Hyperascorbemia, or high concentrations of ascorbic acid, is a physiologic consequence of certain forms of critical illness. Plasma ascorbic acid concentrations decrease over time in certain human critical illnesses, whereas in critically ill cats concentrations increase. Like cats, dogs can synthesize ascorbic acid, but it has been hypothesized that critically ill dogs develop hypoascorbemia, possibly from increased use and excretion relative to production. Because ascorbic acid supplementation decreases duration of intensive care hospitalization and risk for multiple-organ failure in critically ill humans, it may be beneficial as an antioxidant and antiinflammatory agent in critically ill dogs.

To evaluate the need for ascorbic acid supplementation, plasma ascorbic acid levels were measured in 2 groups of critically ill dogs with systemic inflammatory response syndrome: 16 had measurements taken on days 1 and 2 of hospitalization; 20 had measurements taken on days 1, 2, and 3. There were 13 healthy controls. Both groups of ill dogs had higher plasma ascorbic acid levels on days 1 through 3 when compared with healthy dogs. Dogs may have an upregulation of ascorbic acid synthesis during critical illness or a more efficient ascorbic acid recycling system. Supplementation during critical illness may not be necessary.

Commentary
The study characterized endogenous vitamin C levels in dogs with systemic inflammatory response syndrome during the first days of hospitalization but did not statistically correlate vitamin C levels with changes in clinical parameters. However, it is not known if supplementation with vitamin C IV at different doses contributes to shorter, less expensive hospitalization or fewer adverse events than do conventional medications. Holistic practitioners have commonly used high-dose IV vitamin C therapy with success in critically ill patients, but this practice is not well described. Further studies are warranted, as this well tolerated antioxidant could provide adjunctive or alternative therapy, especially when aggressive or salvage therapy is employed.—Heather Troyer, DVM, DABVP, CVA

Source
Hyperascorbaemia in dogs admitted to a teaching hospital intensive care unit. Groth E, Honaker A, Osterbur K, et al. J SMALL ANIM PRACT 53:652-656, 2012.