Lye exposure

What caustic exposure from the pictured item can lead to ocular injury?

  1. Acetic Acid
  2. Hydrofluoric Acid
  3. Potassium Hydroxide
  4. Sodium Hydroxide

[Image from Istockphoto]

4. Sodium Hydroxide (Lye)

While automobile airbags are an important life-saving device, sodium hydroxide powder and aerosol released by their inflation can cause significant ocular injury for which prompt ocular irrigation is indicated [1,2].

Why in the world is lye used in airbags? [1,2]

  • To create rapid airbag inflation, sodium azide is ignited producing hydrocarbon gas.
  • This reaction releases powdered sodium hydroxide, sodium bicarbonate, and fine metallic oxides.
  • Upon impact, sodium hydroxide may escape through the fabric resulting in ocular exposure.

What is caustic ocular exposure? [3-5]

  • Both acid and alkali substances can cause corrosive ocular injury
  • Alkali substances, such as lye, are more harmful than acidic substances partly due to rapid tissue penetration.
  • Alkali solutions saponify the cell membranes and penetrate the corneal stroma causing tissue damage.
  • The damaged tissue secretes proteolytic enzymes, further worsening the injury.
  • Other caustic alkali agents include ammonia, potassium hydroxide, magnesium hydroxide, and calcium oxide.
  • Caustic eye injury symptoms include irritation, pain, redness, and visual disturbance.

How do I treat caustic ocular exposure? [3-6]

  • Whether acidic or alkaline, treatment is the same.
  • Prompt irrigation is of paramount importance and should not be delayed to perform a thorough ophthalmologic examination
  • Remove contaminated clothing.
  • To facilitate irrigation, proparacaine HCL 0.5% or tetracaine HCl 0.5% solution may be used to anesthetize the eye.
  • You can measure an initial pH a minimum of 5 minutes after initiation of irrigation.
  • Consider anxiolytics or analgesics if systemic symptoms or other sites of injury are a barrier to prompt irrigation.

What is the best way to irrigate the eye? [5-7]

  • Begin by anesthetizing the eye with proparacaine or tetracaine.
  • While a sterile solution such as normal saline or lactated ringers is preferred, tap water can be used as well.
  • Avoid neutralizing solutions as this can worsen damage.
  • A Morgan™ lens, if available, or a nasal cannula can be used to irrigate the eye(s).
    • If you utilize the nasal cannula method, you may connect it directly to the IV tubing and the bag of irrigation fluid.
    • If a Morgan lens is used, start the flow of irrigation solution before the lens is placed on the eye to avoid a suction contact injury to the cornea.
  • Irrigation should be continued for a minimum of 30 minutes using 1-3 L of fluid or continued until a physiological pH is reached at 7.0.

What should I do after irrigation is completed? [2,4,5,8]

  • Assess visual acuity.
  • Perform a detailed examination of the limbus, cornea, and iris. Chemical ocular injury is classified by ophthalmologists based on limbal ischemia via the Roper-Hall classification or the Dua classification [4,8].
  • Evaluate intraocular pressure.
  • If greater than mild injury is suspected, ophthalmologic consultation is warranted.
  • In patients who are discharged, discuss treatment and follow up with ophthalmology.

Bedside Pearls

  • Suspect caustic eye injury in patients with eye pain after airbag deployment
  • Do not delay irrigation if caustic eye injury is suspected.
  • Perform irrigation until pH is physiologic.
  • Perform a thorough eye examination after the irrigation is complete.
  • Consult with ophthalmology

References

  1. Richards A. Beware traumatic conjunctivitis: airbags can cause severe alkali eye injuries. Clinical & Experimental Ophthalmology. 2016;44(8):732-734. PMID: 27083383
  2. Barnes SS, Wong W Jr, Affeldt JC. A case of severe airbag related ocular alkali injury. Hawaii J Med Public Health. 2012;71(8):229-231. PMID: 22900239
  3. Chemical (Alkali and Acid) Injury of the Conjunctiva and Cornea – EyeWiki. eyewiki.aao.org. Accessed May 3, 2024.
  4. Hemmati H, Colby K. Treating Acute Chemical Injuries of the Cornea. American Academy of Ophthalmology. Published October 1, 2012. Accessed May 3, 2024. http://www.aao.org/eyenet/article/treating-acute-chemical-injuries-of-cornea.
  5. Olson E and Murphy C. ToxCard: Caustic Eye Injuries – emDOCs.net – Emergency Medicine Education http://www.emdocs.net/toxcard-caustic-eye-injuries/.emDOCs.net (2020) Accessed May 3, 2024.
  6. Ikeda N, Hayasaka S, Hayasaka Y, Watanabe K. Alkali burns of the eye: effect of immediate copious irrigation with tap water on their severity. Ophthalmologica. 2006;220(4):225-228. PMID: 16785752
  7. Lin M. Trick of the trade: Eye irrigation setup. ALiEM. Published April 7, 2010. Accessed May 3, 2024. https://www.aliem.com/2010/04/trick-of-trade-eye-irrigation-setup/
  8. Kam KW, Patel CN, Nikpoor N, Yu M, Basu S. Limbal ischemia: Reliability of clinical assessment and implications in the management of ocular burns. Indian J Ophthalmol. 2019;67(1):32-36. PMID: 30574887
Hannah Corral, MD

Hannah Corral, MD

Emergency Medicine Resident
Carolinas Medical Center, Charlotte, NC
Hannah Corral, MD

Latest posts by Hannah Corral, MD (see all)

Ann-Jeannette Geib, MD

Ann-Jeannette Geib, MD

Medical Toxicologist Faculty
Department of Emergency Medicine
Carolinas Medical Center, Charlotte, NC