Introduction and epidemiology

In 2009, the NSW Poisons Information Centre received in excess of 50 000 calls from around Australia regarding paediatric exposures to pharmaceuticals, chemicals, plants and animals. There is a bimodal distribution in the frequency of exposures, with the larger peak occurring in the toddler age group (ages 1–3 years) and a much smaller peak in the mid to late teens. The latter peak relates to deliberate self-poisoning in adolescents. Over eighty percent of poisons centre calls relating to childhood exposures are advised to stay at home as no acute management is necessary. Pharmaceuticals are by far the commonest exposure in children as per American Poison Control Center data. The top ten unintentional exposures in children (under the age of 18 years) reported to Australian Poisons Information Centres are listed in Table 21.1.1. It is important to note that paracetamol is present in many preparations as well as in combination products (e.g. with codeine, pseudoephedrine, doxylamine, dextromethorphan).

Table 21.1.1 Top 10 exposures in children

No. Agent 1 Paracetamol 2 Detergents 3 Household cleaning agents 4 Dessicants (e.g. silica gel) 5 Ibuprofen 6 Cough & cold preparations 7 Rodenticides 8 Light sticks/glow toys 9 Zinc-containing barrier creams 10 Bleach (containing hypochlorite)

Diagnosis

As opposed to overdose in the adult population, exposures in children are nearly always accidental or unintentional. The circumstances around the exposure or ingestion are often unknown or difficult to elucidate. Parents and carers are usually uncertain about time of exposure or dosage of drug ingested. As such, the clear history required to make an accurate risk assessment is difficult or sometimes impossible. Regardless of whether the entire history and circumstances surrounding the exposure are available, it is prudent to plan for a ‘worst-case scenario’, assuming maximal exposure.

Important elements of the focused history include:

Deliberate self-poisoning in adolescents warrants further enquiry into previous ingestions, pre-existing psychiatric illness and management, drug use and social circumstances. In cases of unknown drug exposure, it is important to explore the availability of pharmaceuticals and/or chemicals to which the child may have had access. Plant and mushroom ingestion is common in children and needs to be considered in the acutely unwell child who has been outdoors.

Non-accidental (or deliberate) poisoning of a child requires mandatory reporting to child protection authorities in all jurisdictions within Australia. The index of suspicion is higher in children under the age of 1 year, or where the circumstances of the exposure do not fit the capabilities of the child in question. Rare cases of Munchausen’s syndrome by proxy are also reported in the literature, involving deliberate poisoning of children by their parent/carer.

Physical examination of the potentially poisoned child is usually unremarkable, particularly in asymptomatic children or in the early stage of ED presentation. However, in children presenting with symptoms or patients with altered level of consciousness, a thorough physical examination is vital. Key elements of the toxicological examination include:

Children may also present with a cluster of symptoms and signs suggestive of poisoning, i.e. a toxidrome. Although most cases do not manifest the full spectrum of signs and symptoms, pattern recognition amongst clinicians may provide a clue to diagnosis. Toxidromes and corresponding causative agents commonly seen in children are listed in Table 21.1.2.

Table 21.1.2 Common toxidromes

Toxidrome Agents Clinical features Sympathomimetic Amphetamines
Pseudoephedrine
Caffeine Tachycardia
Hypertension
Mydriasis
Sweating
Agitation
Delirium
Fever Anticholinergic Atropine
Hyoscine
Antihistamines
Plants
Mushrooms Tachycardia
Mydriasis
Loss of visual accommodation
Flushed skin
Dry skin/mouth/eyes
Fever
Delirium Opiate Opiates
Tramadol
Clonidine Sedation
Respiratory depression
Hypotension
Miosis Cholinergic Organophosphates
Carbamates Delirium
Coma
Seizures
Excess secretions (DUMBELS)
Weakness
Fasciculations Serotonergic SSRIs
Cyclic antidepressants
Opiates
Tramadol
Lithium
MDMA (ecstasy) Delirium/agitation
Hyperreflexia
Hypertonia
Tremor
Clonus
Diaphoresis
Fever

SSRI, selective serotonin reuptake inhibitor.

