What is the Best Solution for Irrigating an Alkali Chemical Eye Burn?

Unless you’ve slept through every chemistry lab orientation, you know that treating a chemical splash of the eye involves continuous irrigation. It may take more than one person to do this because the reflexive blepharospasm that occurs must be overcome in order to bathe the globe.[1] You should also try to avoid contamination of the unaffected eye. There is consensus among emergency physicians and ophthalmologists that time to irrigation is the most important factor in mitigating the damage to the eye regardless of whether the substance is an acid or a base.[2, 3, 4] Tap water is probably the first thing you would think to use. It is cheap, universally available, dilutes regardless of base or acid contamination, and does not require any special training to use. All these factors make it easy to initiate irrigation within 10 seconds of exposure as is recommended by the American National Standards Institute.[4, 5] However, other options do exist, and each has advantages and disadvantages. We will explore some of those now.

 

An explanation of the differences between alkali and acid burns of the eye is beyond the scope of the current discussion. If you would like insight beyond this site, consult your local Eye of Thundera.

Lion-O

Our focus will be on the best fluid therapy for alkali eye burns (which occur more commonly than acid burns).[5] Is there something more than meets the eye when selecting the ideal irrigation solution? Lets review the literature!

Optimus Prime

Three types of rinsing solution exist[6]:

  1. Non-buffering substances such as tap water and 0.9% saline solution
  2. Agent-dependent buffers (works best on acids or on bases but not both)
  3. Amphoteric substances (works on both bases and acids).

Let’s look at each type individually. One final, not-so-fun fact before the discussion begins: all of these experiments were conducted on rabbit eyes. There are no human data that that examines this treatment.

One last thing, the information in the tables at the end of each section is adapted from Rihawi, Frentz, and Schrage [5] and Kuckelkorn [1] and they are included for those interested in the details concerning composition of solutions.

No Buffer Zone!

Take that cat

As we have mentioned, tap water rinse should begin within 10 seconds of exposure. Rinsing should last 15 minutes with a volume of at least 500-1000 mL. Tintinalli recommends continuing irrigation until the pH measured by litmus test is < 7.4 in the lower fornix.[3] Tap water can penetrate the cornea and dilute the offending chemical agent because of its tonicity; however, it can also cause an increase in edema and corneal clouding. At the cellular level, cell lysis and release of inflammatory mediators may occur. This is a known, common complication of rinsing with hypotonic solutions.[4, 7] In contrast, isotonic normal saline does not cause significant stromal edema, because it does not significantly penetrate the stroma. Unfortunately, it does not effectively normalize pH in the chemically burned eye. Some experts consider normal saline unacceptably inferior to tap water and discourage its use.[4, 5, 7, 8]

Fluid Osmolarity/Osmolality Contents Buffer Capacity Administration
Corneal stroma 420 mosm/L Na, K, Cl, Ca, S, SO4,PO4, proteins, lipids, glycosaminoglycans 0.0004 Not applicable
Tap water Varies by geographic location but practically zero Water For practical purposes 0. Faucet, eye wash station, syringe, etc.
NaCl solution 0.9% 289 mosm/kg Na+ 154 mmol/l; Cl 154 0.0002 Morgan lens friendly

Buffering: Not Just For Netflix

Buffyerring

In tech talk, a buffer is intended to stave off cataplexy and uncontrolled, incoherent ranting at your screen by saving a little data ahead of what you are watching to compensate for a difference in the speed of the video stream.

In chemistry, a buffer is usually intended to keep pH at a constant level within a solution. In the case of eye irrigation, it is meant to bring the pH within the eye (corneal stroma and vitreous) more quickly toward neutral by buffering the offending substance and limiting its penetration thereby protecting the deeper structures.

Ringer’s lactate solution is isotonic and the lactate can act as a buffer. Because of the lactate buffer, some experts believe it is a better option than NS.[5] However, it its isotonicity is also unable to return intraocular pH to normal. In addition, lactate is a buffer for acid and won’t buffer alkali burns. Balanced saline solution (BSS) is another buffering solution. It contains both acetate and citrate, which gives it the ability to bind to unspecific metallic ions. The drawbacks are that BSS is not generally as available in the ED and also does not restore intraocular pH.[8]

A more effective buffering option is Cederroth Eye Wash Solution (borate in NS). It has a high capacity for buffering alkali, though it is less effective at buffering acid.[4] It is also very good at lowering intracameral (inside the eye chamber) pH compared to the electrolyte solutions and tap water.[4, 5, 8, 10] It should be noted that the company that produces Cederroth sponsored one of the studies.[8] This is not to say that the study is unequivocally biased, but the disclaimer is only to give you “sight beyond sight”. (I really like Thundercats, ok?) Borate-buffered fluid is also closer to the cornea’s osmolarity leading to less penetration into the stroma. This means decreased cell lysis and, theoretically, less damage to and clouding of the cornea. [4]

