Approach To Neonatal CYANOSIS

Approach To Neonatal CYANOSIS

Cyanosis commonly divided into 2 :

• Central Cynosis
• Peripheral Cyanosis

Central cyanosis is a bluish discoloration of the skin, mucus membranes and tongue that is observed when deoxygenated hemoglobin is > 3g/dL in arterial blood or > 5g/dL (>3.1mmol/L) in capillary blood. It is associated with a low arterial partial pressure of oxygen (PaO2) and low hemoglobin oxygen saturation (SaO2) as measured by oxymetry. 

Another type of cyanosis, called peripheral cyanosis, involves a bluish discoloration of the skin but sparing of the mucus membranes & tongue. In this type, a normal PaO2 value is detected. In this case, increased oxygen extraction due to sluggish movement through the capillaries leads to increased deoxygenated blood on the venous side. Vasomotor instability, and vasoconstriction caused by cold, low cardiac output and polycythemia can all cause this slow movement through the capillaries.

Cyanosis is dependent on the absolute concentration of deoxy Hb, not on the ratio of oxy Hb/deoxy Hb. 

Peripheral cyanosis is often a normal finding in newborns, especially when only the extremities are affected (acrocyanosis) due to vasoconstriction as a result of transient hypothermia; however, it is important to rule out serious causes of peripheral cyanosis, such as sepsis.

History 

Explore pregnancy and labor history as suggested below. Also ask about family history of congenital heart disease and fetal ultrasound results, as the latter may reveal structural deformities such as congenital heart disease, diaphragmatic hernia and congenital cystic adenomatoid malformation (CCAM).

Pregnancy History ?

• Gestational diabetes mellitus (GDM) 
• Pregnancy induced hypertension 
• Lithium intake (1st trimester) 
• Advanced maternal age 
• Oligohydramnios 

Labour History ?

• PROM, fever, GBS +ve 
• Sedatives/anesthetics 
• C-section 
• Preterm infant 
• Meconium 

Associated causes of cyanosis ?

• Pulmonary hypoplasia
• TTN, RDS, hypoglycemia, TGA
• IUGR, polycythemia, hypoglycemia
• Ebstein’s anomaly
• Trisomy 21 associated with many congenital heart defects (cyanotic and acyanotic)
• Sepsis
• Respiratory depression, Apnea
• Transient tachypnea of the newborn 
• Persistent pulmonary hypertension of the newborn
• Respiratory Distress Syndrom
• Meconium Aspiration Syndrome(pneumonia)

Physical Examination

Determine whether the cyanosis is central or peripheral

Check the vitals: signs of respiratory distress such as tachypnea, retractions, nasal flaring & grunting usually indicate a respiratory problem.

• Congenital heart disease is often accompanied by absent or effortless tachypnea.
• Sepsis often has the following findings: peripheral cyanosis, HR, Increase RR, Decrease BP, Increase/Decrease temp (DDX: left-sided obstructive lesions: hypoplastic left heart syndrome, critical aortic stenosis & severe coarctation of the aorta).
• Rule out choanal atresia. If in doubt, attempt to insert a catheter through the nares

Inspection

• Dysmorphic features of genetic/congenital malformations (ie. Down’s syndrome is associated with endocardial cushion defects, Turner’s syndrome associated with coarctation of aorta)
• Look for the signs of peripheral (nail beds) and central (mucous membranes) cyanosis
• Differential cyanosis (oxygen saturation in lower limbs < upper limbs)

Cardiac Examination

• Heart rate, pulse oximetry, palpate central and peripheral pulses and/or measure blood pressure in upper and lower extremities
• Palpate for loud heart sounds, parasternal heave, apical impulse and thrill.
• Auscultate for abnormal (ie. single or widely split S2) and extra heart sounds and murmurs (Grade, timing, location, radiation, intensity and maneuvers)
• Signs of heart failure: parasternal heave and palpable P2 (pulmonary hypertension), elevated JVP, hepatomegaly, and peripheral edema (right-sided failure), displaced apical impulse (enlarged LV)

Listen for murmurs: a systolic murmur audible in most forms of cyanotic CHD (exception: d-TGA with intact ventricular septum & no pulmonary stenosis)

