[Effect of vitamin C on prognosis of critically ill patients: a Meta-analysis]

To systematically evaluate the effect of vitamin C on prognosis of critically ill patients.

Randomized controlled trials (RCT) about vitamin C treatment for critically ill patients were searched in CNKI, CBM, VIP database, Wanfang database, PubMed, Springer Link, Embase, Web of Science, and Cochrane Library from their inception to May 2019. Patients in the treatment group received ascorbic acid while patients in the control group received placebo or other treatment. Outcome measures included mortality, the length of intensive care unit (ICU) stay, the length of hospital stay, and incidence of atrial fibrillation. Two researchers were responsible for literature screening, data extraction and quality evaluation independently. Meta-analysis was performed with RevMan 5.2 software. The publication bias was analyzed by funnel plot.

A total of 28 RCTs were enrolled and 4 420 patients were included (2 207 in intervention group and 2 213 in control group). Meta-analysis showed that there was no significant difference in mortality between intervention group and control group [odds ratio (OR) = 0.90, 95% confidence interval (95%CI) = 0.75 to 1.08, P = 0.27]. The length of ICU stay [mean difference (MD) = -0.23, 95%CI = -0.29 to -0.16, P < 0.000 01] and the length of hospital stay (MD = -0.96, 95%CI = -1.21 to -0.70, P < 0.000 01) in intervention group were less than those in control group. Subgroup analysis showed that mortality of patients with sepsis and septic shock in intervention group was lower than that in control group (OR = 0.65, 95%CI = 0.43 to 0.99, P = 0.04). For patients undergoing cardiac surgery, the incidence of postoperative atrial fibrillation in intervention group was lower than that in control group (OR = 0.43, 95%CI = 0.34 to 0.54, P < 0.000 01). It was shown by funnel plot that there was less publication bias among studies.

Vitamin C does not reduce mortality in critically ill patients, but it can reduce the length of ICU stay and hospital stay. In addition, vitamin C can reduce mortality of patients with sepsis and septic shock and reduce the incidence of atrial fibrillation post operation in patients undergoing cardiac surgery.