Toxicology

Question 1

Fomepizole

Answer 1

Competitive inhibitor of alcohol dehydrogenase.
Preferred antidote for overdoses of methanol or ethylene glycol.

Question 2

Methanol intoxication

Answer 2

Is metabolized by alcohol dehydrogenase (ADH) to formaldehyde, which is then converted to formic acid by aldehyde dehydrogenase.
Formic acid is toxic to the optic nerve = blindness with as little as 30 mL ingested. Early formation of formic acid leads to metabolic acidosis.

Question 3

TCA overdose

Answer 3

Altered mental status, dilated pupils, and wide QRS complex on ECG.
TCAs have anticholinergic properties: dry/flushed skin, decreased bowel sounds, constipation, hyperreflexia, and dilated pupils.
treatment: sodium bicarbonate.

Question 4

Iron intoxication

Answer 4

Abdominal pain, bloody emesis, metabolic acidosis, and radiopaque tablets on radiography.
Symptoms can begin within 30-60 minutes following ingestion and escalate to circulatory shock after 48 hours.
Free iron’s toxicity to the vasculature, release of serotonin and histamine: injury to mitochondria, lipid peroxidation, and the uncoupling of oxidative phosphorylation. The treatment: stabilize the patient and administer deferoxamine.

Question 5

Vitamin D toxicity

Answer 5

Polyuria, polydipsia, nocturia, hypercalcemia, and hypercalciuria. Abdominal pain, nausea, vomiting, and occasionally pancreatitis can be seen.

Question 6

Osmolar gap

Answer 6

is an indication of unmeasured solute in the blood

Question 7

In a patient who presents with symptoms of alcohol toxicity, an elevated anion gap and osmolar gap + calcium oxalate crystals in their urine strongly suggests?

Answer 7

ethylene glycol toxicity

Question 8

Salicylates toxicity

Answer 8

Stimulates the respiratory center leading to hyperventilation= respiratory alkalosis.
Early in the presentation of aspirin overdose= isolated respiratory alkalosis. Concomitant production of endogenous acids (not the aspirin itself) leads to a metabolic acidosis.
Salicylates uncouple oxidative phosphorylation leading to numerous end-organ effects.
The diagnosis is confirmed with serum salicylate levels.
Treatment involves administration of sodium bicarbonate and dialysis.

Question 9

For patients with suspected tricyclic antidepressant (TCA) overdose and widening of the QRS complex, the most appropriate next step in management is?

Answer 9

Administration of sodium bicarbonate.

Question 10

TCAs toxicity

Answer 10

Have anticholinergic. anti-alpha-adrenergic, anti-histamine, and sodium channel blocking properties, which contribute to their side effects and toxicity.
3 C’s: convulsions, coma, and cardiotoxicity. Cardiotoxicity is the best predictor for TCA overdose and manifests as QRS prolongation.

Question 11

Patient is presenting from a fire with evidence of smoke inhalation, and should be treated empirically for?

Answer 11

Both carbon monoxide and cyanide poisoning, which involves 100% oxygen and hydroxycobalamin.

Question 12

Hypophosphatemia and alcoholism

Answer 12

Poor oral intake
Hypocalcemia from poor diet, low magnesium, and low vitamin D all lead to secondary hyperparathyroidism and increased phosphate wasting in the kidney. They are given nutrition, which leads to a refeeding syndrome————-refeeding triggers an increased release of insulin, shifting phosphate (and potassium) back into the cells.
Respiratory alkalosis during the withdrawal: facilitates phosphate (and potassium) shift into the cells via the decreased serum hydrogen concentration.

Most cases of hypophosphatemia are asymptomatic, severe or chronic cases may present with confusion, weakness, bone/muscle pain, and even rhabdomyolysis.