Poisoning - Salicylates

Disclaimer These guidelines have been produced to guide clinical decision making for the medical, nursing and allied health staff of Perth Children’s Hospital. They are not strict protocols, and they do not replace the judgement of a senior clinician. Clinical common-sense should be applied at all times. These clinical guidelines should never be relied on as a substitute for proper assessment with respect to the particular circumstances of each case and the needs of each patient. Clinicians should also consider the local skill level available and their local area policies before following any guideline.  Read the full CAHS clinical disclaimer

Aim

To guide PCH Emergency Department staff with the assessment and management of salicylate poisoning in children.

This guideline is a general approach to salicylate poisoning. For specific details:

• contact Poisons Information on 13 11 26
• refer to the Toxicology and Toxinology – Therapeutic Guidelines

Background^1,2

• Accidental overdose from aspirin is very uncommon in the paediatric population, but methyl salicylate overdose is associated with significant toxicity even with very small ingestions.
• Chronic toxicity has been reported from frequent application of teething gels.
• Life-threatening consequences of salicylate overdose include:
  • Seizures
  • Cerebral and pulmonary oedema

Resuscitation

Airway, Breathing, Circulation

• Severe salicylism causing coma or respiratory compromise requires intubation and ventilation
  • Controlled hyperventilation should be employed to maintain compensatory respiratory alkalosis
• Intravenous (IV) fluid - maintenance plus replacement (gastrointestinal and insensible losses)

Seizures

• Treat with benzodiazepines, urgent intubation and hyperventilation

Risk assessment^1,2

• The principles of assessment of a potential salicylate overdose include:
  • Nature of salicylate preparation
  • Maximum potential dose ingested
  • Time of ingestion
  • Other potential co-ingestions
  • Reason for ingestion
  • Clinical or laboratory features of toxicity
• Clinical symptoms following a salicylic acid (aspirin) overdose progresses over hours.
• Patients who ingest a large dose of salicylate may not manifest significant signs of toxicity before 6-12 hours, with subsequent rapid clinical deterioration.
  • Early effects will be present before 6 hours.
  • If large numbers of tablets are ingested, a large concretion (bezoar) may form in the gut, delaying absorption.
• Most acute accidental paediatric exposures of aspirin do not result in life threatening toxicity. Paediatric patients rarely ingest sufficient amounts of aspirin to cause toxicity.
• The severity of clinical features is dose related.
• A 10 kg child can develop life threatening poisoning with the ingestion of a small sip of preparations of methyl salicylate.
• If there is suspicion of deliberate self-poisoning patients are to be referred for evaluation in hospital, regardless of the dose ingested.

Agents

• Acetyl salicylic acid (aspirin)
• Methyl salicylic acid / methyl salicylate
  • Active ingredient of Oil of Wintergreen: 1mL = 1400 mg of aspirin³
  • Methyl salicylate: 5mg = 7.5 mg of aspirin¹
• Choline salicylate
  • Active ingredient in infant teething gels (e.g. Bongela^®, Seda-Gel^®)
• Salicylic Acid
  • Available in a range of topical preparations including skin peeling agents

Typical clinical course^1,2

Common early effects following acute salicylate ingestion include:

• Gastrointestinal distress
• Tinnitus or altered hearing
• Hyperventilation

Life threatening effects following significant salicylate overdose are:

• Altered mental status
• Seizures
• Fever
• Pulmonary oedema
• Acid-base abnormalities
  • Early - Respiratory alkalosis and metabolic acidosis
  • Late - Respiratory acidosis and high anion gap metabolic acidosis
• Hyper / hypo glycaemia
• Hypokalaemia

 

Ingested dose of aspirin (or equivalent dose of other Salicylate)	Symptoms and Disposition
< 150mg/kg	Minimal Toxicity Patients do not require decontamination or referral to hospital except in cases of deliberate overdose
150 - 300mg/kg	Mild to moderate intoxication Nausea, vomiting Hearing disturbance, tinnitus Increased respiratory rate Primary respiratory alkalosis Patients should be referred to hospital for evaluation and observation and may be discharged only if asymptomatic at six hours post ingestion. Supportive care, decontamination and enhanced elimination are likely if symptomatic.
> 300mg/kg	Life-threatening effects Metabolic acidosis (late onset and pre-morbid) Seizures Altered mental state Hypotension Patients are to be admitted to PICU for decontamination and enhanced elimination techniques. Intubation and hyperventilation may be required.
> 500mg/kg	Potential lethal dose Patients are to be admitted to PCC for decontamination and enhanced elimination techniques. Intubation and hyperventilation are likely to be required.

Supportive Care

• If intubation and ventilation are required for coma or respiratory insufficiency, ensure controlled hyperventilation is implemented in order to maintain respiratory alkalosis.
• Control seizures
• Ensure sufficient fluid replacement with intravenous crystalloid to account for gastrointestinal and insensible losses.

Nursing

• Record a full set of observations on the Observation and Response Tool, noting respiratory rate and depth, heart rate and temperature increase in salicylate intoxication. Additional comments can be recorded on the Clinical Comments chart.
• Record a full set of neurological observations.
• Observations should be done at least hourly until these parameters normalise.
• Observe for signs of tinnitus, hearing loss, agitation, restlessness, diaphoresis and central nervous system (CNS) disturbance.
• Continuous cardiac monitoring
• Consider topical local anaesthetic e.g. lidocaine (lignocaine) 2.5% with prilocaine 2.5% cream (EMLA^®) if IV access required.
• Strict, accurate fluid balance monitoring.
• Blood glucose level – all patients with altered mental status.

