Salicylate (Aspirin) Overdose

Meet the patient

A 22-year-old woman is brought in agitated, sweating and breathing deeply two hours after swallowing a bottle of aspirin. Her ears are ringing, her temperature is raised, and she can still tell you her name — but her blood gas already shows a mixed respiratory alkalosis and high anion-gap metabolic acidosis.[13][6]

Two exam questions are now live: what is the one bedside finding that points to salicylate above every other high-anion-gap acidosis, and what happens the moment you take over her breathing? The danger is the compensating patient — she looks alert because she is hyperventilating, and severe salicylate toxicity is classically an initial respiratory alkalosis followed by a rising anion-gap metabolic acidosis as the poisoning progresses.[22]

What salicylate overdose is — and why the well-looking patient is the trap

Salicylates are a family of drugs derived from salicylic acid, available as over-the-counter tablets, combination analgesics and topical formulations (creams, ointments, lotions, liniments and medicated oils containing methyl salicylate, including oil of wintergreen).[13][16] Salicylate poisoning is toxicity from any of these; methyl salicylate is a liquid, concentrated and lipid-soluble preparation that poses the threat of severe, rapid-onset poisoning, and the two highest admission concentrations in one comparative series (4.3 and 3.5 mmol/L) came from topical medicament ingestions rather than tablets.[9]

Salicylate toxicity produces a syndrome that is physiologically distinctive and clinically dangerous: direct stimulation of the respiratory centre (respiratory alkalosis), uncoupling of oxidative phosphorylation, inhibition of citric-acid-cycle dehydrogenases, increased keto-acid production and decreased ATP production, together generating a high anion-gap metabolic acidosis — and, in severe poisoning, non-cardiogenic pulmonary oedema, CNS toxicity and cardiovascular collapse.[13]

The clinical skill in salicylate overdose rests on seven decisions, made in sequence: (1) recognise the toxidrome (hyperventilation, tinnitus, mixed acid-base disorder, fever); (2) measure a salicylate concentration and repeat it serially — for acute ingestions blood concentrations are good prognostic indicators, but for chronic salicylism they are of limited value[3]; (3) resuscitate with fluids and correct electrolyte disturbances (fluid and electrolyte management is the mainstay of therapy)[3]; (4) decontaminate the gut with activated charcoal, which is recommended after salicylate ingestion[19]; (5) institute urinary alkalinisation for moderately severe poisoning not meeting dialysis criteria[10]; (6) recognise the EXTRIP indications for extracorporeal treatment[7]; and (7) respect the airway — patients with severe overdose require a high minute ventilation, and if they are intubated, timely haemodialysis improves survival.[21]

The signature trap of this overdose is the well-looking patient who is compensating. The respiratory alkalosis is achieved through hyperventilation driven by direct stimulation of the respiratory centres in the medulla — a compensatory mechanism to avoid acidaemia; in later stages patients become increasingly obtunded, lose airway reflexes, and intubation may become necessary.[22] In the classic outcome series, failure to hyperventilate appropriately contributed to acidaemia in fatal cases.[15]

[13] [12] [10] [16]

Acute, chronic, and the formulation that multiplies the dose

Salicylate overdose is classified by clinical pattern (acute versus chronic) and by formulation — because both axes change the threshold for treatment and dialysis.[3]

[3] [4] [14] [23]

Two formulation lessons anchor the topic. Methyl salicylate (oil of wintergreen, 98 percent methyl salicylate) is the most dangerous preparation by volume: in children under 6 years of age a teaspoon (5 mL) or less has been implicated in several well-documented deaths.[16] And enteric-coated aspirin absorbs late — delayed absorption may complicate management and, historically, use of the Done nomogram in enteric-coated poisoning underestimated severity.[17]

The acid-base disturbances of salicylism unfold over time: an initial respiratory alkalosis followed by an anion-gap metabolic acidosis is the classic sequence, and non-cardiogenic pulmonary oedema may appear as an atypical, easily missed presentation.[22][24]

How common, how lethal — and who dies

Salicylate poisoning remains commonly encountered in emergency medicine.[6] In the classic adult outcome series of 2,204 admissions, patients who died or survived peak concentrations of 700 mg/L or greater comprised only 4 percent — the overall mortality of acute poisoning was 0.3 percent, but the seven deaths were significantly older than survivors, and mortality was as high as 33 percent in patients over the age of 70.[15] Acute toxicity arises from accidental ingestions in preschool children, suicidal overdoses in adults and teenagers, and therapeutically acquired intoxication in all ages; chronic, therapeutically induced salicylism may be mistaken for the underlying illness.[3]

Both acute and chronic salicylate toxicity often goes unrecognized, with high mortality when the patient is not treated properly — salicylates must be considered in any adult with acid-base abnormalities of uncertain cause, especially with concurrent neurologic symptoms.[14]

[15] [4] [17] [9] [7]

Why the gas is mixed — mechanisms and one signature blood gas

The cellular cascade is well understood and explains every feature of the syndrome — the respiratory alkalosis, the high anion-gap metabolic acidosis, the hyperthermia, the CNS toxicity, and the rationale for each treatment.[13]

