Dr. Held discussed the case of a young female who presented to the emergency department with nonspecific complaints including nausea and vomiting: she was ultimately found to have salicylate toxicity.
Salicylates are a commonly found ingredient in many prescription and OTC medications.
Salicylate toxicity can present early in the course with a variety of nonspecific symptoms, including nausea, vomiting and diarrhea, but patients can also complain of tinnitus (buzzword for boards!) and vertigo. Later in the course, patients can develop altered mental status, fever, noncardiogenic pulmonary edema, coma, and death.
Vital sign abnormalities can create a picture similar to sepsis, with hypotension, tachypnea, tachycardia, and elevated temperature. Patients can develop hearing loss, dysrhythmia, agitation, confusion, restlessness, tremor, or even cerebral edema.
Phases of Salicylate Toxicity
Phase 1: 0 to 12 hours.
During this time, patients begin hyperventilating thanks to the action of salicylates on the respiratory center of the medulla. This results in a respiratory alkalosis. Patients then develop a compensatory alkaluria as well as excretion of potassium and HCO3-.
Phase 2: 12-24 hours
Patients shift to a paradoxical aciduria with persistent respiratory alkalosis and sufficient loss of potassium from the kidneys.
Phase 3: 24+ hours
Patient develop hypokalemia as a result of renal losses as well as dehydration and a progressive metabolic acidosis.
Diagnosing Salicylate Toxicity
History is key in diagnosing salicylate overdose. Try to figure out how much was ingested over what time. Don't forget to determine if this was intentional. Also, don't forget to ask about over-the-counter medications.
Labs can be helpful in this diagnosis. Salicylate toxicity presents with a pretty unique acid-base picture: a primary respiratory alkalosis with a primary anion-gap metabolic acidosis. Additional lab findings can include a leukocytosis.
The most important test for diagnosis is a plasma salicylate level. The levels you evaluate for are below:
The therapeutic range = 10 to 30 mg/dL
Intoxication usually with plasma levels > 30-50 mg/dL
Levels of > 100 mg/dL in acute or > 60 mg/dL in chronic ingestion are indications for dialysis
Always repeat the level several hours after presentation to evaluate for delayed/prolonged absorption.
Management
The goals in management of acute salicylate toxicity are as follows:
ABCs (Airway, breathing, circulation)
Correct fluid and electrolyte imbalances
Reduce Serum Salicylate Levels (Enhance excretion of salicylate and prevent absorption of further levels)
#1- ABCs
Intubation with mechanical ventilation should be reserved only for cases of true respiratory failure (i.e. patients with hypoventilation) because of the tenuous acid-base physiology taking place. After intubation, ventilator settings should mimic pre-intubated state with high tidal volumes and a high rate, as hyperventilation is a protective mechanism (Alkalization traps salicylates in the blood, to prevent crossing the BBB).
#2- Fluid and electrolyte imbalances
Patients often present volume down related to sensible and insensible fluid losses in toxicity. Therefore, aggressive fluid and electrolyte repletion is warranted in settings outside of pulmonary or cerebral edema. Be cautious with potassium: patients tend to need aggressive repletion. Additionally, don't forget to check a glucose (it's warranted in any patient with altered mental status).
#3-Reduce Serum Salicylate Levels
First, determine if your patient is a candidate for GI decontamination. The best choice for decontamination is Activated charcoal. Charcoal can be given for Aspirin: give at least one dose (1g/kg up to 50g max) in all alert, cooperative patients and all intubated patients who present within 2 hours of ingestions.
Next, increase the natural elimination of salicylates by alkalinizing the urine. The renal excretion depends mostly on urine pH (goal urine pH = 7.5-8 ). This is achieved by IV administration of sodium bicarb + crystalloid. A common solution is D5W with 3-amps bicarb + 30-40 mEq K. You should increase rate of infusion to maintain urine output of 2-3 mL/kg/h and labs (BMP, urine pH, and salicylate levels) should be frequently checked.
You can discontinue this fluid therapy when the serum salicylate < 40 mg/dL, with a normal pH, resolution of metabolic acidosis, and your patient is asymptomatic with normal respiratory effort. Lab monitoring should be continued after discontinuation to ensure resolution. Resume alkalinization if symptoms or lab abnormalities return.
Dialysis may be needed in some patients. The indications for dialysis are as follows:
Significant CNS abnormalities
Acute lung injury
Impaired GFR not responsive to volume repletion
Deteriorating clinical condition
Significant hyperthermia
Refractory acidemia or electrolyte disturbance
Inability to administer sodium bicarb
Rising serum salicylate levels despite sodium bicarb administration
Salicylate level > 100 mg/dL
References