Common Toxidromes (Paracetamol, Iron, Caustics, Button Batteries) and Decontamination

Paediatric Toxicology: Toxidrome Recognition, Ingestions, and Critical Interventions

Poisonings and foreign body ingestions account for a substantial volume of paediatric emergency presentations. Paediatric ingestions follow a distinct bimodal age distribution:

1. Toddlers and Young Children (1 to 5 years): Exploratory, accidental ingestions typically involving a single household substance or pharmaceutical formulation.
2. Adolescents (12 to 18 years): Deliberate self-harm or recreational substance ingestions, frequently involving multiple concurrent agents and co-ingested ethanol.

Successful management relies on an organized resuscitation approach: stabilizing vital functions via the ABCDE protocol, recognizing systemic toxidromes, identifying specific antidotes, and applying timely interventions to prevent catastrophic secondary tissue damage.

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The Major Paediatric Toxidromes

A toxidrome is a constellation of physical signs and clinical symptoms characteristic of a specific pharmacological drug class. Rapid toxidrome identification guides immediate life-saving interventions before toxicological screening results return:

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Poison-Centre and Clinical Toxicology Advice

Stabilisation and risk assessment proceed together. Contact the local poison information centre or clinical toxicologist for potentially serious, uncertain or unusual exposures and before specialist decontamination or enhanced elimination. Give the child's weight, agent/product and formulation, route, time, maximum possible dose, co-ingestants, symptoms, examination findings and treatment already given. Keep packaging or a photograph of the label. The service helps identify ingredients, expected toxicity, monitoring and observation needs, antidotes and referral requirements; consultation must not delay immediate resuscitation. Use the appropriate national service rather than assuming one telephone number applies throughout Europe.

Source: RCH acute poisoning guidance.

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Gastrointestinal Decontamination: Evidence-Based Indications and Pitfalls

Routine gastrointestinal decontamination is no longer recommended. Decontamination carries substantial risks and must be deployed only when strict clinical criteria are met.

1. Single-Dose Activated Charcoal (SDAC)

• Dosing: $1\text{ g/kg}$ orally or via nasogastric tube (maximum dose $50\text{ g}$ in children, $50\text{ to }100\text{ g}$ in adolescents).
• Indications: Consider for a potentially serious ingestion of an adsorbable poison after poison-centre assessment. Give as early as possible; 1 hour is not an absolute cutoff. Selected poisons may benefit up to 6 hours, or later if absorption continues, depending on formulation and dose.
• Absolute Contraindications:
  • Depressed conscious state or impaired airway protective reflexes without endotracheal intubation (catastrophic pulmonary aspiration pneumonitis risk).
  • Intestinal obstruction, perforation, or ileus.
  • Caustics: Charcoal obscures endoscopic assessment and does not treat the burn.
  • Hydrocarbons: Aspiration and vomiting risks usually outweigh any benefit.
  • Iron, lithium and toxic alcohols (methanol, ethylene glycol, ethanol): No useful adsorption.

Pesticides are not uniformly nonadsorbable: selected organophosphorus insecticide or paraquat ingestions may warrant charcoal with specialist advice. Do not insert an NG/OG tube solely to give charcoal to a non-intubated patient.

2. Whole Bowel Irrigation (WBI)

• Technique: Enteral administration of an iso-osmolar polyethylene glycol electrolyte solution (PEG-ELS) via nasogastric tube at $25\text{ to }40\text{ mL/kg/h}$ until the rectal effluent is completely clear.
• Indications: Reserved strictly for large ingestions of sustained-release or enteric-coated medications, massive iron ingestions with visible radiopaque pills on abdominal radiographs, or ingested packages of illicit drugs ("body packers").

3. Obsolete and Dangerous Practices

• Syrup of Ipecac: Strictly obsolete and contraindicated. It induces protracted emesis, delays charcoal administration, and increases aspiration risk.
• Routine Gastric Lavage: Strictly contraindicated. It does not improve clinical outcomes and risks mechanical esophageal perforation, hypoxia, and laryngospasm.

