Recommendations
Urgent
If the patient is stable, ask them or their carer how much salicylate has been ingested and when, or how much topical salicylate the patient has been exposed to, and when. Any patient who might have ingested ≥125 mg/kg salicylate or any amount of methyl salicylate and any patient who is symptomatic will need medical assessment in hospital.[2][6]
Escalate severe poisoning for senior review immediately. Severe poisoning is usually associated with a peak salicylate concentration of >700 mg/L (>5.1 mmol/L).[2]
Look for typical features of severe poisoning, such as:[1][2]
Cardiac dysrhythmias
Acute non-cardiogenic pulmonary oedema
Cerebral oedema
Convulsions
Confusion
Coma
Hyperpyrexia
Heart failure
Acute kidney injury
Worsening metabolic and lactic acidosis.
Moderate poisoning is usually associated with a salicylate concentration of 300 to 700 mg/L (2.2 to 5.1 mmol/L).[2]
If severe clinical features develop at any stage:[2][7]
Resuscitate (airway, breathing, circulation [ABC])
Check arterial blood gases
Discuss with the National Poisons Information Service and intensive care unit
Consider haemodialysis.
Take a plasma salicylate concentration at least:[2]
2 hours (symptomatic patients) after ingestion
4 hours (asymptomatic patients) after ingestion.
Ascertain whether the overdose was intentional (self-harm or attempted suicide) and, if so, seek senior review within 1 hour. See Suicide risk mitigation.
Be aware that patients with chronic salicylate intoxication may present with only non-specific features such as confusion, malaise, and dyspnoea.[2] Consider chronic salicylate poisoning as part of delirium screening in older adult patients.[1] In practice, seek senior review of a patient with chronic poisoning within 1 hour of presentation.
Have a high level of suspicion for chronic salicylate intoxication in older adult patients with:[1]
Tachypnoea
Acid-base disturbances (particularly an unexplained respiratory alkalosis)
Non-focal neurological abnormalities
Deterioration in activities of daily living of unknown cause.
In remote areas in the community, discuss the patient with the nearest accident and emergency department consultant and consider taking samples for salicylate concentrations.
Key Recommendations
In addition to thinking about poisoning with aspirin, be aware that salicylates occur in other commonly available substances including:[1][5]
Non-steroidal anti-inflammatory drugs (topical or oral)
Oil of wintergreen (topical or oral) (highly concentrated methyl salicylate, very toxic)
Some antacids and antidiarrhoeals.
In symptomatic patients, take blood at presentation to check the following parameters:[2][7]
Acid base status
Do not be misled by the absence of a raised serum anion gap in patients if the rest of the presentation supports the diagnosis of salicylate poisoning
Urea and electrolytes (for hypokalaemia and to assess renal function)[2][7]
Also check calcium, magnesium, and phosphate if the patient has convulsions[2]
International normalised ratio (INR) (for disseminated intravascular coagulation, which may rarely be associated with salicylate poisoning)[2][7]
Full blood count (to differentiate from an infectious cause for symptoms, and to identify thrombocytopenia, which may rarely be associated with salicylate poisoning)[2][7]
Capillary blood glucose for hypoglycaemia or hyperglycaemia (which are more commonly found in young children).[2]
Be aware that salicylate poisoning usually occurs after ingestion, but may also occur after skin exposure to topical preparations.[2]
Aspirin is the most common form of salicylate ingested.[8]
Salicylates are commonly available over the counter, which can result in unintentional poisoning in people trying to self-medicate, and in children, through accidental ingestion. In the UK, examples of salicylates commonly found on supermarket shelves and in medicine cabinets include:
Non-steroidal anti-inflammatory drugs such as ibuprofen, naproxen (topical or oral)
May be included in over-the-counter preparations for cold and flu
Methyl salicylate liniment BP used in topical agents for muscular aches and pains
Some antacids and antidiarrhoeals, in the form of bismuth subsalicylate, a 50% aspirin equivalent
Toxicity with this agent is rare.
Note that most patients will present immediately after an accidental exposure to an overdose of salicylates.
Some people present later, including those who have taken an overdose with the intent to self-harm.
