Transcript 1._Poisoning

Prepared by:
Dr.Mohamed Shekhani.
References: Davidson PP of Medicine.
Introduction:
• Poisoning is a major cause of death in young adults& 10% of
hospital admissions.
• Most deaths occur before patients reach medical attention&
mortality is much <1% in those admitted to hospital.
Introduction: In developed countries
• The most frequent cause is intentional drug overdose in the context
of self-harm& usually involves prescribed or ‘over-the-counter’ OTC
medicines.
• Accidental poisoning is also common, esp in children& elderly.
• Household /agricultural products such as pesticides/ herbicides are
common sources of poisoning &associated with a much higher case
fatality.
• Toxicity also may occur as a result of alcohol or recreational
substance use, or following occupational or enviro exposure.
General approach:Triage/resuscitation:
• Those seriously poisoned must be identified early so that
appropriate management is not delayed.
• Vital signs:
• Identifying the poison(s) by obtaining adequate information.
• Prevent reattempt by identifying those at risk.
• Those with external contamination with chemical or environmental
toxins should undergo appropriate decontamination.
• Critically ill patients must be resuscitated(abc).
• (GCS) is commonly employed to assess conscious level or AVPU
(alert/verbal/painful/unresponsive).
General approach:Triage/resuscitation:
General approach: Triage/resuscitation:
• An (ECG) should be performed & cardiac monitoring instituted in
all patients with CV features or where exposure to potentially
cardiotoxic substances is suspected.
• Those who need antidotes given according to weight.
• Benzodiazepine/flumazenil
• Opiods/Nalorphine.
• Paracetamol/N-Acetyl cysteine.
• Substances that are unlikely to be toxic in humans should be
identified so that inappropriate admission & intervention are
avoided
General approach: Triage/resuscitation:
General approach: Triage/resuscitation:
Clinical assessment:
• History &examination .
• Patients may be unaware or confused about what they have
taken, or may exaggerate (or less commonly underestimate) the
size of the overdose, &rarely mislead medical staff deliberately.
• Toxic causes of abnormal physical signs SHOULBE BE KNOWN.
• Cluster of clinical features (‘toxidrome’) suggestive of poisoning
with a particular drug type IDENTIFIED.
• Poisoning is a common cause of coma, especially in younger people,
but it is important to exclude other potential causes, unless the
aetiology is certain.
• Anticholinergic
– Hot As Hades
– Blind As A Bat
– Dry As A Bone
– Red As A Beet
– Mad As A Hatter
Investigations:
• Urea, electrolytes, creatinine should be measured in most patients.
• Arterial blood gases should be checked in those with significant
respiratory or circulatory compromise, or when poisoning with
substances likely to affect acid–base status is suspected.
• Calculation of anion and osmolar gaps may help to inform diagnosis
for a limited number of specific substances.
• Management may be facilitated by measurement of the amount of
toxin in the blood.
• Qualitative urine screens or potential toxins including nearpatient testing kits have a limited clinical role.
• Occasionally, for medicoegal reasons, it is useful to save blood
and urine for subsequent measurement of drug concentrations.
psychiatric assessment
• All patients presenting with deliberate drug overdose should
undergo psychosocial evaluation by a health professional with
appropriate training prior to discharge ,once the patient has
recovered from any features of poisoning, unless there is an urgent
issue such as uncertainty about his or her capacity to decline
medical treatment.
General management
• Patients presenting with eye or skin contamination should
undergo appropriate local decontamination procedures.
Gastrointestinal decontamination
• Patients who have ingested potentially life- threatening
quantities of toxins may be considered for GIT decontamination if
poisoning has been recent.
• Induction of emesis using ipecacuanha is now never recommended.
Activated charcoal
• Given orally as slurry, activated charcoal absorbs toxins in the bowel
as a result of its large surface area.
• If given sufficiently early, it can prevent absorption of an
important proportion of the ingested dose of toxin.
• The efficacy decreases with time.
• Current guidelines do not advocate use >1 hour after overdose in
most circumstances,EXCEPT when delayed-release preparation has
been taken or when gastric emptying may be delayed.