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Paracetamol (Acetaminophen) Toxicity

Paracetamol is the most common pharmaceutical involved in paediatric overdose.

Toxic Thresholds

• Acute single ingestion: $>150\text{ mg/kg}$ in children ($>200\text{ mg/kg}$ in healthy toddlers $<6$ years, or $>7.5\text{ g}$ in adolescents).

Pathophysiological Cascade

                  [Paracetamol Ingestion]
                             |
      +----------------------+----------------------+
      |                                             |
      v                                             v
[Major Non-Toxic Pathways (~90%)]            [Minor Toxic Pathway (~5-10%)]
- Hepatic Glucuronidation & Sulfation        - Cytochrome P450 (CYP2E1)
- Water-soluble non-toxic metabolites        - Generates NAPQI (reactive toxic metabolite)
- Excreted safely in urine                          |
                                                    v
                                         [Glutathione Neutralization]
                                         - Under normal conditions, glutathione
                                           conjugates NAPQI to non-toxic cysteine
                                                    |
                                        (In Massive Overdose: >150 mg/kg)
                                                    |
                                                    v
                                         [Glutathione Depletion (>70%)]
                                                    |
                                                    v
                                      [Unbound NAPQI Covalent Binding]
                                      - Binds to hepatocyte macromolecular sulfhydryls
                                      - Mitochondrial dysfunction & lipid peroxidation
                                      - Zone 3 Centrilobular Hepatic Necrosis

The Four Clinical Stages of Paracetamol Hepatotoxicity

1. Stage 1 (0 to 24 hours): Asymptomatic or mild, non-specific gastrointestinal symptoms (anorexia, nausea, vomiting, diaphoresis). Hepatic transaminases are normal.
2. Stage 2 (24 to 72 hours): "Quiescent latent phase." Nausea improves, but subclinical hepatocyte necrosis begins: transaminases (ALT/AST) and bilirubin rise, the prothrombin time (INR) prolongs, and right upper quadrant abdominal tenderness emerges.
3. Stage 3 (72 to 96 hours): Peak hepatotoxicity. Fulminant hepatic failure manifests with jaundice, profound coagulopathy (INR $>5-6$), hypoglycaemia, hyperammonaemic hepatic encephalopathy, acute kidney injury (acute tubular necrosis), and severe metabolic lactic acidosis.
4. Stage 4 (4 to 14 days): Gradual clinical resolution and complete histological liver regeneration, or progression to multi-organ failure and death.

The Rumack-Matthew Nomogram and Dosing Window

• Interpretation: For a single acute ingestion at a known time, plot serum paracetamol concentration against time post-ingestion, from 4 hours onward, using the local nomogram. Do not use this method for an unknown ingestion time or repeated/staggered overdose; obtain poison-centre advice.
• The 4-Hour Rule: Serum levels drawn earlier than 4 hours post-ingestion are completely uninterpretable because gastrointestinal absorption and hepatic distribution are ongoing. A level drawn at 2 hours cannot be plotted on the nomogram.
• Treat with N-acetylcysteine (NAC) at or above the locally applicable treatment line. The UK uses 100 mg/L at 4 hours; many other protocols use 150 mg/L (approximately 1,000 micromol/L). Start NAC empirically after a potentially toxic ingestion if awaiting the result would delay treatment beyond 8 hours, then reassess when results return.

Antidotal Therapy: N-Acetylcysteine (NAC)

• Mechanism: NAC acts as a glutathione precursor and glutathione substitute, directly conjugating and detoxifying NAPQI into non-toxic mercapturic acid.
• Timing: Virtually $100\%$ effective in preventing hepatotoxicity and mortality when started within 8 hours of acute ingestion. Even with delayed presentation ($>8\text{ to }24\text{ hours}$) or in established fulminant liver failure, NAC remains highly beneficial by reducing cerebral oedema and improving microvascular oxygen delivery.
• Adverse Effects: Non-IgE hypersensitivity reactions occur in up to 10–15% with traditional IV regimens, usually during the initial infusion. Pause the infusion and assess ABC. Treat anaphylaxis immediately with IM adrenaline 0.01 mg/kg (maximum 0.5 mg), with airway/oxygen and IV fluid support as needed. Antihistamines treat skin symptoms; salbutamol is an adjunct for wheeze. Once the reaction resolves, restart indicated NAC at a reduced rate with poison-centre advice.

