Effects of Vitamin C on Shock Duration and Microcirculation in Patients With Vasoplegia Syndrome After Cardiac Surgery

Vasoplegia syndrome is a frequent and severe complication after cardiac surgery (incidence 5-50%), marked by hypotension, normal/high cardiac index, and continuous vasopressor need, leading to prolonged ICU stay, acute kidney injury, and death. Its pathophysiology involves systemic inflammation, excessive nitric oxide, vasopressin depletion, and endothelial dysfunction impairing microcirculation.

Vitamin C, a potent antioxidant, scavenges reactive oxygen species, protects glycocalyx, supports norepinephrine synthesis, and limits iNOS expression, improving microperfusion in experimental models. Plasma vitamin C drops significantly after cardiopulmonary bypass, suggesting increased consumption and potential benefit.

However, clinical evidence is conflicting. Neither trial assessed microcirculatory endpoints, leaving this gap unexplored in randomized studies. Thus, this study aims to evaluate vitamin C's effects on both shock duration and sublingual microcirculation in post-cardiac surgery vasoplegia, addressing the unresolved clinical and mechanistic questions.

• Vit C (Drug), also known as vitamin C, standard care: Patients in the vitamin C group received standard care (fluid resuscitation, norepinephrine infusion to maintain MAP >65 mmHg, additional vasopressors and hydrocortisone as judged by the attending clinicians) plus intravenous vitamin C (1.5g of vitamin C injection in 100 mL normal saline) over 30 minutes, repeated every 6 hours for a total of 4 doses.
• Standard Preparation (Drug), also known as standard care: Patients in the control group received standard care.

Primary outcomes

• shock duration [28 days after treatment]: The primary outcome was shock duration, defined as the time from the start of vasopressor therapy to the complete discontinuation of all vasopressors. Complete discontinuation defined as no vasopressor being administered to maintain a MAP >65 mmHg for a consecutive period of 24 hours.

Secondary outcomes

• proportion of perfused vessels (PPV) [24 hours after treatment]: A core parameter in sublingual microcirculation monitoring, used to quantify the proportion of microvessels that are actually perfused with red blood cells.
• perfused vessel density (PVD) [24 hours after treatment]: A core parameter in sublingual microcirculation monitoring, used to quantify functional capillary density.
• heterogeneity index (HI) [24 hours after treatment]: A parameter in sublingual microcirculation monitoring used to quantify the spatial heterogeneity of microvascular perfusion.
• ICU length of stay [28 days after treatment]: Time from admission to ICU until discharge from ICU
• mechanical ventilation duration [28 days after treatment]: the time from the start of mechanical ventilation therapy to the complete discontinuation of mechanical ventilation
• 28-d Mortality [28 days after treatment]: patients with sepsis who died after treatment from any cause within 28 days

Sex: All, ages: 18 Years to 85 Years

Inclusion Criteria:

* Age 18-85 years;
* Patients who develop vasoplegia syndrome within 6 hours after being admitted to the ICU following cardiac surgery
* Signing informed consent.

Exclusion criteria included:

* Emergency surgery;
* Sepsis shock, postoperative cardiogenic shock or hemorrhagic shock;
* Pregnancy or lactation;
* Allergy to vitamin C;
* Inability to obtain clear sublingual microcirculatory images due to any cause;
* Judgment by the attending physician that the patient was unsuitable for enrollment.

• Jingyuan Xu, M.D., Principal investigator, Zhongda Hospital