11/14/24, 10\:45 AM Salicylate Overdose

Salicylate Overdose

Table of contents
Key points ⚡
Succinct notes to superpower your revision
Salicylates\: group of medications, most common is aspirin (acetylsalicylic acid); other salicylates include magnesium
salicylate, di
Household preparations\: include NSAIDs (oral/topical), oil of wintergreen, and selected antacids and antidiarrhoeal
medications.
Overdose\: can be intentional (self-harm/suicide) or accidental (incorrect dosing, multiple products containing salicylates).
Pathophysiology\:
Mild toxicity\: irritates gastric lining, ototoxicity.
Moderate/severe toxicity\: respiratory alkalosis (hyperventilation) and metabolic acidosis (anaerobic metabolism, heat
production, lactic acid).
Symptoms\:
Mild toxicity\: nausea, vomiting, epigastric pain, tinnitus, dizziness, lethargy.
Moderate toxicity\: sweating, fever, dyspnoea.
Severe toxicity\: confusion, convulsions, coma.
Clinical
oedema.
Investigations\:
Bedside\: observations, ECG (monitor QRS, QT), capillary blood glucose, arterial blood gas.
Laboratory\: plasma salicylate concentration, plasma paracetamol concentration, FBC, U&Es, LFTs, coagulation (INR, PT).
Imaging\: CT head if altered mental state.
Management\:
Initial\: ABCDE approach, activated charcoal (if within 1 hour of ingestion), IV
bicarbonate (for urinary alkalinisation).
Ongoing\: cooling measures (if hyperthermia), haemodialysis (for severe toxicity, renal failure, severe metabolic acidosis), IV
benzodiazepines (for seizures), CPAP (for pulmonary oedema), psychological support (if overdose was intentional).
Complications\:
ARDS\: manage with intubation and ventilation.
Seizures\: manage with benzodiazepines, may require intubation and ventilation.
Drug-induced hepatitis\: usually resolves with toxicity resolution.
Cardiac arrest\: follow advanced cardiac life support guidelines, consider sodium bicarbonate administration.
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A comprehensive topic overview

Introduction

Salicylates are a group of medications of which aspirin (acetylsalicylic acid) is the most common.
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Other salicylates exist, including magnesium salicylate, di
anti-in
doses.
1

Aetiology

Types of salicylates
Even though aspirin is the most commonly used salicylate, other common household preparations that contain salicylates
include\:
2
Non-steroidal anti-in
Oil of wintergreen\: a mint smelling fragrance used in many products, and low concentrations are found in chewing gum
and mints
Selected antacids and antidiarrhoeal medications
Intentional overdose
An intentional overdose can be a means of causing self-harm or a suicide attempt. Exploring the intention of an overdose
is a key part of assessing a patient's psychological state and associated risk.
Accidental overdose
With the widespread use of salicylates, accidental ingestion of more than the recommended dose is common. Incorrect
dosing in children and the elderly may also result in overdose.
Many non-prescription aspirin-containing products are available, and many cold and
increasing the risk of patients unknowingly exceeding the safe dose.
2
Pathophysiology
In mild toxicity, salicylates directly irritate the gastric lining. They can also cause ototoxicity through a multifactorial
process, involving reduced cochlear blood
In higher doses, the pharmacodynamics of salicylate poisoning leads to a mixed respiratory alkalosis and metabolic
acidosis. In moderate/severe toxicity, salicylates stimulate the cerebral medulla, leading to hyperventilation and
respiratory alkalosis.
Metabolisation of salicylates then causes uncoupling of oxidative phosphorylation, resulting in anaerobic metabolism. This
causes heat production and pyrexia and increased lactic acid production, resulting in metabolic acidosis. The acidic
e
until the body can no longer compensate.
3,4

