one clinical trial used high intravenous doses of vitamin c (66 mg/kg/hour for 24 hours, for a total dose of around 110 grams) after severe burn injury, but despite being described as promising, it has not been replicated by independent institutions and thus is not a widely accepted treatment. based on that study, the american burn association (aba) considers high-dose ascorbic acid an option to be considered for adjuvant therapy in addition to the more accepted standard treatments. cardiac effects atrial fibrillation (af) is a common cardiac rhythm disturbance associated with oxidative stress. four meta-analyses have concluded that there is strong evidence that consuming 1–2 g/day of vitamin c before and after cardiac operations can decrease the risk of post-operative af. however, five randomized studies did not find any such benefit in the united states, so that the benefit was restricted to less wealthy countries. exercise-induced bronchoconstriction exercise-induced bronchoconstriction (eib) indicates acute narrowing of the airways as a result of vigorous exercise. eib seems to be caused by the loss of water caused by increased ventilation, which may lead to the release of mediators such as histamine, prostaglandins, and leukotrienes, all of which cause bronchoconstriction. vitamin c participates in the metabolism of these mediators and might thereby influence eib. a meta-analysis showed that 0.5 to 2 g/day of vitamin c before exercise decreased eib by half. endothelial function a meta-analysis showed a significant positive effect of vitamin c on endothelial function. benefit was found of vitamin c in doses ranging from 0.5 to 4 g/day, whereas lower doses from 0.09 to 0.5 g/day were not effective. no effect on endothelial function was seen in healthy volunteers or healthy smokers. common cold further information: vitamin c and the common cold a frequently cited meta-analysis calculated that various doses of vitamin c (daily doses under 0.2 grams were excluded) do not prevent the common cold in the general community, although 0.25 to 1 g/day of vitamin c halved the incidence of colds in people under heavy short-term physical stress. another meta-analysis calculated that, in children, 1–2 g/day vitamin c shortened the duration of colds by 18%, and in adults 1–4 g/day vitamin c shortened the duration of colds by 8%. there is evidence of linear dose-dependency in the effect of vitamin c on common cold duration up to 6–8 g/day. as noted above, there is an absence of large-scale, formal trials in the 10 to 200+ grams per day range, so no information is available for these higher dosages. additionally, the cited studies of larger daily doses of vitamin c do not take into account the fast excretion rate of vitamin c at gram-level doses, which makes it necessary to give the total daily amount in smaller, more frequent doses to maintain higher plasma levels. as of 2014, at least 16 studies had found that vitamin c supplements did not prevent the common cold and had minimal effect at best in shortening cold lengths.