Diagnostic Use
Isopropanol is frequently found in rubbing alcohol and hand sanitiser. Poisoning may manifest as soon as 30 – 60mins after ingestion or as late as 2 – 4hrs later with features including abdo pain, nausea, vomiting, diarrhoea, CNS depression and hypotension. Unlike other volatile alcohols, isopropanol does not generally cause metabolic acidosis (though secondary lactic acidosis may occur with hypotension).
There are no antidotes for isopropanol poisoning. Supportive treatments are often sufficient, but haemodialysis may be needed if the serum concentration is greater than 8.3 mmol/L or if hypotension or lactic acidosis is present. Since the primary metabolite (acetone) is less toxic than isopropanol, unlike methanol poisoning there is no indication for ethanol following isolated isopropanol ingestion.
After ingestion of isopropanol, acetone can be detected in the serum 30 minutes later and in the urine 3hrs later. Even if isopropanol is not detected in serum, acetone concentration above what would normally be expected from endogenous production could indicate recent isopropanol exposure.
Interpretation
Note: While theoretically possible, there is not convincing evidence that a false positive result occurs from samples collected after use of hand sanitiser or an alcohol (isopropanol) wipe.
Serum isopropanol concentration does not necessarily correlate well with clinical status, though levels > 8.3 mmol/L have been described as toxic, > 25 mmol/L has been associated with deep coma and > 33 mmol/L may lead to death.
Isopropanol may be detected at low concentrations in the serum of patients with severe diabetic or alcoholic ketoacidosis, due to endogenous reduction of acetone to isopropyl alcohol. Similarly, acetone can also be raised in diabetic or alcoholic ketoacidosis. As circulating acetone can be reduced to isopropanol, in the setting of ketoacidosis, acetone levels are usually higher than isopropanol levels (in millimolar terms). Unlike patients with isopropanol poisoning, these patients will usually present with metabolic acidosis and increased blood glucose level if diabetic.
There is no specific antidote for isopropanol poisoning, though supportive treatment is often sufficient. Haemodialysis may be indicated with levels > 8.3 mmol/L, hypotension or lactic acidosis.
Reference Intervals
Reference intervals
Isopropanol
Not detected
Acetone*
Not detected
*Acetone is measured together as it is the major metabolite of isopropanol.
Conversion factor:
Isopropanol
mg/dL x 0.166 = mmol/L
mmol/L x 6.01 = mg/dL
Acetone
mg/dL x 0.172 = mmol/L
mmol/L x 5.81 = mg/dL
Test Method
Gas chromatography
Limitations / Interference
Acetone interferes with Jaffe creatinine assay (as above).
Note: The enzymatic test routinely used for ethanol measurement does not measure isopropanol or other related substances (methanol, ethylene glycol, acetone, acetaldehyde). These must be specifically requested, as they are measured by a separate method.
Uncertainty of Measurement
Isopropanol = 12% at 13 mmol/L
Acetone = 13% at 13 mmol/L