normal neonate after birth.
• Deviations from these may result in pathological conditions requiring immediate interventions; infants, especially those born prematurely, would require medical assistance for this phenomenal transition.
• In peripheral cyanosis, there's normal SaO2 with a rise in oxygen uptake by the tissues leading to a wide arteriovenous difference within the venous aspect of the capillaries. Vasoconstriction could be a cause. This kind of cyanosis is seen majorly at the extremities.

Causes

• A structured way of grouping the common causes of cyanosis in newborns is by using the ABC which stands for Airway, Breathing, and Circulation.

Epidemiology and Demographics

• Persistent pulmonary hypertension of the newborn and Congenital heart diseases (CHD) are the common causes of newborn cyanosis. Common in older kids are respiratory diseases.
• Tetralogy of Fallot (TOF) followed closely by the Transposition of Great Arteries (TGA) are the commonest causes of CHD.

Age

• Newborns are more prone to cyanosis due to the peculiarities of birth and the changes that occur during the transition from fetal to neonatal life and/or due to congenital or acquired disorders.

Risk Factors

• Common risk factors for the development of cyanosis in newborns are evident in the pregnancy and labor period.
• Pregnancy-related risk factors include:
  • Advanced age of the mother
  • Pregnancy-induced hypertension
  • Gestational diabetes
  • Intake of Lithium (Ebstein's anomaly)
  • Oligohydramnios
  • Polyhydramnios
• Labor and birth-related risk factors include:
  • Cesarean section
  • Preterm/prematurity
  • Use of anesthetic drugs and/or sedatives
  • Premature rupture of membranes (PROM)
  • Meconium aspiration
  • Difficult/assisted vaginal delivery

Natural History, Complications and Prognosis

• Potential complications seen in these patients can include:
  • Stroke
  • Sudden Cardiac Arrest
  • Repeated respiratory tract infections in infants with unrepaired heart defects which can be severe
  • Developmental delays ranging from motor to cognitive
  • Various forms of disabilities
  • Arrhythmias
  • Heart failure
• Prompt recognition, and administration of treatment modalities, with appropriate referral to the ideal hospital setting equipped to manage the diagnosis, can improve the prognosis.
• Mortality is high in newborns with critical CHD however, there has been an encouraging improvement in one-year survival to 75% following advances in treatment. 69% of these babies can survive to the age of 18 years.

Diagnosis

Symptoms

• Primary symptom is the bluish/dark colored lips, mucous membranes, and/or hands and feet
• Other symptoms include the following:
  • Breathing difficulties evident as:
    • Nasal flaring
    • Chest retractions
    • Fast breathing
    • Slow breathing
    • Irregular breathing
    • History of momentary cessations of breathing
  • Pausing/excessive sweating or crying while feeding
  • Small volume of feeds
  • Small for age/poor weight gain
  • Large for age
  • Fixed/immobile arms suggesting paralysis from birth trauma
  • Increasing head circumference with\without scalp injuries resulting from a difficult delivery
  • Hypo/hyperactive child

Physical Examination

• Patients usually appear cyanotic.
• Depending on the underlying etiology, other examination findings may include the following:
  • Lethargy
  • Conjunctival injection
  • Features of shock
  • Tachypnea
  • Periodic breathing
  • Apneic spells
  • Use of accessory muscles of respiration
  • Flaring of the alar nasa
  • Tube or catheter carefully inserted into the nasal cavity if suspicion is high for choanal atresia
  • Tachycardia
  • Abnormal heart sounds/murmurs
  • Weak peripheral pulses especially femoral pulse
  • Fine crackles in lower lung fields
  • Hepatomegaly
  • Scaphoid abdomen (in diaphragmatic hernia)
  • Erb's paralysis
  • Scalp injuries
  • Seizures