1. Direct stimulation of the respiratory centre. The respiratory alkalosis is achieved through hyperventilation, driven by direct stimulation of the respiratory centres in the medulla, and is considered a compensatory mechanism to avoid acidaemia.[22] Hyperventilation is significantly more frequent in chronic poisoning than in acute poisoning at comparable concentrations.[4]

2. Uncoupling of oxidative phosphorylation and inhibition of intermediary metabolism. In overdose, salicylates cause uncoupling of oxidative phosphorylation, inhibition of citric-acid-cycle (Krebs) dehydrogenases, increased keto-acid production, and decreased ATP production — leading to the progression of signs and symptoms.[13] Alkalaemia or acidaemia, alkaluria or aciduria, hypoglycaemia or hyperglycaemia, and water and electrolyte imbalances may all occur.[3]

3. The classic adult blood gas — a MIXED disorder. Because salicylate simultaneously drives a respiratory alkalosis and an anion-gap metabolic acidosis, patients develop respiratory alkalosis and an anion-gap metabolic acidosis; a mixed acid-base disturbance is typical, and a case series of chronic intoxication documented mixed acid-base disturbances with non-cardiogenic pulmonary oedema.[13][25]

Why the kidney matters — the alkalinisation principle

This is the rationale for urinary alkalinisation, the key non-dialysis treatment.[10] Urine alkalinisation is a treatment regimen that increases poison elimination by the administration of intravenous sodium bicarbonate to produce urine with a pH of at least 7.5 — the term emphasises that urine pH manipulation rather than a diuresis is the prime objective, and the terms forced alkaline diuresis and alkaline diuresis should be discontinued.[10]

The mechanism is subtler than the textbook ion-trapping story. Because the ionisation constant (pKa) is a logarithmic function, a small change in urine pH has a disproportionately larger effect on salicylate clearance — elimination of salicylic acid by the kidneys is increased substantially in alkaline urine. However, as salicylic acid is almost completely ionised within physiological pH limits, the conventional ion-trapping explanation has been challenged as incomplete, and further work is required to clarify how alkalinisation enhances elimination.[11] The renal excretion of salicylate depends much more on urine pH than on flow rate.[5]

Why hypokalaemia matters

Hypokalaemia is the most common complication of urine alkalinisation, and it can be corrected by giving potassium supplements; aggressive replenishment of potassium (and magnesium) is part of the supportive cornerstones of treatment.[10][28]

Non-cardiogenic pulmonary oedema

Salicylate intoxication is frequently overlooked as a cause of non-cardiogenic pulmonary oedema and altered mental status in adults; it may present as recurrent pulmonary oedema requiring intubation, and it is successfully treated with haemodialysis and urinary alkalinisation, leading to rapid resolution.[23] A near-miss case stresses that non-cardiogenic pulmonary oedema is an atypical presentation demanding an early toxicology screen — the initial considerations were pneumonia, pulmonary embolism, sepsis and heart failure.[24]

Central nervous system toxicity

CNS features — altered mental status, agitation, disorientation, hallucinations, seizures and coma — are described across the classic reviews, together with tinnitus and hyperpyrexia; systemic acidosis and severe CNS manifestations are significantly more frequent in chronic poisoning.[3][13][4] Encephalopathy, coagulopathy (disseminated intravascular coagulation) and hypotension were prominent in a reported series of chronic intoxication presenting as SIRS.[25]

[13] [10] [3] [7]

The spectrum — tinnitus first, collapse last

Patients present with a range of symptoms including nausea, vomiting, diarrhoea, tinnitus, altered mental status, agitation, seizures, pulmonary oedema and coma.[13] The classic reviews add hyperpnoea, hyperpyrexia, disorientation and convulsions, with water and electrolyte imbalances and either hypoglycaemia or hyperglycaemia.[3] Tinnitus is the characteristic early clue that survives every exam syllabus.[3][13]

Severe poisoning — what the fatal cases teach

The classic outcome series of patients who died or survived peak concentrations of 700 mg/L or greater shows what severe salicylate poisoning looks like: delayed presentation, coma, hyperpyrexia, pulmonary oedema and acidaemia were all more common in the fatal cases, and failure to hyperventilate appropriately may contribute to the development of acidaemia.[15] A chronic-intoxication series adds temperature disturbances, non-cardiogenic pulmonary oedema, mixed acid-base disturbances, coagulopathy (DIC), encephalopathy and hypotension.[25] Haemodialysis is the treatment of choice for severe salicylate intoxication and should be used more liberally than it has been.[15]

Atypical presentations — the examiner's favourites

Examiners test atypical presentations deliberately.[6]

The elderly (chronic salicylism): chronic toxicity often goes unrecognised, with delayed diagnosis causing increased morbidity and mortality particularly in the elderly; the symptoms of therapeutically induced salicylism may be mistaken for those of the illness being treated.[14][3] Severe CNS manifestations, hyperventilation, dehydration and systemic acidosis are all significantly more frequent in chronic than in acute poisoning at comparable concentrations.[4]