King's College Hospital Criteria for Emergency Liver Transplantation

The classical King’s College criteria identify poor prognosis in paracetamol-induced acute liver failure and prompt urgent transplant-centre assessment. Children with acute liver failure need early specialist contact; do not wait for these criteria before referral. Transplantation should be considered if:

• Arterial blood $\mathbf{pH < 7.30}$ after adequate fluid resuscitation (regardless of the degree of encephalopathy),

OR ALL THREE OF THE FOLLOWING WITHIN A 24-HOUR PERIOD:

1. Grade III or IV hepatic encephalopathy
2. Serum creatinine $>300\text{ micromol/L}$ ($>3.4\text{ mg/dL}$)
3. International Normalized Ratio ($\mathbf{INR > 6.5}$) or Prothrombin Time $>100\text{ seconds}$.

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Iron Toxicity

Paediatric iron poisoning typically occurs when toddlers ingest colorful maternal prenatal iron supplements.

Toxicity Thresholds (Elemental Iron)

Always calculate the dose of elemental iron, not the total salt weight (e.g., ferrous sulfate contains $20\%$ elemental iron; ferrous fumarate contains $33\%$; ferrous gluconate contains $12\%$):

• $<20\text{ mg/kg}$: Non-toxic; gastrointestinal symptoms unlikely.
• $20\text{ to }60\text{ mg/kg}$: Mild to moderate gastrointestinal toxicity.
• $>60\text{ mg/kg}$: Severe, potentially lethal systemic toxicity requiring aggressive intervention.

Four Clinical Phases of Iron Poisoning

1. Phase 1 (0.5 to 6 hours): Direct corrosive injury to the gastrointestinal mucosa: nausea, severe vomiting, haematemesis, abdominal pain, and bloody diarrhea (melena).
2. Phase 2 (6 to 24 hours): "Deceptive latent period." Gastrointestinal symptoms abate as iron shifts from the bloodstream into hepatocytes and mitochondria, giving false reassurance while systemic cellular toxicity develops.
3. Phase 3 (12 to 48 hours): Severe systemic cellular toxicity. Free circulating ferric ions uncouple oxidative phosphorylation and inhibit the Krebs cycle, triggering profound high-anion-gap metabolic lactic acidosis, cardiogenic/hypovolaemic shock, acute hepatic failure, coagulopathy, and hypoglycaemia.
4. Phase 4 (2 to 6 weeks): Cicatricial healing phase: gastric outlet obstruction and intestinal strictures secondary to corrosive scarring.

Diagnostics and Chelation Therapy

• Diagnostics: Abdominal plain radiography demonstrates radiopaque intact iron tablets in the stomach or bowel. Measure serum iron at 4 to 6 hours post-ingestion ($>90\text{ micromol/L}$ or $>500\text{ mcg/dL}$ indicates severe toxicity; $>180\text{ micromol/L}$ or $>1000\text{ mcg/dL}$ indicates lethal toxicity).
• Chelation Therapy: Intravenous Deferoxamine (Desferrioxamine):
  • Infusion rate: 15 mg/kg/h IV initially with toxicologist supervision. Reduce as clinical status permits, usually after 4–6 hours, to keep the usual total at 80 mg/kg per 24 hours; persistent severe toxicity needs specialist-directed reassessment.
  • Mechanism: Binds free ferric iron ($Fe^{3+}$) to form ferrioxamine, a water-soluble complex excreted harmlessly by the kidneys, classic for turning the urine an orange-red "vin rosé" color.
  • Indications: Significant systemic illness (shock, severe acidosis, altered consciousness or worsening symptoms), serum iron >90 micromol/L, or 60–90 micromol/L with symptoms or visible tablets. Do not await iron results in a critically ill child. Visible tablets without these criteria primarily guide WBI, not automatic chelation.

