2025 RCEM实践指南：急诊室内疑似但不明中毒患者的管理

BACKGROUND

Poisoning can present with a variety of symptoms and should be considered as a cause in perplexing presentations. In general, deliberate self-harm with known substances is commoner than exposure to an unknown substance. However, children are at higher risk of accidental ingestion of inadequately secured medications or household products. They are also at increased risk of transdermal and respiratory absorption of toxins due to their different anatomy (higher body surface area to volume ratio) and physiology (increased respiratory rate).

# ABOUT THE CURRENT GUIDELINE

This is a Royal College of Emergency Medicine (RCEM) Best Practice Guide-line published with the National Poisons Information Service (NPIS) in April 2025. It outlines a general approach for assessing and treating all patients suspected of being poisoned by an unknown substance.

# Previous guideline(s)

This 2025 guideline should be used alongside TOXBASE and the NPIS which provide up to date guidelines which are poison specific. Advice on antidote availability in the emergency department was published jointly by the RCEM and NPIS include Day Month Year].

Resources are shown in box 1.

# Box 1 Guideline and resources

RCEM Best Practice Guideline Management of Patients with Suspected but Unidentified Poisoning in the Emergency Department. April 2025 https://rcem.ac.uk/rcem-clinical-guidance/

RCEMLearning: Paediatric Toxicology Considerations https://www.rcemlearning.co.uk/reference/paediatric-toxicology-considerations/

Life in the Fast Lane: Toxicology Library https://litfl.com/category/toxicology-library/

KEY ISSUES

# Toxidrome recognition (annex A of guideline)

A toxidrome is a collection of signs, symptoms and investigation findings suggesting a particular poison. If it is unclear what substance(s) the child has been exposed to, it may be possible to identify the toxin by comparing the symptoms and signs to those in known toxidromes. Treatment can then be initiated based on toxidrome. The classic toxidromes are shown in table 1.

TOXICOKINETICS

Toxicokinetics describes how the body handles toxins including absorption, distribution, metabolism and excretion. Toxicokinetics can be used to predict the likely clinical course following exposure, including, if absorption is ongoing, when

Guideline review

||Opioids (morphine, codeine)|Cholinergics (organophosphates)|Anticholinergics (antihistamines, tricyclic antidepressants, antipsychotics, atropine)|Sedative/hypnotics (benzodiazepines)|Sympathomimetic (cocaine, amphetamines)| |---|---|---|---|---|---| |Level of consciousness|Reduced|Reduced|Agitated/confused/reduced level of consciousness|Reduced|Agitation| |Respiratory rate|Reduced|Increased → reduced/stopped|Increased|Reduced|Increased| |Eyes|Pinpoint pupils|Pinpoint pupils|Dilated pupils/blurred vision|Variable effects (agent specific)|Dilated pupils| |Secretion|Normal|Increased|Decreased|Decreased|Thickening of secretions| |Skin|Normal|Diaphoresis|Flushed/dry|Normal|Pallor| |Heart rate|Decreased|Variable effect|Increased|Decreased|Increased| |Blood pressure|Decreased|Unchanged|Increased|Decreased|Increased| |Temperature|Decreased|Unchanged|Increased|Unchanged/decreased|Increased| |Other key features|Naloxone responsive|Diarrhoea, vomiting, increased urination, bronchospasm|Urinary retention|Hyporeflexia|Tremor|

peak plasma concentration is likely to be achieved and the agents' half-life.

Co-existence of poisoning with other pathologies: always consider the possibility of co-existing major trauma and safeguarding issues in paediatric patients.

What should I stop doing/do differently?

1. Do not wait for the causative agent to be identified to start emergency treatment.

2. Do not use point of care urine toxicology screening. It is largely inaccurate and may give false reassurance.

3. Modify your systematic approach to the patient with suspected but unidentified poisoning (figure 1) to include

consideration of team safety, consciousness, respiration, eyes, secretions and skin assessment, specific investigations (box 2) and toxidrome recognition.

4. When undertaking an A-E assessment, consider specific and additional issues that may arise in the patient with suspected but unidentified poisoning (figure 2).

5. When assessing ECG, consider toxidrome specific changes table 2.

WHAT SHOULD I START DOING?

Identify toxidromes (guideline annex A) early to guide initial treatment and use toxicokinetic to predict likely clinical course.

