MED-NERD
Salicylate Poisoning (Diagnosis, Management, and Prognosis)
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Outline:
- Diagnosis
- Differential diagnosis
- Management and treatment
- Prognosis
- Complications
- References
Diagnosis of Salicylate Poisoning:
Diagnosis depends on history, symptoms, blood tests (Serum salicylate level, Arterial blood gases {ABGs}), urine pH, serum creatinine, serum electrolytes, plasma glucose, and blood urea nitrogen (BUN). Electrocardiogram (ECG) may be used. Serum creatine kinase (CK) and urine myoglobin are measured if rhabdomyolysis is suspected.
Salicylate poisoning is suspected in case of :
-Repeated ingestion of therapeutic doses
-History of a single acute overdose
-Unexplained fever and confusion or any changes in mental status especially in older patients
-Unexplained metabolic acidosis
-Findings suggesting sepsis such as dehydration, fever, hypoxia, hypotension, and non-cardiogenic pulmonary edema
1-History:
Includes important information that should be obtained such as the amount of salicylate ingested, time of ingestion, accidental or intentional, any other substance ingested, and the formulation. Moreover, presence of other medical conditions (eg, cardiac, renal diseases) should be questioned.
Patients of long-term ingestion of salicylates present with anxiety, diaphoresis, tachypnea, agitation, delirium, difficulty concentrating, and hallucinations. If there is an underlying psychiatric illness, patients present with symptoms of exacerbation of their underlying psychiatric illness such as mania and psychosis.
2-Symptoms of Salicylate poisoning:
3-Blood tests:
Used to measure serum aspirin level, blood pH, and the level of carbon dioxide or bicarbonate, help in determination of the severity of toxicity, and are repeated to detect recovery of patients.
-Serum salicylate level:
Salicylate poisoning is suggested in serum salicylate level is found greater than therapeutic level ((therapeutic range, 10 to 20 mg/dL [0.725 to 1.45 mmol/L]) 6 hours after ingestion after the absorption is almost complete. When serum salicylate level becomes greater than 30 mg/dL, tinnitus occurs as a symptom suggesting salicylate poisoning.
Serum salicylate level used to confirm the diagnosis and for follow up after management to detect recovery. Serial salicylate levels may help determine if the absorption of salicylate is continuing. However, serum salicylate levels may be misleading and diagnosis should be confirmed clinically and by other tests.
-Arterial blood gases (ABGs):
During the first few hours after ingestion, ABGs show primary respiratory alkalosis. Then, ABGs show compensated metabolic acidosis or mixed metabolic acidosis/respiratory alkalosis. As the usually as salicylate levels decrease, ABGs show poorly compensated or uncompensated metabolic acidosis. ABGs show combined metabolic and respiratory acidosis in case of respiratory failure in addition to chest x-ray that shows diffuse pulmonary infiltrates.
-Serum electrolytes:
Signs of salicylate poisoning include hypercalcemia, hypokalemia, acidemia, dehydration, and Syndrome of inappropriate antidiuretic hormone secretion (SIADH). Hypokalemia may occur as a result of treating patients with urinary alkalization without appropriate potassium supplementation.
-Plasma glucose level:
Levels of plasma glucose may be normal, low, or high so they are not reliable.
-Leukocytosis and thrombocytopenia may be found. Prolonged prothrombin time suggest hematologic effects of salicylate poisoning including coagulopathy and major bleeding.
-Electrocardiogram (ECG):
ECG is used to detect dysrhythmias and may show abnormalities such as QT prolongation due to hypokalemia, U waves, and flattened T waves.
-Imaging:
Computerized tomography (CT) of the head if patients present with altered mental status. Chest X-ray to detect pulmonary infiltrate.
Differential diagnosis of salicylate poisoning:
-Iron toxicity
-Hydrocarbon toxicity
-Chlorine gas toxicity
-Ethylene glycol toxicity
-Theophylline toxicity
-Organophosphate and carbamate toxicity
-Caffeine toxicity
-Drug withdrawal symptoms
-Acute respiratory distress syndrome
-Schizophrenia
-Sepsis and septic shock
-Pulmonary embolism
Management and treatment of salicylate poisoning:
Measuring patient’s vital signs (pulse, blood pressure, breathing rate, temperature) is done in emergency room.
1-Activated charcoal:
Activated charcoal reduces aspirin absorption and should be given as soon as possible. It may be repeated every 4 hours until charcoal appears in the stool if bowel sounds are detected. Activated charcoal may be contraindicated such as patients presenting with altered mental status.
Activated charcoal and gastric lavage are useful in acute poisoning bur not chronic cases of salicylate toxicity.
