Acute respiratory failure due to COVİD-19 pneumonia has poor prognosis and high mortality . Both the lack of an effective antiviral treatment and the low level evidence of the recommendations presented in the guidelines on other treatment methods have highlighted supportive treatments. Studies suggest that high-dose vitamin C treatment reduces mortality in patients with sepsis and ARDS, and may also be beneficial in COVİD-19 disease. In the study; the investigator aimed to determine the effect of Vitamin C on short-term mortality and length of intensive care stay in COVID-19 patients.

SARS-CoV-2 causes tissue damage in the endothelium and epithelium, increased vascular permeability and increased plasma levels of IL-6, IL-2, IL-7, IL-10 causing interstitial fibrosis in the lung is considered. Considering these factors in pathogenesis, a picture with high mortality from acute respiratory failure to severe ARDS emerges in critically ill COVID-19 patients. However, despite numerous studies, an effective antiviral treatment has not yet been found in COVID-19 disease. The low level of evidence for the recommendations presented in the guidelines on both treatment and mechanical ventilation has brought supportive treatments to the agenda. Recently, many articles have been published on the potential effects of anti-inflammatory and antioxidant treatments such as high-dose vitamin C, vitamin D, zinc and ozone therapy. In particular, high-dose intravenous vitamin C treatment is inexpensive, easily accessible, and it reduces mortality in patients with sepsis and ARDS in studies, suggesting that it may be beneficial in COVID-19 disease. this is a retrospective cohort study. The main goal of the study; to compare patients who did not receive high-dose vitamin C treatment in the first period of the epidemic and those who received treatment in the next period. the investigator aimed to determine the effect of Vitamin C on short-term mortality and length of stay in intensive care in critically ill COVID-19 patients. All patients' data on age, gender, body mass index, comorbidities (diabetes mellitus, hypertension, coronary artery disease, chronic obstructive pulmonary disease, other), PaO2 / FiO2 ratios, SOFA scores, ferritin, C-Reactive Protein, procalcitonin, lactate, neutrophil and lymphocyte values will be collected by scanning the hospital information system.

Inclusion Criteria:

• Hospitalized with diagnosis of COVID-19, diagnosis confirmed by PCR test
• pneumonia due to COVID-19 was diagnosed with clinical and radiological findings
• Patients who developed acute respiratory failure (PaO2 / FiO2 300 despite the use of 6 l / min reservoir mask) caused by COVID-19 pneumonia
• Older than 18 year

Exclusion Criteria:

• Renal failure
• Hepatic failure
• End-stage malignity
• Primary lung disease (lung cancer, cardio-pulmonary edema)
• Patients who treated with tocilizumab
• Presence of diabetic ketoacidosis, use of insulin infusion, or frequent need for point-of-care glucose monitoring (>6 times/24 hour period) as determined by treating physician
• Active kidney stone
• patients with hospitalization in ICU less than 96 hours

patients who admitted to the intensive care unit with the diagnosis of acute respiratory failure due to COVID-19 pneumonia