Low acetaldehyde levels in blood, breath and cerebrospinal fluid of intoxicated humans as assayed by improved methods.

A sensitive method for determination of human blood acetaldehyde (AcH), which avoids artefactual ethanol-derived Ach formation, was developed. AcH was trapped by collecting blood directly into isotonic semicarbazide, the plasma separated, AcH liberated by perchloric acid and analyzed by gas chromatography. Breath AcH was also trapped in semicarbazide and analyzed similarly. Using an experimentally determined blood:breath partition ratio of 190, calculated pulmonary blood and measured antecubital blood AcH were very similar at various concentrations. Blood AcH was found generally to be very low (< 10 microM) at moderate ethanol levels. Calcium carbimide (0.25 mg/kg) caused moderate flushing reactions and elevated AcH to 25-188 microM. 4-Methylpyrazole (5 mg/kg i.v.) rapidly attenuated AcH levels and symptoms, indicating its potential use in the treatment of disulfiram-ethanol reactions. AcH in the cerebrospinal fluid of 5 highly intoxicated patients was almost absent (0-5 microM). Blood AcH in occasional or chronic alcohol abusers were generally low (< 10 microM), elevated AcH levels being observed only in association with clinical abnormalities. The results indicate that in general, previously reported human blood AcH levels are erroneously high and that breath levels reflect blood levels. Blood AcH may play a lesser role in the actions of ethanol in humans than is often assumed.