Hypercyanotic Spells

Blue Baby


We are all familiar with Tetralogy of Fallot, primarily because it is a great topic for test writers to torture us with questions about.  One of the cool things about pediatric cardiology is that it really makes you consider physiology and plumbing… ok… maybe I’m just a geek.  But, before you judge me too harshly, let us consider the Hypercyanotic Spell (aka, ‘Tet spell’).

Hypercyanotic Spell Basics

  1. Paroxysmal hypoxemic events, that can lead to quite heroically low oxygen saturations (today the kid in the ED had an initial sat of 20 – that’s on the “low-ish” side I think).
  2. Don’t only occur in patients with Tetralogy of Fallot.
  3. Can be in other cyanotic heart lesions with VSD and decreased pulmonary blood flow.
  4. Occur do to:
    1. Reduced Pulmonary Blood Flow (PBF)
      1. Recall that with VSD and pulmonary artery stenosis, PBF will be affected by pulmonary vascular resistance (PVR) and systemic vascular resistence (SVR).
      2. Anything that will increase PVR or decrease SVR will decrease pulmonary blood flow (shunt more blood to systemic side).
      3. Additionally, preload and afterload play a significant role
      4. Low preload and/or low afterload states will lead to decreased PBF also.
    2. Unfortunately, the hypoxia leads to increased PVR itself, thus perpetuating the problem.

Common precipitation events:

  1. Crying
  2. Defecation
  3. Feeding
  4. Awakening from naps
  5. Fevers
  6. Dehydration
  7. Tachycardia (decreased filling time leads to reduced end diastolic volume)
  8. Medications (ACE inhibitors)

Management of Hypercyanotic Spell – Decrease PVR, Increase SVR, Improve PBF.

  1. Knee-Chest Position (increases Preload and increases SVR)
    • Can even compress abdominal aorta to increase SVR more.
  2. Calm the child
    • Ideally having the child in family member’s lap would be best… but not always possible.
  3. Oxygen
    • Realizing that oxygen is a medicine! Try to determine what the patient’s baseline oxygen saturations should be.
    • Oxygen will help decrease PVR.
  4. Morphine (calms, decreased tachypnea, and also decreases PVR)
    • With more minor events, IM would be preferred, as you will not cause more crying with IV placement…

If those are not working… time to advance care!

  1. Place IV for Normal Saline Bolus
    • Improve Preload and End Diastolic Volume of right ventricle.
    • Now you have an IV… and can give more Morphine IV
  2. Ketamine
    • I am always looking for new reasons to use ketamine… !
    • This will calm the child as well as increase SVR.
  3. Propranolol / Esmolol
    • Thought to decrease infundibular obstruction
    • Decreases tachycardia leading to greater diastolic filling
  4. Phenylephrine
    • Alpha-adrenergic med that will increase SVR
    • Generally used as last line medication
  5. Bicarb
    • To correct any metabolic acidosis, if present.
  • AVOID Epinephrine and isoproterenol – as these will decrease SVR!


Van Roeken s CN, Zuckerberg AL. Emergency management of hypercyanotic crises in tetralogy of Fallot. Ann Emerg Med. 1995 Feb; 25(2): 256-8.

“Tetralogy of Fallot” in Best Practice: BMJ.

“Hyper-cyanotic Spell: Management” in Cardioap.org. http://www.cardioiap.org/Hyper_cyanotic_Spell.aspx


  1. Radhika says:

    Conscise yet comprehensive -can add a chart on pathophysiology for completion

  2. Jacob says:

    Great post, thanks. You might clarify what “infundibulum” you mean. I assume it’s the right ventricular outflow tract, but it could also possibly mean the terminal bronchiole just before reaching the alveolus. There are a lot more infundibula in the body also.

    • Sean Fox says:

      Yes, you are correct… there are many infundibula in the body (by the way, “infundibula” is a fun word to say)… but in this case I was referring to the one in the outflow tract. Thank you for keeping me on my toes.

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