From a Barky Cough to a Squeaky Voice: Heliox for Croup

The Case

 Figure 1: Chest X-ray showing inflammatory changes consistent with a viral respiratory infection. Case courtesy of Dr Luke Danaher,  Radiopaedia.org . From the case  rID: 16821

Figure 1: Chest X-ray showing inflammatory changes consistent with a viral respiratory infection. Case courtesy of Dr Luke Danaher, Radiopaedia.org. From the case rID: 16821

A 22 month old otherwise healthy female presents to the ED with respiratory distress. Patient has had cough and congestion for two days. She was seen in the ER the day prior for a fever to 105F. A chest x-ray at that time showed inflammatory changes but no obvious pneumonia. The patient had no increased work of breathing and was thus discharged with antipyretics with initial improvement in symptoms. The patient now presents in respiratory distress with a barky cough and stridor consistent with croup.

The patient was given three treatments of nebulized racemic epinephrine, IV dexamethasone, and a normal saline bolus with mild improvement in her symptoms, however, she still had significant intercostal retractions and increased work of breathing. She was started on heliox (80% helium, 20% O2) via high-flow nasal cannula with near total improvement in her retractions. She was admitted to the PICU where she remained on heliox overnight and received dexamethasone every 6 hours. The next day she was weaned form heliox and discharged home.

Discussion

Laryngotracheitis, or croup, is inflammation of the larynx and trachea. It is most frequently caused by parainfluenza type 1 virus and most commonly seen in children 6 – 36 months of age. Inflammation causes narrowing of the airway which leads to increased resistance to air movement, favoring turbulent versus laminar flow of air into the lungs. Its clinical course typically starts with congestion, coryza, and fever which progresses to a barky cough, hoarseness, and stridor over 12-48 hours. The cough usually resolves after 3 days with the other symptoms lasting up to a week. The main treatments for croup are steroids and nebulized racemic epinephrine. In severe cases, patients may need intubation to secure the airway while steroids take effect.

In an attempt to support the patient while waiting for steroids to take effect, clinicians may try a helium / oxygen gas mixture (Heliox) to improve oxygen delivery to the lungs and decrease work of breathing. Helium is a low density, inert gas, which is insoluble in human tissue, non-reactive with cell membranes, and not known to have any negative effects on lung tissue.

Physics

The Reynolds number (Re) is used to determine if air flow is turbulent or dynamic.

Re = [p x d x V] / [u]

Where:

  • p = gas density
  • d = tube diameter
  • V = gas velocity
  • u = gas viscosity

In general, for a straight non-branching tube, a Re < 2,000 correlates with predominately laminar flow whereas a Re > 4,000 correlates with a predominately turbulent flow. Air and helium have similar viscosities however helium is ~1/10 the density of air thus significantly decreasing the Re.

 Figure 2: (a) Pattern of laminar flow as seen with heliox mixture, (b) Pattern of turbulent flow seen with a more viscous mixture such as atmospheric air alone.

Figure 2: (a) Pattern of laminar flow as seen with heliox mixture, (b) Pattern of turbulent flow seen with a more viscous mixture such as atmospheric air alone.

Evidence

While in theory heliox should ease work of breathing, there is little evidence to support a significant clinical benefit in croup. Cochrane did a review in 2013 to determine the efficacy of heliox in croup. Unfortunately, they were only able to find 3 randomized control trials with a total of 91 participants that met inclusion criteria. In one of the studies the investigators compared heliox to humidified oxygen and found no difference in Westley score at 20 minutes. The Westley score is a clinical tool used to quantify the severity of croup by assessing level of consciousness, cyanosis, stridor, air entry, and retractions. That study, however, only had 15 subjects, the patients had mild disease, and they were not given any other treatment, such as steroids or racemic epinephrine. In another study they looked at the difference between heliox and intermittent saline administration (placebo) vs humidified oxygen with up to two doses racemic epinephrine. This was also a small study with only 29 participants. Both the heliox and racemic epinephrine groups had improvements in their croup scores; however, there was no significant difference in croup score, oxygen saturation, respiratory rate, or heart rate between the groups. This suggests heliox is equally as effective as racemic epinephrine but doesn’t address the benefit of heliox as an adjunct therapy.

