0071643192.pdf

TOXICOLOGY

INDICATIONS

■ For HD to be useful in a poisoned patient, the ingested poison should

have the following characteristics:

■ Low molecular weight

■ Low plasma protein-binding

■ Small volume of distribution

■ Poor endogenous clearance

■ HD can also treat severe acidosis caused by a toxin, even if the toxin itself

is not readily dialyzable.

CONTRAINDICATIONS

■ Toxins that do not satisfy the conditions listed above.

RISKS

■ HD requires central venous access, with all the usual accompanying risks

(bleeding, pneumothorax, etc.).

■ HD must be used cautiously in patients that are hemodynamically unstable.

ECG PRINCIPLES IN TOXICOLOGY

The ECG is used as a screening tool in the evaluation of the patient with a

suspected ingestion/overdose. Specific ECG findings may be associated with

ingestion of certain classes of drugs (see Table 6.4).

A 35-year-old male presents to the ED with a complaint of abdominal

pain, nausea and blurry vision. He has a history of ETOH abuse and reports

ingesting “something from the garage” earlier in the day. On examination,

he appears inebriated and tachypnic. His labs reveal an osmolal gap and a wide-

anion-gap metabolic acidosis. What is the most appropriate initial treatment?

This patient has likely ingested methanol, based on his presentation of inebri-

ation with visual changes (“blind drunk”) and wide-anion-gap acidosis. Initial ther-

apies include administration of fomepizole or ethanol (via drip) to decreased for-

mation of formic acid (the toxic metabolite) and urinary alkalinization to increase

its clearance. Visual changes are an indication for treatment with hemodialysis.

ALCOHOLS

The alcohol ingestions most commonly seen in the ED include ethanol,

methanol, ethylene glycol, and isopropyl alcohol.

Alcohols are primarily metabolized in the liver via alcohol dehydrogenase

(ADH) using NAD as a cofactor. In the case of methanol and ethylene glycol

it is a metabolite (notthe parent compound) that causes severe toxicity, mak-

ing ADH blockade a key factor in the treatment of these ingestions.

Ethanol

Ethanol is the most common poison seen in the ED.