Ep 1: The Case of Baby Boy Blue Part 1: Neo Approach to the Cyanotic Newborn

Learning Objectives

By the end of this episode, NICU Grads will be able to:
1. Review the pathophysiology of cyanosis
2. Discuss how to approach the evaluation of cyanosis in a newborn

Guest Speaker
Ashley Lucke, MD, FAAP
Neonatologist, Chair of Trainees and Early Career Neonatologists (TECaN) Section on Neonatal Perinatal Medicine, #NavigatingNAS co-chair, @AAPSOPT Past Chair

Cyanosis

• Definition
  • 5 g/dL of deoxygenated hemoglobin in the capillaries generates the dark blue color appreciated 
• Peripheral vs Central cyanosis 
  • Peripheral Cyanosis aka acrocyanosis
    • Generally a common physiologic finding 
    • Limited to the extremities
  • Pathophysiology
    • In effort to increase tissue oxygen extraction to end organs, peripheral vasoconstriction occurs and acrocyanosis develops
  • Central cyanosis
    • Present throughout the body, especially in the mucous membranes and tongue
    • Indicates the presence of potentially serious and life-threatening disease
    • Requires immediate evaluation
• Factors that impact the presence of central cyanosis
  • Absolute concentration of reduced hemoglobin 
    • NOT affected by oxygen saturation or the ratio of reduced hemoglobin to oxyhemoglobin 
    • Polycythemic infant will achieve 5 g/dL of deoxygenated hemoglobin at relatively high arterial saturations and may exhibit cyanosis soon than anemic patient
    • Anemic infant will achieve 5 g/dL of deoxygenated hemoglobin at oxygen saturation that are extremely low
  • Type of hemoglobin (Fetal vs Adult Hemoglobin)
    • Fetal hemoglobin has higher affinity for oxygen
    • Resulting in a left shift in the oxygen saturation curve for fetal hemoglobin when compared to adult hemoglobin 
    • Infants with a high proportion of fetal hemoglobin may exhibit cyanosis later and at lower PaO2 levels than infants with more adult hemoglobin

• Central cyanosis is a reflection of: 
  • Poor oxygen delivery
  • Arterial hypoxemia
  • Low PaO2
• Differential for Central Cyanosis
  • Approach based on pathophysiology
    • #1 – High Altitude
    • #2 – Hypoventilation
    • #3 – Diffusion Disorder
    • #4 – Shunt
    • #5 – VQ Mismatch
• History
  • Assessment of the pregnancy, labor, and newborn risk factors, and delivery history to rule in/out differential diagnoses
• Physical Exam
  • Gestation
  • ABC
  • Vitals- Temp, HR, BP, O2 saturations
  • Growth characteristics 
  • Evidence of dysmorphic features
    • Dysmorphic features can result in a obstructive/ hypoventilation process
      • Ex: micrognathia, cleft palate, glossoptosis, etc
    • Can indicate there is genetic disorder/syndrome that may be associated diffusion disorders, shunts or VQ mistmatch
  • Respiratory exam 
    • Level of Respiratory Distress is KEY 
      • Absence of respiratory distress –> congenital heart disease or methemoglobinemia
      • Present of respiratory distress –> consider noncardiac etiology, including diffusion disorders or VQ mismatch disease processes
  • Cardiac exam 
    • Heart rate, peripheral pulses, perfusion, auscultation of the heart to identify presence of shunt
  • Neuro exam
    • Assess for hypoventilation with special focus on conciousness, activity, tone, reflexes, seizure activity
  • Evidence of birth trauma
    • Birth trauma can cause paralysis or respiratory depression
      • Ex: subdural hemorrhage, erb’s palsy, stridulous cry, etc
• Initial Delivery Room Evaluation
  • Pulse oximetry 
    • Non-invasive and continuous assessment of oxygen saturation
    • Location:
      • Right hand = reflection of flow patterns through the ductus arteriosus aka “preductal” saturations
      • Left hand can be pre or post ductal depending on location/origin of left subclavian artery in relation to ductus
      • Umbilical vein and legs are postductal samples/saturation
  • Hyperoxia test
    • Used historically to differentiate cardiac from noncardiac causes of neonatal cyanosis
    • The test is performed by measuring the PaO2 in the right radial artery (preductal) on room air and again after 10 minutes of supplementation with 100% oxygen
    • The hyperoxia test is interpreted as follows: 

References: 

1. Dasgupta S, Bhargava V, Huff M, Jiwani AK, Aly AM. Evaluation of The Cyanotic Newborn: Part I—A Neonatologist’s Perspective. Neoreviews. 2016;17(10):e598 LP-e604. doi:10.1542/neo.17-10-e598.
2. Dasgupta S, Bhargava V, Huff M, Jiwani AK, Aly AM. Evaluation of the cyanotic newborn: part 2—a cardiologist’s perspective. NeoReviews. 2016;17(10):e605-e620. doi: 10.1542/neo.17-10-e605.
3. Hua N, Yieh L, Dukhovny D, Armsby L. Important considerations in the management of newborns with cyanosis. Neoreviews. 2017;18(4):e258-e264. doi: 10.1542/neo.18-4-e258.
4. Martin TC. Reverse differential cyanosis: a treatable newborn cardiac emergency. NeoReviews. 2011;12(5):e270-e273. doi: 10.1542/neo.12-5-e270.
5. Richard J. Martin, Avroy A. Fanaroff, Michele C. Walsh. (2015). Fanaroff and Martin’s neonatal-perinatal medicine : diseases of the fetus and infant. Philadelphia, PA: Elsevier/Saunders.
6. Brodsky, Dara, and Camilia Martin. Brodsky and Martin’s Neonatology Review Series. 3rd ed., Lulu, 2020.
7. Brodsky, Dara. Neonatology Review: Q&A. 3rd ed., Lulu, 2016.
8. Chess, Patricia. Avery’s Neonatology Board Review: Certification and Clinical Refresher. 1 ed., Elsevier, 2019.
9. Polin, Richard A., and Mervin C. Yoder. Workbook in Practical Neonatology. 5th ed., Saunders, 2014.

Credits

• Written and Produced by: Neena Jube-Desai MD, MBA FAAP
• Cover Art and Infographic by: Neena Jube-Desai MD, MBA FAAP
• Host: Neena Jube-Desai MD, MBA FAAP
• Editor: Neena Jube-Desai MD, MBA FAAP
• Guest: Ashley Lucke, MD, FAAP