Carbon dioxide: Global warning for nephrologists

Table 1 Errors in prediction of the expected pressure of carbon dioxide in hemodialysis patients

	Blood samples featuring HCO3 < 24 mmol/L	Blood samples claimed for metabolic acidosis
“Winters’ formula” pCO2 = 1.5 HCO3 + 8	4.85	2.06
“Practical rule” pCO2 = 1.2 HCO3 + 11.2	3.14	1.50
“Very simple formula” pCO2 = HCO3 + 15	3.09	1.56

Errors (root mean square errors in mmHg) in computing the expected pCO₂ in a dataset of blood gas measurements from chronic hemodialysis patients. Reproduced with permission from Ref. [19]. HCO₃: Bicarbonate concentration; pCO₂: Pressure of carbon dioxide.