The artist Nate Lewis left his job as a nurse three years ago, but life on the neurocritical intensive care unit produces memories that don’t readily fade.

The patients battling strokes, seizures, and head injuries. The specialists debating treatment based on test numbers and images. The anxious families keeping watch, looking to the nurse for explanation and reassurance.

“I would show up and these families are giving me everything, telling me their life stories,” Mr. Lewis, 34, recalled of his years at a hospital near Washington, D.C. “I realized what an honor it was to take care of them at this time in their lives.”

One high-stakes drill became familiar: When a patient’s brain, heart or lung functions exceeded the safe range, an alarm would sound, and the monitor would start printing out the relevant graph until the situation was addressed.