Chronic salicylism masquerading as sepsis: chronic salicylate toxicity should be considered as a cause of the systemic inflammatory response syndrome in the absence of a source of infection, since survival appears dependent on prompt diagnosis and management.[25]

Pregnancy: unique features of perinatal physiology predict an increased sensitivity of the fetus to aspirin poisoning — in a reported case at 37 weeks with a maternal concentration of 620 mg/L the fetus died in utero while the mother survived after alkaline diuresis and haemodialysis; the fetus is at greater risk than the mother, and consideration should be given to emergent delivery of term or near-term aspirin-poisoned fetuses.[26]

Non-cardiogenic pulmonary oedema is the specific severe-salicylate presentation that gets missed: dyspnoea and hypoxia with bilateral infiltrates investigated as pneumonia, embolism, sepsis or heart failure before the salicylate concentration returns.[24][23]

The mimics — and the one finding only salicylate gives

The differential of hyperventilation plus metabolic acidosis plus agitation is broad, but the mixed respiratory alkalosis with high anion-gap metabolic acidosis and tinnitus is highly characteristic.[13] Salicylates belong on every list of common and serious poisonings alongside paracetamol, opioids and tricyclic antidepressants, and co-ingestion must be excluded — salicylate is one of the poisons for which a specific level and disease-specific management exist.[8]

[25] [3] [13] [23]

The bedside minute — hyperventilation, tinnitus, and the nine-point history

The history is the single most important step: establish (1) the agent (aspirin tablets, methyl salicylate or topical medicaments, combination products); (2) the dose; (3) the timing of ingestion; (4) whether acute or chronic (over days to weeks of therapeutic dosing); (5) co-ingestants; (6) regular medications; (7) comorbidity including kidney function; (8) intent (deliberate self-harm versus accidental); and (9) the patient's age — accidental preschool ingestions, suicidal overdoses in adults and teenagers, and therapeutically acquired intoxication in all ages are the three classic patterns.[3][6]

The focused bedside examination follows ABCDE, with emphasis on: rate AND depth of breathing (hyperventilation is the cardinal sign and its loss is ominous); temperature (hyperpyrexia); consciousness state; and signs of dehydration and electrolyte imbalance, because fluid and electrolyte management is the mainstay of therapy.[3][15]

Recognise the cannot-miss clinical gestalt: a febrile, hyperventilating, agitated patient with a mixed respiratory alkalosis and high anion-gap metabolic acidosis is salicylate-toxic until proven otherwise.[13] Psychological assessment is part of the initial management of the acutely poisoned patient, and deliberate self-harm must not go unassessed once the patient is medically stable.[8]

The concentration, the units trap, and why a single number misleads

The essential panel in every salicylate overdose is a serum salicylate concentration repeated serially, an arterial or venous blood gas, electrolytes and kidney function, glucose, coagulation, and — as indicated — concentrations of co-ingestants such as paracetamol.[3][8]

The salicylate concentration — thresholds that are actually evidence-based

The Done nomogram (1960) — historical context

The Done nomogram derives from Done's 1960 Pediatrics paper on the significance of blood salicylate measurements in acute ingestion.[1] A formal validity evaluation in 55 acute adult intoxications found a predictive index of only 0.42 (best in the mild category at 0.79), and the nomogram tends to overpredict the severity of intoxication in the moderate and severe categories; it performed better for concentrations drawn six to twelve hours after ingestion.[2] The conclusion of that evaluation — and the modern position — is that decisions should be based on clinical presentation and good judgement as well as the serum salicylate concentration in relation to the time of ingestion.[2] With enteric-coated aspirin, delayed absorption means the nomogram may underestimate severity.[17]

The arterial blood gas — interpret with care

Acute salicylate toxicity is classically associated with an initial respiratory alkalosis, followed by an anion-gap metabolic acidosis.[22] In severe chronic intoxication, mixed acid-base disturbances with systemic acidosis are the rule.[25][4]

Serial concentrations — the modern standard

For acute ingestions, blood concentrations are good prognostic indicators — but the concentration must always be read with the clinical picture: the prognosis of acute salicylate poisoning cannot be determined from the plasma concentration alone; clinical features, particularly impaired consciousness, and the arterial hydrogen-ion concentration must be taken into consideration.[3][15] In chronic salicylism, concentrations are of limited value — severe manifestations occur at ranges where acute poisoning is milder.[3][4] Absorption is erratic with some formulations (enteric-coated and modified-release preparations), so concentrations must be repeated until they are clearly falling.[6][17]

The first hour — fluids, decontamination, alkalinisation, and the dialysis decision

The time-critical bundle for any significant salicylate overdose is gastrointestinal decontamination, serum alkalinisation and fluid resuscitation, with haemodialysis reserved for the severely poisoned.[13]