Clinical features

History
Typical symptoms of salicylate overdose are dependent on the severity of the poisoning.
3
Symptoms of mild toxicity include\:
Nausea and vomiting
Epigastric pain
Tinnitus
Dizziness
Lethargy
Symptoms of moderate toxicity include\:
Sweating
Fever
Dyspnoea
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Symptoms of severe toxicity include\:
Confusion
Convulsions
Coma
Other important areas to cover in the history include\:
The amount and preparation of the salicylate taken
Intentional or accidental overdose
Isolated or mixed overdose
Mixed overdose
Consider the possibility of a mixed overdose in any patient presenting with acute drug toxicity.
Patients may even be unaware that they have consumed potentially toxic quantities of several substances. It is
important to determine the exact preparations, ingredients and doses of each medication consumed. The
management of diTOXBASE provides comprehensive guidance.
Clinical examination
Clinical
Typical clinical
Warm peripheries and bounding pulse
Tachypnoea and hyperventilation
Cardiac arrhythmia
Acute pulmonary oedema

Investigations

Bedside investigations
Relevant bedside investigations include\:
2
Observations\: to indicate patient stability and guide physiological support (e.g. oxygen). Tachypnoea and tachycardia are
common
ECG\: to monitor for arrhythmias. It is essential to monitor QRS duration and QT interval for evidence of prolongation.
Capillary blood glucose\: to exclude hypoglycaemia or ketoacidosis if the main presenting complaint is vomiting and
confusion. However, hypoglycaemia or hyperglycaemia may be seen in salicylate toxicity.
Arterial blood gas\: to monitor acid-base balance. Initially, hyperventilation causes respiratory alkalosis, but this will then
progress to metabolic acidosis with a partial respiratory compensation, with a normal or high pH.
Laboratory investigations
Relevant laboratory investigations include\:
2
Plasma salicylate concentration\: taken at least 2 hours after ingestion and repeated every 2 hours until salicylate
concentration peaks.
overdose.
Plasma paracetamol concentration\: paracetamol concentration should be measured in all patients to identify mixed
FBC\: to exclude an infectious aetiology for the presenting features.
U&Es\: to assess for electrolyte disturbances. Hyperkalaemia is common and should be monitored closely and promptly
corrected. Urea and creatinine may be raised, indicating an acute kidney injury.
LFTs\: to assess for hepatic dysfunction.
Coagulation\: INR and prothrombin time may be increased in hepatic dysfunction.
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Imaging
Relevant imaging investigations may include\:
CT head\: if the patient has an altered mental state and an intracranial pathology is suspected.
4

Diagnosis

TOXBASE classi
salicylate levels\:
3
Mild toxicity\: \<300 mg/L
Moderate toxicity\: 300 to 700 mg/L
Severe toxicity\: >700 mg/L