Risk assessment

Following the history and examination of the potentially poisoned child, the clinician must undertake a risk assessment of the likely exposure and probable course of toxicity, if any. This requires knowledge of the toxicodynamics and kinetics of the agents, an understanding of potential complications and experience with previous similar cases. At this stage, it is prudent to obtain advice from expert clinicians in paediatric toxicology, such as through the Australasian Poisons Information Centres (Australia: 13 11 26; New Zealand: 0800 764 766). These centres are available 24/7 and provide expert advice on the assessment and management of poisoning in children. The majority of paediatric exposures do not present to hospital, and even those that do, require observation only. However, there are a few highly toxic pharmaceuticals and chemicals that, even in small doses, can cause severe toxicity. Patients exposed to these select few agents may require close monitoring and potentially aggressive resuscitation – these are discussed in Chapter 21.2.

Investigations

The vast majority of children exposed to a substance require no investigations at all. There are some instances where a specific agent is ingested and a specific investigation may aid diagnosis and/or management. Screening tests in the poisoned child should be performed based on the risk assessment. Specific investigations, which may be invasive or time-consuming to return a result, should be discussed with an expert toxicologist prior to embarking on these tests. Table 21.1.3 summarises the potential indications for screening and specific investigations in paediatric poisoning. Baseline blood investigations (blood counts, electrolytes, renal function test) should be performed if any of the screening or specific laboratory investigations are ordered.

Table 21.1.3 Investigation of the poisoned child

Investigation Potential toxicological indication(s) Screening tests   Blood glucose level Altered mental status
Deliberate self-poisoning
All exposures to insulin or oral hypoglycaemic agents β-HCG pregnancy test Female patients of childbearing age presenting with overdose Paracetamol level Deliberate self-poisoning (of any substance) Urine drug screen Known or suspected exposure to illicit substances/drugs of abuse
Altered mental status (delirium, psychosis, coma) ECG Heart rate outside normal parameters for age
Haemodynamic instability or shock
Poisoning with specific agents:

Blood gas measurement Known or suspected acid–base abnormality
Poisoning with specific agents:

Specific investigations   Chest/abdominal X-ray Radio-opaque tablet or foreign body ingestion
Known or suspected aspiration pneumonitis
Tube (e.g. endotracheal, gastric) placement Liver function tests Known or suspected paracetamol poisoning
Suspected hepatotoxicity from any systemic poisoning Coagulation panel Snake bite
Suspected coagulopathy from poisoning/envenoming
Poisoning with specific agents:

Paracetamol level In all cases of paracetamol ingestion (incl. deliberate self-poisoning, accidental, supratherapeutic, chronic) Specific drug levels Known or suspected poisoning from:

Notes:

Salicylate levels should not be routinely ordered as their screening value is negligible

Tricyclic antidepressant levels are not useful in the management of poisoning from these agents, nor are they a useful screening test

Rarely performed investigations for specific toxins include cholinesterase levels, carboxyhaemoglobin and methaemoglobin amongst others.

Computerised tomography of brain is not routinely required in the comatose child with a reliable history of poisoning; it may be warranted when the history is unclear, or there is suspicion of trauma or non-accidental injury.

HCG, human chorionic gonadotrophin.

Resuscitation

In the severely poisoned child, timely and effective resuscitation is the key to better outcomes. Thankfully, this scenario is uncommon in Australasia. Resuscitation of the poisoned child should follow standard advanced paediatric guidelines with regards to promoting haemodynamic stability, preventing secondary brain injury and best practice supportive care.

The majority of cases require no more than oxygen therapy and intravenous fluid boluses. In the presence of coma or cardiovascular collapse, resuscitation involves airway protection and ventilatory support as well as the potential use of agent-specific antidotes. In cases where early decontamination is required, such as exposure or ingestion of chemicals, decontamination should occur concurrently with, and not to the detriment of, active resuscitation.

