On Mon, 07 Jun 2004 00:37:53 +0100, The Natural Philosopher
wrote:
Eyes yes, but skin burns are nothing. I have had dozens of minor caustic
spalshes and never once went to hospital.
My comment referred to eye injuries, I did not make that clear.
For eyes, its a question of massive and immediate dilution. Time is of
the essence. Don't rush to A & E, get the eye washed with clean cold
water again and again and THEN get to A & E.
I agree, you should wash the eye (as in let the water from a running
tap pour over the eyeball not just dribble a bit of water in) for at
least 20 minutes and ideally continue to provide some irrigation for
the journey to hospital. At A&E any alkali eye burns should be
referred to an ophthalmologist either immediately or, for mild burns,
within 24 hours. Acid burns look much worse than alkali burns
initially but are (with the notable exception of hydrofluoric acid)
generally far less damaging than alkali burns.
Caustic Soda dissociates into a hydroxyl ion and a cation in the eye
surface. The hydroxyl ion saponifies cell membrane fatty acids, while
the cation interacts with stromal collagen and glycosaminoglycans.
This interaction helps the caustic soda penetrate deeper into and
through the cornea and into the anterior segment of the eye.
This results in corneal clouding. Collagen hydration causes fibril
distortion and shortening, leading to increased intraocular pressure.
Additionally, the inflammatory agents released during this process
stimulate the release of prostaglandins, which can further increase
in intraocular pressure.
The combination of scarring, tissue damage and raised pressure in the
eyeball make opthalmic follow-up essential. As an aside the most
dangerous alkali as far as eye damage is concerned is Ammonia.
Liquified Ammonia gas (anhydrous ammonia) is used in the USA as a
fertiliser, it is directly injected into the soil, and a number of
agricultural workers are blinded every year in accidents with it.
But they won't do anything much more than wash it again.
If its damaged, its damaged, and the only
treatment is something to stop it hurting ad keep infection at bay, and
hope it heals itself.
Not so. Apart from irrigation, treatment of opthalmic alkali burns
would comprise:-
Control of inflammation to reduce the secondary effects of the
damage. Topical steroids are useful during the early recovery phase.
Cycloplegics also reduce inflammation by stabilising the
blood-aqueous barrier.
Prevention of infection: The corneal epithelium serves as a barrier
to infection. When this layer is absent, the eye is susceptible to
infection.
Reduce intraocular pressu Aqueous suppressants are used to reduce
IOP secondary to chemical injuries, both as an initial therapy and
during the later recovery phase.
Promotion of epithelial healing: Chemically injured eyes have a
tendency to poorly produce adequate tears; therefore, artificial tear
supplements play an important role in healing.
Control pain: Severe chemical burns can be extremely painful.
Ophthalmic referral for even seemingly minor burns is quite usual as
they can be far worse than they look.
As we both agree - keeping it out of the eye in the first place is a
really good idea. The danger of putting caustic soda in crystalline
form down a sink and then adding water is that in the process of
dissolving the caustic soda generates a lot of heat. In a sink drain
this can easily be enough to cause the concentrated solution to boil
and there is nowhere for the steam pressure to go which results in it
exploding the caustic liquid violently upwards out of the drain and
forwards out of the overflow.
Mixing the caustic soda properly and pouring the resultant liquor
down the drain is equally effective as far as clearing the drain is
concerned and far less risky. I agree its also a lot less exciting -
but with some things being boring is quite sufficient thank you :-)..
--
Peter Parry.
http://www.wpp.ltd.uk/