The patient's condition was critical, so the doctors worked quickly.

of or relating to a crisis or a time of intense difficulty or danger
The situation is critical now.
This is a critical moment.
His health is critical.
critical condition
critical juncture
critical phase
crucial
pivotal
urgent
Getting enough sleep is critical for your health.

of or relating to the essential nature of something; crucial or decisive.
This is a critical moment for us.
His feedback was critical.
The situation is critical.
critical thinking
critical condition
critical mass
crucial
vital
essential