At Walgreens, Goff says, the training meant that new arrivals shadowed veteran pharmacists for a week before filling their first prescriptions. At Summerlin, the pharmacy director was commuting between Pennsylvania and Nevada. There was no formal training. Goff reasoned that the job as lead clinical pharmacist, however difficult, was a stepping-stone to her ultimate goal: specializing in pediatric pharmacy. It also offered more flexible hours, as she was caring for a toddler and working toward a doctorate in pharmacy.

Though Goff worked at the Summerlin pharmacy, she was not employed by the hospital. She had been hired by the giant health-care-services company McKesson Corp., headquartered in San Francisco, which ran the pharmacy for U.H.S. and was technically its owner. McKesson was the third company to manage Summerlin's pharmacy in a decade. Before that, Cardinal Health had been in charge, replaced at the end of its contract when McKesson offered better terms to U.H.S.  Between 2000 and 2006, six pharmacy directors had come and gone. There was so much "interbreeding," Goff says, that you never knew who had been hired by which company or trained under what protocol.

More than 8 percent of the nation's 5,500 hospitals outsource the management of their pharmacies to companies like McKesson. These companies can seem like a godsend for hospital C.E.O.'s facing soaring pharmaceutical costs and a nationwide shortage of pharmacists. McKesson and Cardinal Health, which are two of the largest, promise to do it all: staff the pharmacies, set up inventory-management systems that can increase efficiency and safety, and be a one-stop shop for drugs, all at a reduced price.

But a fundamental problem exists, says Kurt Patton, former executive director of hospital-accreditation services for the Joint Commission, an independent oversight agency that inspects and certifies hospitals. Hospitals that turn over their pharmacies to management companies often cede nearly total control. This can create a dangerous disconnect between the hospital's medical staff and the pharmacy.

At the nurses stations, according to Goff, bags of saline, some with potassium and some without, were jumbled together in the same bins, without separate color coding—a practice frowned on by the Joint Commission, since a mix-up can be lethal. The nurses kept supplies of long-acting insulin on the floor, whereas the Joint Commission recommends only regular insulin as floor stock. The long-acting kind requires a special pharmacy order, because its accidental use can induce diabetic shock.

In the fall of 2006, the Summerlin pharmacy appeared to take a leap forward when a highly sensitive compounder known as a Baxa machine arrived, replacing an outmoded one. The new machine could mix medicine in amounts smaller than humans can accurately measure, reducing the chances for error in making T.P.N. bags for babies. But the policies at Summerlin for making the bags were not updated accordingly. They had not been changed since 2003, a year before the hospital opened its high-level NICU.

In almost any pharmacy, the policy-and-procedure manual serves as the pharmacists' bible. But the Summerlin manual had not been changed to reflect the new policies, as pharmacist Jackson Yu would testify before the Nevada State Board of Pharmacy, "because we had gone through so many directors. They would take on a task but never stay long enough for it to come to fruition." Goff found two separate procedure manuals floating around, both outdated and containing conflicting information.