: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:• 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
: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 near- patient 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 laxa- tive 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 • Heavy Metals Glycols – Iron• Corrosives – Lead – Alkalis – Lithium – Acids – Mercury• Cyanide • Hydrocarbons• Saline Cathartics
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 2,4- dichlorophenoxyacetic 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.
:Study SCQs• 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• 2.The most way of poisoning is:• A.Accidental.• B.Intentional.• C. Agricultural products intake.• D. Alcolol.• E. Opoid intake.
:Study SCQs• 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• 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.