Conclusion

While heliox theoretically should decrease work of breathing in croup, the evidence is lacking. That being said, in the case presented above, heliox appeared to help avoid intubation. In addition to the need for more studies addressing the overall benefit of using heliox in treating croup, there are many other factors to analyze. In the studies mentioned above, heliox was administered via facemask. In our case, we administered it via high flow nasal canula. Does the route of administration make a significant difference? Also, does heliox affect the distribution of nebulized medications delivered? An additional factor to consider is, while heliox seems benign and a good tool to provide time for steroids to take action, will taking the time to trial heliox on a patient who ultimately needs intubation, make for a more dangerous intubation, in a patient with a narrower airway, and less respiratory reserve?

Faculty Reviewer: Jane Preotle, MD

References

UpToDate: Croup: Clinical features, evaluation, and diagnosis

UpToDate: Croup: Pharmacologic and supportive interventions

UpToDate: Physiology and clinical use of heliox

Terregino CA, Nairn SJ, Chansky ME, Kass JE. The effect of heliox on croup: a pilot study. Acad Emerg Med. 1998 Nov;5(11):1130-3.

Weber JE, Chudnofsky CR, Younger JG, Larkin GL, Boczar M, Wilkerson MD, Zuriekat GY, Nolan B, Eicke DM. A randomized comparison of helium-oxygen mixture (Heliox) and racemic epinephrine for the treatment of moderate to severe croup. Pediatrics. 2001 Jun;107(6):E96.

Moraa I, Sturman N, McGuire T, van Driel ML. Heliox for croup in children. Cochrane Database Syst Rev. 2013 Dec 7;(12):CD006822. doi: 10.1002/14651858.CD006822.pub4.

Thumb’s Up for Diagnosing and Managing UCL Injuries

Case:

32 year old right handed man presents with right thumb pain after a mechanical fall from standing onto steps.  While falling, his outstretched thumb caught on a step.  He denies other injury.  On exam, he has pain and swelling at the thumb MCP joint.  There is a palpable lump on the ulnar side of the base of his thumb.  He has full ROM and intact strength in the affected digit.

What are the next steps in this patient’s management?

Epidemiology:

  • Most commonly occur in athletes when a force causes thumb abduction
  • Skiing accidents in which the thumb is abutted against a fixed pole are the prototypical injury
  • More common in males with a ratio of 3:2
  • Complete ulnar collateral ligament tears can occur by non-sport related falls, motor vehicle crashes in which the hands are on the steering wheel, or bicycle injuries from handlebars

UCL anatomy:

  • Runs from middle of metacarpal head to the volar aspect of the proximal phalanx
  • Provides structural strength to the thumb
  • Resists valgus load to thumb

Mechanism of Injury:

  • Hyper-extension or abduction of the thumb causes the UCL to avulse from the proximal    phalanx
  • Acute injuries result in a complete or partial tear of the ligament
  • Avulsion fractures of proximal phalanx may or may not be present

Clinical Presentation:

  • Acute injuries present with pain and swelling of the base of the thumb
  • Chronic injuries, also known as Gamekeeper’s thumb, present with loss of strength of the   thumb and deformity

Traditionally, this injury was originally described in people who manually and repetitively sacrificed small game by breaking the animal’s neck.

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Exam:

  • Cornerstone of diagnosis
  • Goal of exam is to evaluate joint stability
  • Valgus stress of the MCP joint reveals increased laxity
  • Test in both neutral position and with MCP joint fully flexed.  Fully flexing the joint isolates the UCL from the volar plate, which can provide additional stability
  • Angulation of >35 degrees, or a difference of >15 degrees between hands signifies a        positive test.
  • In partial tears, the loss of a distinct endpoint while stressing may be noted

Stener lesion:

Occurs when the proximal end of the completely torn ligament is pulled from its normal location deep to the abductor aponeurosis and then fails to reduce itself properly, remaining superficial to the aponeurosis   