1. ABCDE assessment and baseline bloods (salicylate concentration, blood gas, electrolytes and kidney function, glucose, coagulation, paracetamol concentration).[8]
2. Fluid and electrolyte management is the mainstay of therapy — dehydration is significantly more frequent in severe poisoning, and water and electrolyte imbalances are expected.[3][4]
3. Correct hypokalaemia — it is the most common complication of urine alkalinisation and is corrected with potassium supplements; aggressive potassium and magnesium replenishment is a cornerstone of supportive care.[10][28]
4. Cardiac monitoring and close monitoring of acid-base status and serum salicylate concentrations — deterioration can be rapid.[28]

GI decontamination

Activated charcoal is appropriate after salicylate ingestion, and an additional dose to complete gastrointestinal decontamination is also appropriate for salicylates, because drug may remain in the gastrointestinal tract for prolonged periods.[19] The maximum time post-ingestion for administration differs for each poison and formulation; according to an individualised risk assessment, charcoal is appropriate up to 6 hours post-ingestion for many poisons, and beyond 6 hours if ongoing absorption is suspected — for example with pharmacobezoar formation or modified-release preparations.[19] Multiple-dose activated charcoal for enhanced elimination is NOT endorsed for salicylates: its use in salicylate poisoning is controversial, and data in poisoned patients are insufficient to recommend it.[18] With enteric-coated aspirin, delayed absorption may complicate management and prolongs the period of risk.[17]

Indications for urgent extracorporeal treatment (EXTRIP 2015)

The classic outcome series put it bluntly: haemodialysis is the treatment of choice for severe salicylate intoxication and should be used more liberally than it is at present.[15]

The airway — the trap that has killed patients

Patients with severe salicylate overdose require a high minute ventilation. Early in the course they hyperventilate; if they become too fatigued to compensate, mechanical ventilation may be needed — and it can be impossible to recreate such a high minute ventilation with mechanical ventilation, placing patients at high risk of decompensation and death.[21] A published case documents profound hypercarbia and acidaemia despite mechanical ventilation with high minute ventilation and tidal volumes after intubation of a severely poisoned patient.[22]

The counterpoint every modern candidate should know: a 14-year single-centre cohort of 32 adults with severe poisoning (median concentration 64.2 mg/dL) found that the 11 patients who were intubated showed no substantial perturbation of serum pH and no severe complications, challenging the paradigm that these interventions should be avoided.[20] The synthesis: do not intubate a compensating salicylate patient for convenience; if intubation is genuinely required, expect the need for high minute ventilation, and start haemodialysis early — among intubated patients with concentrations over 50 mg/dL, survival was 83.9 percent with haemodialysis versus 56 percent without, and at concentrations over 80 mg/dL, 83.3 percent with dialysis versus 0 percent without.[21]

Seizures and altered mental status mark severe poisoning: seizures appear in the progression of toxicity, and altered mental status is itself a 1D indication for extracorporeal treatment.[13][7] Hyperpyrexia was significantly more common in fatal cases — it signals severe poisoning, not a treatable set-point fever.[15]

Urinary alkalinisation — the key non-dialysis treatment

The cornerstone of enhanced elimination in salicylate poisoning is urinary alkalinisation: the administration of intravenous sodium bicarbonate to produce urine with a pH of at least 7.5.[10]

[10] [12]

Mechanism and evidence: urinary alkalinisation increases salicylate elimination, and because the pKa is a logarithmic function, a small change in urine pH has a disproportionately larger effect on salicylate clearance — though the conventional ion-trapping explanation has itself been challenged.[11] The randomised comparison that settled practice treated 44 adults with oral fluids only, standard forced alkaline diuresis, forced diuresis alone, or sodium bicarbonate (alkali) alone: alkali alone was at least as effective and possibly more effective than forced alkaline diuresis, it did not cause fluid retention or biochemical disturbances, and the renal excretion of salicylate depends much more on urine pH than on flow rate.[5] In overdose, aspirin itself causes sodium and fluid retention and may impair renal function, so attempts to force a diuresis are potentially hazardous — and the spurious fall in plasma salicylate caused by haemodilution gives a false impression of improvement.[5]

Monitoring: clinical guidelines recommend serial urinary pH measurements during treatment — yet in a five-year poison-centre series urine pH was documented in only 41 percent of bicarbonate-treated cases and the pH target was achieved in only 34 percent of those documented.[12] In a severe case managed with bicarbonate infusion, the explicit targets were a blood pH of 7.5 and a urine pH over 7.5.[28]

Stepwise management ladder

[3] [19] [10] [12] [6] [7] [28] [8]

Haemodialysis — modality and dose

Intermittent haemodialysis is the preferred modality (1D); salicylates are readily removed by extracorporeal treatment.[7] Haemodialysis and urinary alkalinisation together produced rapid resolution of pulmonary oedema and successful extubation in the index chronic-salicylism case.[23] Post-dialysis rebound is real: after a first run, one severely poisoned patient's concentration rebounded from 98.2 to 129 mg/dL with a visible decline in mental status, resolving only after further haemodialysis — so concentrations and mental state must be monitored after dialysis.[28]

