Approach to a neonate with cyanosis

Approach to a Neonate with Cyanosis

Dr. Sunil Agrawal

1st yr MD pediatrics

Contents

• Introduction• Central, Peripheral and Differential cyanosis• Mechanism• Etiology• Approach• Principles of Treatment• Conclusion• References

Introduction

• Bluish discoloration of the tissues that results when the absolute level of reduced hemoglobin in the capillary bed exceeds 3 g/dL

• Depends upon the total amount of reduced hemoglobin rather than the ratio of reduced to oxygenated hemoglobin.

Central cyanosis

• Pathologic condition caused by reduced arterial oxygen saturation.

• Involves highly vascularized tissues, such as the lips and mucous membranes, through which blood flow is brisk and the arteriovenous difference is minimal.

• Cardiac output typically is normal, and patients have warm extremities.

Peripheral cyanosis

• Normal systemic arterial oxygen saturation and increased oxygen extraction, resulting in a wide systemic arteriovenous oxygen difference

• The increased extraction of oxygen results from sluggish movement of blood through the capillary circulation

Peripheral cyanosis

• Causes-– vasomotor instability, vasoconstriction caused

by exposure to cold, venous obstruction, elevated venous pressure, polycythemia, and low cardiac output

• Affects the distal extremities and circumoral or periorbital areas .

Differential cyanosis

• Upper half of the body is pink and the lower half cyanotic, or vice versa

• Requires pulmonary vascular resistance elevated to a systemic level and a patent ductus arteriosus.

Mechanism of cyanosis

• Alveolar hypoventilation

• Diffusion impairment

• Ventilation-perfusion mismatch

• Right-to-left shunting at the intracardiac, great vessel, or intrapulmonary level

• Hemoglobinopathy (including methemoglobinemia) that limits oxygen transport

Factors affecting the detection of cyanosis in the newborn

• Hemoglobin concentration -– Detected at higher levels of saturation in

polycythemic than in anemic patients.

– Significant oxygen desaturation can be present in an anemic patient without clinically detectable cyanosis.

The arterial oxygen saturation level at which cyanosis is detectable at different total hemoglobin concentrations is illustrated above. The solid red portion of each bar represents 3 gm/dL reduced hemoglobin. Reproduced with permission from: Lees, MH. Cyanosis of the newborn infant. J Pediatr 1970; 77:484.


• Fetal hemoglobin — – Binds oxygen more avidly than adult hemoglobin. – The oxygen dissociation curve is shifted to the left, so

that for a given level of oxygen tension (PO2), the oxygen saturation (SO2) is higher in the newborn than older infants or adults

– It also follows that for a given level of oxygen saturation, the PO2 is lower in newborns.

– As a result, cyanosis is detected at a lower PO2 in newborns compared with older patients. Thus, in evaluating a cyanotic newborn, PO2 should be measured in addition to SO2 to provide more complete data.


• Other physiologic factors common in sick newborns affect the oxygen dissociation curve.

The oxygen-dissociation curve of human blood and the effects of changes in the H+ ion concentration, Pco2 temperature and level of 2, 3-diposphoglycerate (2,3-DPG) are depicted above. For fetal hemoglobin, the normal curve (a) is shifted to the left (b). Reproduced with permission from: Levin, AR. Management of the cyanotic newborn. Ped Ann 1981; 10:127. Copyriht ©1981 SLACK, Inc.


• Skin pigmentation -– Less apparent in the skin of patients with

darker pigmentation. – Examination should include the nail beds,

tongue, and mucous membranes, which are less affected by pigmentation.

Etiology

Non- cardiac causes

• Alveolar hypoventilation – Central nervous system depression: asphyxia,

maternal sedation, intraventricular hemorrhage, seizure, meningitis, encephalitis

– Neuromuscular disease: Werdnig-Hoffman disease, neonatal myasthenia gravis, phrenic nerve injury

– Airway obstruction: choanal atresia, laryngotracheomalacia, macroglossia, Pierre Robin syndrome

Non- cardiac causes

• Ventilation/perfusion mismatch – Airway disease: pneumonia, aspiration, cystic

adenomatoid malformation, diaphragmatic hernia, pulmonary hypoplasia, labor emphysema, atelectasis, pulmonary hemorrhage, hyaline membrane disease, transient tachypnea of the newborn

– Extrinsic compression of lungs: pneumothorax, pleural effusion, chylothorax, hemothorax, thoracic dystrophy

Non-cardiac causes

• Hemoglobinopathy – Methemoglobinemia: congenital or secondary to toxic

exposure – Other hemoglobinopathies

• Diffusion impairment – Pulmonary edema: left-sided obstructive cardiac

disease, cardiomyopathy – Pulmonary fibrosis – Congenital lymphangiectasia

Cardiac causes

• Decreased pulmonary blood flow-– Tetralogy of Fallot– Tricuspid valve anomaly– Pulmonary valve atresia– Critical valvular pulmonary steanosis

• Increased pulmonary blood flow-– Transposition of great arteries– Truncus arteriosus– Total anomalous pulmonary venous connection

Cardiac causes

• Severe heart failure-– Hypoplastic left heart syndrome– Coarctation of the aorta– Interrupted aortic arch– Critical valvular aortic steanosis

Mnemonic

• Cardiac causes- "five Ts" of cyanotic CHD: – Transposition of the great arteries – Tetralogy of Fallot – Truncus arteriosus – Total anomalous pulmonary venous connection – Tricuspid valve abnormalities.