Respiratory Examination

• Observe for signs of respiratory distress like tachypnea, dyspnea (ie. accessory muscles, paradoxic diaphragm) and hypoventilation
• Palpate for asymmetric diaphragmatic expansion, and in older children percussion for consolidation, pleural effusions, and pneumothorax
• Auscultate for air entry, listen for rales/crackles (consistent with effusions and/or consolidation)
• Congestive heart failure: Poor air entry and dullness to percussion at the bases (pleural effusion), along with basal rales/crackles (pulmonary edema)

Assess the abdomen: scaphoid abdomen in diaphgragmatic hernia

Consider neurological disorders: observe for apnea and periodic breathing, which may be related to immaturity of the nervous system. Seizures can cause cyanosis if the infant fails to breathe during the episodes.

Differential Diagnosis

To determine the underlying cause of cyanosis in a newborn, it is important to think about the various mechanism of cyanosis. Then, organize your thoughts by anatomical systems.

Ventilation/perfusion mismatch

• Airway disease: transient tachypnea of the newborn (TTN), respiratory distress syndrome (RDS), pneumonia, aspiration (meconium, blood, amniotic fluid), atelectasis, diaphragmatic hernia, pulmonary hypoplasia, pulmonary hemorrhage, CCAM
• Extrinsic compression of the lungs: pneumothorax, pleural effusion, hemothorax

Right-to-left shunt

• Intracardiac: The 5 T’s: Tetralogy of Fallot, Tricuspid atresia, Transposition of the great arteries, Total anomalous pulmonary venous return, Truncus arteriosus; and pulmonary atresia, Ebsteins anomaly (abnormal tricuspid valve), hypoplastic left heart
• Great vessel level: persistent pulmonary, hypertension of the newborn
• Intrapulmonary level: pulmonary arteriovenous malformation

Alveolar Hypoventilation

• CNS depression: asphyxia, maternal sedation, intraventricular hemorrhage, seizure, meningitis, encephalitis
• Airway obstruction: choanal atresia, laryngomalacia, Pierre Robin syndrome
• Neuromuscular disease: phrenic nerve inury, neonatal myasthenia gravis

Diffusion Impairment

• Pulmonary edema: left-sided obstructive cardiac disease (aortic stenosis), cardiomyopathy
• Pulmonary fibrosis

Decrease Hemoglobin O2 affinity

• Methemoglobinemia (congenital, drugs)

Decrease Peripheral circulation (peripheral cyanosis)

• Sepsis, shock of any cause, polycythemia, hypothermia, hypoglycemia, low cardiac output(hypocalcemia, cardiomyopathies, etc)

Another way of approaching to neonatal cyanosis is to determine either cardiac or non cardiac causes of cyanosis. 

Non-Cardiac Causes of Neonatal Cyanosis

Differentiating Cyanotic Congenital Heart Lesions

Initial Management

• Monitor Airway, breathing, circulation (ABCs) with respiratory compromise, establish an airway & provide supportive therapy (e.g., oxygen, mechanical ventilation)
• Monitor Vital signs
• Establish vascular access for sampling blood & administering meds (if needed): umbilical vessels convenient for placement of intravenous & intraarterial catheters
• If sepsis is suspected or another specific cause is not identified, start on broad spectrum antibiotics (e.g., ampicillin and gentamycin) after obtaining a CBC, urinalysis, blood & urine cultures (if possible). Left untreated, sepsis may lead to pulmonary disease & left ventricular dysfunction.
• An infant who fails the hyperoxia test & does not have PPHN or a CXR showing pulmonary disease likely has a congenital heart defect that’s ductus-dependent. If cardiac disease is suspected, immediately start PGE1 infusion. Complications of PGE1 infusion include hypotension, tachycardia, apnea. Secure a separate intravenous catheter to provide fluids for resuscitation and ensure accessibility of intubation equipment should they be required.

Conclusion

Central cyanosis in a newborn is an abnormal finding and one must consider all of the possible etiologies with a complete history, physical examination and relevant investigations. 

Remember to think about the various mechanisms causing cyanosis and go through each systematically until you have your diagnosis. Prompt management should be undertaken while you are trying to figure out your diagnosis. Putting all of this together, you will be sure not to miss an important diagnosis and keep your patient safe at the same time.

Source :www.learnpediatrics.com