Lippincott Chapter 48: Clinical Toxicology Flashcards
48.1 A 3-year-old boy is brought to the emergency
department by his mother, who reports that he has
been crying continuously and “does not want to play or
eat” for the last few days. She also states that he has not
had regular bowel movements, with mostly constipation
and occasional diarrhea, and frequently complains of
abdominal pain. The child now has an altered level
of consciousness, is difficult to arouse, and begins to
seize. The clinician rules out infection and other medical
causes. Upon questioning, the mother states that the
house is in an older neighborhood, that her house has
not been remodeled or repainted since the 1940s,
and that the paint is chipping around the windows and
doors. The child is otherwise breathing on his own and
urinating normally. Which toxin would you expect to be
producing such severe effects in this child?
A. Iron.
B. Lead.
C. Carbon monoxide.
D. Cyanide.
E. Ethylene glycol.
Correct answer = B. Lead poisoning is common among chil-
dren in older homes painted before lead was removed from
paint. Paint chips with lead are easily ingested by toddlers,
and excessively high lead levels can lead to the signs and
symptoms described plus clumsiness, confusion, headaches,
coma, constipation, intestinal spasms, and anemia. Death is
rare when chelation therapy is instituted. Iron can produce
abdominal pain, but more often would cause diarrhea, vomit-
ing, and volume loss. If he had cyanide poisoning, death would
have occurred quickly following respiratory arrest of oxidative
phosphorylation and production of adenosine triphosphate,
but this child has been exhibiting symptoms over several
days. Carbon monoxide would affect the entire household,
depending on the source. Clinical effects from carbon monox-
ide would include headache, nausea, and CNS depression.
Ethylene glycol is sweet and may be ingested by a toddler.
The presentation of ethylene glycol toxicity would include ini-
tial appearance of intoxication, which was not mentioned.
48.2 A 41-year-old male pocket watch maker presents to the
emergency department after he was found unconscious
on the floor of the shop by a coworker. The coworker
states that the patient complained of being cold this
morning around 8 am (the central heat was broken, and
the outdoor temperature was 34°F) and that since noon,
he had been complaining of headache, drowsiness,
confusion, and nausea. The clinician notices that he has
cherry red skin. What is the most likely toxin causing his
signs and symptoms?
A. Ethylene glycol.
B. Cyanide.
C. Acetaminophen.
D. Carbon monoxide.
E. Methanol.
Correct answer = D. Although watch makers and other pro-
fessionals who use electroplating may be at higher risk for
cyanide exposure because many plating baths use cyanide-
containing ingredients (for example, potassium cyanide), this
patient shows signs of carbon monoxide poisoning, such as
cherry red skin, headache, confusion, nausea, and drowsi-
ness leading to unconsciousness. The history also leads us
to believe that this person may have been using a space
heater to stay warm, which would be consistent with the
description. A carboxyhemoglobin level should be obtained
to confirm the exposure. Cyanide in low doses from such an
occupational exposure can present with loss of conscious-
ness, flushing, headache, and confusion. Chronically, work-
ers may develop a rash after handling cyanide solutions.
Also, an odor of bitter almonds may be present. An arte-
rial blood gas and a venous blood gas could be obtained
and compared to determine if cyanide is present (a lack of
oxygen extraction would be present on the venous side).
Ethylene glycol and methanol toxicity may cause alterations
in mental status, but the history did not include anything
suggesting a toxic alcohol ingestion. Acetaminophen toxicity
is not consistent with this presentation.
48.3 A 50-year-old migrant worker comes to the emergency
department from the field he was working in and
complains of diarrhea, tearing, nausea and vomiting,
and sweating. The clinician notices that he looks
generally anxious and has fine fasciculations in the
muscles of the upper chest as well as pinpoint pupils.
Which antidote should he receive first?
