Arterial blood gases in Toxicology

Arterial blood gases in Toxicology

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Arterial blood gases are an important investigation in overdose patients for two major conditions.

Respiratory depression: many drugs in overdose cause CNS depression and respiratory depression. The most sensitive test for respiratory depression is a pCO2 on an arterial blood gas. An arterial blood gas should be undertaken in any drug overdose where there is evidence of respiratory depression (respiratory rate less than 12), or where the ingested drug(s) are known to cause profound respiratory depression (eg opioids).

Metabolic acidosis: this is an important complication for a number of drug/toxins in overdose and an arterial blood gas (including a lactate level) will help determine the severity and aetiology of any metabolic acidosis