Management

As with any acutely unwell patient, they should be managed using an ABCDE approach. Patients with severe salicylate
toxicity may lose control of their airway and so it’s crucial to ensure airway patency and adequate ventilation is maintained.
There is no antidote for salicylate poisoning, and the mainstay of management is supportive care. ICU admission should
be considered for those with moderate to severe toxicity.
2
TOXBASE
The National Poisons Information Service has created a clinical toxicology database listing nearly every toxin. They
provide gold-standard information and management guidance for toxin consumption in the UK. Information can be
found via their website or by calling the service. A login is required to access the website, and most institutions will
provide this.
Initial management
The initial management of salicylate overdose includes\:
2,3,5
Activated charcoal\: this should be considered for patients presenting within 1 hour of ingestion of >125mg/kg salicylates
unless there are concerns around airway protection.
Intravenous
chloride is typically used).
Potassium replacement\: hypokalaemia should be treated urgently with an intravenous infusion. The aim is to maintain
plasma potassium of 4-4.5 mmol/L. Bicarbonate therapy can precipitate hypokalaemia, so any pre-existing
hypokalaemia must be urgently corrected.
Sodium bicarbonate\: this reduces the transfer of salicylates into the central nervous system and enhances the urinary
excretion of salicylates (otherwise known as urinary alkalinisation). Urine pH should be monitored with the optimal pH
7.5-8.5. As mentioned, plasma potassium should be corrected before starting sodium bicarbonate, as it can potentiate
hypokalaemia.
Ongoing management
The ongoing management of salicylate overdose includes\:
2,3
Cooling measures\: hyperthermia should be addressed by removing clothes and using wet towels, fans and icepacks.
More invasive internal cooling devices or sedation are indicated in temperatures exceeding 39°C.
Haemodialysis\: the treatment of choice for severe salicylate poisoning with renal failure, severe metabolic acidosis or
seizures. Haemodialysis should be arranged urgently for those with a salicylate concentration ≥900 mg/L (≥700 mg/L
with a metabolic acidosis) or coma secondary to salicylate poisoning.
Intravenous benzodiazepines (e.g. lorazepam)\: for the management of frequent or prolonged convulsions.
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Continuous positive airway pressure (CPAP)\: this is considered for patients with acute pulmonary oedema or acute lung
injury, secondary to the salicylate overdose.
Psychological support\: patients require access to psychological services if the overdose was intentional. If the patient
refuses treatment, a psychiatric assessment should be organised to assess capacity.
Haemodialysis vs Haemo
Haemodialysis involves the di
semipermeable membrane. Haemo
the dialysis 6
Haemodia
Haemo
to remove salicylates from the plasma and correct the metabolic acidosis.

Complications

Complications due to salicylate poisoning are common. The speci
addition to the management of the acute overdose.
Acute respiratory distress syndrome
Acute respiratory distress syndrome (ARDS) is typi
by heart failure. Its incidence in salicylate poisoning is dose-dependent, with a high incidence in salicylate levels ≥800
mg/L.
Management involves intubation and ventilation with elevated positive end-expiratory pressures to prevent alveolar
collapse.
2
Seizures
Like ARDS, the incidence of seizures rises with the ingested dose. Anticonvulsants are generally unnecessary if single and
brief. However, benzodiazepines are used to terminate prolonged seizures.
With frequent seizures comes the risk of failure to ventilate, and these patients may require intubation and ventilation.
2,3
Drug-induced hepatitis
The incidence of hepatitis is low and generally resolves with the resolution of toxicity. It’s important to be aware of this when
reviewing the LFTs.
2
Cardiac arrest
Salicylate toxicity can signi
lead to polymorphic ventricular tachycardia and/or ventricular
Advanced cardiac life support guidelines should be followed as standard, with good CPR, IV adrenaline and de
indicated. Sodium bicarbonate administration is recommended in salicylate-induced cardiac arrest, although there is no
evidence base behind this.
2

References

Steven B Abramson. Aspirin\: Mechanism of action, major toxicities, and use in rheumatic diseases. UpToDate. Published
2021. Available from\: [LINK]
BMJ Best Practice. Salicylate poisoning. Published 2021. Available from\: [LINK]
National Poisons Information Service. TOXBASE®. Salicylic Acids and Salicylates (Salicylates). Published 2019. Available
from\: [LINK]
https\://app.geekymedics.com/notebook/2667/ 5/611/14/24, 10\:45 AM Salicylate Overdose
Tyler J. Runde TMN. Salicylates Toxicity. In\: S t a t P e a r l s [ I n t e r n e t ] . StatPearls Publishing; 2021. Available from\: [LINK]
Joint Formulary Committee. Poisoning, emergency treatment. In\: B r i t i s h N a t i o n a l F o r m u l a r y ( O n l i n e ) . BMJ Group and
Pharmaceutical Press.
Hall NA, Fox AJ. Renal replacement therapies in critical care. C o n t i n E d u c A n a e s t h C r i t C a r e P a i n . 2006;6(5)\:197-202.
doi\:10.1093/bjaceaccp/mkl038

Reviewer

Dr Grace McKay
Honorary Clinical Lecturer
Cardi

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Contents

Introduction
Aetiology
Clinical features
Investigations
Diagnosis
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