When to stop treatment

One evidence-based stopping strategy is to wait for two consecutive serum salicylate concentrations under 300 mg/L (2.17 mmol/L) that are declining before ceasing the bicarbonate infusion.[27] After stopping, rebound occurred in only 2.1 percent of 377 cases (all acute ingestions); of the eight rebounds, five rose above 300 mg/L and only one produced recurrent symptoms (tinnitus) — so even supratherapeutic rebound concentrations are often asymptomatic or mild, and routine repeat concentrations after stopping may be unnecessary unless symptoms recrudesce.[27]

Drugs with NO role

There is no specific antidote for aspirin — the goals of therapy are limiting absorption, enhancing elimination, and supportive care: euvolaemic hydration, alkalinisation, aggressive potassium and magnesium replenishment, activated charcoal, and haemodialysis.[28] Forced alkaline diuresis as a high-fluid-volume regimen is obsolete: urine pH manipulation rather than diuresis is the objective, and the terms forced alkaline diuresis and alkaline diuresis should be discontinued.[10]

Scenarios you will actually meet

Enteric-coated or sustained-release aspirin

Absorption is delayed, which complicates management — historically the Done nomogram underestimated severity in enteric-coated poisoning, and charcoal can be given beyond the usual window when ongoing absorption is suspected.[17][19]

Methyl salicylate (oil of wintergreen)

Oil of wintergreen is 98 percent methyl salicylate; because it is liquid, concentrated and lipid-soluble, it poses the threat of severe, rapid-onset salicylate poisoning — in children under 6, a teaspoon (5 mL) or less has been implicated in several well-documented deaths.[16] In a comparative series, proportions of symptomatic patients were similar for tablets and topical medicaments, and the two highest admission concentrations (4.3 and 3.5 mmol/L) both followed topical medicament ingestion.[9]

Chronic salicylism (the elderly)

Chronic toxicity is more severe than acute poisoning at comparable concentrations — hyperventilation, dehydration and severe CNS manifestations are significantly more frequent — and it is often unrecognised, particularly in the elderly, where delayed diagnosis increases morbidity and mortality.[4][14] It can present as non-cardiogenic pulmonary oedema requiring haemodialysis, as SIRS without an infective source, or as a confounded delirium work-up.[23][25]

Pregnancy

Salicylate poisoning in pregnancy carries increased fetal sensitivity: at 37 weeks, despite maternal survival after alkaline diuresis and haemodialysis at a maternal concentration of 620 mg/L, the fetus died in utero. The fetus is at greater risk than the mother, and consideration should be given to emergent delivery of term or near-term aspirin-poisoned fetuses.[26]

Children

In the paediatric comparison, chronic poisoning produced greater morbidity than acute: hyperventilation (P under 0.01), dehydration (P under 0.001) and severe CNS manifestations (P under 0.001) were all more frequent in the chronic group, and systemic acidosis (pH under 7.32) was significantly more frequent in chronic poisoning.[4]

Non-cardiogenic pulmonary oedema

Oxygen, and haemodialysis plus urinary alkalinisation, which produced rapid resolution in the reported case; avoid fluid overload — forced diuresis is hazardous in aspirin overdose because the drug itself causes sodium and fluid retention.[23][5]

Seizures, coma and altered mental status

Seizures and coma belong to the progression of severe toxicity, and altered mental status is a 1D indication for extracorporeal treatment regardless of concentration.[13][7]

The patient requiring intubation

Severe overdose requires a high minute ventilation; if the patient is too fatigued to maintain it, mechanical ventilation may be needed but can be impossible to match to the patient's own compensatory hyperventilation — hypercarbia and acidaemia despite high minute ventilation and tidal volumes have been documented.[21][22] A recent cohort found intubation itself did not substantially perturb pH, but the survival data are unambiguous: timely haemodialysis for intubated salicylate-poisoned patients decreases mortality (83.9 versus 56 percent survival over 50 mg/dL; 83.3 versus 0 percent over 80 mg/dL).[20][21]

Mixed overdose

Salicylate is one of the common and serious poisonings whose specific management must run alongside general supportive care of the poisoned patient; co-ingestants (paracetamol, opioids, tricyclics) are common and each is treated on its own merits.[8]

Rebound toxicity

After stopping bicarbonate, rebound by tissue redistribution or delayed gastrointestinal absorption occurred in 2.1 percent of 377 poison-centre cases, almost always without recurrent symptoms; after haemodialysis, rebound with recurrent confusion has been described — monitor for recurrent symptoms and recheck concentrations if they recrudesce.[27][28]

How the patient comes to harm — the preventable list

Disease complications

[3] [13] [15] [25] [5]

Classical pitfalls

[6] [25] [15] [21] [14] [10] [7]

The unit-confusion pitfall

Salicylate is reported in mg/dL, mg/L or mmol/L, and the EXTRIP thresholds are deliberately quoted in both systems — 7.2 mmol/L is 100 mg/dL — because acting on a misread unit either delays or triggers unnecessary dialysis. Always confirm the local unit before deciding on extracorporeal treatment.[7]

