Hypercyanotic Spells


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

Sean M. Fox
Sean M. Fox

I enjoy taking care of patients and I finding it endlessly rewarding to help train others to do the same. I trained at the Combined Emergency Medicine and Pediatrics residency program at University of Maryland, where I had the tremendous fortune of learning from world renowned educators and clinicians. Now I have the unbelievable honor of working with an unbelievably gifted group of practitioners at Carolinas Medical Center. I strive every day to inspire my residents as much as they inspire me.

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  1. Good presentation 👍 am having a patient 2 years old you have helped me alot.

    • Epinephrine can cause both vasoconstriction (mediated by Alpha1 Receptor) and vasodilation (mediated by Beta2 Receptor). The overall effect is often dose dependent, because beta2 receptors are more sensitive to epinephrine. At low doses, vasodilation more avidly than constriction. So, you can actually have a reduction in SVR with initial doses of epinephrine. Yes… it will eventually clamp everything down and increase SVR, but for TET Spell, there are better options.

  2. Morphine is always available in the Adults Emergency (used in MI), so it is a matter of co-ordination.

  3. Good after noon Dr.Fox, excellent review mixed with witty comments. Nice stratification of the severity of the problem. From general measures – IM – IV. now i can add ETT
    If the child presents with convulsions, posturing, depressed level of consciousness, shock or if develops during the course of treatment don’t delay to intubation and ventilation. Thanks

  4. Just the content I needed to learn.Very comprehensive yet precise presentation.I love the way you have presented it with the background of targets of management…goo luck for your future endeavors .love from Sri lanka

  5. Dose of oral propanolol? As I/v not available….also morphine not available…. alternative?

    • It can’t be overstated how important the knee to chest or transabdominal aortic compression is. You must increase SVR to encourage blood to flow through that PA.
      NO IV? Be calm, let the parents hold the kid against their chest forward facing (ergobaby style) in knee to chest. Give 1-2mcg/kg intranasal fentanyl -or- 0.2mg/kg intranasal versed or 3mg/kg intranasal ketamine, or give the ketamine or morphine IM to calm/decrease hyperpnea and then get the IV/IO and then give 20cc/kg NS bolus- increases preload and more importantly, afterload/SVR.
      Most spells will resolve without the use of the B-blocker (after all, most spells happen AT HOME and resolve w/ parents comforting their child). The b-blocker may help, but the single most important action is to calm the kid and increase SVR.

  6. Thanks for the educative write up.
    The challenge we have is unavailability of I.v propranolol, so we increase the dose of oral form during a spell.
    Does iron deficiency have a role in recurrent spells?

  7. Very apt and precise post on TOF. I would want to know the causes of death in a child with intractable tet spell

  8. lovely and educative write up on Hypercyanotic spells.I want to know if you have had any experience with the use of IV Metroprolol in severe hypercyanotic spells.

  9. good day thanks for the information
    does promethazine have a role in the management of cyanotic spells

  10. If pt is infant .how can we make knee chest position????!and if inj morphine not available.its alternate and dose??!(0.1mg/kg)????

    • Dr. Sabir,
      For the very young, you can place the child supine and manually flex hips and put child in Knee-Chest position.

      Morphine dose – I’d start with 0.05-0.1mg/kg.

      Thank you,

  11. Hi, I think your website might be having browser compatibility issues.
    When I look at your blog in Chrome, it looks fine but when opening in Internet Explorer, it has some overlapping.
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  12. Any thoughts on using intranasal fentanyl/midazolam to calm the kid while avoiding a poke (used instead of the IM morhpine in this example)? Thanks.

  13. […] Systolic BP Guide, use of PGE1, Syncope, Subtle signs of heart failure, Complications of fontans, Hypercyanotic spells, and Coarctation of the Aorta just to name a few), we should take a minute to discuss one of the […]

  14. 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.

    • 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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