Selenium is an important trace element for human for its multiple roles such as the antioxidant activity. Previous evidences showed that critically ill patients may benefit from selenium supplement but the dose and results are controversial.

Patients after operations for acute abdomen usually suffer from sepsis and stress. The aim of this study is to investigate the efficacy of selenium replacement in critical patients of acute abdomen, to see the impact on prognosis.

Acute abdomen is a common surgical emergency and is often the result of peritonitis due to an acute inflammatory process within abdominal cavity. Many of the patients with acute abdomen have severe sepsis and are critically ill that require an emergency surgery.

The mortality rate of such patients are high because these patients usually have a profound pathophysiological dysregulation and multiple organ dysfunction. One of the mechanism of is the loss of anti-oxidative capacity of cells that fail to recover from ischemic-reperfusion injury.

Selenium is an important cofactor that participate in the antioxidant activity of glutathione peroxidase reaction. There are evidences that critically ill patients may benefit from selenium supplement by better outcome and less mortality but the dose and results are still heterogenous and inconclusive.

The aim of this study is to investigate the efficacy of selenium replacement in critical patients of acute abdomen, to see if there is a significant impact on prognosis, and to establish a clinical guide in the future.

Inclusion Criteria:

• Intensive care unit (ICU) patients receiving abdominal surgeries for acute abdomen
• within 48 hours post-operatively
• stay in ICU for more than 48 hours
• meets sepsis criteria of Sepsis-3 (2016)

Exclusion Criteria:

• liver cirrhosis Child-Pugh score B or C
• breastfeeding or pregnancy
• allergy yo selenium
• vegetative status or irreversible diseases with life-expectancy fewer than 28 days
• End-stage renal disease under dialysis
• Human immunodeficiency virus infection
• neutropenia not due to sepsis (granulocyte < 1000/mm3)
• Heart failure (New York Heart Association class III-IV) or recent myocardial infarction (within 6 weeks)
• post cardiopulmonary cerebral resuscitation within 4 weeks
• taking immunosuppressants
• receiving anti-cancer therapy
• signed do not resuscitation
• joined other clinical research