Patients with chronic accidental poisoning may present late, often only with non-specific features such as confusion, malaise, and dyspnoea.[1][2]
Have a high level of suspicion for chronic salicylate intoxication in older adult patients with:[1]
Tachypnoea
Acid-base disturbances (particularly an unexplained respiratory alkalosis)
Non-focal neurological abnormalities
Deterioration in activities of daily living of unknown cause.
Consider salicylate poisoning in all patients with a history of toxin ingestion or topical exposure, particularly in the presence of an unexplained metabolic acidosis.
Presenting features vary depending on the severity of poisoning.[2] If severe clinical features develop at any stage:[2][7]
Resuscitate (ABC)
Check arterial blood gases
Discuss with your local poisons unit (in the UK, the National Poisons Information Service) and intensive care
Consider haemodialysis.
Severe poisoning
Usually associated with a peak salicylate concentration of >700 mg/L (>5.1 mmol/L).
Concentrations >900 mg/L (>6.4 mmol/L) are associated with very severe toxicity.[2]
Look for typical features:[1][2]
Cardiac dysrhythmias
Acute non-cardiogenic pulmonary oedema
Cerebral oedema
Convulsions
Confusion
Coma
Hyperpyrexia
Heart failure
Acute kidney injury
Worsening metabolic and lactic acidosis.
In children, central nervous system features including coma, confusion, convulsions, and disorientation are more common.
Most adult deaths occur in patients with salicylate concentrations >700 mg/L (>5.1 mmol/L).[2][9]
Patients are more likely to die if they are aged >70 years, or if they develop coma, convulsions, confusion, agitation, hyperpyrexia, pulmonary oedema, or metabolic acidosis.[2][9]
Moderate poisoning
Usually associated with a salicylate concentration of 300 to 700 mg/L (2.2 to 5.1 mmol/L).[2]
Increased respiratory rate
Hyperventilation
Respiratory alkalosis
Often present at lower (moderate poisoning) concentrations; metabolic acidosis may co-exist
Dehydration
Restlessness
Sweating
Warm extremities with bounding pulses.
Mild poisoning
Usually associated with a peak salicylate concentration of <300 mg/L (<2.2 mmol/L).[2]
Nausea and vomiting
Tinnitus
Deafness
Lethargy
Dizziness.
Chronic poisoning
Be aware that patients with chronic salicylate intoxication may present with only non-specific features such as confusion, malaise, and dyspnoea.[2]
Have a high level of suspicion for chronic salicylate intoxication in older adult patients with:[1]
Tachypnoea
Acid-base disturbances (particularly an unexplained respiratory alkalosis)
Non-focal neurological abnormalities
Deterioration in activities of daily living of unknown cause.
Do not dismiss the diagnosis if plasma salicylate levels fall within the upper end of the therapeutic range.[1]
Salicylate concentrations in chronic poisoning tend to cause symptoms at lower levels than in acute salicylate poisoning.[1]
Practical tip
When assessing a patient with suspected chronic poisoning, do not rely only on drug levels as this can lead to underestimation of poisoning severity and delayed therapy, and can contribute to worse outcomes. Take into account the severity of presenting symptoms, acid-base status, medication history (both oral and topical), and overall clinical condition of the patient, along with salicylate levels.[1]
Establish a history of the salicylate poisoning. Was it:
An intentional overdose, taken in the context of self-harm?
Assess suicide risk. Take all patients with suicidal thoughts seriously and respond with compassion and in a timely and proportionate way. See Suicide risk mitigation
Assessment of the patient’s mental state and risk of repeated episodes of self-harm should ideally be done by a psychiatrist or psychiatric liaison nurse[7]
Ascertain whether there is a history of previous overdose
Find out whether the patient took any other substances or alcohol with the overdose
Acute accidental therapeutic excess (i.e., taken with intent to treat pain) without understanding the safe use of the agent?
Chronic therapeutic excess: for example, an older adult patient ingesting salicylates for a chronic condition such as one of the arthritides?