2- Alkaline diuresis:
Alkaline diuresis is used after correction of volume and electrolyte abnormalities. Alkaline diuresis is used to elevate urine pH up to ≥ 8. It is indicated and should not be delayed in patients of salicylate poisoning with any symptoms. Alkaline diuresis acts by increasing excretion of salicylate. A solution consisting of (1 L of 5% D/W, 3 50-mEq (50-mmol) ampules of sodium bicarbonate, and 40 mEq (40 mmol) of potassium chloride at 1.5 to 2 times the maintenance IV fluid rate) is given to patients as hypokalemia may interfere with alkaline diuresis. Serum potassium and fluid are monitored. Fluid overload may lead to pulmonary edema.
3-Drugs such as acetazolamide that increase urinary bicarbonate should be avoided as they may worsen metabolic acidosis and decrease blood pH.
4-Drugs that decrease respiratory function should be avoided as they may decrease blood pH through impairment of hyperventilation and respiratory alkalosis.
5-Symptomatic treatment:
-Treatment of fever through physical measures such as external cooling.
-Treatment of seizures with benzodiazepines.
6-Management of rhabdomyolysis:
Adequate hydration and urine output are essential, in addition to alkaline diuresis to prevent renal failure.
7-Hemodialysis:
Hemodialysis may be used to increase salicylate elimination in case of renal or respiratory insufficiency, severe neurologic deterioration, acidemia in spite of other measures, and very high serum salicylate levels (>100 mg/dL [> 7.25 mmol/L] with acute overdose or > 60 mg/dL [> 4.35 mmol/L] with chronic overdose).
8-Airway support:
Endotracheal intubation and mechanical ventilation for airway protection or oxygenation.
9-Glucose boluses:
In euglycemic patients with salicylate-induced delirium, glucose boluses may Improve mental status so, glucose should be given to any patient with salicylate poisoning and alteration in mental status despite the level of serum glucose.
10-Follow-up:
Accidental ingestion of less than 150 mg/kg without signs of toxicity can be discharged 6 hours after administration. Follow-up in these cases is done in 24 hours. Follow-up is necessary. A 17-year-old female had ingested 126-mg/kg of non-enteric coated aspirin 3.9 hours post-ingestion without toxic salicylate concentration, developed tinnitus and vomiting nearly 8 hours post-ingestion and had a toxic salicylate concentration 22.7 hours post-ingestion.
Patients with Intentional ingestion of salicylate should be referred to psychiatric consultation before discharge.
Prognosis:
Toxic aspirin dose is 200 to 300 mg/kg (milligrams per kilogram of body weight), ingestion of 500 mg/kg may be fatal. A lower level of aspirin can lead to serious results in chronic poisoning. In children, much lower levels can lead to significant effects.
If treatment is delayed, the condition will get worse. Prognosis also depends on the amount of aspirin absorbed.
Mortality rate is almost 1% and morbidity rate 16% in acute aspirin poisoning. In chronic poisoning, the morbidity rate is about 30% and mortality rate 25%. About 33% of analgesic-related deaths are a result of aspirin alone or aspirin in combination with other drugs according to the American Association of Poison Control Centers. Early management is lifesaving.
Categories of toxicity are used to determine the potential severity and morbidity of an acute, single-event, non–enteric-coated salicylate ingestion:
-Less than 150 mg/kg ingested >> Ranges from no toxicity to mild toxicity
-From 150-300 mg/kg ingested >> Mild-to-moderate toxicity
-From 301-500 mg/kg ingested >> Serious toxicity
-Greater than 500 mg/kg ingested >> Potentially fatal toxicity
Complications:
-Dyspnea, Apnea
-Aspiration pneumonitis
-Respiratory Arrest
-Asystole and dysrhythmias
-Seizures, Encephalopathy
-Coma
References:
(1) Aspirin Overdose: Symptoms, Diagnosis, Emergency Treatment.Drugs.com
https://www.drugs.com/medical-answers/aspirin-overdose-symptoms-diagnosis-emergency-3558001/
(2) Aspirin overdose, National Institutes of Health National Library of Medicine (NIH).
https://medlineplus.gov/ency/article/002542.htm
(3)Gerald F. O’Malley , DO, Grand Strand Regional Medical Center; Rika O’Malley , MD, Grand Strand Medical Center, Aspirin and Other Salicylate Poisoning,Merck Sharp & Dohme (New Zealand) Limited (MSD).
(4)Muhammad Waseem, MBBS, MS, FAAP, FACEP, FAHA, Salicylate Toxicity, Medscape.
https://emedicine.medscape.com/article/1009987-overview
(5)Runde TJ, Nappe TM. Salicylates Toxicity. [Updated 2022 Jul 11]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2022 Jan-. Available from: https://www.ncbi.nlm.nih.gov/books/NBK499879/
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