Investigations^1,2

Screening tests in deliberate overdoses

• 12 lead electrocardiogram (ECG)
• Blood glucose level
• Paracetamol level

Specific tests

• Blood gas:
  • Respiratory alkalosis (from hyperventilation)
  • High anion gap metabolic acidosis
  • Actual acidaemia is late stage and heralds imminent demise without intervention
• Plasma salicylate level
  • 3 mL required (Lithium Heparin-PST (GREEN)⁵ preferable in non-gel tube)
  • Therapeutic range is 140-300 mg/L
  • To be measured in all patients whom significant salicylate intoxication is suspected
  • Result should be interpreted in conjunction with clinical findings, particularly the plasma pH
  • In the event of significant intoxication, serial levels may be taken every 2-4 hours to identify ongoing or delayed absorption.
• Other tests:
  • Urea, electrolytes and creatinine – monitor for hypokalaemia 

Decontamination^1,2

• Activated charcoal (oral) 1g/kg (maximum 50g) should be given to any patient with clinical signs of salicylate poisoning
  • Activated charcoal can be given up to 8 hours² after an acute ingestion of > 150mg/kg
• A second dose of activated charcoal is indicated after four hours if serum salicylate levels continue to rise
• Ensure that the airway is secure prior to administration of charcoal.

Enhanced elimination

Urinary alkalinisation

• At levels greater than 200 mg/L, hepatic metabolism of aspirin is saturated and renal elimination becomes more important. However, in acid urine, aspirin is not ionized and is rapidly reabsorbed by the proximal tubule.
• Alkalinisation of the urine traps ionized aspirin in the renal tubule and markedly increases its elimination.

Indications for urinary alkalinisation:

• patient is symptomatic
• serum salicylate level exceeds 300mg/L
• history of ingestion greater than 300mg/kg

Method²

• Note – if urinary alkalinisation is required, PCCU and toxicology services should be engaged.
• Give 1-2 mmol/kg of sodium bicarbonate¹ (maximum 100 mmol) as an initial intravenous bolus over 5 minutes.
  • Child < 2 years: dilute to 0.5 mmol/mL with glucose 5% or water for injections⁴
  • Child ≥ 2 years: administer undiluted⁴
• Start infusion of 150 mmol of sodium bicarbonate in 850 mL of glucose 5%, with initial rate of 2-4 mL/kg/hr (equivalent to 0.3 - 0.6 mmol/kg/hr of sodium bicarbonate).¹
• An infusion pump is required to prevent accidental volume overload in small children.
• Check the urine pH hourly and titrate the sodium bicarbonate infusion (up to a maximum of 1 mmol/kg/hour⁴) to maintain a urinary pH greater than 7.5.²
• Check serum potassium and serum pH every 2-4 hours (along with salicylate level).
  • Hypokalaemia is common with urinary alkalinisation and intravenous potassium supplementation is often required.

Cease urinary alkalinisation when:¹

• patient is clinically well
• serum salicylate level is below 300 mg/L
• normal acid-base status

Haemodialysis

Haemodialysis is the definitive therapy for severe salicylate intoxication. It rapidly removes aspirin from the serum and extracellular space, assists rapid movement of salicylate out of the brain, and assists correction of metabolic disorders.

Indications:

• Evidence of impending severe intoxication:
  • Altered mental status
  • Seizures
  • Cardiovascular instability
  • Hyperthermia
  • Pulmonary oedema (rare in children and young adults)
• Rising serum salicylate levels above 500 mg/L beyond 6 hours after ingestion, despite aggressive decontamination and urinary alkalinisation
• Mixed respiratory alkalosis/metabolic acidosis on arterial blood gases but pH in the normal range (i.e. patient no longer has alkalotic serum pH)
• Patient acidaemic (pH less than 7.35) with mixed respiratory and metabolic acidosis
• Serum level greater than 1000 mg/L at any time
• Failure of elimination
• Renal failure

Antidote

There is no specific antidote for salicylate poisoning.

Disposition¹

Patients who can be managed at home:

• Asymptomatic paediatric patients with accidental potential ingestion of less than or equal to 150 mg/kg

Patients who require monitoring in a health care facility:

• Asymptomatic patients with a history of ingestion of potentially greater than 150 mg/kg
• All patients with abdominal pain, nausea, vomiting or altered hearing (usually tinnitus)
• All patients with deliberate self-poisoning
• Patients requiring urinary alkalinisation or observation for periods greater than 8 hours should be admitted.

Discharge criteria

• Patients may be discharged from the emergency department if they are clinically well and serum salicylate levels have not increased over a period of 8 hours.
• If salicylate levels rise above the therapeutic range (300 mg/L), then two consecutive decreasing salicylate levels are required before discharge.

References

1. Toxicology and Toxinology – Therapeutic Guidelines
2. Toxinz Poisons Information online, 2013 National Poisons Centre, New Zealand.
3. Barnett AK and Boyer EW (2013) Salicylate Poisoning in Children and Adolescents. Uptodate. Last updated: 26 February 2021. Cited 17 February 2022. Available from: www.uptodate.com
4. Paediatric Injectable Guidelines Online, The Royal Children’s Hospital Melbourne Update 2020, Cited: 17 February 2022. Available from: Sodium Bicarbonate | Paediatric Injectable Guidelines Online (health.wa.gov.au)
5. PathWest Test Directory – Salicylate. Last updated 2 October 2020. Cited:17 February. Available from: pathlines.health.wa.gov.au/testdirectory/

 

 

 

 

 

 

 

 

 

 

Endorsed by:	CAHS Drug and Therapeutics Committee	Date:	May 2023
		Review date:	Mar 2024

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