Poisoning in children

Overview

Poisoning is a common emergency in children. Toddlers explore by putting things in their mouths, so most poisonings are accidental, happen at home and involve one substance: medicines (especially painkillers and iron), cosmetics and personal care products, cleaning products (bleach, detergents), kerosene and pesticides. Adolescents more often take deliberate overdoses, sometimes of several drugs. Most ingestions cause little harm, but some (iron, tricyclics, organophosphates, caustics, kerosene) can kill a small child.

When to suspect poisoning

Think of poisoning in any child with unexplained:

• Coma or altered behaviour.
• Seizures.
• Arrhythmia or shock.
• Metabolic acidosis or other metabolic upset.
• Vomiting and diarrhoea with odd features.

Poisoned children usually present with one of six patterns: coma, direct organ toxicity, metabolic acidosis, arrhythmia, gastrointestinal upset, seizures.

Initial management

1. Stabilise first

• Treat the patient, not the poison.
• A, B, C of resuscitation; add D (disability): Glasgow Coma Scale, pupils.
• If consciousness is depressed and poisoning is suspected: give oxygen, check and correct glucose (Nelson: glucose 1 g/kg IV) and consider naloxone.
• Treat seizures with a benzodiazepine.

2. History

• What: name of the product, ingredients; bring the container; all medicines in the house.
• How much: work out the maximum possible amount (tablets at start minus tablets left); the amount is usually underestimated.
• When: time of ingestion.
• Symptoms so far, treatment given at home, parents' occupation (pesticides, lead), previous episodes.

3. Examination and toxidromes

Useful clues from Nelson:

• Odours: bitter almonds (cyanide), garlic (organophosphates, arsenic), wintergreen (methyl salicylate), acetone (salicylates, isopropyl alcohol).
• Small pupils: opioids, organophosphates, clonidine, phenothiazines. Large pupils: atropine, tricyclics, amphetamines, cocaine, antihistamines.
• Bradycardia: digoxin, opioids, clonidine, organophosphates, beta-blockers, calcium channel blockers.

4. Investigations

• Blood glucose, electrolytes, urea and creatinine, blood gases (acidosis), calcium, liver tests, osmolality.
• Anion gap and osmolar gap (a raised osmolar gap suggests methanol or ethylene glycol).
• 12-lead ECG in every poisoned child (wide QRS with tricyclics; long QT with phenothiazines and antihistamines).
• Drug levels where they guide treatment: paracetamol, salicylate, iron, digoxin, lithium, theophylline, anticonvulsants.
• Urine toxicology screen; chest X-ray (aspiration); abdominal X-ray for radio-opaque tablets.

Decontamination

Enhanced elimination

• Multiple-dose charcoal: carbamazepine, phenobarbitone, theophylline, dapsone, quinine (and salicylates, digoxin per Akbar).
• Urinary alkalinisation: salicylates, methotrexate.
• Haemodialysis: small, water-soluble, poorly protein-bound poisons: methanol, ethylene glycol, salicylates, lithium, theophylline.

Antidotes

Specific poisons

Paracetamol (acetaminophen)

• Safe in normal doses; a single ingestion of 150 mg/kg or more risks serious liver damage (Akbar).

• Measure serum paracetamol level, ALT, AST, bilirubin, PT/INR, glucose and renal function. Liver tests may stay normal for up to 72 hours.
• Charcoal if seen within about 4 hours (Akbar).
• N-acetylcysteine: oral 140 mg/kg loading, then 70 mg/kg every 4 hours for 17 doses; an IV regimen is also used. Nearly fully protective if started within 8 hours, but still worth giving even after 24 hours.
• Refer for liver transplant assessment in severe liver failure.

Kerosene and other hydrocarbons

• Kerosene, petrol and other petroleum products are often kept in drink bottles; bright colours and fruity smells attract children.
• Low viscosity and low surface tension let them spread into the lungs on swallowing or vomiting, causing chemical (aspiration) pneumonitis and reducing surfactant.
• Features: coughing, choking, breathlessness, tachypnoea, grunting, cyanosis, wheeze and crackles; fever is common (chemical pneumonitis); vomiting; drowsiness, seizures or coma.
• Chest X-ray: patchy shadows that may merge, appearing within hours.
• Management:
  • ABC and oxygen; ventilation if needed.
  • Never induce vomiting or do gastric lavage.
  • Bronchodilators for wheeze.
  • Steroids do not help; antibiotics are not given routinely, only if secondary infection develops.

Iron

• Common and dangerous in young children because iron tablets look like sweets.
• Iron is corrosive to the gut and a mitochondrial poison (shock, acidosis, liver damage).

• No symptoms within 6 hours makes serious toxicity unlikely.
• Serum iron about 4 hours after ingestion; over 500 micrograms/dL means significant toxicity.
• Abdominal X-ray: tablets are radio-opaque (a negative film does not exclude ingestion).
• Charcoal is useless; lavage is not recommended (tablets are large). Whole bowel irrigation may help.
• Deferoxamine IV infusion (up to 15 mg/kg/hour) for moderate to severe poisoning; the IM route is not advised.

