Blood concentrations

Digoxin is the only commonly measured drug presenting with this syndrome. An urgent concentration is indicated if hyperkalaemia or other factors indicate digoxin poisoning is possible.

Quantitative tests for these drugs are of little use and not readily available.

Illicit drug use is often denied. If it is important, urine drug screens for drugs of abuse will often clarify which toxin is involved.

Iron concentrations should be taken, particularly in children, as this is a common, treatable poisoning.

There are simple qualitative tests for amatoxin (death cap mushroom) and paraquat.

Paracetamol and carboxyhaemoglobin may be undetectable in late presentation

Alcohol, lithium, theophylline, anticonvulsant drugs (carbamazepine, phenytoin, valproate), salicylate, carboxyhaemoglobin and plasma cholinesterase concentrations may confirm poisoning, but should be used where other evidence supports the diagnosis.

Paracetamol concentrations should be done in all unconscious patients.

Theophylline concentrations should be done urgently, as there are a number of specific treatments that may dramatically improve outcome.

Carbamazepine concentrations may be helpful if patients are markedly sedated with anticholinergic signs.

Paracetamol concentrations should be obtained in all patients who are unable to give a coherent history to exclude coingestion (including combination products).

Ethanol, ethylene glycol, and methanol should be measured especially if there is a raised osmolal gap.

Carbon monoxide may be quickly measured on expired air and, if present, confirmed with formal testing of carboxyhaemoglobin.

Salicylate poisoning should be excluded as it is relatively common and has specific treatment.

Digoxin is the only drug for which it may be worth testing urgently in this setting. Hyperkalaemia, underlying atrial fibrillation, and coexisting tachyarrhythmias make the diagnosis more likely.

Quantitative tests for these drugs are of little use and not readily available.

Illicit drug use is often denied. If it is important, urine drug screens for drugs of abuse will often clarify which toxin is involved.

Digoxin is the only commonly measured drug presenting with this syndrome. An urgent concentration is indicated if hyperkalaemia or other factors indicate digoxin poisoning is possible.

Digoxin may be worth testing for urgently in this setting, as there are specific antidotes. Hyperkalaemia, underlying atrial fibrillation, and coexisting tachyarrhythmias make the diagnosis more likely.

A salicylate concentration should be done if there is a metabolic acidosis with a large anion gap.

Theophylline is suggested by seizures, hypokalaemia, hyperglycaemia, acidosis and a lack of QRS/QT prolongation.