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Link to [[:wikitox:3.2.1.1.1_acidosis_teaching_resources|Acidosis Teaching Resources]]

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====== Arterial Blood Gases ======

Arterial blood gases should be taken on any patients who appear to have respiratory depression or are unconscious, and on patients who have taken [[:wikitox:2.1.11.9.2.1_tricyclic_antidepressants|tricyclic antidepressants]].

The presence of CO<sub>2</sub> retention, particularly if the pCO<sub>2</sub> is rising progressively, may be an indication for ventilation.

The presence of acidosis is usually secondary to some other effect of the poison:

  * respiratory depression leading to respiratory acidosis
  * seizures or shock leading to lactic acidosis

However, the acidosis will occasionally be due to a direct effect on metabolism from specific drugs leading to a high [[:wikitox:anion_gap_acidosis|anion gap acidosis]].

Acidosis can increase the toxicity of a number of drugs:

  * acidosis significantly increases toxicity of tricyclic antidepressants
  * acidosis significantly increases CNS [[:wikitox:2.1.1.4_salicylates|salicylate]] concentrations
  * acidosis directly increases the risk of arrhythmias with a wide range of [[:wikitox:cardiotoxic_drugs|cardiotoxic drugs]]

Thus, in the management of poisonings, it is important to prevent acidosis and correct it if it occurs with [[:wikitox:bicarbonate|sodium bicarbonate]] and/or [[:wikitox:alkalinisation|hyperventilation]] as appropriate.