When is ABG useful to investigate oxygenation?

pulse-ox

Almost never. For patients with an adequate oximetry waveform, pulse oximetry is usually superior to ABG for measuring oxygenation. ABG is only useful to investigate oxygenation when:

  • Pulse oximetry waveform is unreliable.
  • Diagnosis of methemoglobinemia.
  • Calculation of the PaO2/FiO2 ratio to guide a specific therapeutic decision.

 

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Blood gas measurements in DKA

  • Guidelines recommend checking an ABG or VBG in all patients with DKA.  This practice is not evidence-based and should be abandoned.
  • ABG or VBG provides little information about whether or not the patient has DKA (beyond what is already known from the serum chemistries).
  • Rather than pH, serum bicarbonate may be used to gauge the severity of acidosis.
  • There is no evidence that detecting or reacting to a very low pH is helpful.
  • Decisions about the level of ventilatory support that a patient needs can almost always be made on a clinical basis.  When in doubt, close attention to the patient with serial examination is often a sound approach.  Focus on the patient, not the blood gas.
  • VBG might be helpful in cases where it is unclear whether the patient requires intubation, or if there is a significant underlying respiratory disease (e.g. COPD or obesity hypoventilation syndrome).

 

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Keep Calm AND Get a Venous Blood Gas

Unless you want to know a patient’s oxygenation (because your pulse oximeter has failed), stop turning your patient into a pin cushion looking for the radial artery and get a venous blood gas


Sodium bicarbonate therapy in DKA…DO NO HARM!!!

Sodium bicarbonate therapy in DKA (or any other acidosis for that matter) is associated with risks that outweigh NO BENEFITS…DO NO HARM!!!

  • Neither a recent systematic review nor the largest single retrospective cohort of severe DKA support routine use of bicarbonate therapy in DKA
  • Bicarbonate is associated with risk of cerebral oedema and prolonged hospitalisation in paediatric DKA

 

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