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ER50 Emergency Medicine
Toxicology
Toronto Notes 2019
Urine drug screen is costly and generally not helpful in the ED management of the poisoned patient
D2 – Draw Bloods
• essentialtests
■ CBC, electrolytes, BUN/Cr, glucose, INR/PTT, osmolality ■ ABGs, O2 sat
■ ASA, acetaminophen, EtOH levels
• potentiallyusefultests
■ drug levels – this is NOT a serum drug screen
■ Ca2+, Mg2+, PO43–
■ protein, albumin, lactate, ketones, liver enzymes, CK – depending on drug and clinical presentation
Serum Drug Levels
• treatthepatient,notthedruglevel
• negative toxicology screen does not rule out a toxic ingestion – signifies only that the specific drugs
tested were not detectable in the specimen
• specificdrugsavailableongeneralscreenvarybyinstitution;checkbeforeordering
• urinescreensalsoavailable(qualitativeonly;notoftenthoughttochangemanagement)
Anion Gap
= Na+ – CI– – HCO3– Normal AG ≤12 mM/L
Table 30. Toxic Gaps (see Nephrology, NP16)
METABOLIC ACIDOSIS
Increased AG: “GOLDMARK” (* = toxic)
Glycols* (ethylene glycol, propylene glycol)
Oxoproline (metabolite of acetaminophen)*
L-lactate
D-lactate (acetaminophen, short bowel syndrome, propylene glycol
infusions for lorazepam & phenobarbital) Methanol*
ASA*
Renal failure
Ketoacidosis (DKA, EtOH*, starvation)
Decreased AG
Electrolyte imbalance (increased Na+/K+/Mg2+) Hypoalbuminemia (50% fall in albumin ~5.5 mmol/L decrease in the AG)
Lithium, bromine elevation
Paraproteins (multiple myeloma)
Normal AG
High K+: pyelonephritis, obstructive nephropathy, renal tubular acidosis IV, TPN
Low K+: small bowel losses, acetazolamide, renal tubular acidosis I, II
Increased osmolar gap: “MAE DIE” (if it ends in “-ol”, it will likely increase the osmolar gap)
Methanol
Acetone
Ethanol
Diuretics (glycerol, mannitol, sorbitol) Isopropanol
Ethylene glycol
Note: normal osmolar gap does not rule out toxic alcohol;
only an elevated gap is helpful
Increased O2 saturation gap
Carboxyhemoglobin Methemoglobin Sulfmethemoglobin
Table 31. Use of the Clinical Laboratory in the Initial Diagnosis of Poisoning
Test
ABG Electrolytes
Glucose
Osmolality and Osmolar Gap
ECG
Abdominal X-Ray
Serum Acetaminophen
Finding
Hypoventilation (high pCO2)
Hyperventilation (low pCO2)
AG metabolic acidosis Hyperkalemia Hypokalemia
Hypoglycemia Elevated osmolar gap
Wide QRS complex Prolonged QT interval Atrioventricular block
Radioopaque pills or objects
Elevated level (>140 mg/L or 1,000 μmol/L 4 h after ingestion)
Selected Causes
CNS depressants (opioids, sedative-hypnotic agents, phenothiazines, EtOH)
Salicylates, CO, other asphyxiants
“GOLDMARK”: see Table 30
Digitalis glycosides, fluoride, potassium
Theophylline, caffeine, β-adrenergic agents, soluble barium salts, diuretics, insulin
Oral hypoglycemic agents, insulin, EtOH, ASA “MAE DIE”: see Table 30
TCAs, quinidine, other class Ia and Ic antidysrhythmic agents Terfenadine, astemizole, antipsychotics
Ca2+ antagonists, digitalis glycosides, phenylpropanolamine
“CHIPES”: Calcium, Chloral hydrate, CCl4, Heavy metals, Iron, Potassium, Enteric coated Salicylates, and some foreign bodies
May be only sign of acetaminophen poisoning