Laboratory Findings

• Complete blood count and differentials:
  • Increased packed cell volume (PCV)- polycythemia
  • Increased white cell count- septicemia
• Complete metabolic panel- electrolyte imbalance (metabolic acidosis)
• Serum glucose- hypo or hyperglycemia
• Hyperoxia Test- differentiates pulmonary from a cardiovascular cause. An increase in PaO2 to a 100 mmHg or more after administering 100% oxygen suggests a pulmonary etiology. Seldom used due to the availability of echocardiography.
• Arterial Blood Gases (ABGs)
  • PaCO2, ↑ suggests hypoventilation of CNS, pulmonary or cardiac etiology.
  • PaO2, ↓ confirms cyanosis
  • PH, a ↓ pH suggests hypoxemia,or/and sepsis
  • 'Chocolate-brown' color of blood with normal levels of PaO2 and reduced SaO2 methemoglobinemia

Electrocardiogram

• It is seldom used, however, may be helpful in the diagnosis of arrhythmias and dextrocardia to show a left axis deviation seen in tricuspid atresia due to left ventricular hypertrophy.
• It could give a normal reading in very serious heart defects such as TGA.

X-ray

• Can identify:
  • Pulmonary causes such as pulmonary hypoplasia
  • Increased lung vascular markings in pulmonary edema, bronchopneumonia
  • Reduced pulmonary markings in pulmonary atresia, pulmonary stenosis, and persistent pulmonary hypertension of newborns
  • Location of abdominal contents in diaphragmatic hernia
  • Elevation of the affected hemidiaphragm in phrenic nerve injury
  • Cystic adenomatoid malformation
• Characteristic features of some congenital heart diseases may be seen such as:
  • 'Snowman' or 'Figure 8' in TAPVR
  • 'Boot-shaped heart' in TOF
  • 'Egg-on-string' in TGA
  • Cardiomegaly in Ebstein's anomaly

Echocardiography or Ultrasound

• Can be used when the diagnosis is equivocal or when physical exam findings and/or failed hyperoxia test suggests the presence of congenital heart disease.
• It is usually used with doppler to define the direction of shunts.

CT scan

• Used as an adjunct to further define cardiac and other anatomical anomalies in preparation for the definitive management.

MRI

• Used as an adjunct to further define cardiac and other anatomical anomalies in preparation for the definitive management.

Other Imaging Findings

• Cardiac catheterization and angiography:
  • Sometimes used as an adjunct to further define cardiac and other anatomical anomalies in preparation for the definitive management.

Other Diagnostic Studies

• Pre-ductal and post-ductal PaO2 measurements.

Treatment

Medical Therapy

• The immediate priority is to optimize the neonate, especially in severe cyanosis. This includes:
  • Establishing assisted ventilation in respiratory distress.
  • Keep infant in a radiant warmer.
  • Stop all per oral feeds and give intravenous fluids through peripheral or central access such as umbilical vein.
  • Give glucose for hypoglycemic infants and monitor serum glucose levels.
  • Consult should be sent to the neonatologist.
  • Oxygen administration should be done with caution. Care must be taken not to begin with very high concentrations of 100% due to damage to the lung tissue and pulmonary vessels.
  • Prostaglandin E1 (PGE1) given as an infusion to keep the ductus patent for pulmonary blood flow in CHDs.
  • Definitive treatment can be planned in stages once infant is optimized and a diagnosis has been made.
  • Antibiotics coverage for sepsis if suspected, after blood samples are taken for culture and sensitivity, and urine samples have been collected.

Surgery

• This a treatment modality for diagnoses associated with anatomic deformities in CHDs or airway obstructions.
• Surgical treatment is tailored to the underlying cause of cyanosis that requires surgical intervention. An example is a Balloon Atrial Septostomy for acute TGA allowing for blood mixing.

Prevention

• Prevention can be challenging as some of its causes are prevalent in-utero before the birth of child while others occur during the actual labor and birthing process.
• The preventive measures that can be adopted include:
• Counsel expectant mothers especially women who are above the age of 35 years.
• Routine prenatal and postnatal care for early detection of congenital anomalies and adequate preparedness for its management during pregnancy, labor, and delivery.
• Early detection and management of gestational diabetes and pregnancy-induced hypertension.
• Parents of a child with congenital malformations should be counseled on the risk of having another child with the same or similar deformities.
• Prophylaxis against respiratory syncytial virus (RSV).
• Follow up for polycythemia, excessive dehydration, and iron-deficiency anemia.