Night Float Can Affect Resident Performance and Patient Safety
As graduate medical training programs implement changes to minimize sleep deprivation and fatigue among residents, does one solution – the night float – present its own risks?
Yes, says new research by Anita Cavallo, MD, of the Division of General and Community Pediatrics at Cincinnati Children's. Due to the well-known effects of shift work, the night float places participating residents at risk for committing errors and jeopardizing patient safety – as well as being victims of motor vehicle accidents when they drive home.
Started in the late 1980s, the night float is a time-limited period of night shift work designed to diminish the workload of the residents on call, who work all day and subsequently all night. During their second year of residency at Cincinnati Children's, residents are assigned to two periods of two-week night float with no daytime duties. They begin their shift at 11 pm, taking all new overnight admissions, and end their shift at 8 am.
On-call residents, on the other hand, cover their daytime patients and new admissions until 11 pm; during the night, they are responsible only for the patients they covered before 11 pm. Theoretically, this arrangement allows on-call residents to get more sleep.
Fighting the Biological Clock
"When the night float was created, I was worried – for all institutions – that no one seemed to be concerned about residents doing shift work," says Dr. Cavallo. "We know that shift work is bad for everyone, because humans are created to be active during the day and sleep at night. Our internal biological clock keeps us synchronized to this 24- hour rhythm."
She notes that night shift work is equivalent to a time zone difference of 12 hours, requiring seven days for the body to adjust. However, previous studies in industry and health care have shown that most night shift workers never fully adjust, because on their days off, they revert to the schedule of daytime workers. Because night float residents at Cincinnati Children's have a weekend off during their two-week night float, Dr. Cavallo suspected that they, too, would follow this pattern.
So the research was designed to discover whether the well-known effects of shift work – difficulty maintaining alertness, increased irritability, and a higher likelihood of depressive symptoms – would apply to residents at Cincinnati Children's, even though the night float is only two weeks long. Residents completed a daily sleep diary, used an activity monitor daily, and took tests of attention and mood three times a week during the two-week night float and during equivalent blocks of time in their daytime rotations.
Greater Fatigue, Less Energy
The research confirmed what a previous retrospective study at Cincinnati Children's had shown. Night float residents slept almost an hour less than during their daytime rotations, even though they had all day to sleep. Their fatigue was greater, as measured by fatigue-inertia scores. They had increased errors of omission, with a strong association between fatigue and omission errors. And they had decreased vigor, based on vigor-activity scores.
"The reality is that any nighttime coverage – on-call or night float – involves higher risks for patient safety. It's important to note that the new work hour limitations established by the Accreditation Council for Graduate Medical Education do not eliminate this risk, because the body's biological clock is programmed to be more alert during the day," Dr. Cavallo says.
To minimize these risks, she believes that hospitals of the future should adopt new approaches, including lighting work areas brightly, encouraging residents to nap whenever possible, creating singlebed call rooms that keep residents from being awakened by their roommate's pager, and offering more education on how to help the body's biological clock adjust to shift work.
"We cannot function without 24-hour coverage in health care," Dr. Cavallo says. "So the best we can do is to understand the biological clock and develop measures to help the body adjust to shift work."
Dr. Cavallo is professor of clinical pediatrics in the Division of General and Community Pediatrics at Cincinnati Children's. Her study was published in Ergonomics (46[7]:653-63, 2003 June 10) and was supported by funding from the Centers for Disease Control & Prevention, National Institute for Occupational Safety and Health, and from the National Center for Research Resources, General Clinical Research Centers Program, National Institutes of Health.