Organophosphates (insecticides)

• Irreversibly inhibit acetylcholinesterase, so acetylcholine builds up at muscarinic, nicotinic and CNS receptors. Absorbed through skin, gut, lungs and eyes; children are exposed to stored pesticides or recently sprayed fields.
• Muscarinic: salivation, lacrimation, urination, defecation, gut cramps, emesis (SLUDGE), bronchorrhoea and bronchospasm, sweating, bradycardia, miosis.
• Nicotinic: fasciculations, weakness, paralysis including respiratory muscles; tachycardia and hypertension.
• CNS: restlessness, confusion, seizures, coma, central respiratory failure.
• Diagnosis: clinical; low red cell cholinesterase confirms.
• Treatment:
  • Remove clothes and wash the skin; staff wear gloves.
  • ABC, oxygen, suction; ventilation if needed.
  • Atropine IV, repeated every few minutes and titrated until secretions dry and the chest is clear (dose ranges differ between the two textbooks; follow the local protocol), then continued for at least 24 hours.
  • Pralidoxime 25-50 mg/kg IV over several minutes, repeated, early, for nicotinic weakness.
• Most deaths are from respiratory failure.

Salicylates (aspirin)

• Toxic dose: over 150 mg/kg (Akbar).
• Triad: vomiting, hyperpnoea, hyperpyrexia; also tinnitus, sweating, lethargy, coma.
• Acid-base: early respiratory alkalosis (direct respiratory centre stimulation), then metabolic acidosis (uncoupled oxidative phosphorylation); children under 4 years usually present with acidosis.
• Also abnormal blood glucose and a bleeding tendency (reduced platelet adhesiveness).
• Treatment: ABC, charcoal (multiple doses), fluids, urinary alkalinisation with sodium bicarbonate and potassium, cooling, vitamin K for bleeding; haemodialysis in severe cases. No specific antidote.

Tricyclic antidepressants

• Very toxic in small children; a few tablets can kill.
• Anticholinergic features, drowsiness, coma, seizures, hypotension.
• ECG: QRS over 100 ms predicts seizures and arrhythmias; long PR and QT.
• Treatment: ECG monitoring, charcoal, sodium bicarbonate (1 mEq/kg bolus, Akbar) to keep blood pH about 7.5 for wide QRS, arrhythmia or hypotension; benzodiazepines for seizures; observe asymptomatic children for at least 6 hours. Dialysis does not help.

Caustics (acids, alkalis, bleach)

• Alkalis cause liquefaction necrosis that penetrates deeply (risk of perforation); acids cause coagulation necrosis, which limits depth, and their sour taste usually stops the child drinking much.
• Features: drooling, dysphagia, pain, vomiting, stridor. Absence of mouth burns does not exclude oesophageal injury.
• Never induce vomiting or do lavage; no charcoal. Wash skin and eyes.
• Endoscopy to assess injury; steroids are controversial.
• Late complication: oesophageal stricture, later cancer risk.
• A button battery stuck in the oesophagus must be removed endoscopically urgently.

Lead

• Sources: old paint (with pica), batteries, some cosmetics, parents' industrial work; iron deficiency increases absorption.
• Features: abdominal pain, constipation, anorexia, irritability, learning and behaviour problems, anaemia; encephalopathy with raised intracranial pressure in severe cases.
• Tests: blood lead level (diagnostic; 10 micrograms/dL or more is abnormal in the textbooks); microcytic anaemia with basophilic stippling; lead lines at the metaphyses; radio-opaque flakes on abdominal X-ray.
• Treatment: remove the source, treat iron deficiency, chelation (DMSA by mouth; EDTA and BAL for severe poisoning or encephalopathy). Chelation is not advised below a venous level of 45 micrograms/dL.

Carbon monoxide

• From poorly ventilated heaters, generators and fires.
• Headache, dizziness, nausea (mistaken for flu), confusion, coma; a red skin colour suggests CO poisoning.
• Symptoms match the carboxyhaemoglobin (COHb) level: usually from about 15%, severe neurological effects above 40% (Akbar).
• 100% oxygen shortens the COHb half-life from several hours to much less; hyperbaric oxygen for neurological signs or COHb over 25% in children (Akbar).

Prevention

• Store medicines, kerosene and pesticides out of reach, in original labelled containers (never in drink bottles).
• Child-resistant containers.
• Warn parents how dangerous a few tablets of iron or tricyclics can be.
• Teach first aid and when to seek help.

Quick revision

• Accidental in toddlers at home; deliberate in teenagers.
• ABC, glucose, oxygen, naloxone if depressed consciousness.
• Charcoal 1 g/kg within 1 hour; not for iron, lead, lithium, alcohols, caustics, kerosene.
• Kerosene: aspiration pneumonitis; no emesis or lavage; no steroids.
• Paracetamol 150 mg/kg toxic; NAC 140 then 70 mg/kg 4-hourly × 17.
• Iron: 20 mg/kg toxic, 60 systemic, 250 lethal; deferoxamine; pyloric stricture later.
• Organophosphate: miosis, secretions, bradycardia, fasciculations; atropine plus pralidoxime.
• Salicylate: respiratory alkalosis then metabolic acidosis; alkalinise urine.
• Tricyclic: QRS over 100 ms; sodium bicarbonate.
• CO: 100% oxygen; hyperbaric if COHb over 25% or neurological signs.

Written by The House Job from standard references (Basis of Paediatrics by Pervez Akbar; Nelson Essentials of Paediatrics).

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