Chronic poisoning:[1]
Is more common in older adult patients
Often occurs in patients who are treated by more than one clinician and therefore are at risk of inadvertent inappropriate prescribing
Pre-existing kidney disease or a salicylate-induced decrease in kidney function can contribute to increased plasma levels
Prescription of a drug that unbinds salicylate from protein, particularly in a patient with chronic kidney disease and hypoalbuminaemia, can increase free salicylates in the blood and lead to toxicity
May result from patients using non-prescription drugs (e.g., cold remedies and stomach remedies) in an attempt to relieve symptoms, causing accidental intoxication.
Practical tip
If the patient has taken more than one non-steroidal anti-inflammatory drug, toxicity is increased.[2]
Specifically determine:
Dose of salicylate; calculate dose per kilogram of the patient’s body weight (either ingested, or topical exposure)
Time taken
Formulation (i.e., immediate-release or sustained-release)
Any co-ingestants
Be aware that some salicylate preparations contain other agents including opiates, paracetamol, and caffeine.
Take a careful drug history, including oral and topical agents, covering:
Regular medication
Prescribed drugs
Over-the-counter medication.
Ask about the patient’s social history and current support network.
This will help determine whether they can be discharged safely.
Note or enquire about any risk factors, which include:
Ingestion of ≥125 mg/kg salicylate
In the UK, the National Poisons Information Service recommends that children and adults who might have ingested ≥125 mg/kg salicylate, or those who are symptomatic, should be assessed for toxicity[2]
Ingestion of any amount of oil of wintergreen[5]
Found in some topical liniments and non-prescription medications
Ingestion of bismuth subsalicylate
Many non-prescription antidiarrhoeal medications contain bismuth subsalicylate, a 50% aspirin equivalent
Salicylate overdose from these products is rare
History of self-harm or suicide attempt
Salicylate-containing products may be ingested intentionally in overdose as a means of self-harm or with suicidal intent[5]
Children aged ≤3 years and adults aged ≥70 years
Incorrect salicylate dosing in children and older people can result in toxic salicylate exposure
Accidental ingestion is also of particular concern at extremes of age.[5]
Check the patient’s vital signs, including:
Temperature (may be high, or very high, and may be associated with sweating and warm extremities)
Pulse rate (may be high, or irregular and bounding in nature)
Respiratory rate (may be high and may be Kussmaul’s in nature)
Blood pressure (may be low)
Urine output (may be low)
Level of consciousness (may be low)
Oxygen saturation (may indicate heart failure or impending respiratory failure if low).
Note general features, such as:
Skin rash (which may indicate topical application)
Petechiae/purpura/bleeding, which may indicate disseminated intravascular coagulation
Volume depletion.
Practical tip
Diagnosing chronic salicylate poisoning is difficult because there is often no clear history of poisoning. Classic symptoms and signs may be attributed to other diseases, including viral illness, sepsis, diabetic or alcoholic ketoacidosis, and pre-existing lung or cardiac disease.[1]
Measure plasma salicylate levels if you suspect intoxication based on clinical symptoms – even in the absence of a documented history of ingestion.[1]
Look for signs that may indicate the severity of the poisoning, as indicated in the table below.[1][2]
[Figure caption and citation for the preceding image starts]: Signs of salicylate poisoningCreated by the BMJ Knowledge Centre [Citation ends].
In addition to the tests detailed below, monitor the patient’s vital signs and cardiac rhythm.[2]
Salicylate level
Take blood for a plasma salicylate concentration at least:[2]
2 hours (symptomatic patients) after ingestion
4 hours (asymptomatic patients) after ingestion.
Bear in mind that the salicylate concentration at presentation can be an unreliable guide to the severity of poisoning.[7]
Some salicylate preparations contain other agents such as opiates, paracetamol, and caffeine; these will need separate consideration and appropriate management.[7] See Paracetamol overdose in adults and Opioid overdose.
In remote areas in the community, discuss the patient with the nearest accident and emergency department consultant and consider taking samples for salicylate concentrations.
