Hereditary Hemorrhagic Telangiectasia


EMS scooped up the limp child and raced directly to the local ER. They knew the child had some congenital issue, but it was unclear how bad it really was. Upon our arrival, he was limp, being ventilated by BVM. We’ve heard it said so many times:


“Most cardiac arrests in children are respiratory or heart defect-driven.”


But there are situations when this is not the case, and this was one of them. While there are so many congenital issues that a clinician may encounter,


Hereditary hemorrhagic telangiectasia (HHT) is a genetic disorder caused by a lack of a capillary bed between the artery and veins in certain body areas.


Typically this results in pink pin-head-sized lesions from the blood vessels widening as the high pressure from the arterioles enters the venules.


The most common symptom of HHT is nose bleeds or telangiectases on the lips, mouth, and hands. In some cases, it causes arteriovenous malformations larger than telangiectasis. An arteriovenous malformation (AVM) directly connects arteries and veins, bypassing the normal capillary bridge where oxygen and other nutrients are exchanged.


As an expansive vasculature network, capillaries have such a large surface area they can slow blood velocity without affecting overall blood flow in the cardiovascular system. This allows the more fragile veins to handle incoming blood from the capillaries.


Why is this malformation so dangerous? 

Because when the artery and vein are directly connected, the force of blood from thicker arteries can put increased pressure on the thinner walls of the vein without the normal drop in velocity that occurs between the arterioles and capillaries.


When veins cannot handle the direct pressure, they stretch in an attempt to accommodate and accept the extra blood, thus creating aneurysms. If the pressure is too much on a weakened vessel, or the malformation is affected by external pressure, like head trauma, it can rupture and hemorrhage.


Often times HHT does not present itself until adolescence. Even less common is for cerebral AVMs to occur, happening in only 10% of individuals with HHT. (2) Infants sometimes present early and are affected by cerebral AVMs. That was the case with seven-month-old Silas. In Silas' situation, his arterial and venous circulation connected inappropriately, creating an arteriovenous fistula in his right frontal lobe.

What started as a normal morning for Silas (playing and climbing around) quickly turned emergent. Silas was unresponsive on the ground. Unable to detect a pulse or breathing, Silas' mom initiated CPR and called 911.


EMS took Silas directly to the local, rural ER. En route, he had multiple episodes of seizure-like activity. Upon our arrival, he was limp, being ventilated by BVM. We’ve heard it said so many times: “most cardiac arrests in children are respiratory or heart defect-driven.” But there are situations when this is not the case. Silas had already been diagnosed with HHT and had even been scheduled for routine imaging to check on any potential abnormalities. Silas did not receive a head CT at the ER before our arrival.


However, knowing his history was imperative to how we approached this call. Our goal was neuro-protective care to minimize the chance of secondary injury to the brain. We prioritized airway, ventilation, seizure prevention, intracranial pressure (ICP), and blood pressure management.


Airway considerations included patency and avoiding hypoxic episodes. Cerebral hypoxia is strongly associated with worse outcomes in brain injury patients. Hypoxia occurs more rapidly in pediatric patients due to lower functional residual capacity. Early intervention is indicated when the respiratory status is compromised. Silas was placed on the ventilator utilizing pressure-controlled ventilation and avoiding hypercapnia, which puts the patient at risk for brain hypoxia.


Children have lower seizure thresholds, and Silas had already presented with seizure activity before our arrival. In addition to post-intubation sedation, other medications to consider on this call included benzodiazepine administration and Keppra 20mg/kg. Without being able to fix the actual problem, the best thing we could do was optimize perfusion to Silas' brain while avoiding labile episodes of hypo or hypertension.


Even without knowing someone’s ICP in the prehospital setting, understanding the equation and application for cerebral perfusion pressure (CCP) is important.


Cerebral Perfusion Pressure = MAP-ICP


If Silas had a normal ICP of 7 and a normal mean arterial pressure (MAP) of 60, his CPP is 53, a relatively normal range. With the inability to know his actual ICP, but assuming it is increased based on presentation, we can know that he will have a significantly lower CPP with a normal MAP or low map from hypotension. 


This stresses the importance even more of targeting a higher MAP to keep adequate CPP. CPP < 40mmHg for prolonged periods in patients 0-5-years-old shows decreased survival rates. (1) Should hypotension occur, consider a 20ml/kg bolus of isotonic/crystalloid fluid. If that is unsuccessful in treating hypotension, vasopressors may be indicated. Although not as widely studied in the pediatric population, hypertonic saline at a dose of 5ml/kg should be considered for pediatric patients showing rapid decompensation or signs of impending herniation.


How could a pediatric intracranial hemorrhage cause sudden respiratory or cardiac arrest? There are a few viable possibilities. A sudden spike in ICP can cause a loss of brainstem reflexes, resulting in respiratory compromise and arrest. Furthermore, hypoxia can trigger the endogenous release of adenosine which impairs contractility and electrical conduction in the heart. If the damage is so profound that the patient experiences the Cushing reflex, this will result in bradycardia and, eventually, cardiac arrest. (3)


Silas and his mother were flown to Arkansas Children’s Hospital, where he underwent multiple surgeries. Overall, Silas received a craniotomy to remove a section of the skull, drain placement, and ICP monitoring.

After stabilization, the neurosurgeon addressed the still hemorrhaging vessel by coil embolization.

His chances of bleeding from this brain area after intervention are less than 3%. The biggest question initially was if Silas would make a full recovery. Battling hypertension, clotting issues, repeat seizures, swelling, and hemorrhage, it seemed the odds were against him. But Silas showed signs early on of intentional movement. Silas went on to make a full neurological recovery with no deficits. An impressive feat considering the limited studies we have show around half of the pediatric intracranial hemorrhage patients experience cognitive deficits. 


Chain of events:

  • Early intervention from mom to maintain perfusion 

  • Recognizing Silas' inability to maintain an airway by EMS and hospital staff

  • Utilizing additional resources with the flight crew to initiate RSI 

  • Head elevated 30° to aid in draining venous blood

  • Target CPP and ICP control, seizure prevention, size-appropriate ventilation, and sedation

  • Avoiding episodes of hypoxia and hypotension.

  • Maintaining normal glucose levels. Abnormal glucose levels are associated with poor outcomes in related conditions.

  • Decreasing time to definitive care and an OR.

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References

1. Allen BB, Chiu YL, Gerber LM, Ghajar J, Greenfield JP. Age-specific cerebral perfusion pressure thresholds and survival in children and adolescents with severe traumatic brain injury*. Pediatr Crit Care Med. 2014 Jan;15(1):62-70. doi: 10.1097/PCC.0b013e3182a556ea. PMID: 24196011; PMCID: PMC4077612.

2. McDonald, J., Bayrak-Toydemir, P., & Pyeritz, R. E. (2011). Hereditary hemorrhagic telangiectasia: An overview of diagnosis, management, and pathogenesis. Genetics in Medicine, 13(7), 607–616. https://doi.org/10.1097/gim.0b013e3182136d32

3. Zachariah J, Stanich JA, Braksick SA, Wijdicks EF, Campbell RL, Bell MR, White R. Indicators of Subarachnoid Hemorrhage as a Cause of Sudden Cardiac Arrest. Clin Pract Cases Emerg Med. 2016 Mar 16;1(2):132-135. doi: 10.5811/cpcem.2017.1.33061. PMID: 29849421; PMCID: PMC5973610.