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Caustic Ingestions: Acids versus Alkalis

Caustic injuries result from accidental ingestion of commercial cleaning agents, drain unblockers, or dishwashing detergents:

Absolute Contraindications in Caustic Ingestions

• DO NOT induce emesis: Re-exposes the esophagus, pharynx, and airway to the corrosive chemical.
• DO NOT attempt chemical neutralization: Administering a weak acid to neutralize an alkali (or vice versa) produces a vigorous exothermic reaction, superimposing a catastrophic thermal burn onto the chemical burn.
• DO NOT dilute with large volumes of water or milk: Distends the stomach and triggers spontaneous vomiting.
• DO NOT insert a blind nasogastric tube: High risk of mechanically perforating the friable, necrotic esophageal wall.
• DO NOT administer activated charcoal: Does not bind caustics and completely obscures mucosal visualization on endoscopy.

Management and Endoscopy Timing

• Maintain NPO, secure airway if stridor or hoarseness is present, provide IV fluid resuscitation, and administer analgesia.
• Flexible Upper Gastrointestinal Endoscopy: After airway and circulatory stabilization, perform EGD within 24 hours in children with oral lesions, drooling, dysphagia, vomiting, pain, bleeding or respiratory signs. It may be withheld if the child is entirely asymptomatic without mouth lesions and reliable follow-up is assured. Suspected perforation or a late presentation requires specialist imaging/surgical/endoscopic assessment: tissue friability increases procedural risk.

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Button Battery Ingestions

An ingested button (disc) battery lodged in the esophagus represents one of the most critical surgical emergencies in paediatrics:

          [Button Battery Lodged in Esophagus]
                           |
                           v
     Generation of External Electrical Microcurrent
     (Tissue fluids bridge anode and cathode)
                           |
                           v
     Electrolysis of Tissue Water at the Negative Pole (Anode)
     [2 H2O + 2 e- -> H2 + 2 OH-]
                           |
                           v
     Rapid Generation of Concentrated Sodium Hydroxide (Alkali)
                           |
                           v
     [Severe Transmural Liquefactive Necrosis within 2 Hours]
                           |
         +-----------------+-----------------+
         |                                   |
         v                                   v
[Tracheoesophageal Fistula]      [Aorto-Esophageal Fistula]
- Severe respiratory distress    - Erosion into thoracic aorta
- Stridor, aspiration            - Catastrophic, exsanguinating
- Mediastinitis                    hematemesis days to weeks later

Mechanisms of Tissue Destruction

1. Electrical current generation (Primary Mechanism): The battery generates an electrical microcurrent through adjacent moist mucosa, hydrolyzing tissue water and generating concentrated sodium hydroxide (caustic alkali) at the negative pole (anode). This causes devastating liquefactive necrosis within 2 hours of impaction.
2. Direct pressure necrosis: Mechanical pressure on the mucosa impairs blood flow.
3. Chemical leakage: Battery contents (alkaline electrolyte) can leak if the casing degrades.

Catastrophic Complications

• Aorto-esophageal fistula: The battery erodes through the anterior wall of the descending thoracic aorta. This can cause fatal, exsanguinating hematemesis days or even weeks after the battery has been endoscopically removed.
• Tracheoesophageal fistula (TEF), vocal cord paralysis (recurrent laryngeal nerve injury), esophageal perforation, and mediastinitis.

Radiographic Differentiation: Battery versus Coin

• Anteroposterior (AP) Chest/Abdominal Radiograph: A button battery displays a characteristic "double-ring" or "halo sign" (a double concentric radiopaque ring). In contrast, a coin appears as a single, uniform radiopaque disc.
• Lateral Radiograph: A button battery displays a "step-off" contour at the junction between the narrower negative side and the broader positive side; the negative step-off side causes the deepest injury. A coin has flat, smooth, uniform margins.