The last buffered eye irrigation fluids we will look at are phosphate containing solutions. These are effective at lowering the pH of a chemically burned eye but are not a good option because phosphate tends to cause calcification of the injured cornea. Calcification greatly hinders management toward restoration of normal cornea.[4, 8]

If you wanted to be McGyver when you grew up there are alternative irrigation fluids you can create such as adding sodium bicarbonate to normal saline. Unfortunately, the only data we could find on these solutions pertains to patient comfort/acceptance of eye irrigation.[9] Pubmed and Google Scholar searches revealed no studies on the efficacy points as has been described for other fluids in this review.

Fluid Osmolarity/Osmolality Contents Buffer Capacity Administration
Lactated Ringer’s (Baxter) 273 mosm/l 6 g/l NaCl; 3.1 g/l sodium lactate; KCl 0.3 g/l; calcium chloride 0.2 g/l 0.00069 Morgan lens friendly
Phosphate buffer (PBS Dulecco’s Powder without Ca and Mg) 279 mosm/kg NaCl 8,000 mg/l; KCl 200 mg/l; potassium phosphate monobasic 200 mg/l; sodium phosphate dibasic anhydrous 1,150 mg/l. (9.55 g of powder required to make 1 liter of solution) 0.0625 Usually comes in packaging designed to wash affected eye.
Cederroth Eye Wash Solution (borate)` 296 mosm/kg Borate buffer, NaCl 0.9% solution Not listed Usually comes in packaging designed to wash affected eye.

Amphoterates: The Hip Hoppopotamous of Eye Wash

Hiphoppopotamus

 

Diphoterine (marketed in Europe under the name Previn) is an amphoteric solution meaning it works well on both bases and acids. It is hyperosmolar compared to the cornea, which decreases likelihood of cell lysis and corneal clouding. When compared to tap water and electrolyte solutions (including lactated Ringer’s) it performed better at significantly reducing intracameral pH.[4, 5] One study also showed that within 5 minutes, diphoterine had already begun lowering the pH of the eye. Despite these advantages, no statistically significant difference in severity or healing was noted in alkali burns simulated on rabbit eyes between diphoterine and normal saline.[6]

Fluid Osmolarity/Osmolality Contents Buffer Capacity Administration
Diphoterine 876.3 mosm/kg 3.8 g diphoterine 5/100 ml; NaCl 1.8 g; glycine as stabilizer 0.75 g; Na mandelate 0.05 g (preservative); water demineralized to 100 ml. 0.02 Usually comes in packaging designed to wash affected eye.

Shouldn’t I be worried about clinical outcomes though?

In short: yes. There has only been one study on clinical outcomes. It compared various ionic solutions. But unfortunately, the outcome they measured was how well the patients tolerated the treatment. This outcome may be less relevant considering that the issue of tolerance can be mediated with tetracaine or other anesthetic drops.[1, 9]

As mentioned previously, all studies involving burnt corneas were performed on ex vivo rabbit eyes (with the exception of Schrage, Kompa, et al., which involved live, anesthetized rabbits) with a controlled alkali burn that was meant to be severe.

Bunny cry

Severe chemical burns may compose up to 26% of traumatic ocular injuries. While that is not a small number, we are more likely to see milder burns for which immediate irrigation will play a role in improving outcomes.[1, 5] Therefore, the most important thing for us to remember in the ED is to irrigate copiously regardless of fluid type. Diphoterine and borate may be helpful, but treatment should not be delayed while attempting to procure one of these solutions. In the end, most patients will need an ophthalmology consult in the ED because re-evaluation and management of sequelae such as corneal damage and secondary glaucoma will be necessary.[1]

 

In the future, we may find that the buffered and amphoteric solutions we have just discussed do significantly help patients with very painful and debilitating eye injuries. But because of the heterogeneity of these burns and the conditions under which they occur, a randomized controlled trial unlikely to take place. [10]

 

For now the only firm rules we can apply from the literature are:

  1. Flush an injured eye within 10 seconds of contamination (tap water will do and the patient should start this on their own: faucet, shower, garden hose, absolutely anything will do).
  2. Avoid using normal saline alone once the patient arrives in the ED (LR or continue with tap water).
  3. Irrigate until you return the eye to normal pH (<7.4)

 

Of less-clear importance are:

  1. Diphoterine may have the most beneficial immediate effects
  2. Buffered solutions are better than hypotonic or isotonic solutions at quickly reducing pH in the injured eye

 

It is discouraging that despite its immediate beneficial effects there are no data showing any long-term advantages for diphoterine vs. other fluids.[4] The possibility does exist and given a choice, I would use diphoterine if it were available.

megaman splash

Any take-away points for the ED?

