0071643192.pdf

TOXICOLOGY

Unlike methanol and ethylene glycol, isopropanol is notmetabolized to an

organic acid. It is converted directly to acetoneby alcohol dehydrogenase.

MECHANISM/TOXICITY

■ Toxicity is primarily due to CNS depression and hemorrhagic gastritis.

SYMPTOMS/EXAM

■ Intoxication, CNS depression, coma

■ Abdominal pain, N/V, hemorrhagic gastritis

DIAGNOSIS

■ Isopropanol can be directly measured in serum.

■ Ingestion should be suspected in patients who appear intoxicated but have

low or undetectable ethanol levels.

■ Other clues include an increased osmolal gap and detectable serum acetone.

■ Isopropanol does notdirectly cause a metabolic acidosis.

TREATMENT

■ Supportive care only

A 33-year-old female with a history of depression and chronic pain is

brought to the ED via EMS for a suspected overdose. On arrival, her BP is

80/40 with an HR in the 120s. She is lethargic but responds to tactile

stimuli. Her ECG shows sinus tachycardia with a QRS duration of 130 msec.

What is the best treatment for this patient’s hypotension?

Any patient with a suspected ingestion who presents with CNS depression

and QRS widening >100 msec should be presumed to have tricyclic antidepressant

(TCA) toxicity. TCA-mediated Na++channel blockade may result in life-threatening

cardiovascular toxicity, manifesting as hypotension with QRS widening >100 msec.

The drug of choice is sodium bicarbonate, given initially in boluses and followed

by a continuous infusion.

ANTIDEPRESSANTS

The broad classes of antidepressants are:

■ Tricyclic antidepressants (TCAs)

■ Selective serotonin reuptake inhibitors (SSRIs)

■ Monoamine oxidase inhibitors (MAOIs)

■ Newer drugs that act at multiple CNS receptors

Tricyclic Antidepressants

TCAs are associated with life-threatening CNS and cardiovascular toxicity.

Safer medications, such as SSRIs, have decreased the use of TCAs for depres-

sion, and they are now more commonly used at lower doses for treatment of

chronic pain syndromes, migraine prophylaxis, and enuresis.

Isopropanol intoxication (as

compared to ethanol) = “twice

as drunk for twice as long.”

All alcohols will cause an

elevated osmolal gap. Only

methanol and ethylene glycol

metabolism cause an anion

gap metabolic acidosis.