Activated charcoal
• Some toxins do not bind to activated charcoal so it will not affect
their absorption.
• In patients with an impaired swallow or a reduced level of
consciousness, the use of activated charcoal, even via a nasogastric
tube, carries a risk of aspiration pneumonitis.
• This risk can be reduced but not completely removed by
protecting the airway with a cuffed endotracheal tube.
• Multiple doses of oral activated charcoal (50 g every 4 hours) may
enhance the elimination of some drugs at any time after
poisoning and are recommended for serious poisoning with some
substances .
Activated charcoal
• They achieve their effect by interrupting enterohepatic circulation
or by reducing the concentration of free drug in the gut lumen, to
the extent that drug diffuses from the blood back into the bowel to
be absorbed on to the charcoal: so-called ‘GIT dialysis’. A laxative is generally given with the charcoal to reduce the risk of
constipation or intestinal obstruction by charcoal ‘briquette’
formation in the gut lumen.
• Recent evidence suggests that single or multiple doses of
activated charcoal do not improve clinical outcomes after poisoning
with pesticides or oleander.
SUBSTANCES NOT BOUND BY
CHARCOAL
• Alcohols And
Glycols
• Corrosives
– Alkalis
– Acids
• Cyanide
• Saline Cathartics
• Heavy Metals
– Iron
– Lead
– Lithium
– Mercury
• Hydrocarbons
Gastric aspiration & lavage
• Gastric aspiration and/or lavage is now very infrequently
indicated in acute poisoning, as it is no more effective than
activated charcoal, and complications are common, especially
aspiration.
• Use may be justified for life-threatening overdoses of some
substances that are not absorbed by activated charcoal
Whole bowel irrigation
• This is occasionally indicated to enhance the elimination of ingested
packets or slow-release tablets that are not absorbed by activated
charcoal (e.g. iron, lithium), but use is controversial.
• It is performed by administration of large quantities of polyethylene
glycol and electrolyte solution (1–2 L/hr for an adult), often via a
nasogastric tube, until the rectal effluent is clear.
• Contraindications include inadequate airway protection,
haemodynamic instability, gastrointestinal haemorrhage,
obstruction or ileus.
• Whole bowel irrigation does not cause osmotic changes but may
precipitate nausea and vomiting, abdominal pain and electrolyte
disturbances
Urinary alkalinisation
• Urinary excretion of weak acids& bases is affected by urinary pH,
which changes the extent to which they are ionised.
• Highly ionised molecules pass poorly through lipid membranes and
therefore little tubular reabsorption occurs and urinary excretion
is increased.
• If the urine is alkalinised (pH > 7.5) by the administration of
sodium bicarbonate (e.g. 1.5 L of 1.26% sodium bicar-bonate over 2
hrs), weak acids (e.g. salicylates, methotrexate , herbicides 2,4dichlorophenoxyacetic acid and mecoprop) are highly ionised and
so their uri-nary excretion is enhanced.
• This technique should be distinguished from forced alkaline
diuresis, in which large volumes of fluid with diuretic are given in
addi-tion to alkalinisation(no longer used because of the risk of
fluid overload).
Urinary alkalinisation
• Urinary alkalinisation is currently recommended for patients
with clinically significant salicylate poi-soning when the criteria
for haemodialysis are not met
• It is also sometimes used for poisoning with methotrexate.
• Complications include alkalaemia, hypokalaemia, occasionally
alkalotic tetany.
• Hypocalcaemia is rare.
Haemodialysis & haemoperfusion
• These can enhance the elimination of poisons that have a small
volume of distribution & a long half-life after overdose, useful when
the episode of poisoning is sufficiently severe to justify invasive
elimination methods.
• The toxin must be small enough to cross the dialysis membrane
(haemodialysis) or must bind to activated charcoal
(haemoperfusion) .