Repeat salicylate concentrations every 2 hours in all symptomatic patients, or those with initial plasma salicylate concentrations of ≥200 mg/L (≥1.4 mmol/L), until concentrations are falling and any clinical features have improved.[2]
Ongoing absorption may cause the salicylate concentration to continue rising.[7]
Concentrations of enteric-coated preparations may take up to 12 to 18 hours after ingestion to peak.[2]
However, be aware that salicylate levels taken after 12 hours may underestimate the degree of toxicity owing to tissue binding.[8]
Practical tip
Do not measure salicylate concentrations in patients who are conscious, who report that they have not taken salicylate-containing preparations, and who have no features suggesting salicylate toxicity.[2]
Other blood tests
All symptomatic patients
In symptomatic patients, request an arterial blood gas (ABG) at presentation. In practice, continue monitoring acid-base status:
Every 2 hours until the patient’s symptoms have improved, or salicylate levels have peaked and are showing a downward trend[2][7]
With any significant deterioration.
ABG may show a mixed respiratory alkalosis and metabolic acidosis with normal or high arterial pH (normal or reduced hydrogen ion concentration); serum anion gap is usually increased in severe cases.
In practice, calculate the serum anion gap using the formula [(Na + K) - (Cl + HCO3)]. When using this formula, note the normal range is 8 to 16 mEq/L.
Do not be misled by the absence of a raised serum anion gap if you suspect salicylate poisoning on clinical grounds.
Also check the following bloods on presentation in all patients who are symptomatic:[2][7]
Serum electrolyte panel, and urea and creatinine (for hypokalaemia and to assess renal function)[2][7]
Potassium and bicarbonate may be low
Urea and creatinine may show renal insufficiency; however, in practice, a single elevated creatinine concentration does not indicate chronic poisoning (creatinine results repeatedly raised beyond the acute presentation [over several days] are required)
International normalised ratio (INR)
The National Poisons Information Service in the UK only recommends checking INR.[2] In practice, INR alone will not detect all instances of disseminated intravascular coagulation (DIC)
Also request serum prothrombin time (PT) and activated PTT; these parameters may be abnormal
DIC is rarely associated with salicylate poisoning[2]
Full blood count (to differentiate from an infectious cause for symptoms)
Capillary blood glucose
Hypoglycaemia or hyperglycaemia may be present (both are more commonly found in young children than in adults).[2]
Patients with convulsions
In patients with convulsions, request the above and:
Calcium, magnesium, and phosphate[2][7]
Hypocalcaemia and/or hypomagnesaemia may be present
Capillary glucose.[2]
ECG
Perform a 12-lead ECG in all patients who require assessment. Check cardiac rhythm, QRS duration, and QT interval.[2]
In patients with salicylate poisoning, tachycardia is common; ECG may show a prolonged QRS or QT interval, ventricular dysrhythmia, monomorphic ventricular tachycardia, and torsades de pointes.
Asystole may occur.
Repeat 12-lead ECGs especially in symptomatic patients or in those who have ingested sustained-release preparations.[2] In practice, do this every 4 to 6 hours.
If available, monitor cardiac function continuously.
Practical tip
Think about the possibility of co-ingestion of other cardiotoxic drugs such as tricyclic antidepressants if ventricular dysrhythmia, monomorphic ventricular tachycardia, and torsades de pointes occur.
Other toxicology
In practice, conduct a broader work-up for suspected poisoning in patients who have intentionally self-harmed or attempted suicide.
This may show increased concentrations of co-ingestants.
Measure serum paracetamol levels in all cases of suspected or confirmed salicylate poisoning: patients and carers may err when reporting analgesic exposures.
Order serum ethanol levels, and levels of other toxicants that cause metabolic acidosis (e.g., methanol, ethylene glycol).
Order urine screens for drugs of misuse if clinically indicated.
In practice, results of urine screens may not be available soon enough to influence emergency management, but they may be important in identifying child abuse.
Chest x-ray
If the patient has rales and low oxygen saturation, a chest x-ray may be helpful to differentiate between pre-existing cardiac failure and acute pulmonary oedema that may be present as a symptom of toxicity.
In practice, differentiating between pre-existing heart failure or acute pulmonary oedema is difficult, particularly in older people who may have pre-existing heart failure and develop new, acute pulmonary oedema due to salicylate poisoning. Take into account the whole clinical picture.
A chest x-ray may also identify aspiration pneumonia related to the vomiting and depressed level of consciousness that can be associated with salicylate poisoning.
Localised consolidation, often in the right lower lobe, may indicate aspiration.
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