  • Present in up to 50% of complete UCL tears.
  • Exam may note a palpable lump
  • Surgical intervention is required
  • Stressing the MCP has NOT been shown to cause a Stener lesion where one did not already exist.
  • Pinch grip may be reduced in both acute and chronic injuries

ED Evaluation:

  • Plain films to evaluate for avulsion fracture of proximal phalanx
  • Stener lesion will not be evident of plain films
  • Ultrasound has not been fully validated in diagnosis UCL tears
  • MRI is not cost effective in the ED, but may be obtained in follow-up in consultation with a hand surgeon

ED Management:

  • Thumb spica is hallmark of ED management, allowing for immobilization of thumb MCP joint
  • If joint deemed unstable, follow-up within 1 week to a hand surgeon is advised to allow for surgical planning.  A delay in surgery can cause contracture of the UCL and increases  likelihood of chronic instability
  • For stable injuries, non-urgent follow-up within 4 weeks is recommended.

References:

  • Germano, T.  Falls on the Out-Stretched Hand and Other Traumatic Injuries of the Hand and Wrist: Part II.  Emergency Medicine Reports:  The Practical Journal for Emergency Physicians.  Volume 28, Number 18.  August 20, 2007.
  • Gammons, M et al.  Ulnar collateral ligament injury (gamekeeper's or skier's thumb).  Retrieved from UpToDate.com.  Accessed 4/21/2018.
  • Richard, JR.  Gamekeeper’s Thumb:  Ulnar Collateral Ligament Injury.  Am Fam Physician.  19

Faculty Reviewer: Dr. Kristina McAteer

Interview with Dr. Amal Mattu

Interviewed by Jessie Werner, MD. Edited by Kristina McAteer, MD.

Brown Emergency Medicine was pleased to welcome Dr. Amal Mattu as our Grand Rounds speaker. He delivered thoughtful commentary on-- you guessed it-- emergent EKG findings, but also offered us a unique tour though his career path.  Give a listen to learn more about one of our beloved leaders in the field of emergency medicine.  He gives us unique feedback on how he developed his career path, tips on navigating academic medicine and how to fit in teaching during hectic ED shifts.  Thank you to Dr. Mattu for your visit and taking the time to share in our podcast experience!

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About Dr. Mattu:

Dr. Amal Mattu completed an emergency medicine residency at Thomas Jefferson University Hospital in Philadelphia, after which he completed a teaching fellowship with a special focus on emergency cardiology. He joined the faculty in emergency medicine at the University of Maryland in 1996. He has received more than twenty teaching commendations including national awards from the American College of Emergency Physicians (ACEP), the American Academy of Emergency Medicine (AAEM), and the Emergency Medicine Residents’ Association (EMRA); and in 2000 he was selected as Founder’s Day Teacher of the Year for the University of Maryland at Baltimore campus. He received the 2005-2006 Rookie Faculty of the Year Award and the Outstanding Speaker of the Year Award from ACEP, Program Director of the Year Awards from the AAEM Resident and Student Association in 2006 and from EMRA in 2011, the 2007 Maryland Emergency Physician of the Year Award from the Maryland Chapter-ACEP, the 2008 “Joe Lex” National Educator of the Year Award from AAEM, and the 2013 “Peter Rosen Award” for outstanding leadership in academic emergency medicine. In 2013 he was awarded ACEP’s highest honor for teaching—the Outstanding Contributions to Education Award.

Dr. Mattu's areas of academic focus are emergency cardiology, geriatric emergency medicine, faculty development, and risk management. He has authored the bestselling texts ECGs for the Emergency Physician Volume 1 and Volume 2, and he has served as an editor for 18 other texts in emergency medicine. Dr. Mattu is the first emergency physician to serve as primary Guest Editor on issues of Cardiology Clinics (twice) and Clinics in Geriatric Medicine, and he serves as the consulting editor for Emergency Medicine Clinics of North America. Dr. Mattu is a frequent speaker at national and international CME conferences in emergency medicine.

Dr. Mattu is currently a tenured Professor, Vice Chair of Education, Director of the Faculty Development Fellowship and Co-Director of the Emergency Cardiology Fellowship in the Department of Emergency Medicine at the University of Maryland.