By BOB WACHTER
How many nurses does it take to care for a hospitalized patient? No, that’s not a bad version of a light bulb joke; it’s a serious question, with thousands of lives and billions of dollars resting on the answer. Several studies (such as here and here) published over the last decade have shown that having more nurses per patient is associated with fewer complications and lower mortality. It makes sense.
Yet these studies have been criticized on several grounds. First, they examined staffing levels for hospitals as a whole, not at the level of individual units. Secondly, they compared well-staffed hospitals against poorly staffed ones, raising the possibility that staffing levels were a mere marker for other aspects of quality such as leadership commitment or funding. Finally, they based their findings on average patient load, failing to take into account patient turnover.
Last week’s NEJM contains the best study to date on this crucial issue. It examined nearly 200,000 admissions to 43 units in a “high quality hospital.” While the authors don’t name the hospital, they do tell us that the institution is a US News top rated medical center, has achieved nursing “Magnet” status, and, during the study period, had a mortality rate nearly 40 percent below that predicted for its case-mix. In other words, it was no laggard.
As one could guess from its pedigree and outcomes, the hospital’s approach to nurse staffing was not stingy. Of 176,000 nursing shifts during the study period, only 16 percent were significantly below the established target (the targets are presumably based on patient volume and acuity, but are not well described in the paper). The authors found that patients who experienced a single understaffed shift had a 2 percent higher mortality rate than ones who didn’t. Each additional understaffed shift carried a similar, and additive, risk. This means that the one-in-three patients who experienced three such shifts during their hospital stay had a 6 percent higher mortality than the few patients who didn’t experience any. If the FDA discovered that a new medication was associated with a 2 percent excess mortality rate, you can bet that the agency would withdraw it from the market faster than you could say “Sidney Wolfe.”
The effects of high patient turnover were even more striking. Exposure to a shift with unusually high turnover (7 percent of all shifts met this definition) was associated with a 4 percent increased odds of death. Apparently, patient turnover – admissions, discharges, and transfers – is to hospital units and nurses as takeoffs and landings are to airplanes and flight crews: a single 5-hour flight (one takeoff/landing) is far less stressful, and much safer, than five hour-long flights (5 takeoffs/landings).Continue reading…