The sudy hypothesis is that in critically ill patients there is a significant difference between electrolyte levels measured using blood gas analysers and by laboratory techniques, and between levels measured on arterial and venous blood samples.~The study aim is determine the agreement between electrolyte levels measure by formal laboratory serum analysis and point-of-care blood gas analysis.~Also, to determine the agreement between electrolyte levels measured on simultaneous arterial and venous blood samples, using both serum and whole blood samples.
The study hypothesis is that in critically ill patients there is significant differences between electrolyte levels measured using blood gas analysers and by laboratory techniques, and between levels measured on arterial and venous blood samples.