Environmental Exposures Answers 477(a)Fresh water activates the nematocyst and should be avoided. (b, d,
and e)Vegetable oil, toothpaste, and household window cleaners should
also be avoided as they might cause further irritation and pain.
425.The answer is b.(Rosen, pp 2117-2118.)Chemical burns are a common
occupational hazard and can be caused by a variety of solvents containing
acidic or alkali mixtures. Initially, it is important to remove the patient from
the offending chemical and irrigate with copious amounts of water to dilute
the agent. It is important to assess the affected area, size, and depth of the
burn, as some patients will need transfer to a burn center. This patient was
chemically burned by a rust-removing agent, which commonly contains
hydrofluoric acid (HF).Other solvents include high-octane gas and germi-
cides.Pain out of proportion to sustained injuryis usually seen in these
cases. As HF is a relatively weak acid, its extreme electronegativity however
makes it very dangerous. Fluoride avidly binds to available cations, such as
calcium and magnesium, thereby causing cell death. Profound hypocalcemia
has been demonstrated in HF exposure. ECG monitoring and administration
of exogenous cations, such as topical calcium gluconate gel,can act as
chelating agents to the fluoride ions. IV or intradermal calcium gluconate
may also be used. Calcium chloride should be avoided given its ability to cause
tissue necrosis upon extravasation.
(a)Placing a tourniquet upon the limb may cause ischemia and further
cell death. (c)Alkalinization of urine would not be of benefit in this type of
exposure. (d)Silver sulfadiazine may be applied later on for wound care.
(e)The extent of this injury at this time does not warrant surgical debridement;
however, close wound-care monitoring should be instilled to recognize cases
when tissue necrosis progresses.
426.The answer is e.(Rosen, pp 816-818.)This patient was exposed to
lime,which is present in cement.When water interacts with dry cement,
hydrolysis occurs forming an alkali with a pH of 10 to 12. Alkali burns form
a liquefaction necrosis,causing quick dissolution of involved tissue. Acid
burns form a coagulation necrosis, which is somewhat slower in nature. The
best treatment is intense irrigationupon initial contact, a ritual performed
by the more experienced individuals who work with lime. This patient will
need further debridement and wound care because of his exposure.
(a)Hydrocarbons are present in mainly gasoline and paint thinners.
(b)Phenol is found in dyes, deodorants, disinfectants, and agriculture solvents,