Vitamin C could shorten ventilation in critically ill patients

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Vitamin C administration may shorten the duration of mechanical ventilation in critical care patients, but the effect depends on the severity of illness, according to a new study published in the Journal of Intensive Care.

In five controlled trials including 471 patients requiring ventilation for over 10 hours, vitamin C shortened ventilation time on average by 25 percent, the study said.

Vitamin C has numerous biochemical effects, the researchers said. It can influence the cardiovascular system through its involvement in the synthesis of norepinephrine and vasopressin, and energy metabolism through its participation in the synthesis of carnitine. In randomized trials, vitamin C has lowered blood pressure, decreased the incidence of atrial fibrillation and decreased bronchoconstriction. A previous meta-analysis of 12 controlled trials found that vitamin C reduced intensive care unit stay on average by 8 percent.

Critical care patients often have very low vitamin C plasma levels, according to the study. In healthy people, 0.1 grams per day of vitamin C is usually enough to maintain a normal plasma level. However, much higher doses, in the order of grams per day, are needed for critically ill patients to increase their plasma vitamin C levels to within the normal range. Therefore, high vitamin C doses may be needed to compensate for the increased metabolism in critically ill patients, the researchers said.

On average, vitamin C administration shortened ventilation time by 14 percent, but the effect of vitamin C depended on the duration of ventilation. Patients who are more seriously ill require longer ventilation than those who are not as sick. Therefore, the authors hypothesized that the effect of vitamin C might be greater in trials with sicker patients who need longer ventilation.

Vitamin C had no effect when ventilation lasted for 10 hours or less. However, in five trials including 471 patients who required ventilation for over 10 hours, dosage of one to six grams per day of vitamin C shortened ventilation time on average by 25 percent.

"Vitamin C is a safe, low-cost essential nutrient,” said Harri Hemilä, MD, PhD, co-author of the study from the University of Helsinki, Finland, in a statement. “Given the strong evidence of benefit for more severely ill critical care patients along with the evidence of very low vitamin C levels in such patients, [intensive care] patients may benefit from the administration of vitamin C. Further studies are needed to determine optimal protocols for its administration. Future trials should directly compare different dosage levels.”