Decontamination

Decontamination involves the removal of a toxic substance to which a child has been exposed in order to minimise its absorption into the systemic circulation. In a child with dermal, eye or mucosal exposure to a substance, decontamination simply involves removal of the toxic substance and irrigation or washing of the contaminated skin, eye or mucosa. Inhalational injury to toxic fumes or gases should include the removal of the patient from the source of exposure and, if necessary, administration of supplemental oxygen. In extreme situations, these patients may need advanced airway and ventilatory support. The use of universal precautions (gown, gloves, goggles) by staff during the process of decontamination is sufficient for the vast majority of poisoning situations, including hydrocarbons and organophosphate insecticides.

Oral exposure to pharmaceuticals, chemicals or plants requires a risk assessment-based approach as to whether decontamination is deemed worthwhile. The need for active oral decontamination in paediatric poisoning is rare. Clinicians are advised to seek expert advice prior to decontamination in children with oral exposures.

Syrup of ipecacuanha (derived from the root of a South American plant) is no longer recommended in the management of poisoning. The induced emesis does little to prevent drug absorption and potentially can cause a myriad of complications including protracted vomiting, aspiration and oesophageal tears and haemorrhage. Gastric lavage (‘stomach pumping’), involving the injection of fluid into the stomach via a tube and aspirating gastric contents, is also a discontinued practice which has little or no role in the management of poisoned children. Whole bowel irrigation involves the administration of a polyethylene glycol solution through the gastrointestinal tract for the purpose of promoting tablet residue in effluent and thus preventing drug absorption. It is reserved for specific ingestions such as sustained-release preparations or metals; expert advice should be sought prior to instituting whole bowel irrigation.

Activated charcoal is a colloidal suspension of charcoal particles able to bind to most pharmaceuticals. Charcoal does not adsorb metals, hydrocarbons, corrosives or alcohols. Although the need for activated charcoal in children is uncommon, it is potentially indicated when a child ingests a highly toxic substance, which is bound by charcoal, and the charcoal can be administered within an hour post-ingestion to an alert child (or in the case of intubated children, via a gastric tube). Clinicians should avoid inserting a gastric tube for the purpose of administering charcoal to a patient with altered level of consciousness. The presence of bowel sounds should always be confirmed prior to the administration of oral charcoal. When indicated, the activated charcoal dose is 1 g kg⁻¹. Expert advice should be sought regarding the use of charcoal in situations beyond an hour post-ingestion or multi-dose activated charcoal (discussed below). Common side effects of charcoal administration include vomiting and the passage of black stools. Aspiration of charcoal can lead to chemical pneumonitis and potentially acute respiratory distress syndrome.

Antidotes

The need for agent-specific antidotes in children is uncommon. Knowledge of antidotes and their potential utility may, in rare cases, be life-saving. Table 21.1.4 lists select antidotes used in paediatric poisoning and their indications. The use of these agents should be discussed with a toxicologist.

Table 21.1.4 Antidotes

Antidote or specific therapy Dose Potential indications Atropine 0.02–0.05 mg kg^–1, repeat every 5–10 minutes (use doubling regimen) Known or suspected cholinergic toxidrome from organophosphate or carbamate pesticide poisoning. Titrate to pupil size, heart rate, blood pressure and drying of chest secretions. Calcium Calcium gluconate
10%, 0.6 mL kg^–1
Calcium chloride 10%, 0.2 mL kg^–1 Calcium-channel blockers:

Desferrioxamine 15 mg kg^–1 hr^–1 Iron toxicity:

Digoxin Fab antibodies Empiric dose:
Acute poisoning – 5 vials
Chronic poisoning – 1?2 vials Digoxin toxicity:

Ethanol PO/NG route preferred
Loading dose: 750 mg kg^–1
Infusion: 80–150 mg kg^–1 hr^–1 Known or suspected poisoning from toxic alcohols (ethylene glycol, methanol):

Maintain blood ethanol at 100 mg dL^–1 Flumazenil 0.005–0.01 mg kg^–1
(max 2 mg) Benzodiazepine poisoning:

N.B. Titrate to respiratory rate Glucagon 0.05–0.1 mg kg^–1 β-Blockers
Bradycardia
Hypotension Insulin (high dose + dextrose) Initial dose 1 unit kg^–1
Infusion: 1–2 units kg^–1 hr^–1 β-Blockers
Calcium channel blockers
Bradycardia or heart block
Hypotension N-Acetylcysteine 1^st: 150 mg kg^–1 over 15–30 min,
2^nd: 50 mg kg^–1 over 4 hours,
3^rd: 100 mg kg^–1 over 16 hours Paracetamol poisoning:
Patients at risk of, or with established, hepatotoxicity Naloxone Bolus: 0.005-0.01 mg kg^–1 (max 2 mg);
Infusion: 0.01 mg kg^–1 hr^–1 Known or suspected opiate toxidrome. Titrate to respiratory rate Octreotide Bolus: 1 mcg kg^–1 IV or SC
Infusion: 0.5 mcg kg^–1 hr^–1 IV Sulfonylurea poisoning with recurrent hypoglycaemia Physostigmine 0.02 mg kg^–1 (max 0.5 mg) Anticholinergic poisoning with delirium Sodium bicarbonate 1–2 mmol kg^–1 IV bolus (serum alkalinisation) Cyclic antidepressants (and other cardiac sodium channel blocking agents):

Vitamin K 5–10 mg, PO
1–2 mg, IV or IM Poisoning from warfarin (or other coumadin anticoagulants) with established, or risk of, coagulopathy

IM, intramuscular; IV, intravenous; PO, per oram; SC, subcutaneous.

Enhanced elimination

Techniques used to promote drug elimination from the body are employed in a limited number of poisonings. These methods include haemodialysis, multidose activated charcoal and alkaline diuresis. Various forms of haemodialysis methods are utilised in paediatric poisoning after insertion of a temporary vascular catheter. Agents that are potentially dialysable include potassium, salicylates, toxic alcohols, theophylline and carbamazepine, amongst others. Multidose activated charcoal is rarely used when promoting charcoal adsorption and elimination of poisons that undergo enterohepatic circulation, such as carbamazepine. Urinary alkalinisation with sodium bicarbonate is indicated in salicylate poisoning to promote the renal excretion of salicylate ions. These techniques are seldom used in childhood poisonings and expert advice should be sought prior to their institution.

Supportive care

Active resuscitation of the severely poisoned child is paramount and should be followed by meticulous attention to supportive care in a high dependency or intensive care environment. Although specific poisoning scenarios are dealt with in the next chapter, the guiding principles of excellent supportive management of the poisoned child are likely to be more crucial.

All children with altered level of consciousness should have close glucose monitoring. Coma from drug overdose should be managed with advanced airway and ventilatory manoeuvres. In general, non-invasive ventilation does not have a role in the poisoned child. Drug-induced seizures from all causes should be treated with parenteral benzodiazepines as the first-line agents of choice. Phenytoin should be avoided as its sodium channel blocking properties may exacerbate the problem.

Cardiovascular collapse and asystole in the poisoned child should be managed as per standard advanced paediatric life support guidelines. Drug-induced arrhythmias may warrant agent-specific strategies, such as antidotes. Wide QRS complex tachyarrhythmias, usually due to sodium channel blocking agent poisoning, should in the first instance be treated with boluses of sodium bicarbonate (1–2 mmol kg^–1).

Close monitoring and maintenance of normothermia, euglycaemia, acid–base balance and electrolyte levels are vital in the severely poisoned child. Other potential complications in this group of patients include rhabdomyolysis (seen in snake bite, prolonged coma), aspiration pneumonitis, and persistent delirium (commonly due to anti-cholinergic drugs or plants).

Consultation and disposition

Poisoning in children, as in adults, is a symptom of an underlying issue, be it psychological, parental neglect or accidental access to harmful substances. The mainstay of management involves observation in the ED. Occasionally the child is exposed to an unusual substance or develops severe toxicity that requires input from clinical toxicologists. Clinicians should seek advice from local experts in the field and/or their local Poisons Information Centre.

The underlying issue or disease process also requires attention, such as mental health assessment or counselling. Children who are overdosed with analgesics or antipyretics may warrant investigation into the cause of pain or fever. In the case of neglect or deliberate poisoning the child is likely to need referral to relevant child protection authorities. All carers involved in accidental poisoning should have counselling with regards to safe storage of medicines and chemicals in the home.