  1. The so-called Morgan lens is a very useful tool that helps irrigate the eye continuously and almost uniformly. But it can miss particles in the fornices. Care must be taken with burns caused by particulate matter (e.g. cement, lime) or other chemicals that can crystalize and cause continual burns and irritation. [1, 2] Always look in the fornices prior to irrigation!
  2. Unfortunately, at the moment there is no way to irrigate with tap water as passively as with NS or LR bags when using a Morgan lens. And it is likely to be labor intensive.morgan lens
  3. No Morgan lens in your department? You can still McGyver something! You can use paper clips to retract the eyelids and ensure continuous irrigation with either an angiocath attached to a syringe (out of which some poor med student is going to have to keep pushing fluid) or that same angiocath attached to IV tubing and placed to bathe the entire eye. [2, 11] Alternatively, you can use a nasal cannula for “gentle drops” into the eye.Macgyver
  4. Numb the pain! Prior to irrigation and regardless of what method you choose use a local anesthetic eyedrop to decrease discomfort. You should also consider oral anti-inflammatory medication to decrease pain. [2]damn your eyes
  5. Even if there is no strong data that shows statistically significant differences in terms of burn severity and healing, saline may no longer be the best choice. In practical terms, changing the practice of irrigating with normal saline in the ED is easy and probably should happen. This leaves us with LR or tap water. If you’re really against the prepared solutions and want to use tap water you can always just cut a hole in the top of a bag of NS or LR (preserving the place where you hang it), pour it out, and replace it with tap water.

Happy irrigating!

hose face

 

References:

  1. Kuckelkorn R, Schrage N, Keller G, Redbrake C. Emergency treatment of chemical and thermal eye burns. Acta Ophthalmol Scand. 2002 Feb;80(1):4-10.
  2. Spector J, Fernandez WG. Chemical, thermal, and biological ocular exposures. Emerg Med Clin North Am. 2008 Feb;26(1):125-36, vii. doi: 10.1016/j.emc.2007.11.002.
  3. Walker RA, Adhikari S. Eye Emergencies. In: Tintinalli JE, Stapczynski J, Ma O, Yealy DM, Meckler GD, Cline DM. eds. Tintinalli’s Emergency Medicine: A Comprehensive Study Guide, 8e. New York, NY: McGraw-Hill; 2016.http://accessmedicine.mhmedical.com.newproxy.downstate.edu/content.aspx?bookid=1658&Sectionid=109444274. Accessed April 11, 2016.
  4. Schrage N. Rinsing therapy of eye burns. In: Schrager et al, ed. Chemical ocular burns: new understanding and treatments. Heidelberg, Germany; 2011: 77-92.
  5. Rihawi S, Frentz M, Schrage NF. Emergency treatment of eye burns: which rinsing solution should we choose? Graefes Arch Clin Exp Ophthalmol. 2006 Jul;244(7):845-54. Epub 2005 Dec 20.
  6. Schrage NF, Kompa S, Haller W, Langefeld S. Use of an amphoteric lavage solution for emergency treatment of eye burns. First animal type experimental clinical considerations. Burns. 2002 Dec;28(8):782-6.
  7. Kompa S, Redbrake C, Hilgers C, Wüstemeyer H, Schrage N, Remky A. Effect of different irrigating solutions on aqueous humour pH changes, intraocular pressure and histological findings after induced alkali burns. Acta Ophthalmol Scand. 2005 Aug;83(4):467-70.
  8. Rihawi S, Frentz M, Reim M, Schrage NF. Rinsing with isotonic saline solution for eye burns should be avoided. Burns. 2008 Nov;34(7):1027-32. doi: 10.1016/j.burns.2008.01.017.
  9. Herr RD, White Jr GL, Bernhisel K, Mamalis N, Swanson E. Clinical comparison of ocular irrigation fluids following chemical injury. Am J Emerg Med 1991;9:228–31.
  10. Scott WJ, Schrage N, Dohlman C. Emergency eye rinse for chemical injuries: new considerations. JAMA Ophthalmol. 2015 Mar;133(3):245. doi: 10.1001/jamaophthalmol.2014.5045.
  11. Cheng LH-H, Kumar P. Retraction of Oedematous Eyelids with Paper-Clips.Annals of The Royal College of Surgeons of England. 2008;90(3):253. doi:10.1308/003588408X285720a.

 

 

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Raul Hernandez

PGY III EM Resident

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