Investigations

As most ingestions in children will be non-toxic, most cases will not require any investigations. In those that do, they tend to be basic bedside tests with the occasional use of analytical tests to detect significant levels of certain drugs in the blood. Rarely will blood, urine and other biological samples need to be sent for specific drug or chemical assays except in the cases where deliberate poisoning is considered, see below:

Bedside blood sugar measurement (BM)

This should be one of the first considerations in poisoned children as it is one of the deleterious effects of poisoning that is easily remedied and is mandatory in cases where the mental status is altered. If the first measurement is within normal limits and the patient remains well there is no evidence to advocate serial measurements unless the toxin ingested is known to cause hypoglycaemia or the child deteriorates [5].

ECG

Where the ingested substance is known to cause arrhythmias then a 12-lead ECG is mandatory, along with any child with altered mental status or abnormal heart rate or blood pressure. The interpreting clinician will need to be aware of normal differences between adult and paediatric ECGs.

Blood gas analysis

In children capillary blood gases are chosen in preference to arterial or venous sampling and can be used to assess acid-base balance and will provide valuable information for certain poisonings. Some machines will also allow a sodium to be checked. This measurement should be considered if deliberate poisoning is suspected.

Paracetamol

This will tend to be less commonly considered in Paediatric toxicology than in adults, and should not be routinely requested except where there is concern about access to paracetamol by the child. This tends to occur in relation to deliberate self-poisoning rather than accidental ingestions. In cases of deliberate self-harm, paracetamol levels should be considered routine as it is a common co-ingestant and any symptoms as a result of overdose tend to be delayed.

X-rays

These may be considered where there is suspicion of ingestion of radio-opaque substances or foreign bodies. A useful mnemonic is COINS [5]:

Learning Bite

Button batteries rarely cause systemic toxicity but can result in localised mucosal ulceration with the inherent risk of gastrointestinal haemorrhage or perforation if they remain in the oesophagus or stomach. Once the battery has passed the pylorus it is unlikely to cause toxicity. When one or more magnets is ingested there is a risk of their becoming adherent with intervening bowel tissue which may become eroded and perforate or cause gastrointestinal bleeding. These will need endoscopic, if not surgical, removal. See the Royal College of Emergency Medicine advice regarding button batteries as a cause of haematemesis in children.

Qualitative urine toxicology screen

As most accidental paediatric poisonings will not involve the drugs which are screened for by standard bedside urine testing strips then this will not play a role in investigation, or alter management, of these patients. Even in the older paediatric population who may experiment with recreational drugs or abuse prescription drugs of other family members tox screens have not been shown to improve patient outcome or change management of poisoned patients in various studies examining their use in the ED setting [5].

The important caveat to this, however, is where there is a suspicion of the deliberate poisoning of a child. In that situation, samples of biological substances such as blood, urine and gastric aspirates will need to be sent for qualitative analysis. For forensic purposes a positive sample will need confirmation using a second methodology. Samples sent from the ED may be used as evidence in subsequent legal action and thus consideration should be paid to ensuring a chain of custody for such samples (follow your local departmental policy).