Poisonig; treatment, causes, managment

Poisoning

Triage

Assess vital signs immediately.

Identify poison(s) involved and

obtain information about it/them.

 Identify patients at risk of

further self-harm and remove remaining hazards from them.

Poison


History

The diagnosis of poisoning is usually apparent from the history,

although occasionally patients may conceal information, or exaggerate

or deliberately mislead staff. Try to establish:

What toxin(s) have been taken and how much?

When and how were they taken?

 Have alcohol or other drugs been taken too?

Can any witness corroborate the information?

 What drugs have

the GP prescribed?

What is the risk of suicide?

 Is the patient

capable of rational decisions?

Are there any other significant

medical conditions?

In envenomed patients, establish:

When was the patient exposed to the bite/sting?

 What did the

causal organism look like?

 How did it happen?

 Were there multiple

bites/stings?

 What first aid was given?

 What are the patient’s symptoms?

 ● Do they have other medical conditions, regular treatments,

previous similar episodes or known allergies?

Risk factors for suicide

• Psychiatric illness (depression, schizophrenia)

• Male sex

• Living alone

• Recent bereavement, divorce or separation

• Suicide note written

• Age > 45

• Unemployment

• Chronic physical ill health

• Drug or alcohol misuse

• Previous attempts (violent method)

Clinical examination

There may be needle marks or evidence of previous self-harm, e.g.

razor marks on forearms. Pupil size, respiratory rate and heart rate

may help to narrow down the potential list of toxins. The Glasgow

Coma Scale (GCS;  is most frequently used to assess the

degree of impaired consciousness. The patient’s weight helps to

determine whether toxicity is likely to occur, given the dose ingested.

When patients are unconscious and no history is available, other

causes of coma must be excluded (especially meningitis, intracerebral

bleeds, hypoglycaemia, diabetic ketoacidosis, uraemia and

encephalopathy). Certain classes of drug cause clusters of typical

signs, e.g. cholinergic or anticholinergic, sedative or opioid effects,

which can aid diagnosis.

Investigations

U&Es and creatinine should be measured in all patients, and ABGs

in those with circulatory or respiratory compromise. Drug levels are

a useful to guide treatment for some specific toxins, e.g. paracetamol,

salicylate, iron, digoxin, carboxyhaemoglobin, lithium and

theophylline. Urinary drug screens have a limited clinical role.

Psychiatric assessment

All patients who have taken a deliberate drug overdose should

undergo psychiatric evaluation by a trained professional before discharge,

but ideally after recovering from poisoning. The purpose is

to establish the short-term risk of suicide and to identify potentially

treatable problems, either medical, psychiatric or social. Risk factors

for suicide are shown in.

MANAGEMENT OF THE POISONED PATIENT

Eye or skin contamination should be treated with appropriate

washing or irrigation. Patients who have recently ingested

significant overdoses need further measures to prevent absorption

or increase elimination:

Activated charcoal (50 g orally) can be given, if a potentially toxic

amount of poison has been ingested < 1 hr before presentation.

Agents that do not bind to activated charcoal include ethylene

glycol, iron, lithium, mercury and methanol. Whole-bowel irrigation

with polyethylene glycol can be used for toxic ingestions of iron,

lithium and theophylline, or to flush out packets of illicit drugs.

Urinary alkalinisation using IV sodium bicarbonate enhances

elimination of salicylates, methotrexate and the herbicide 2,4-D.

Haemodialysis is occasionally used for serious poisoning with salicylates,

theophylline, ethylene glycol, methanol or carbamazepine.

Infusions of lipid emulsion can be used to reduce tissue concentrations

of lipid-soluble drugs such as tricyclic antidepressants.

Specific antidotes are only available for a small number of poisons

. In serious cases, meticulous supportive care, including the

treatment of seizures, coma and arrythmias, with ventilatory support

where required, is critical to good outcome.

Antidotes available for the treatment of specific poisonings

Poison Antidote

Anticoagulants (e.g. warfarin) Vitamin K, fresh frozen plasma

β-adrenoceptor antagonists

(beta-blockers)

IV glucagon, adrenaline (epinephrine)

Calcium channel blockers Calcium gluconate, calcium chloride, glucagon

Cardiac glycosides, e.g. digoxin Digoxin-specific antibody fragments (Fab)

Cyanide Oxygen, dicobalt edetate, nitrites, sodium

thiosulphate, hydroxocobalamin

Ethylene glycol/methanol Ethanol, fomepizole

Iron salts Desferrioxamine

Lead DMSA, DMPS, disodium calcium edetate

Mercury DMPS

Opioids Naloxone

Organophosphorus

insecticides, nerve agents

Atropine, oximes (e.g.pralidoxime)

Paracetamol N-acetylcysteine, methionine

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