Various pages relating to blood gas analysis have been updated to indicate the almost complete clinical uselessness of most of the calculations performed on blood gases. Many of the calculations produce highly inaccurate results and do not alter management (e.g. if someone has incomplete respiratory compensation for their metabolic acidosis, what do you do – tell them to breathe harder?). The information about these calculations has been retained in the manual for the theorists and because of the annoying prevalence of questions relating to them in medical examinations.
However most of the compensation calculations, the Delta ratio, and most of the information about the A-a gradient will now be removed when the practice edition filter is applied.
The blood gas calculations that may be clinically useful in Emergency Medicine practice are: pH adjusted potassium, calculation of the anion gap, calculation of expected HCO3 in respiratory acidosis (to determine how acute it is) and possibly A-a gradient (if it is grossly abnormal). Other calculations on non blood gas derived variables such as albumin adjusted calcium and glucose corrected sodium may have some clinical utility.