Fig. 3

Predicted compared with measured vitamin C concentrations in critically ill patients. Vitamin C concentrations predicted from enteral and/or parenteral administration (filled circles) were compared with measured plasma vitamin C concentrations (filled triangles). Predicted levels were obtained by fitting a four-parameter log-logistic response model to the pharmacokinetic data reported elsewhere [23]. Data represent mean and SD. All measured values were significantly lower than predicted values (P < 0.0001). Dotted lines indicate inadequate vitamin C cutoff (50 μmol/L), hypovitaminosis C cutoff (23 μmol/L) and vitamin C deficiency cutoff (11 μmol/L)