A comprehensive summary of the literature presented by Professor Anne-Maree Kelly in June 2009 at 4ème SYMPOSIUM INTERNATIONAL BLOOD GASES AND CRITICAL CARE TESTING in France can be viewed on her presentation slides at the link below.
She summarises:

• pH – Close enough agreement for clinical purposes in DKA, isolated metabolic disease; more work needed in shock, mixed disease
• Bicarbonate – Close enough agreement for clinical purposes in most cases; more work needed in shock, mixed disease, calculated vs measured gap
• pCO2 – NOT enough agreement for clinical purposes; potential as a screening test
• Potassium – Insufficient agreement between serum and BG values for clinical purposes
• Base excess – Insufficient data

Can venous blood gas analysis replace arterial in emergency and critical care?