In most babies with biliary atresia (BA) bile ducts on the inside and outside of the liver are affected eventually leading to a complete blockage of bile flow from the liver. This in turn causes scarring (fibrosis) in the liver. The surgery called the Kasai procedure and eventually, a liver transplant could treat biliary atresia. However, children with BA have poor liver function, poor renal reserve, and poor ability to regulate water and electrolytes. Therefore, A reasonable and effective perioperative fluid management is more significant. Considering the high chlorine of saline, the liver burden of Lactated Ringer's solution and Acetated Ringer's solution, the Bicarbonate Ringer's solution which composition is similar to plasma, could be the best choice for perioperative fluid management of BA children. Therefore, we hypothesize that compared with other crystalloids, Bicarbonate Ringer's solution is a better choice to maintain water, electrolyte and acid-base balance in BA children.

Inclusion Criteria:

1. patients diagnosed with biliary atresia before surgery.
2. age less than 90 days.
3. American Society of Anesthesiologists score of 1~2.

Exclusion Criteria:

1. patients with severe allergies.
2. patients with severe deformities or lesions.
3. other situations not suitable for enrollment judged by researchers.

Study Population was diagnosed with biliary atresia, who need Intravenous infusion.