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Letter to the Editor
Editor, – I read with concern the article on arterial blood gases (Aust Prescr 2010;33:124-9). I believe the emphasis of arterial blood gases over venous blood gases is no longer representative of what is being taught and practised in acute care medicine.
Venous blood gases are easier to obtain, hurt less, are safer and provide extra information about tissue oxygen use that arterial blood gases do not. In combination with a pulse oximeter reading, venous blood gases can be used to guide clinical decision making in the majority of situations where arterial blood gases have previously been thought to be necessary. Venous blood gases are therefore better than arterial blood gases most of the time.
Arterial blood gases are now rarely obtained from patients in emergency departments, especially children, unless there is repeated sampling from an arterial line, usually inserted for haemodynamic monitoring. This is because venous blood gases (along with pulse oximetry) provide adequate information for the majority of acute paediatric and adult clinical scenarios, including sepsis, asthma, chronic lung disease, toxicology, diabetic ketoacidosis, and therapy adjustments for invasive and non-invasive ventilation. Reviews in the literature aim to educate that venous blood gases can replace arterial blood gases in most acute care clinical scenarios.12
Decisions involving oxygenation can be made with information from a pulse oximeter, unless there is poor waveform. Modern pulse oximeters are accurate +/– 2% down to saturations as low as 70%. Given this accuracy, it is questionable concerning the value of arterial verses venous blood gases and pulse oximetry to assess the need for domiciliary oxygen therapy.
Although local anaesthetic reduces the pain of arterial blood gases sampling without decreasing success rates, a better option is to just not do them at all.
Director of Emergency Medicine Training
Ringwood East, Vic.