Immediate Emergency Management Protocol

1. Immediate Mitigation While Arranging Removal:
   • If the child is stable, able to swallow and ingestion was within 12 hours, give honey 10 mL every 10 minutes, up to 6 doses, for children 12 months or older, including during transport. Do not delay transport or endoscopy to obtain or administer it.
   • In a clinical setting, sucralfate suspension 1 g/10 mL, 10 mL every 10 minutes, up to 3 doses, may be used while awaiting removal under the same swallowing/time precautions.
   • These weakly acidic barriers reduce hydroxide-related injury but do not prevent it. Do not give oral mitigation if swallowing is unsafe, perforation is suspected or impaction may exceed 12 hours. Never give honey below 12 months because of botulism risk.
2. Emergent Endoscopic Removal:
   • An esophageal button battery is an absolute medical and surgical emergency. Remove it immediately by rigid or flexible endoscopy under general anaesthesia, preferably within 2 hours of ingestion; do not wait for fasting.
   • A battery in the stomach requires risk assessment. Symptoms or magnet co-ingestion warrant urgent removal; consider oesophageal assessment/removal after unwitnessed or delayed (>12-hour) ingestion, particularly with a ≥20 mm battery in a child under 5. Selected early, asymptomatic cases can be observed with reliable follow-up; confirm passage, repeating X-ray at 7–14 days if not seen in stool, and remove a retained gastric battery.

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Multiple Magnet Ingestions

Ingestion of multiple high-powered rare-earth (neodymium) magnets represents a unique mechanical hazard in children:

Pathophysiology of Magnetic Entrapment

• A single ingested magnet will almost always transit the gastrointestinal tract uneventfully.
• However, when two or more magnets (or a magnet plus a metallic ferromagnetic foreign body) are ingested, they travel through different bowel loops at different rates.
• The powerful magnetic attraction pulls the magnets together across intervening intestinal walls. The trapped bowel wall undergoes continuous compression ischaemia, leading to pressure necrosis, intestinal perforation, entero-enteric fistulae, volvulus, peritonitis, and septic shock.

Management Protocol

• Obtain multi-view plain abdominal radiographs (supine and lateral or cross-table lateral) to verify whether magnets are clustered together or separated.
• If multiple magnets are located within the stomach, perform emergent endoscopic retrieval.
• Multiple magnets beyond the pylorus need urgent joint paediatric surgical and gastroenterology assessment. Retrieve endoscopically if reachable. Selected stable, asymptomatic distal cases may be monitored in hospital with short-interval radiographs; do not continue observation beyond 6 hours without progression. Symptoms, obstruction/perforation, failed retrieval or non-progression require prompt intervention, including surgery when indicated.

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Poisoning Prevention, Medicines, Plants and Complementary Products

Prevention

Child-resistant packaging is a proven prevention measure. Advise families to store medicines and household chemicals locked away, out of sight and reach, in their original containers; never decant chemicals into drink bottles; dispose of unused medicines safely; secure button-battery compartments; and keep liquid laundry capsules out of reach. Give this anticipatory guidance as infants become mobile, together with the national poison-centre number.

Medicines

Paracetamol, ibuprofen, iron and antihistamines are common exposures. Some adult medicines can be dangerous after one or two tablets in a toddler, including calcium-channel blockers, sulfonylureas (which can cause delayed hypoglycaemia), tricyclic antidepressants, clonidine and opioids such as buprenorphine or methadone. Discuss these exposures with the poison centre even if the child looks well.

Plants and Mushrooms

Most household-plant ingestions cause little or no toxicity, but identify the plant. Foxglove and oleander contain cardiac glycosides (vomiting, bradyarrhythmia and hyperkalaemia), and deadly nightshade or Datura cause an anticholinergic toxidrome. Amatoxin-containing mushrooms such as the death cap cause delayed vomiting and diarrhoea 6–24 hours after ingestion, followed by liver failure.

Complementary and Herbal Products

Camphor and some essential oils such as eucalyptus oil can cause seizures after small ingestions. Herbal and traditional products may contain heavy metals or undeclared drugs, so ask specifically about them.

Poisoning as Maltreatment

Suspect maltreatment if the child could not have reached the substance independently, if drug levels are found for medicines not prescribed to the child, if the explanation is absent or unsuitable, or if ingestions recur in the child or siblings.

Sources: WHO World report on child injury prevention; NICE CG89 poisoning alerting features.