A 2 month old boy is brought into the resus room of your community hospital looking completely blue. The mother rather anxiously states that they have been followed at the large pediatric hospital for Tetralogy of Fallot and are awaiting elective repair. Now their child is completely blue, and you were the closest hospital. They were warned about “spells” but can’t remember what to do. The child appears severely cyanotic, is crying loudly, and the nurses are unable to get a saturation reading for you. How do you manage a ‘tet spell’?
The management of Tet Spells was actually the first ever post on First10EM, way back in 2015. The management plan has not actually changed much, but I would like to refresh the evergreen content on the site that looks a little bit dated, and seeing as this is not a presentation we see often in the emergency department, I assume that even readers that have been with me from the beginning could use a refresher.
My approach
This approach assumes you know that the diagnosis is a tet spell. For the approach to the undifferentiated crashing infant, see this post.
This approach is for patients over the age of 1 month with a diagnosis of tetralogy of Fallot. Most tet spells occur between 2 months and 3 years of age. Cyanotic patients 28 days and younger need prostaglandin E1.
Page pediatrics, but anticipate that you are on your own for the first 10 minutes, at least.
This is a very rare, and likely very stressful presentation. Don’t rely on your memory. Pull up a checklist, such as this post on First10EM.
Calm, position, and provide oxygen. Position the child with knees to chest, on mom’s lap if possible. Provide oxygen through a nonrebreather mask. Use every trick in your book to calm the child, because crying and hyperventilation increase the underlying right to left shunt.
Provide morphine or fentanyl. Whether you do this before or after starting an IV will depend on the severity of the cyanosis, the experience of whoever is starting the IV, and other clinical factors. Keeping the child calm is essential, and in a quasi-stable cyanotic child, delaying the IV briefly might make sense. Intranasal midazolam is another option prior to IV access, depending on the comfort level and practice patterns at your hospital.
- Morphine 0.1 mg/kg oral, intravenous, intramuscular, or subcutaneous
- Fentanyl 1.5 mcg/kg intranasal
Obtain IV access and provide an IV fluid bolus (normal saline 10 ml/kg). Communicate a clear plan with the team. If an IV is not successful after 2 attempts in an unstable patient, an IO should be used. While the nurse is working on intravenous access, I am thinking about my next step and mixing up push dose phenylephrine.
If there is no response to positioning, oxygen, and IV fluids, the treatment is phenylephrine. In a perfect world, this would be given as an infusion. Realistically, this is a critically ill cyanotic child, and so push dose is likely the only way to deliver the medication in an appropriate time frame.
- I use the adult concentration that is very familiar, to prevent mistakes (10mg vial in 100ml NS mini bag to make 100mcg/ml solution)
- The dose is 5-20mcg/kg/dose every 1-2 minutes
- In a 5kg child this is 25-100mcg per dose, or 0.25-1ml per dose
If the child is still not calm despite opioids, add ketamine.
If the patient remains significantly cyanotic at this point, it is time to intubate. The goal of intubation is not delivery of higher oxygen concentrations, but to decrease systemic vascular resistance with anesthesia and paralysis, as well as to eliminate the work of breathing.
Final options, if all of the above fails, are bicarbonate (1-2mEq/kg) to correct metabolic acidosis, esmolol (500mcg/kg bolus then 50mcg/kg/min), and perhaps an attempt at compressing the abdominal aorta to increase afterload. (Andy Sloas (@PEMEDpodcast) from the PEM ED podcast says I shouldn’t have to get this far. In his experience, you just have to focus on reversing the shunt with phenylephrine and everything will be OK. Thanks Andy!)
For a broader approach to the crashing infant, see this post.
Neonatal resus (NRP) can be reviewed here.
Understanding tetralogy of Fallot
These days, I care more about the actions that I need to take when faced with a tet spell than the underlying anatomy and pathophysiology. That being said, understanding the pathophysiology helps me understand some of the above actions, and will probably help me remember what to do in a moment of crisis. Therefore, although It is not my primary purpose, let’s briefy review the basics of tetralogy of Fallot and the tet spell.
Tetralogy of Fallot consists of four anatomic features:
- A large ventricular septal defect (VSD)
- Right ventricular outflow tract obstruction
- An overriding aorta
- Right ventricular hypertrophy
A tet spell (also known as a hypercyanotic spell) is an episode of acute severe cyanosis that occurs when there is a decrease in systemic vascular resistance, increasing a right to left shunt. This leads to a self-perpetuating cycle. Crying increases pulmonary pressures. Hyperventilation decreases systemic vascular pressures. More blood shunts from the right to the left heart, worsening cyanosis. (Obviously, this is the very simplified version of complex congenital heart disease.)
This highlights the key aspects of management. We want to calm the child to reduce crying and reduce pulmonary pressures. Like the management of pulmonary hypertension, we want to improve oxygenation, which will also promote pulmonary artery vasodilation. Then the key management steps focus on increasing systemic vascular resistance (knee chest position and phenylephrine) to direct blood flow away from the VSD and back into the pulmonary circulation.
Morgenstern, J. The emergency management of a Tet spell (aka a hypercyanotic episode), First10EM, May 11, 2026. Available at:
https://doi.org/10.51684/FIRS.145774
Other FOAMed Resources
Hypercyanotic Spells – Pediatric EM Morsels
Newborn with Hypercyanotic Episodes on LITFL
Resuscitation of the crashing infant (pediatric resuscitation)
You can find more First10EM resuscitation guides here
Congenital heart disease in PEM on Don’t forget the bubbles
Neonatal (Newborn) Resuscitation
References
Tetralogy of Fallot. Merck Manual.
Horenstein MS, Diaz-Frias J, Guillaume M. Tetralogy of Fallot. [Updated 2024 Dec 2]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2026 Jan-. Available from: https://www.ncbi.nlm.nih.gov/books/NBK513288/
Meyer G, Jansen L, Shaw K, Franklin O. Tetralogy of Fallot: Emergency Management of Hypercyanotic “Tet”Spells. IAEM Guidelines 2024. https://iaem.ie/professional/clinical-guidelines/
Montero JV, Nieto EM, Vallejo IR, Montero SV. Intranasal midazolam for the emergency management of hypercyanotic spells in tetralogy of Fallot. Pediatr Emerg Care. 2015 Apr;31(4):269-71. doi: 10.1097/PEC.0000000000000403. PMID: 25831027
van Roekens CN, Zuckerberg AL. Emergency management of hypercyanotic crises in tetralogy of Fallot. Ann Emerg Med. 1995 Feb;25(2):256-8. PMID: 7832359.
Yee L.L., Meckler G.D. (2011). Chapter 122A. Pediatric Heart Disease: Congenital Heart Defects. In Tintinalli J.E. et al. (Eds), Tintinalli’s Emergency Medicine: A Comprehensive Study Guide, 7e. http://accessmedicine.mhmedical.com/content.aspx?bookid=348&Sectionid=40381594