• A sixth "T" is often added for "tons" of other diseases, such as double outlet right ventricle, pulmonary atresia, multiple variations of single ventricle, hypoplastic left heart syndrome, or anomalous systemic venous connection (left superior vena cava connected to the left atrium).


• With normally related great arteries, oxygen saturation may be higher in the upper than lower extremity in patients if there is right-to-left shunting through the ductus arteriosus.

• Seen with severe coarctation or interrupted aortic arch.

• May also occur in patients persistent pulmonary hypertension of the newborn

• The differential effect is reduced if there is also right-to-left shunting at the level of the foramen ovale, or if there is left-to-right shunting across a coexisting ventricular septal defect


• Reversed differential cyanosis is a rare finding that may occur in patients with transposition of the great arteries associated with either coarctation or pulmonary hypertension.

• In these infants, oxygen saturation is higher in the lower than upper extremity.

Approach

Aim

• Differentiate physiologic from pathologic cyanosis

• Differentiate cardiac from non- cardiac cause of cyanosis

• Find cause which needs urgent treatment or referral

Not so serious

• Acrocyanosis– Bluish color in the hands and feet and around the

mouth (circumoral cyanosis). The mucus membranes generally remain pink.

– Reflects benign vasomotor changes in the diffuse venous structures in the affected areas.

– Does not indicate pathology unless cardiac output is extremely low, resulting in cutaneous vasoconstriction

• Cyanosis soon after birth- transition from intrauterine to extrauterine life

• Hand or leg prolapse

Perinatal history

• Drug intake – Causing neonatal depression– Lithium- Ebstein anomaly– Phenytoin- PS and AS

• Maternal diabetes-– TGA, ventricular septal defect (VSD), and

hypertrophic cardiomyopathy

• Connective tissue disorder- Heart blocks• Congenital intrauterine infections• Antenatal fetal echocardiography

History

• Methemoglobinemia may be acquired following exposure to aniline dyes, nitrobenzene, nitrites, and nitrates.

Onset of cyanosis in cardiac lesions-

• Depends on-– Nature and severity of the anatomic defect– In utero effects of the structural lesion– Alterations in cardiovascular physiology

secondary to the effects of transitional circulation like closure of ductus arteriosus and the fall in pulmonary vascular resistance

Onset of cyanosis in cardiac lesions

Age on admission In order of frequency

0-6 days D- transposition of great arteries

Hypoplastic left ventricles

Tetralogy of fallot

7-13 days Coarctation of aorta

Hypoplastic left ventricle

D-transposition of great arteries

Tetralogy of fallot

14-28 days Coarctation of aorta

Tetralogy of fallot

D- transposition of great arteries

Neonatology- Pathophysiology and management of newborn, 5th edition ed. 1999. Philadelphia; Lippincott Williams and Wilkins

History- Risk factors • Pneumonia/ sepsis-

– PROM– Foul smelling liquor– Maternal pyrexia– Maternal GBS

• TTN –– Birth by cesarean section

with or without labor– Male sex– Family history of asthma

(especially in mother)– Macrosomia– Maternal diabetes

• Polycythemia-– small-for-gestational age

• MAS-– Post maturity– Small for gestational age– Placental dysfunction– Fetal distress– Meconium stained liquor

• Pneumothorax-– Aggressive resucitation– IPPV– Meconiun aspiration– HMD– Hypoplastic lung– Staph pneumonia

• Hyaline membrane disease-– Premature infant– Infant of diabetic mother

History

• Choanal atresia- – Cyanosis decreases during crying– Confirmed by failure to pass a soft No. 5F to

8F catheter through each nostril

Physical Examination

• Vital signs-

– Hypothermia or hyperthermia- infection.

– Tachycardia-hypovolemia.

– Weak pulses- Hypoplastic left heart syndrome or hypovolemia.

– Pulses or blood pressures stronger in the upper than in the lower extremities- coarctation of the aorta.


• Congenital heart disease-– Respirations often are unlabored unless there is

pulmonary congestion or complicated by the development of heart failure or acidosis, which will affect the respiratory pattern.

• CVS-– Presence or absence of a heart murmur is of little

assistance. Loud S2 suggests pulmonary or systemic hypertension or malposition of the aorta.

•

Physical Examination• Inspiratory stridor-

– upper airway obstruction

• Chest-– Asymmetric chest movement combined with

severe distress- • alarming sign for tension pneumothorax,

diaphragmatic hernia

– Transillumination of the chest-• Pneumothorax on an emergent basis


P/A-– Scaphoid abdomen

• Congenital diaphragmatic hernia

– Hepatosplenomegaly-• congestive heart failure, maternal diabetes,

or congenital infection.


