This is a prospective, multicenter observational trial for patients who develop critical illness after hematopoietic cell transplantation. Patients who are admitted to the intensive care unit after undergoing hematopoietic cell transplantation at the participating medical centers will be enrolled in this study. The clinical characteristics, laboratory profiles, managements, and clinical outcomes will be prospectively collected.

Inclusion Criteria:

• Patients who underwent hematopoietic cell transplantation at any of the participating medical centers.
• Patients who are admitted to ICU for the management of critical illness following hematopoietic cell transplantation.

Exclusion Criteria:

• Admitted to ICU for a reason other than critical illness (e.g., routine postoperative monitoring) and discharged within 2 days of ICU admission.
• Unavailable in-ICU clinical outcomes or absent key baseline characteristics.
• Any other conditions that, in the opinion of the investigator, can interfere with the interpretation of data.

Patients who are admitted to ICU after undergoing hematopoietic cell transplantation at any of the participating medical centers.