Critical Care

PubMed:

"Critical Care"[Mesh] OR "Intensive Care Units"[Mesh] OR "Critical Illness"[Mesh] OR "Life Support Care"[Mesh]

If you are looking for absolutely everything, or want In Process articles, you can also add:
"critical care"[tiab] OR "intensive care"[tiab] OR "life support"[tiab] OR "close support"[tiab] OR "critically ill"[tiab] OR "critical illness"[tiab] OR icu[tiab] OR "critical unit"[tiab] OR "critical units"[tiab] OR "intensive unit"[tiab] OR "intensive units"[tiab]

EMBASE:

exp intensive care/ OR exp intensive care unit/ OR exp critical illness/ OR exp critically ill patient/

CINAHL:

MH "Critical Care+" OR MH "Critical Care Nursing+" OR MH "Critical Illness+" OR MH "Critically Ill Patients+"

Thanks to my colleague, Karen, for the suggestion of "close support"[tiab].