Venous versus arterial blood for blood gas analysis – revisited

Arterial blood is the “gold standard” sample for blood gas analysis. Compared with venous blood sampling, arterial blood sampling is technically more difficult as well as being more painful and hazardous to the patient. These are among the considerations that drive the continuing research interest in establishing whether or not venous blood is an acceptable alternative to arterial blood.

The latest of many studies to address this issue is recently published. This is a meta-analysis of 18 studies conducted over many years, involving a total of 1768 individuals (healthy controls and patients requiring blood gas analysis). 

For each of these individuals, arterial and venous blood was collected simultaneously, and both samples were immediately submitted for blood gas analysis, allowing comparison of venous and arterial pH, pCO₂ and pO₂.

Statistical analysis of these 1768 paired results allowed the authors to conclude that venous blood is an acceptable alternative to arterial blood if only pH is of interest. However, venous blood is not suitable for pCO₂ measurement and even less suitable for pO₂ measurement.