Fig. 3.84  Experimental setup for simulation of a chemical burn

Internal pH

Evacuation tube

Magnetic

stirrings

Fig. 3.85  Schema of experimental setup for simulation of a chemical burn

due to amphoteric property). Experimentally, it is noticeable that the hypertonicity reduces this time by a 30% factor only; while an active and safe neutralization – with the meaning of the amphoteric solution used in this experiment – reduces the washing time by a factor 4.

3.6  What is Now the Extent of Our Knowledge About Ocular Chemical Burns?

We are now able to know the intimate nature of the chemical aggression by an irritant or a corrosive on the “fragile” biological structures of an eye. We can also evaluate the strength of this aggression.

We better understand the kinetics of spreading and the histological processes of destruction of the different ocular tissues. The pathophysiology of chemical lesions, in case of an ocular burn, will be strongly illustrated, thanks to new technologies which can bring the experimental evidence of the theories developed in the following chapters.

We all know that the time available before the settlement of burns is very short and very valuable. Particularly in professional environment, we must be ready to react not only in case of an acid or a base projection but also when chemical reagents, such as oxidizing, reducing, or chelating agents, and so on, might be involved, because these other aggressors are widely used in industry and might cause severe chemical ocular accidents. So short delay for decontamination and polyvalence are key parameters of the expected efficiency of the chemical decontamination. These notions are gathered and illustrated in Fig. 3.87.

The universal and unconditional use of water is due to its polyvalence, its effect of mechanical draining and dilution at the surface of the tissues. However, water has limits. It requires an extremely fast intervention with the necessity of using a huge quantity to get results that might be neither reproduced nor reproducible. Therefore, the use of water does not guarantee a safe situation, especially when corrosives are concentrated.

When using specific chemical concepts, we are now able to conceive effective practical answers so that really efficient first aid wash solutions can be available for victims of eye projections, in case of an emergency.

The approach developed in this chapter already shows some axis of prevention and optimal care of the ocular chemical accident:

•Precocity of the intervention.

•Effect of dilution and mechanical draining.

•Polyvalence because of the diversity of substances and often because of the misknowledge of the precise composition of the irritant or corrosive chemicals involved.

Fig. 3.86  Evolution of ocular pH with different decontamination solutions

Evolution of the internal pH exposed to 1N soda

with an increased volume of different decontamination solutions at a flow rate of 150 mL/min

Time (min)

Fig. 3.87  Summary of chemical burn knowledge

Type of elementary chemical reaction

Acido−basic

Oxido−reduction Solvatation Alkylation

Energetic level of the reaction

Intrinsic harmful potential of the product pKa and pKb Rdeox potential...

Molar concentration

< 0.2 N

> 0.2 N

Area of affected tissu

Eye «only» +/− Eyelid ? +/− Face ?

Period of chemical contact

Time elapsed before starting active washing Delay because of first washing with water

Non active rinsing solution

Aggravating factors

Temperature Solid particules

(example caustic soda flakes)

Splash under pres sure

Viscosity...

Restititio ad integrum

(Return to normal)

Sequelae

Corneal opacity

Astigmatism

Lower visual acuity...

•Innocuousness: the solution must not be irritant or toxic, have no deleterious effect, must cause no sensitization,­ and be sterile and compatible with secondary ophthalmologic treatments.

In the following chapters, we will study the experimental and clinical dimensions due to the gathering of a modern knowledge mixing chemistry and medicine.

Beyond the basic requirements mentioned above, the difference in efficiency of a wash solution is bound to a real ability to react and thus to control the aggressiveness of all the irritants and corrosives on the side of their specific elementary reactivity:

•Acid–base reaction

•Redox

•Chelation

•Addition

•Substitution

•Solvation

In practice, this ability to control the aggressor supplies some precious extra seconds in order to start an efficient decontamination. Without requiring huge quantities of wash liquid because the efficiency can be reached even with a small amount of the solution to use and without needing one duration of washing as prolonged as that of water.

The last consequence is that the chemical lesion is avoided or minimized. This facilitates the simplicity of the follow-up care in case of a secondary medical

treatment. All these elements bring the patients real advantages:

•Very early analgesic effect that makes a careful wash more comfortable and efficient and avoids blepharospasm

•Quickness and simplicity of evolution

•Diminution of the risk not only of functional sequelae but also of psychological damages

References

1.Liao, C.-C., Rossignol, A.M.: Burns 26, 422 (2000)

2.Burgher, F., Mathieu, L., Blomet, J.: Le Risque chimique et la Santé au Travail [Chemical risk and occupational medicine]. Prevor editions 1996

3.Merle, H., Donnio, A., Ayeboua, L., Michel, F., Thomas, F., Ketterle, J., Leonard, C., Josset, P., Gerard, M.: Alkali ocular burns in Martinique (French West Indies) Evaluation of the use of an amphoteric solution as the rinsing product. Burns 31(2), 205–211 (2005)

4.Gérard, M., Merle, H., Chiambaretta, F., Rigal, D., Schrage, N.: An amphoteric rince used in the emergency treatment of a serious ocular burn. Burns 7, 670–673 (2002)

5.Hall, A.H., HI, Maibach: Water decontamination of chemical skin/eye splashes: a critical review. Cutan Ocul Toxicol 25(2), 67–83 (2006)

6.Burgher, F., Blomet, J., Mathieu, M.: La magie des solvants,­ Principes, Toxicologie, Risque Ecologique, Solutions alternatives­ [Magics Solvents, Principals, Toxicology, Ecological risk, Alternative Solutions]. Prevor editions 1998