Blood investigations

Apart from the recommended screening investigations, patients with suspected poisonings do not generally require routine blood investigations.

The following situations warrant urgent assessment of serum electrolyte, urea, creatinine and creatine kinase concentrations:

  • abnormal ECG
  • seizures1
  • rhabdomyolysis
  • hyperthermia.

Serum drug or toxin concentrations are only indicated for specific drugs or toxidromes if the results will influence management decisions. These assays are rarely available in a time frame adequate to inform clinical management of poisoning; however, they are useful for suspected poisonings involving:

  • paracetamol
  • some antiepileptic drugs, including carbamazepine, phenobarbital (phenobarbitone), phenytoin, sodium valproate
  • aspirin
  • digoxin
  • iron
  • lithium
  • potassium
  • theophylline
  • toxic alcohols.

See the individual drug or toxin monographs for more details.

Serum ethanol concentrations are readily measured, but easily misinterpreted2. Even when the serum ethanol concentration is high, consider possible co-ingestion of other substances.

1 If the cause of seizures is unclear, other blood investigations (eg full blood count to detect infection) may be warranted.Return
2 A serum ethanol concentration of 1 mmol/L is equivalent to a blood alcohol concentration (BAC) of 0.00461 g/100 mL. A BAC of 0.05 g/100 mL (0.05%) is equivalent to a serum ethanol concentration of 11 mmol/L.Return