A. N-acetylcysteine.
B. Sodium nitrite.
C. Deferoxamine.
D. Atropine.
E. Fomepizole.
Correct answer = D. Atropine is appropriate for this patient,
who has symptoms consistent with organophosphate
(insecticide) poisoning. The mnemonic DUMBBELS (diar-
rhea, urination, miosis, bronchorrhea/bradycardia, emesis,
lacrimation, salivation) can be used to remember the signs
and symptoms of cholinergic toxicity. An anticholinergic
antidote, atropine, controls these muscarinic symptoms,
whereas the antidote pralidoxime treats the nicotinic symp-
toms like fasciculations (involuntary muscle quivering or
twitching). N-acetylcysteine is the antidote for acetamino-
phen overdose and acts as a sulfhydryl donor. Sodium nitrite
is one of the antidotes included in the old cyanide antidote
kit (sodium nitrite and sodium thiosulfate). Deferoxamine is
the chelating agent for iron. Fomepizole is the antidote for
methanol and ethylene glycol.
48.4 A 45-year-old male presented to the emergency
department 18 hours after ingesting an unknown product.
On presentation, he is tachycardic, hypertensive,
tachypneic, and complaining of flank pain. A metabolic
panel is obtained, and the patient has a large anion gap
acidosis, an increased creatinine, and hypocalcemia.
Which substance was most likely ingested?
A. Methanol.
B. Acetaminophen.
C. Ethylene glycol.
D. Iron.
E. Opioids.
Correct answer = C. Ethylene glycol produces a metabolic
acidosis from the toxic metabolites. The formation of calcium
oxalate crystals, which can be found on urinalysis, leads to
hypocalcemia and renal failure. The treatment regimen for
this patient would include intravenous fomepizole, if some
of the parent compound was still present, and hemodialy-
sis. Thiamine and pyridoxine are the cofactors involved in
the metabolism of ethylene glycol. Methanol may produce
a metabolic acidosis as well, but its target organ of toxicity
is the eyes instead of the kidneys as with ethylene glycol.
Acetaminophen toxicity may produce upper quadrant pain
within the first 24 hours, but vital sign abnormalities are not
usually found during this time frame. Iron toxicity may also
produce a metabolic acidosis and tachycardia. However,
hypocalcemia does not occur. Opioid toxicity, as mentioned
in Chapter 14, usually presents with CNS and respiratory
depression, not tachycardia and hypertension.
48.5 A 27-year-old female presents to the emergency
department 6 hours after reportedly ingesting 20 tablets
of acetaminophen 500 mg. An acetaminophen level
is drawn, but it has to be sent out to another lab and
will not return for another 6 hours. What is the most
appropriate next step in management of this patient?
A. Administer a dose (50 g) of activated charcoal.
B. Empirically start N-acetylcysteine therapy.
C. Administer a dose of intravenous naloxone.
D. Wait for the level to return and then decide what
to do.
E. Draw a NAPQI level.
Correct answer = B. N-acetylcysteine should be started
empirically on the basis of the history, and then, once the
level returns and is plotted on the Rumack-Matthew nomo-
gram, a final decision on whether to continue therapy can
be made. Activated charcoal would not be of any benefit
6 hours post–acetaminophen ingestion. Naloxone is utilized
for opioid toxicity, not acetaminophen toxicity. The optimal
time frame to give N-acetylcysteine is within 8 to 10 hours
postingestion. So, waiting on the level to return would put
the patient more than 12 hours postingestion. Therefore,
initiation of N-acetylcysteine therapy should happen, if pos-
sible during the optimal time frame. Clinicians are unable
to draw a NAPQI level and therefore cannot utilize this to
guide therapy.
48.6 A 4-year-old female presents to the emergency
department with CNS depression. Her vital signs
indicate that she is slightly bradycardic and slightly
hypotensive for her age. Upon further questioning,
the mother admits that there are two clonidine 0.2 mg
tablets missing from the home. Which of the following
antidotes might be beneficial for this patient?
A. Flumazenil.
B. Atropine.
C. Deferoxamine.
D. Naloxone.
E. Succimer.
Correct answer = D. Naloxone has a reversal rate of the
CNS effects of approximately 50% in clonidine ingestions.
Flumazenil reverses benzodiazepines and has no effect on
clonidine. Atropine is an anticholinergic agent and would
not improve the CNS depression. Deferoxamine is the che-
lator for iron, and succimer is a lead chelator.
48.7 A 40-year-old male presents to the emergency
department with a complaint of abdominal pain.
