Chemistry Reference
In-Depth Information
kept alive, excretory and detoxicating mechanisms
together with the administration of specifi c antidotes,
when these exist, will be able to ensure eventual elimi-
nation of the poison. Careful symptomatic medical
care is always necessary, with an awareness of delayed
effects that may occur.
intravenously. Prolonged sedation with diazepam may
be necessary to overcome the hyperactivity and other
behavioral disorders that may develop in poisoning
with alkyl lead compounds.
3.3 Elimination of Absorbed Poison
3.3.1 Diuresis
3.2.1 Maintenance of Respiration and Circulation
Maintenance of respiration and circulation should
receive precedence over all other procedures. The pat-
ency of the airway must be ensured, especially at the
site of the accident and the journey to the treatment
center, and artifi cial respiration may be necessary. At
the treatment center, tracheobronchial toilet may be
required. The presence of hypoxia should be assessed
by determining minute ventilation or preferably arte-
rial oxygen and carbon dioxide tensions. Oxygen may
be needed and also mechanical ventilation. Treatment
for acute pulmonary edema may be necessary after
exposure to beryllium or cadmium fumes, to nickel
carbonyl, or to hydrogen selenide.
In an emergency situation, a conscious shocked
patient with a blood pressure less than 80-90 mmHg
should be reassured, covered with blankets, and kept
supine with the legs elevated. Once the patient reaches
the treatment center, the circulatory blood volume can
be restored with suitable intravenous fl uids. Blood
transfusion may be required for severe hemolytic ane-
mia after exposure to arsine.
The promotion of a diuresis will increase the clear-
ance of many poisons by decreasing their passive reab-
sorption from the proximal renal tubules. Diuresis can
be achieved by giving a fl uid load together with osmotic
agents like mannitol or by giving a diuretic (e.g., furo-
semide). Furthermore, the excretion of some poisons
is infl uenced by the pH of the urine, because passive
tubular reabsorption is less effective with increased
ionization of the solute in the tubular fl uid. Although
of great value in some common forms of acute poison-
ing, these methods have limitations in poisoning by
metals, although in general, excretion of the toxic metal
can be accelerated if a high fl ow of urine is maintained,
as, for example, in acute inorganic mercury and lead
poisoning. Forced alkaline diuresis is of limited value
in aiding the elimination of lithium salts.
3.3.2 Biliary Excretion
The action of certain toxic metals is prolonged as a
result of an enterohepatic circulation where excretion
in the bile can occur against a high concentration gra-
dient followed by intestinal reabsorption. The use of
activated charcoal in absorbing certain toxic agents
from the gut is referred to previously. A promising
approach for interrupting the enterohepatic circula-
tion has been described by Clarkson
et al
. (1973). This
involves a complexing agent given by mouth that will
bind with the metal compound excreted in the bile,
prevent reabsorption, and enhance fecal excretion of
those heavy metal compounds that undergo an exten-
sive enterohepatic circulation. This synthetic polysty-
rene resin containing fi xed sulfhydryl groups, when
added to food in a concentration of 1%, doubled the
rate of excretion of methylmercury from mice and low-
ered blood and tissue levels compared with untreated
controls. In man, mercury levels in blood were reduced
and the fecal excretion of methylmercury enhanced
(Bakir
et al
., 1973).
3.2.2 Maintenance of Water and Electrolyte Balance
Imbalance may occur from vomiting, diarrhea, tis-
sue damage, or from measures taken to eliminate the
poison. It may be suffi cient to give fl uids by mouth to
prevent dehydration, but an intravenous infusion with
appropriate biochemical monitoring is often required.
An adequate urinary fl ow should be ensured, and a
catheter may be necessary.
Acute tubular necrosis may give rise to anuria, and
dialysis may be necessary. Careful water and electro-
lyte balance has to be maintained until regeneration of
the tubular epithelium leads to recovery.
3.2.3 Control of Nervous System Effects
The general supportive measures just outlined are
usually adequate for the management of the patient
whose level of consciousness is depressed. There is no
indication for the use of analeptic drugs in acute metal
poisoning. Convulsions, however, require management
with diazepam, 10-30 mg, given parenterally. Cerebral
edema may occur, as, for example, in acute lead poisoning.
This should be treated with dexamethasone given
3.3.3 Dialysis
Hemodialysis will achieve higher clearance rates of
toxic metals not irreversibly bound to tissues than can
be attained by forced diuresis, although, in general,
the yield of metal ion in the dialysate is low. Metals
