Biomedical Engineering Reference
In-Depth Information
accumulation correlates with the acidosis and the decrease of plasma
bicarbonate. Lactic acid also increases as formic acid interferes with
intracellular respiration. The increase of these two acids in the body
leads to anion gap increase that is seen in methanol poisoning.
Ethanol treatment is more difficult tomaintain the proper loading during
treatment. Fomepizole presents less problems during treatment but is much
more costly and may not always be available (Barceloux et al., 2002).
Formic acid metabolism, which can have a long half life (20 hours),
should be enhanced by folic acid or IV folinic acid. Hemodialysis may
be used to enhance methanol and formate elimination and to correct
metabolic abnormalities (Barceloux et al., 2002).
3.9 CONCLUSIONS
In humans, the most common cause of methanol toxicity have been
reported following single overdosing either by accidental or deliberate
ingestion of methanol as a substitute for ethanol. This is still the main
cause of concern for methanol and humans health. Methanol poisoning
in humans starts with signs of intoxication such as CNS effects,
depression, headache, dizziness, nausea, and vomiting followed by
12-24 hours or more of little or no symptoms then visual disturbances
including blindness, abdominal pain, and possible death. In the case of
high exposure to methanol, an increase in formate and hydrogen ion in
the blood results in acidosis, which is thought to be the cause of the
adverse effects including blindness and death.
In the early years, occupational exposure also resulted in methanol
poisoning because of both high inhalation and dermal contact with
methanol. It has been demonstrated in controlled human studies at the
workplace standard (TLV) of 200 ppm that methanol can safely be used
in industrial applications. Workplace practice (prevention of significant
dermal exposure) and controlling inhalation methanol exposure below
200 ppm appears to prevent any toxicity, either acute or chronic.
Treatment of methanol poisoning following a single over exposure
by the oral, dermal, or inhalation route is usually successful in prevent-
ing blindness and death if started as soon as possible after the exposure.