The rebound phenomenon

When urine alkalinisation stops, serum salicylate can rebound from tissue redistribution or delayed gastrointestinal absorption; the measured incidence is low — 8 of 377 cases (2.1 percent), all acute ingestions, five of the eight above 300 mg/L, and only one with recurrent symptoms (tinnitus). The evidence-based conclusion: routine repeat concentrations after stopping may be unnecessary unless symptoms recrudesce.[27]

Who goes home, who is dialysed — clinical status trumps the number

The prognosis of acute salicylate poisoning cannot be determined from the plasma concentration alone — clinical features, particularly impaired consciousness, and the arterial hydrogen-ion concentration must be taken into consideration.[15] Overall mortality in the classic series was 0.3 percent, but chronic toxicity in the elderly carries the worst outcomes because recognition is delayed.[15][14]

Predictors of poor outcome

Older age (mortality up to 33 percent in the over-seventies), delayed presentation, coma, hyperpyrexia, pulmonary oedema and acidaemia were all significantly more common in fatal cases; impaired consciousness and the arterial hydrogen-ion concentration carry the prognosis, and EXTRIP adds the extracorporeal triggers — altered mental status, ARDS on oxygen, failing standard therapy, high concentrations and severe acidaemia.[15][7]

Disposition

[27] [7] [8]

Safety-net on discharge

Discharge when concentrations are clearly falling, the patient is asymptomatic, acid-base is normal, and psychological assessment for self-harm is complete — the initial management of the acutely poisoned patient explicitly includes psychological assessment.[8]

Special populations — pregnancy, children, the elderly, the kidney-impaired

[26] [4] [16] [14] [15] [7] [5] [23]

Evidence and the names that score marks

The evidence base

The Done 1960 paper (Pediatrics) is the foundation of the Done nomogram — the significance of blood salicylate measurements in acute ingestion.[1] A 1989 validity evaluation (55 acute adult intoxications) found a predictive index of 0.42, overprediction of severity in the moderate and severe categories, and concluded that management decisions should rest on clinical presentation and judgement as well as the concentration in relation to ingestion time.[2]

The Temple 1981 review (Archives of Internal Medicine) laid out the acute-versus-chronic distinction — dose-related severity and useful concentrations in acute poisoning, limited concentration value and symptom-mimicry in chronic salicylism, with fluid and electrolyte management as the mainstay.[3]

The Gaudreault 1982 paediatric study (112 cases) demonstrated that chronic salicylism produces greater morbidity than acute poisoning at comparable concentrations, with more hyperventilation, dehydration, severe CNS manifestations and systemic acidosis.[4]

The Prescott 1982 BMJ randomised comparison (44 adults) established that alkali alone is at least as effective as forced alkaline diuresis, that excretion depends on urine pH rather than flow, and that forced diuresis is hazardous in aspirin overdose.[5]

The AACT/EAPCCT Position Paper on urine alkalinization (2004) defined the regimen — IV sodium bicarbonate to a urine pH of at least 7.5 — retired the term forced alkaline diuresis, recommended alkalinisation as first-line treatment for moderately severe salicylate poisoning not meeting haemodialysis criteria, and flagged hypokalaemia as its commonest complication.[10] Its companion review asked why alkalinisation works and found the conventional ion-trapping account incomplete — the pKa logarithm means small urine-pH shifts move clearance disproportionately.[11]

The EXTRIP 2015 recommendations (84 articles; clinical data on 143 patients, 14 fatalities) graded every statement: extracorporeal treatment for severe poisoning (1D) including altered mental status (1D), ARDS on oxygen (1D) and failing standard therapy (1D) regardless of concentration; high-concentration thresholds over 7.2 mmol/L (100 mg/dL, 1D) and over 6.5 mmol/L (90 mg/dL, 2D), lower with impaired kidney function; severe acidaemia pH at or under 7.20 (2D); and intermittent haemodialysis as the preferred modality (1D).[7]

The Chapman 1989 outcome series defined the high-concentration cohort (700 mg/L or greater, 4 percent of 2,204 admissions) and showed that the concentration alone does not determine prognosis — impaired consciousness and acidaemia do — while calling for more liberal haemodialysis.[15]

The Chan 1996 comparison established that topical methyl-salicylate medicaments can produce severe, rapid-onset poisoning — the two highest concentrations in the series followed topical ingestions.[9] The Davis 2007 review quantified the wintergreen danger for toddlers: 98 percent methyl salicylate; a teaspoon or less has killed children under six.[16]

The intubation evidence: a 2017 case report of hypercarbia and acidaemia despite mechanical ventilation[22]; a 2017 poison-centre series showing timely haemodialysis improves survival in intubated patients[21]; and a 2024 cohort of 32 adults challenging the avoid-intubation paradigm.[20]

The O'Keefe 2023 rebound study (377 cases) found rebound after stopping alkalinisation in 2.1 percent, mostly asymptomatic — routine repeat concentrations after stopping may be unnecessary unless symptoms recrudesce.[27] A 2024 case report documented post-haemodialysis rebound with recurrent confusion requiring a further run.[28]

Regional deltas

Controversies

Forced alkaline diuresis versus urinary alkalinisation is settled: pH manipulation, not high flow, is the objective; forcing a diuresis adds hazard without benefit.[10][5]