The patient appears intoxicated, but an ethanol level
returns as negative and his basic metabolic panel is
unremarkable. Which of these substances did he
probably ingest?
A. Isopropyl alcohol.
B. Methanol.
C. Ethylene glycol.
D. Ethanol.
E. Organophosphates.
Correct answer = A. Isopropyl alcohol produces twice as
much CNS depression as ethanol and is known to cause
GI distress. Isopropyl alcohol is metabolized to acetone, so
a metabolic acidosis does not result (which is in contrast
to the acidosis generated by methanol and ethylene gly-
col). The ethanol level was negative, eliminating ethanol as
an ingestion. Organophosphate toxicity yields nicotinic and
muscarinic effects, which are not described in the history.
48.8 A 5-year-old male is brought in to the health care facility
for being irritable and failure to thrive. He is alert, and
his vital signs are normal. The doctor diagnoses him
with lead toxicity when the blood lead level returns as
50 μg/dL. Which chelator regimen should be started?
A. Dimercaprol.
B. Calcium disodium edetate.
C. Both dimercaprol and calcium disodium edetate.
D. Succimer.
E. Deferoxamine
Correct answer = D. Succimer (dimercaptosuccinic acid,
DMSA) is utilized when the lead level is greater than 45 μg/dL,
without encephalopathy. If encephalopathy is present, or
the lead level is greater than 70 μg/dL in a child, then dual
parenteral therapy with dimercaprol and calcium disodium
edetate is indicated. Dimercaprol intramuscular therapy
is initiated 4 hours prior to the intravenous administration
of calcium disodium edetate when both medications are
required. Deferoxamine is not indicated since it is the chela-
tor for iron.
48.9 A 3-year-old healthy female ingested one of her
mother’s 1 mg alprazolam tablets 45 minutes ago. The
child presented to the emergency department with
CNS depression but a normal heart rate and blood
pressure. Her bedside glucose check is also normal.
Which of the following antidotes might be helpful?
A. Flumazenil.
B. Naloxone.
C. Physostigmine.
D. Atropine.
E. Fomepizole.
Correct answer = A. Flumazenil is a competitive benzo-
diazepine antagonist that reverses the CNS depression
from benzodiazepines such as alprazolam. After fluma-
zenil administration, resedation usually occurs, since the
duration of the benzodiazepine is longer than that of the
flumazenil. Naloxone reverses the effects from opioids and
clonidine, not benzodiazepines. Physostigmine is the anti-
dote for anticholinergic toxicity, and atropine is an anticho-
linergic agent. Fomepizole is the antidote for methanol or
ethylene glycol toxicity.
48.10 A 34-year-old male with a history of a seizure disorder,
maintained on phenytoin and phenobarbital, presented
to the emergency department for CNS depression.
The phenobarbital level was 70 mg/L (15 to 40 mg/L
therapeutic range) and the phenytoin level was
15 mg/L (10 to 20 mg/L therapeutic range). He denies
any acute ingestion. What therapy can be considered
to enhance the elimination of phenobarbital without
impacting the phenytoin?
A. Multiple doses of activated charcoal.
B. Gastric lavage.
C. Urinary alkalinization.
D. Whole bowel irrigation.
E. Urinary acidification.
Correct answer = C. Urinary alkalinization enhances the
elimination of the phenobarbital but does not affect the ther-
apeutic phenytoin level. Sodium bicarbonate, 1 mEq/kg, is
administered intravenously initially and then a sodium bicar-
bonate continuous infusion is titrated to maintain a urine pH
of 7.5 to 8, without exceeding a serum pH of 7.55. Multiple
doses of activated charcoal would lower the concentration
of both medications, rendering the phenytoin subthera-
peutic. Gastric lavage is a GI decontamination technique
employed usually within the first hour after an acute inges-
tion of a life-threatening amount, to remove approximately
30% of the product in the stomach. Whole bowel irrigation is
another GI decontamination modality involving administra-
tion of large quantities (up to 2 L/hour in adults) of a polyeth-
ylene glycol–balanced electrolyte solution via a nasogastric
tube until the patient generates clear rectal effluent. Urinary
acidification is no longer performed for substances such as
amphetamines and quinidine.
