Transcript Document

Poisons and Poisoning
Dr Ian Wilkinson
Clinical Pharmacology Unit
Accidental?
Deliberate?
Suicides in the UK
• ~6,300 suicides pa
– 20% of deaths in young people
• ~140,000 attempted suicides (parasuicides)
– Most common 15-19 year old females
– Most common method is poisoning
• 50% paracetamol
General Comments
• Try and get as much history as possible including
witnesses
• People truly wanting to commit suicide often lie
• Remember the ABCs:
– Airway
Clear mouth & throat, gag reflex
– Breathing
O2 saturation, ABGs
– Circulation Venous access, IV fluids if shocked
• Assess GCS
• Examination
History
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When, what, how much ?
Why?
Circumstances
PMHx, Drug history
Psychiatric history
Assess mental status and capacity
Care with names!
• Distalgesic
• Anadin
Investigations
• Always check blood glucose.
• Send blood & urine for toxicology screening.
• ALWAYS measure paracetamol & salicylate levels
– Failure to diagnose & treat is negligent.
• U&Es, LFTs, glucose, ABG, clotting, bicarbonate
• ECG, CXR
• Specific blood levels
Management
• Supportive
– Correct hypoxia, hypotension, dehydration, hypohyperthermia, and acidosis
– Control seizures
• Monitor
– TPR, BP, ECG, Oxygenation, GCS
• General
–  Absorption
–  Elimination
– Specific antidotes
 Absorption
• NEVER Ipecacuanha
• Gastric lavage
– Only if within 1 hour & life-threatening amount
– Never for corrosives
– If  LOC intubate
• Activated charcoal
– 50 g single or repeated dose ( elimination)
– Doesn’t bind heavy metals, ethanol, acids
 Elimination
• Multiple dose activated charcoal
– Quinine, phenobarbitone
• Charcoal haemoperfusion
– Barbiturates, theophylline
• Diuresis
• Urinary alkalinization
• Dialysis
Paracetamol Overdose
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Most common drug taken in overdose
Few symptoms or early signs
As little as 12g can be fatal
Hepatic and renal toxin
– Centrolobular necrosis
• More toxic if liver enzymes induced or reduced
ability to conjugate toxin
Paracetamol Metabolism
Management
• General measures including
– U&Es, LFTs, glucose, clotting ABG, bicarbonate,
paracetamol and salicylate levels
– Activated charcoal
• <8 hours
– Take level after four hours
– Start N-aceylcysteine if above treatment line
– Patients are usually declared fit for discharge from
medical care on completion of its administration.
However, check INR, creatinine and ALT before
discharge. Patients should be advised to return to hospital
if vomiting or abdominal pain develop or recur
Management 2
• >8 hours
– Urgent action required because the efficacy of NAC
declines progressively from 8 hours after the overdose
– Therefore, if > 150mg/kg or > 12g (whichever is the
smaller) has been ingested, start NAC immediately,
without waiting for the result of the plasma paracetamol
concentration
• >24 hours
– Still benefit from starting NAC
Treatment Graph
N-acetylcysteine
• Supplies glutathione
• Dosage for NAC infusion - ADULT
– (1) 150mg/kg IV infusion in 200ml 5% dextrose over
15 minutes, then
– (2) 50mg/kg IV infusion in 500ml 5% dextrose over 4
hours, then
– (3) 100mg/kg IV infusion in 1000ml 5% dextrose over
16 hours
• Side-effects
– Flushing, hypotension, wheezing, anaphylactoid
reaction
• Alternative is methionine PO (<12 hours)
Aspirin Overdose
• Early features
– hyperventilation, sweating, tremor, tinnitus, nausea /
vomiting, or hyperpyrexia
• Metabolic features
– Hypo- or hyper-glycaemia, hypokalaemia, respiratory
alkalosis, metabolic acidosis
• Others
– renal failure, pulmonary oedema, seizures, coma, death
Management
• General measures
• Bloods
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Salicylate (paracetamol) level >2 hours, and after 2hrs
>700 potentially lethal
>500 moderate-severe poisoning
U&Es, glucose, ABG, bicarbonate
Activated charcoal
Rehydrate, monitor glucose, correct acidosis and K+
If levels >500mg/L alkalanize urine (HCO3-)
Levels > 700 mg/L before rehydration, renal failure
or pulmonary oedema consider haemodialysis
TCAs -Introduction
• Potentially fatal (2.5 to 3.5g of amitriptyline)
• Neurological and cardiac problems common
– Toxicity due to anticholinergic actions, and direct
quinidine-like effect on the myocardium
• Serious toxicity results from:–
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Ventricular dysrhythmias
Seizures
Hypotension
Respiratory depression
• Initial symptoms at presentation may be trivial,
and most major problems occur within 6hrs
TCAs-Features of poisoning
• Peripheral
– Sinus tachycardia, hot dry skin, dry mouth, urinary
retention, hypotension and hypothermia may occur
• CNS
– Dilated pupils, ataxia, nystagmus, squint, LOC, coma,
seizures, respiratory depression, tone,  reflexes, 
plantars
• ECG
– prolonged PR and QRS interval,  QT
– ventricular dysrhythmias
TCAs -Management
• GCS and QRS, best indicators of toxicity
• Supportive
– do not use flumazenil if benzo taken
• Check airway, maintain ventilation, correct hypoxia
– Check ABG, if  CO2 requires ventilation
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Correct hypotension (crystalloids)
Gastric lavage if within 1 hr, and activated charcoal
Rx fits and agitation with diazepam
Rewarm slowly if hypothermic
Close monitoring for 24hrs
TCAs- Dysrhythmias
• Carful ECG monitoring is required
– QRS interval is a guide to cardiac toxicity (>100ms)
• Avoid antidysrhythmic drugs. They may make
matters worse
• Correct hypoxia and acidosis. Aim for a pH of
7.45-7.50 (no higher)
– use iv boluses of sodium bicarbonate
• Sodium loading may also help
• Prolonged CPR may be of use
Tricyclic OD – Initial ECG
Tricyclic OD – Recovery ECG
Benzodiazepine Overdose
• Deaths from poisoning with benzodiazepines alone are rare,
but may be lethal in combination with other CNS depressants
• Treatment is supportive and aimed at maintaining adequate
ventilation whilst supporting cardiovascular depression
• Flumazenil (specific benzodiazepine antidote) is not licensed
(in the UK) for routine use in benzodiazepine overdoses
• Flumazenil may induce seizures; particularly dangerous
where tricyclic antidepressants have been taken
• Flumazenil, may however, be used in the differential
diagnosis of unclear cases of multiple overdoses but expert
advice is ESSENTIAL.
Other agents
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Opiates
Iron
Lead
Digoxin
Calcium blockers
Ethylene glycol
Lithium
Naloxone
Desferrioxamine
Sodium EDTA
FAB
Calcium
Ethanol
Dialysis