The dialysis threshold controversy is really a question of what decides — EXTRIP holds that altered mental status, ARDS on oxygen and failing therapy warrant extracorporeal treatment regardless of concentration, while the high-concentration cutoffs (over 7.2 and over 6.5 mmol/L, lower with kidney impairment) apply regardless of signs and symptoms; the outcome literature adds that the concentration alone never determines prognosis.[7][15]

The intubation controversy: mechanical ventilation has been strongly discouraged on physiological grounds, and catastrophic hypercarbia-acidaemia despite ventilation is documented — but the only dedicated cohort found no substantial pH perturbation or severe complications with intubation, so the modern position is to intubate only when necessary, match the high minute ventilation, and dialyse early.[22][20][21]

Multiple-dose activated charcoal for salicylate enhancement remains unendorsed — the data in poisoned patients are insufficient to recommend it.[18]

The Done nomogram is historical: it overpredicts severity in moderate-to-severe poisoning and is invalidated by delayed absorption — serial concentrations with clinical judgement supersede it.[2][17]

The mantra, and the memory devices

The mantra: the gas is mixed, the potassium leaks when you alkalinise, the concentration alone never decides, and never let the ventilation fall behind the acidosis.[13][10][15]

[10] [12] [27] [7] [16] [21] [13] [4] [2] [20]

Ward-round test — three stems, a minute each

Stem 1 — the concentration is high, but in which units? (answer)

The laboratory calls a salicylate concentration on the woman from the vignette, and the attending asks whether to start planning dialysis. What must you confirm before you answer? Model: The units. Salicylate is reported in mg/dL, mg/L or mmol/L, and EXTRIP quotes its extracorporeal thresholds in both systems precisely to prevent unit confusion — over 7.2 mmol/L (100 mg/dL) warrants extracorporeal treatment regardless of signs and symptoms, over 6.5 mmol/L (90 mg/dL) carries a weaker (2D) recommendation, and thresholds fall further with impaired kidney function (over 5.8 mmol/L, 80 mg/dL, 2D). Confirm the local unit before acting, and never act on a single concentration — absorption is erratic with some formulations, so repeat it serially until it is clearly falling, reading every value against the clinical picture: altered mental status, ARDS on oxygen or failing standard therapy trigger extracorporeal treatment regardless of the concentration.[7][6]

Stem 2 — she is intubated, and now she is crashing (answer)

For a suspected seizure the salicylate-toxic patient was sedated, paralysed and intubated, and the ventilator was set to a normal rate. Within minutes her carbon dioxide has risen and her pH has fallen. What went wrong, and how is it fixed? Model: She was surviving by hyperventilating against her metabolic acidosis. Severe salicylate overdose demands a very high minute ventilation, and it can be impossible to recreate that minute ventilation mechanically — profound hypercarbia and acidaemia despite mechanical ventilation with high minute ventilation and tidal volumes is documented. The fix is to raise minute ventilation immediately, correct the acid-base derangement, and start haemodialysis without delay: in intubated patients with concentrations over 50 mg/dL, survival was 83.9 percent with haemodialysis versus 56 percent without, and over 80 mg/dL, 83.3 percent versus zero. Note the counterpoint for vivas — a recent cohort found intubation did not substantially perturb pH when managed deliberately — so the lesson is not "never intubate" but "never intubate without planning high minute ventilation and dialysis".[21][22][20]

Stem 3 — the confused old man on long-term aspirin (answer)

An 82-year-old who takes aspirin for his heart is brought in confused, with slurred speech and no tinnitus and no obvious hyperventilation. Sepsis and stroke are being worked up. What is being missed? Model: Chronic salicylism. Therapeutically induced salicylism is mistaken for the illness being treated, and acute and chronic salicylate toxicity often goes unrecognised — with high mortality when treatment is delayed, particularly in the elderly, where mortality reached a third of patients in the classic outcome series. At comparable concentrations, chronic poisoning causes significantly more hyperventilation, dehydration, severe CNS manifestations and systemic acidosis than acute poisoning, so the concentration underestimates the danger. Check a salicylate concentration in any adult with an acid-base abnormality of uncertain cause and neurologic features, correct fluids and electrolytes, and apply a low threshold for extracorporeal treatment — altered mental status alone qualifies regardless of concentration.[3][14][15][4][7]