![graph TD\n A1[Are you and the team safe? - is there ongoing risk of exposure from the patient's skin / clothes / secretions? Is PPE(personal protective equipment) required? Where should the patient be cared for? Who needs to be informed? Are there multiple incidents? Is this a major incident?] --> A2[Is the patient safe? - consider decontamination if ongoing exposure is suspected]\n A2 --> A3[A + E = CRESS(consciousness, respirations, eyes, secretions, skin) intervention at each stage as problems identified]\n A2 --> A4[Investigations - Full bloods including blood gas, creatinine, clotting and serum save ECG(compare QT interval to normal)]\n A2 --> A5[Identify toxidrome characteristic presentation / symptoms from a particular toxin]\n A3 --> A4\n A3 --> A6[Consider toxicodynamics Call Toxbase -? / NPS for advice Consider specific diagnostic tests / targeted antidotes]\n A4 --> A5\n A5 --> A7[Further investigation / interventions]\n](1/parseimages/figure4b6397be43724ee3be49ee0bbc514f53_0_14.png) Guideline review

Box 2 Top investigations in the patient with suspected but unidentified poisoning

Investigations

$\bullet$ ECG: should be performed in all patients with suspected poisoning. Serial ECGs may be required

$\bullet$ Venous blood gas (serial may be required), full blood count, urea and electrolytes, liver functions tests, magnesium, creatine kinase and clotting (including international normalised ratio).

* Drug assay: most emergency department poisoning screen care sets include salicylate and paracetamol levels but levels for other agents, for example, digoxin should be included when their ingestion is suspected.

$\bullet$ Serum osmolality: calculated osmolar gap should be compared with calculated anion gap

$\bullet$ Consider imaging (if radiopaque foreign body ingestion or trauma suspected)

Useful calculations

$$ \text{Anion gap} = (\text{Na} + \text{K}) - (\text{HCO3} + \text{Cl}) $$

$\bullet$ Normal 12–16 mmol/L

$\bullet$ Osmolar gap = measured osmolality - calculated osmolality

* Calculated osmolality = (glucose + urea + 1.86 × Na) + 0.93

- Normal osmolar gap is <10 mmol/L

Always remember safeguarding when approaching the paediatric patient with suspected but unidentified poisoning. Consider if this was deliberate self-harm,

neglect (accidental overdose due to inadequate supervision or unsafe storage of medications/toxic substances) or deliberate harm by a caregiver. Involve local child protection and mental health teams as appropriate.

Find out which antidotes are available in your emergency department (category A) which are available from pharmacy within 1 hour (category B) and which are held subregionally (category C).

What can I continue to do as before?

Consult TOXBASE and NPIS for specialist advice.

Take a focused toxicological history from parent/ carer/young person (box 3). If there is uncertainty about what was ingested, when or how much, then assume the worst-case scenario that the child took the maximum amount possible.

Only discharge patients when they are physiologically and biochemically stable and no further deterioration is anticipated based on toxicodynamics.

LIFE-SAVING OR LMB-SAVING POINTS

Even if the presumptive diagnosis is poisoning, consider and treat other causes of reduced level of consciousness/biochemical/metabolic abnormalities.

In compromised patients, treat according to toxidrome (annex A of guidelines); do not wait for the agent to be identified.

Airway (and CRESS assessment)

$\bullet$ Consider early intubation

$\cdot$ CRESS – consciousness, respiration, eyes, secretions, skin)

Breathing - pulse oximetry may not be

reliable in:

* Carbon monoxide poisoning,

$\bullet$ methaemoglobinaemia

* Sulfhaemoglobinaemia

* Exposure to pigmented dyes e.g. methylthioninium chloride.


Circulation - ECG changes

$\bullet$ QRS complex prolongation- in isolation treat with 1 -2mL/kg sodium bicarbonate 8.4% centrally (or 2-4mL/kg 4.2% peripherally) over 20mins if in isolation or as bolus in arrest / VT (ventricular tachycardia)

$\bullet$ QT interval prolongation - 20-50mg/kg MgSO4 (max 2g) over 10-15mins

$\bullet$ PR flattening / PR interval prolongation – correct electrolyte abnormalities

* ST elevation - treat as acute coronary syndrome consider benzodiazepines / nitrates for cocaine

$\bullet$ Bradycardia - atropine

$\bullet$ Braguda pattern (ST elevation leads V1-3) - sodium bicarbonate (see QRS prolongation) / agent specific management

Disability

* Establish seizure control

* Consider possibility of serotonin syndrome / neuroleptic malignant syndrome

* Consider neuroimaging especially if non-toxicological cause of symptoms e.g. trauma is likely

Exposure

* Assess for signs of residual toxic agent (commence decontamination as early as possible)

* Aggressive temperature management

Other considerations

$\bullet$ Rhabdomyolysis – caused by toxins, pressure necrosis, seizures or extreme muscle activity

* Urinary retention - catheterize early

* Is this a sustained release preparation

$\bullet$ Bezoar (packed mass of tablets) formation – breakdown may result in sudden deterioration

$\bullet$ Adulteration of illicit substances

Figure 2: A-E assessment of the patient with suspected but unidentified poisoninging

Figure 2 A-E assessment of the patient with suspected but unidentified poisoning.

