News Release
August 27, 2013

Day of the Week Plays no Role in Mortality Risk for Patients with Acute Kidney Injury, Penn Study Finds

New Research Disproves Commonly Held Beliefs about AKI Mortality on Sundays

PHILADELPHIA — Disproving commonly held beliefs, a new study by researchers at the Perelman School of Medicine at the University of Pennsylvania showed that despite a lower frequency of dialysis on Sunday, patients with acute kidney injury (AKI) have mortality rates similar to that of patients who receive the therapy on any other day of the week.  The study appears online in the Clinical Journal of the American Society of Nephrology.

AKI, previously referred to as acute renal failure, is most often caused by reduced or blocked blood flow to the kidney and can be caused by conditions such as shock, trauma, sepsis, and heart attack. It can also occur during surgical procedures.  Initiation of dialysis is necessary to help remove toxins and excess fluids from the body while the kidneys heal.

 “Initiation of dialysis on Sunday is limited by constraints that do not exist on other days of the week, such as staffing differences, drug availability and patient load, which may lead to triaging of dialysis therapy,” said F. Perry Wilson, MD, MSCE, an instructor of Medicine in the Renal, Electrolyte and Hypertension Division at Penn. “Until now, many in the medical community believed that these potential constraints may lead to negative outcomes, but our research suggests that patients with the most severe AKI are receiving the appropriate intervention regardless of day of the week. The patients in whom dialysis happens to be deferred because the day is a Sunday appear to be able to be deferred safely.”

In the study, Wilson and colleagues reviewed the data of over 4,900 patients from the University of Pennsylvania Acute Kidney Injury (UPHS-AKI) cohort between January 2004 and August 2010. The UPHS-AKI cohort is a retrospective cohort study composed of patients with severe inpatient AKI during admissions to one of the three UPHS hospitals in Philadelphia.

Despite prior research that suggested weekend admission with AKI is associated with higher mortality rates, the current study found no difference in inpatient mortality among patients with severe AKI present on a Sunday (30 percent) compared with those with severe AKI for the rest of the week (31 percent).

The rate of initiation of dialysis for AKI was much lower on Sunday than other days of the week, with 2.5 initiations per 100 patient-days on Sunday versus 3.3 on Monday and 3.9 on Tuesday through Saturday. Despite these differences, the research team found inpatient mortality among those who initiated dialysis on a Sunday was the same (65 percent) as for those initiated Tuesday through Saturday. However, patients who initiated dialysis on Monday had a lower mortality than those who initiated it on another day of the week (52 percent).

“The finding of a lower mortality among patients who initiated dialysis on Monday prompted an exploration of characteristics of these patients compared with those who were initiated on other days of the week,” said Wilson. “Interestingly, there were no statistically significant differences between patients initiated on Monday versus other days of the week across a range of laboratory, demographic, and clinical variables.”

The authors write that given the severity of renal injury among dialyzed patients was higher on Sunday than other days of the week, it may be that clinicians are delaying or not pursuing dialysis in a population of patients who would be expected to derive less benefit from the therapy.

“If this is the case, the “Sunday model” can be entertained as one that could be realistically transferred to other days of the week, reducing resource consumption without compromising patient care,” said Wilson.

Dr. Wilson and his colleagues are actively pursuing research to characterize which patients benefit most from the initiation of dialysis, and in whom a policy of “watchful waiting” might be superior.  In the future, randomized trials of dialysis initiation will help to guide clinicians and patients facing this very difficult treatment decision. 

The study was funded in part by a grant from the by National Institute of Diabetes and Digestive and Kidney Diseases (F32DK093223).

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Penn Medicine is one of the world's leading academic medical centers, dedicated to the related missions of medical education, biomedical research, and excellence in patient care. Penn Medicine consists of the Raymond and Ruth Perelman School of Medicine at the University of Pennsylvania (founded in 1765 as the nation's first medical school) and the University of Pennsylvania Health System, which together form a $4.3 billion enterprise.

The Perelman School of Medicine has been ranked among the top five medical schools in the United States for the past 17 years, according to U.S. News & World Report's survey of research-oriented medical schools. The School is consistently among the nation's top recipients of funding from the National Institutes of Health, with $392 million awarded in the 2013 fiscal year.

The University of Pennsylvania Health System's patient care facilities include: The Hospital of the University of Pennsylvania -- recognized as one of the nation's top "Honor Roll" hospitals by U.S. News & World Report; Penn Presbyterian Medical Center; Chester County Hospital; Penn Wissahickon Hospice; and Pennsylvania Hospital -- the nation's first hospital, founded in 1751. Additional affiliated inpatient care facilities and services throughout the Philadelphia region include Chestnut Hill Hospital and Good Shepherd Penn Partners, a partnership between Good Shepherd Rehabilitation Network and Penn Medicine.

Penn Medicine is committed to improving lives and health through a variety of community-based programs and activities. In fiscal year 2013, Penn Medicine provided $814 million to benefit our community.

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