Transcript Toxicology - University of Auckland

General Approach to
the Poisoned Patient
General Approach
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Every one has a slightly different method of
dealing with an overdose but mostly we follow a
general pattern:
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Resuscitation
Risk assessment
Supportive care
Decontamination
Enhanced elimination
Antidotes (often part of resuscitation)
Dispostion
Resuscitation
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This should always be the first step. There
is no point working out the patient’s risk
from an overdose if they are currently in
VF
This follows the layout taught in ACLS
courses with a few other steps added in
Resuscitation
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Airway
Breathing
Circulation
Disability
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Assess level of unconsciousness
Stop seizures (a common effect in overdoses)
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Benzodiazepines such as lorazepam and diazepam are used
first line for drug-induced seizures
Don’t ever forget glucose
Resuscitation
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Exposure / Environment
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Correct hyperthermia (T > 38.5 in overdose most
often seen with serotonergic syndrome and
neuroleptic malignant syndrome and is associated
with CNS dysfunction and multi-organ failure)
Consider specific antidotes
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A few medications have effective antidotes
Paracetamol is the most common overdose seen with
an effective antidote (N-acetylcysteine)
Risk Assessment
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This determines the patient’s risk for
developing complications
Often the information will need to come
from ambulance staff and family members
Risk Assessment – Questions to Ask
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What drug has been taken?
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Different drugs have different toxicities
It is important to know what formulation of drug it is
E.g. Different types of iron tablets contain different amounts
of iron per tablet (ferrogradumet = 1-5mg iron, ferrotab =
65mg)
How may tablets have been taken?
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If you can not determine the exact number, work on “worst case
scenario”
Eg. if the patient had a script for 100 tablets 2 week ago,
assume they took 100 tablets
Risk Assessment – Questions to Ask
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When were they taken?
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Does the patient have any clinical features of an overdose?
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Each drug has a time to peak effect and this determines how long a
patient should observed
E.g. if the patient took an overdose of paroxetine 18 hours earlier and
was asymptomatic on presentation, they are not going to develop
symptoms
Early onset of symptoms may suggest a large overdose
Does the patient have any co-morbidities that may make the effects
of a drug worse?
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Someone with severe heart failure will not cope with a metoprolol (B
blocker) overdose as well as they lack the cardiac reserves
Supportive Care
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This is all that is needed in a majority of
cases
This includes anti-emetics, IV fluids,
supplemental oxygen, as well as
monitoring for complications and
deterioration
Decontamination
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Inducing emesis with ipecac, gastric lavage and
whole bowel irrigation have all previously been
used to try and remove drugs from the GI tract
and limit absorption
All are ineffective
All have associated risks that outweigh their
benefits
Decontamination
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Induced emesis
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No longer ever done
Risk of aspiration is significant and it does not remove
drugs effectively
Gastric lavage
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Involves placing a tube from the mouth to stomach
and trying to wash the tablets out
Has a very high rate of aspiration
It is only done for severe and life-threatening
overdoses and the patient should be intubated prior
Decontamination
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Whole bowel irrigation
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Consists of giving a course of bowel prep to
flush the medication out (ie. gives the patient
diarrhoea +++)
Probably ineffective
Is still used in large iron overdoses as the
tablets form bezoars in the intestine
Decontamination
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Activated charcoal
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Has large surface area that can bind drugs
and theoretically limit absorption
Limited evidence when given early (<1 hour),
ineffective after 1 hour
High rate of vomiting especially in women
Causes nasty lung injury if aspirated
Use is mostly dying out
Enhanced Elimination
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Rarely done
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2 most common techniques are:
1.
2.
Dialysis
Good for alcohols, lithium, aspirin
Urine alkalinisation
Traps aspirin in the urine
Disposition
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When is the patient safe to go home?
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Have they been assessed by psychiatry?