Guideline review

Table 2 Toxidrome-associated ECG changes.

|ECG change|Associated toxins| |---|---| |Prolonged QRS|Quinine| |Normal ranges in $children^{3}$|Tricyclic antidepressants, local anaesthetic| |Up to 1 years: 50 ms (upper limit of normal 70 ms)|| |1-3 years: 60 ms (upper limit of normal 70 ms)|| |3-8 years: 70 ms (upper limit of normal 80 ms)|| |8-12 years: 70 ms (upper limit of normal 90 ms)|| |12-16 years: 70 ms (upper limit of normal 100 ms)|| |Prolonged QT—consult TOXBASE nomogram (figure 3)$^{4}$|Antipsychotics, SSRIs (selective serotonin reuptake inhibitor), tricyclic antidepressants| |Bradycardia—5th—95th centile by age|Digoxin| |0-6 months: 120-170 beats per minute|Rate limiting calcium channel blockers| |6-12 months: 110-160 beats per minute|Beta blockers| |1-2 years: 100-150 beats per minute|| |2-5 years: 80-140 beats per minute|| |5-8 years: 80-130 beats per minute|| |8-12 years: 70-120 beats per minute|| |12-16 years: 65-115 beats per minute||

Critical appraisal and/or unresolved controversies

This RCEM publication is a general guideline, not specific to paediatrics. Therefore, some key paediatric considerations are not covered. The main omission is that the guideline does not cover specific adult medications that are toxic in small doses to children (so-called ‘one pill can kill’ rules) or specific non-pharmacological agents, for example, button batteries which are covered in other paediatric specific guidelines.$^{1}$ $^{2}$ However, in line with other international guidelines, the RCEM guideline does emphasise the importance of considering non-accidental injury in children who present with toxin ingestion (especially if inconsistent with their developmental stage). Overall, this guideline closely aligns to other international guidelines on managing the patient with suspected but unidentified poisoning.

 Figure 3 Toxbase QT normogram.

Box 3 Toxicological history.

Toxicological history:

$\blacktriangleright$ Time of likely exposure

$\bullet$ Dose

$\blacktriangleright$ Acute versus chronic exposure

$\bullet$ Route of exposure

> Reason for exposure: deliberate/accidental

> Time of symptom onset

$\bullet$ Suspected agent (try to see the original packaging): if unknown what prescribed/OTC medications/ household products/Villicit substances/poisonous plants/

$\bullet$ Other affected individuals are present in the house/ surroundings

$\bullet$ Other affected individuals

$\bullet$ Past medical history, etc

Consider:

* Has peak plasma concentration been reached?

> What is the expected half-life?

$\bullet$ What complications/clinical features may evolve?

$\bullet$ Is deterioration likely?

$\blacktriangleright$ What interventions are needed?

Box 4 Take-home messages.

1. In the unwell patient, treatment can be initiated based on toxidrome before the specific agent is identified

2. Always consider the possibility of non-accidental injury/<br>neglect in paediatric patients with suspected poisoning

3. Use a systematic ABCDE (airway, breathing, circulation, disabilly & exposure) + CRESS (consciousness, respiration, eyes, secretions and skin) to assess a patient who has suspected poisoning

Guideline review

TAKE-HOME MESSAGES

In conclusion, this guideline moves towards a toxidrome-based management of the patient with suspected but unidentified poisoning. The top three take-home messages are shown in box 4.

Contributors SR is guarantor.

Funding The authors have not declared a specific grant for this research from any funding agency in the public, commercial or not-for-profit sectors.

Competing interests None declared.

Patient consent for publication Not applicable.

Ethics approval Not applicable.

Provenance and peer review Commissioned; externally peer reviewed.

ORCID iDs

Sarah Reynolds https://orcid.org/0000-0003-4128-4882

Natasha Ramsden https://orcid.org/0009-0007-0058-8210 Nicholas Richens https://orcid.org/0009-0006-6701-8987

REFERENCES

1. Farrell N, Corio J. American College of Clinical Pharmacy. Paediatric Poisoning 2014. Available: https://www.accp.com/docs/bookstore/pedsap/ped2023b1sample.pdf 2. Royal Children's Hospital Melbourne Clinical Practice Guidelines: Poisoning - Acute Guidelines for Initial Management, Available: https://www.rch.org.au/clinicalguide/guideline_index/Poisoning-AacuteGuidelinesFor_InitialManagement/ 3. Burns E, Buttner R. Life in the Fast Lane Paediatric ECG: Stepwise Approach 2024, Available: https://www.toxbase.org 4. TOXBASE nomogram. n.d. Available: https://www.toxbase.org