Overview
Key investigations for methanol and ethylene glycol poisonings are:
- serum methanol and ethylene glycol concentrations (see also Toxic concentration)
- measure initially in all patients to confirm ingestion, but may need to send sample to a reference laboratory for the assay
- if available in a timely fashion, serial concentrations may guide ongoing management; measure daily until concentration is less than 20 mg/dL (6.24 mmol/L for methanol, 3.23 mmol/L for ethylene glycol)
- blood gas analysis, including blood lactate concentration
- blood lactate concentration (laboratory assay)
- serum electrolyte, urea and creatinine concentrations—usually includes an anion gap calculation ([serum sodium concentration + serum potassium concentration] minus [serum chloride concentration + serum bicarbonate concentration]); serum potassium concentration to detect hyperkalaemia; see also Serum creatinine concentration
- blood glucose concentration
- serum ethanol concentration
- measure initially in all patients—if considering ethanol or fomepizole for antidotal therapy, measure serum ethanol concentration first
- measure serial concentrations if ethanol is used for antidotal therapy
- osmolar gap (see also Osmolar gap, anion gap and serum pH)
- osmolar gap is calculated by: measured serum osmolality minus calculated serum osmolarity ([2 x serum sodium concentration] + serum urea concentration + blood glucose concentration + [1.2 x serum ethanol concentration]), all in mmol/L
- a normal osmolar gap does not exclude toxic alcohol poisoning, because of individual variability and potential errors of calculation
- serum calcium concentration (see Calcium oxalate crystals)
- electrocardiogram—if hyperkalaemia or hypocalcaemia are present
- urine microscopy (see Calcium oxalate crystals).