Biomedical Engineering Reference
In-Depth Information
and the order in which they are done. Complete
information on skin decontamination is described
elsewhere. However, as observed in treatment of
the Tokyo subway victims, after vapor exposure
clothing should be removed because it may contain
“trapped” vapor. The need for ventilation will
dependon the severityof pulmonary symptoms [10].
Three drugs are used to treat nerve agent expo-
sure; atropine, pralidoxime chloride (oxime), and
diazepam.
Table 6.6. It attaches to the nerve agent that is
inhibiting the cholinesterase and breaks the agent-
enzyme bond to restore the normal activity of
the enzyme. This uncoupling of the nerve agent-
enzyme bond regenerates the esterase to resume
hydrolysis of acetylcholine at the neuromuscular
junction, effectively reversing the nicotinic crisis
with a decrease in abnormal activity in skeletal
muscle and return of normal strength. Since the
effects of an oxime are not apparent in organs
with muscarinic receptors, oximes do not cause
a decrease in secretions, it is necessary to co-
administer oximes with atropine to reduce secre-
tions. Oxines also are less useful after aging occurs
(nerve agent de-alkylates to form an irreversible
covalent bond). Sarin (GA) and tabun (GB) age
slowly and pralidoxime may still be effective when
supplies eventually catch up with demand. Soman
(GD), conversely, ages within minutes. However,
Soman (GD) is an unlikely terrorist agent due to
its low volatility.
Pralidoxime chloride should be mixed in normal
saline over 20-30 minutes as more rapid adminis-
tration will cause hypertension.
6.2.5.1 Atropine
Atropine is a cholinergic blocking agent. It is
extremely effective in blocking the effects of
excess acetylcholine at peripheral muscarinic sites.
The end point of therapy is a reduction in symp-
toms. In mild cases that only have ocular symp-
toms this may require atropine (or homatropine)
eye drops. However, a severe injury from nerve
agent vapor exposure will have copious secre-
tions from the nose, mouth and lungs with severe
difficulty breathing and or apnea. Advanced cases
be unconscious and have flaccid or convulsive
activity. Atropine, 2mg, should be repeated at
5-10 minute intervals and should be titrated to
pulmonary symptoms (Table 6.5). The adequacy
of atropine dosing is gauged by improvement in
ventilation with suctioning of secretions and the
reduction in bronchoconstriction. Because of the
short half-life, atropine should be re-administered
every few hours and can easily total 20-50mg/d
in severely injured adults with ventilation being
required from 30 minutes to hours. A moder-
ately exposed patient will need to be administered
atropine until breathing comfortably. The preferred
route of atropine administration for severe expo-
sure is intravenous as therapeutic blood levels
of atropine appear within minutes in healthy
volunteers with intramuscular injection. However,
intramuscular absorption is unpredictable when
muscle perfusion declines as circulation fails in
severe exposure.
Table 6.5
Atropine dosing
Patient
Dosing recommendation
Adults
2mg intravenous every 5-10min
(every 20 minutes for IM
dosing) until decrease in
symptoms
Adolescent
2.0mg maximum single dose
intravenous every 5-10min
(every 20 minutes for IM
dosing) until decrease in
symptoms
Child (2-10 years old)
1mg intravenous dose every
5-10min until decrease in
symptoms mg/kg
Infant (<2 years old)
0.5mg maximum single dose
intravenous every 5-10min
(every 20 minutes for IM
dosing) until decrease in
symptoms repeated as
clinically indicated
6.2.5.2 Pralidoxime chloride
Pralidoxime chloride (Protopam chloride) is an
oxime with dosing recommendations listed in
