Page 628 - ACCCN's Critical Care Nursing

Emergency Presentations 605

binding and inactivation of acetylcholinesterase (AChE), enzyme activity). Levels do not, however, always correlate
a neurotransmitter that metabolises acetylcholine with clinical illness. 139
(ACh). 103,139,140
Mortality rates range from 3% to 25%, and are the most Management
common mode of suicide in some developing countries Initial priorities are ABC, in concert with D (danger), as
(e.g. Sri Lanka and Fiji). In one Australian study, 36% of organophosphates also present considerable risk to staff
patients had suicidal intentions, compared with 65–75% caring for the patient, especially during the initial phases
in developing countries. Men aged 30–50 years were of management. All patients’ clothing should be removed
141
more likely to attempt suicide with organophosphates. and considered hazardous waste. Patient decontamina-
Common complications include respiratory distress, sei- tion with soap and water is a priority, as soap with a high
zures and aspiration pneumonia, with respiratory failure pH breaks down organophosphates. 140,142 Staff should
the most common cause of death. 140 use personal protective equipment (PPE), such as neo-
prene or nitrile gloves, and gowns, when decontaminat-
ing patients. Charcoal cartridge masks for respiratory
Assessment, Monitoring and Diagnostics protection are used, although recent evidence suggests
Clinical findings of organophosphates are divided into that the nosocomial risk may not be as significant as once
142
three broad categories: thought.
1. Muscarinic effects; common manifestations are Intubation is commonly required after significant expo-
summarised by the mnemonic SLUDGE: Saliva- sure due to respiratory distress from laryngospasm, bron-
tion, Lacrimation, Urination, Defecation, GI upset, chospasm or severe bronchorrhoea. Continuous cardiac
pulmonary oEdema. 103,104,138,142 Other symptoms monitoring and an ECG are used to identify bradycardias.
include bradycardia, hypotension, bronchospasm, Activated charcoal is used for gastric decontamination for
cough, abdominal pain, blurred vision, miosis and patients who ingested organophosphate. The mainstay of
sweating. treatment is atropine and pralidoxime, with a benzodi-
138,139,142
2. Nicotinic effects: include muscle fasciculations, azepine used for seizure control. Atropine blocks
cramping, weakness and diaphragmatic failure. acetylcholine receptors and halts cholinergic stimulation.
Autonomic effects include hypertension, tachycar- Large doses of atropine are usually required (1–2 g IV),
dia, pupillary dilation and pallor. and repeated if muscle weakness is not relieved or the
3. CNS effects: include anxiety, restlessness, confu- signs of poisoning recur. Clearing of bronchial secretions
sion, ataxia, seizures, insomnia, dysarthria, tremors, is the endpoint of atropine administration, not pupil size
138,139,142
coma and paralysis; three types of paralysis may or absolute dose. Pralidoxime hydrochloride reac-
present: 103,104,138 tivates acetylcholinesterase and is effective in restoring
l type I: acute paralysis secondary to persistent skeletal muscle function, but is less effective at reversing
depolarisation at the neuromuscular junction; muscarinic signs. Over time, the bond between organo-
occurs shortly after exposure phosphate and cholinesterase becomes permanent and
142
l type II (intermediate syndrome): develops the effectiveness of pralidoxime diminishes. The
24–96 hours after resolution of acute choliner- current recommendation is for administration within 48
142
gic poisoning, and presents commonly as para- hours of poisoning. Benzodiazepines are clinically
lysis and respiratory distress. Proximal muscle indicated as the drug binds to specific receptor sites,
groups are involved, with relative sparing of potentiating the effects of gamma-aminobutyrate (GABA)
distal muscle groups; this may persist for up to and facilitating inhibitory transmitters for management
138,139,142
3 weeks of seizures.
l type III: organophosphate-induced delayed
polyneuropathy (OPIDP) occurs 2–3 weeks CHEMICAL, BIOLOGICAL AND RADIOLOGICAL
after exposure to large doses of certain organo- (CBR) EVENTS
phosphates. Distal muscle weakness with rela- Terrorist incidents and hoaxes involving toxic or infec-
tive sparing of the neck muscles, cranial nerves tious agents are frequent events, and there is now increased
and proximal muscle groups is characteristic. international attention paid to the potential risk of CBR
Recovery can take up to 12 months.
attacks. 143 While a nuclear weapon may be difficult for a
Laboratory diagnosis is based on measurement of cholin- terrorist group to obtain, there is evidence that groups
esterase activity using either erythrocyte or plasma levels; have attempted to acquire nuclear materials. 144,145 In addi-
erythrocyte cholinesterase is more accurate, but plasma tion, non-nuclear radioactive material may be easier to
cholinesterase is easier to test and is more widely avail- obtain and used in an explosive device (referred to as
able. Erythrocyte AChE is found in CNS grey matter, red ‘dirty bombs’). 144,145 Chemical agents or biological agents
blood cells, peripheral nerve and muscle. Plasma cholin- are also relatively easy to obtain, and pose a greater
esterase circulates in plasma and is found in CNS white threat. 143 The availability and the impact of chemical and
matter, pancreas and heart. 139-140 Levels of poisoning are biological threat materials are both relatively high, with
categorized as mild (cholinesterase activity is reduced to potentially devastating impacts. 143,146-149 As biological and
20–50% of normal; moderate (activity is 10–20% of chemical agents are dissimilar, each category is discussed
normal); or severe (less than 10% of cholinesterase separately, although there are common characteristics.