References

1. [1]Done AK. Salicylate intoxication. Significance of measurements of salicylate in blood in cases of acute ingestion. Pediatrics, 1960.PMID 13723722
2. [2]Dugandzic RM, Tierney MG, Dickinson GE, et al. Evaluation of the validity of the Done nomogram in the management of acute salicylate intoxication. Annals of Emergency Medicine, 1989.PMID 2817562
3. [3]Temple AR. Acute and chronic effects of aspirin toxicity and their treatment. Archives of Internal Medicine, 1981.PMID 7469627
4. [4]Gaudreault P, Temple AR, Lovejoy FH Jr. The relative severity of acute versus chronic salicylate poisoning in children: a clinical comparison. Pediatrics, 1982.PMID 7122154
5. [5]Prescott LF, Balali-Mood M, Critchley JA, Johnstone A, Proudfoot AT. Diuresis or urinary alkalinisation for salicylate poisoning? British Medical Journal (Clinical Research Edition), 1982.PMID 6291695
6. [6]O'Malley GF. Emergency department management of the salicylate-poisoned patient. Emergency Medicine Clinics of North America, 2007.PMID 17482023
7. [7]Juurlink DN, Gosselin S, Kielstein JT, Ghannoum M, Lavergne V, Nolin TD, Hoffman RS; EXTRIP Workgroup. Extracorporeal Treatment for Salicylate Poisoning: Systematic Review and Recommendations From the EXTRIP Workgroup. Annals of Emergency Medicine, 2015.PMID 25986310
8. [8]Greene SL, Dargan PI, Jones AL. Acute poisoning: understanding 90% of cases in a nutshell. Postgraduate Medical Journal, 2005.PMID 15811881
9. [9]Chan TY. The risk of severe salicylate poisoning following the ingestion of topical medicaments or aspirin. Postgraduate Medical Journal, 1996.PMID 8871462
10. [10]Proudfoot AT, Krenzelok EP, Vale JA. Position Paper on urine alkalinization. Journal of Toxicology. Clinical Toxicology, 2004.PMID 15083932
11. [11]Proudfoot AT, Krenzelok EP, Ole K, Vale JA. Does urine alkalinization increase salicylate elimination? If so, why? Toxicological Reviews, 2003.PMID 15181662
12. [12]Weigel B, Hays H, Armah K, et al. Urinary Alkalinization for Salicylate Poisoning Is Infrequently Measured nor Achieved. American Journal of Therapeutics, 2025.PMID 40266330
13. [13]Sidlak AM, Lazarchick MS, Wills BK. Acute Salicylate Toxicity: A Narrative Review for Emergency Clinicians. Cureus, 2025.PMID 41049912
14. [14]Pearlman BL, Gambhir R. Salicylate intoxication: a clinical review. Postgraduate Medicine, 2009.PMID 19641282
15. [15]Chapman BJ, Proudfoot AT. Adult salicylate poisoning: deaths and outcome in patients with high plasma salicylate concentrations. Quarterly Journal of Medicine, 1989.PMID 2602553
16. [16]Davis JE. Are one or two dangerous? Methyl salicylate exposure in toddlers. Journal of Emergency Medicine, 2007.PMID 17239735
17. [17]Pierce RP, Gazewood J, Blake RL Jr. Salicylate poisoning from enteric-coated aspirin. Delayed absorption may complicate management. Postgraduate Medicine, 1991.PMID 2008403
18. [18]American Academy of Clinical Toxicology; European Association of Poisons Centres and Clinical Toxicologists. Position statement and practice guidelines on the use of multi-dose activated charcoal in the treatment of acute poisoning. Journal of Toxicology. Clinical Toxicology, 1999.PMID 10584586
19. [19]Hoegberg LCG, on behalf of the Clinical Toxicology Recommendations Collaborative. Recommendations from the Clinical Toxicology Recommendations Collaborative on the administration of activated charcoal in acute oral overdose. Clinical Toxicology (Philadelphia), 2026.PMID 41906697
20. [20]McDonald BA, Su MK, Calello DP, et al. Tracheal Intubation and Mechanical Ventilation in Adults with Severe Salicylate Poisoning. Journal of Emergency Medicine, 2024.PMID 39030088
21. [21]McCabe DJ, Lupu AL, Cienki JJ. The association of hemodialysis and survival in intubated salicylate-poisoned patients. American Journal of Emergency Medicine, 2017.PMID 28438446
22. [22]Fernando SM, Di Peachey D, Fox-Robichaud AE. Hypercapnea and Acidemia despite Hyperventilation following Endotracheal Intubation in a Case of Unknown Severe Salicylate Poisoning. Case Reports in Critical Care, 2017.PMID 28465843
23. [23]Cohen DL, Putterman C. Chronic salicylism resulting in noncardiogenic pulmonary edema requiring hemodialysis. American Journal of Kidney Diseases, 2000.PMID 10977813
24. [24]Yuklyaeva N, Kurmanalina I, Sarybayeva G. Salicylate-induced pulmonary edema—a near-miss diagnosis. American Journal of Emergency Medicine, 2014.PMID 24361138
25. [25]Chalasani N, Roman J. Systemic inflammatory response syndrome caused by chronic salicylate intoxication. Southern Medical Journal, 1996.PMID 8638172
26. [26]Palatnick W, Tenenbein M. Aspirin poisoning during pregnancy: increased fetal sensitivity. American Journal of Perinatology, 1998.PMID 9475686
27. [27]O'Keefe M, Stanton M, Feldman R, Theobald J. Incidence of rebound salicylate toxicity following cessation of urine alkalinization. Clinical Toxicology (Philadelphia), 2023.PMID 37427892
28. [28]Peketi SH, Doshi P, Patel S. Salicylate Poisoning and Rebound Toxicity. Cureus, 2024.PMID 38746490