• Haemodialysis may also correct acid–base and metabolic
disturbances associated with poisoning
Antidotes
• Are available for some poisons
• Work by a variety of mechanisms: for example:
• Specific antagonism (e.g. isoproterenol for β–blockers) or
Pharmacological antagonism( flumazenil for benzodiazepines &
nalorphine for opoids)
• Chelation (e.g. desferrioxamine for iron)
• Reduction (e.g. methylene blue for dapsone).
Supportive care
• For most poisons, antidotes & methods to accelerate elimination
are inappropriate, unavailable or incompletely effective.
• Outcome is dependent on appropriate nursing & supportive care,
& on treatment of complications.
• Patients should be monitored carefully until the effects of any
toxins have dissipated.
Algorithm for management of poisoned patients:
History &physical exam, consider toxidromes to know possible drug or toxin
involved&consider discharge in ingestion of non-toxic drugs
Check & manage ABC
Take drug blood level in certain drugs & consider use of antidote if present
For medico-legal you may store urine or blood samples in serious ill ones.
Measure an ion/osmolar gap in certain drugs/toxins
Acivated charcoal+ laxative, if patients presented within 1 hour,longer for serious
drugs(MDAC),SR drugs, gastropariesis.
GIT decontamination: WBI( for SR or drug packs or AC not effective), induction
of vomiting not beneficial except when the drug not adsorbed by AC
Urine alkalization for MXT, Asp, herbicides.
Symptomatic management ,if serious in ICU
Study SCQs:
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1. In Poisoning all are true except::
A. The most common cause of death in young adults.
B. The most common cause of hospital admissions.
C. Most die before reaching hospital.
D. In-Hospital Mortality should be less than 1%.
E.The most common cause of death in elderly persons.
Study SCQs:
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2.The most way of poisoning is:
A.Accidental.
B.Intentional.
C. Agricultural products intake.
D. Alcolol.
E. Opoid intake.
Study SCQs:
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3.Common drugs involved in poisoning include all except:
A.NSAIDs.
B.Acetaminophen.
C. Antidepresants.
D.Lead.
E.Alcohol.
Study SCQs:
• 4. Poisons with serious effects requiring urgent actions
include all except:
• A.Acetaminophen.
• B.Ethylene glycol.
• C.Oral contraceptives.
• E. CO.
Study SCQs:
• 5.Poisoning is recognized by the following toxidromes
except:
• A.Anticholinergic.
• B. Adrenergic.
• C.Cholinergic.
• D.Stimulants.
• E.Opoid.
Study SCQs:
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6.Regarding poisoning in elderly,all are true except:
A. Commonly caused by intentional poisoning.
B. Mortality in higher.
C. Psychiatric disease as a cause is less than in the young.
D. Higher risk of recurrent attempts if due to chronic
illnesses.
• E. Toxic prescriptions are common.
Study SCQs:
• 7. Drug level as part of management of poisoning is
indicated in all except:
• A.Acetaminophen.
• B. Oral hypoglycemic.
• C.CO.
• D.Iron.
• E.Digoxin.
Study SCQs:
• 9.All these poisons cause acidosis with normal lactate
except:
• A.Aspirin.
• B.Methanol.
• C. Ethelene glycol.
• D.Paraldehyde.
• E.Iron.
Study SCQs:
• 10.The following are not adsorbed by activated charcoal
except:
• A.Cyanide.
• B.Glycols.
• C.Aspirin.
• D.Lead.
• E.Lithium.
Study SCQs:
• 11.The best management of drug-poisoned patient
presenting within 1 hour is:
• A.Whole bowel irrigation.
• B.Tincher ipecan vomint induction.
• C.Activated charcoal.
• D.Hemodialysis.
• E.Hemofiltration.
Study SCQs:
• 12.The antidote that acts by direct pharmacological
antagonism is:
• A.Deferoxamine for iron.
• B.Nalorphine for opoids.
• C.Alkaline diuresis for salycylates.
• D.Praladoxime for organophosphorous poisoning.
• E.Methylene blue for Dapson.
Study SCQs:
• 13.The most urgent treatment of organophosphorous
poisonig is:
• A.Atropin injection.
• B.Praladoxime.
• C.Mechanical ventilation.
• D.O2.
• E.Bronchial lavage.