• Central nervous depression-– Causes shallow, irregular respirations and

periods of apnea.– Affected infants typically appear hypotonic

and lethargic.

Pulse oximetry screening

• Difficulty in visual detection of cyanosis• Potentially severe consequences of missing an

early sign of CHD• “5th vital sign”• Sensitivity and specificity varies-

– Criteria used for abnormal test– Timing of screening– Probe site– Quality of the equipment– Signal quality and neonate behaviour– Health care workers expertise

Pulse Oximetry

• Oxygen saturation should be performed initially on room air to serve as a baseline.

• Subsequently can be served to differentiate between cardiogenic and non-cardiogenic causes

Limitations of pulse oximetry

• effects of ambient light

• skin pigmentation

• dyshemoglobinemia

• low peripheral perfusion states

• motion artifact

Hyperoxia test• If a low-pulse oximeter reading persists, it

may be appropriate to proceed to a hyperoxia test. It is indicated if the pulse oximeter reading is less than 85% in both room air and 100% oxygen

• It is not recommended in preterm infants. • Useful in distinguishing cardiac from

pulmonary causes of cyanosis.

Hyperoxia test

• Arterial oxygen tension is measured in the right radial artery (preductal) and in a lower extremity artery while the patient breathes 100 percent oxygen (postductal).

• Pulse oximetry cannot be used- in neonate given 100% inspired O2 a value of 100% saturation may be obtained with an arterial PO2 ranging from 80 torr( abnormal) to 680 torr (normal)

Hyperoxia test

Disease Result- Increase in PaO2

Lung disease is more likely than CHD

>150 mmHg

TGA or severe pulmonary outflow obstruction

<50 to 60 mmHg

In lesions with intracardiac mixing and increased pulmonary blood flow such as truncus arteriosus-

>75 to 150 mmHg


• To detect differential cyanosis, oxygen saturation should be measured in sites that receive blood flow from both preductal (right hand) and postductal (foot) vessels. It is preferable to use the right (rather than left) upper extremity, since the left subclavian artery arises close to the ductus arteriosus, and some of its flow may come from the ductus and thus not reflect preductal values

Investigation

• Hematocrit or hemoglobin• Sepsis screening• Blood glucose concentration• Arterial blood gases (Pao2, Paco2, pH)• Blood cultures• Electrocardiography• Echocardiography, cardiac catheterisation,

angiocardiography• Hemoglobin electrophoresis- Hb M

Chest X-Ray

• Aberrancy of the cardiothymic silhouette- – Suggest the presence of structural heart

disease, and – Abnormalities of the lung fields may be helpful

in distinguishing a primary pulmonary problem such as meconium aspiration

Chest X- Ray

• Pulmonary vascular markings-– Decreased in CHD with obstructed pulmonary

blood flow such as tetralogy of Fallot, severe pulmonary stenosis or atresia, and tricuspid atresia.

– Increased in admixture lesions like transposition of the great arteries, total anomalous pulmonary venous connection, and truncus arteriosus.

Total Anomalous Pulmonary Venous Return

• Snowman

Tetralogy of Fallot

• Boot shape

Transposition of Great Arteries

• Egg on a string

Investigation

• If central cause-– appropriate scan and drug levels

• Methemoglobinemia- – Place few drops of pt blood on filter paper– Appear chocolate brown

Treatment

• Goals-– Provide adequate tissue oxygen and CO2

removal

• Principles-– Establish airway– Ensure oxygenation– Ensure adequate ventilation– Correct metabolic abnormalities– Alleviate the cause of respiratory distress

Treatment- Buy time

• Prostaglandin E1– For ductal dependant CHD/ reduced

pulmonary blood flow- Fail hyperoxia test( An arterial PO2 of less than 100 torr in the absence of clear- cut lung disease)

– Infusion of prostaglandin E1 at a dose of 0.05- 0.1mcg/kg/min intravenously to maintain patency

Treatment- buy time

• Prostaglandin E1-– S/E- hypoventilation, apnea, edema and low

grade fever– Benefits- Can be stabilized more easily,

allowing for safe transport to a tertiary care center. More time is also available for thorough diagnostic evaluation and patients can be brought to surgery in a more stable condition.

Conclusion

• Identify those that are life-threatening. • complete maternal and newborn history• perform a thorough physical examination• recognize the common respiratory and

cardiac disorders• differentiate among various diagnostic

entities• For ductal dependent lesion, start

prostaglandin E1 and early referral

References

• Nelson textbook of pediatrics• Cloherty manual of neonatal care• Approach To Cyanotic Heart Disease In The First Month

Of Life , Harry J. D'Agostino, Jr., M.D. and Eric L. Ceithaml, M.D.

• Pediatrics in Review. 1999;20:350-352.)© 1999, Consultation with the Specialist, Nonrespiratory Cyanosis, Jon Tingelstad, MD

• UpToDate

Health & Medicine

Approach to a neonate with cyanosis