In late 2011, a seventy-four-year-old woman with colon cancer was admitted to a teaching hospital, to have part of her bowel surgically removed. The doctors put a drain into her abdomen, a standard procedure to prevent infection and facilitate healing. The procedure appeared to go smoothly. But the day after, she developed terrible abdominal pain. One of her ureters, the ducts that transport urine from the kidneys to the bladder, had been nicked; urine was leaking into her abdomen. To divert the urine away from the ureter so that it could heal, another drain was placed through her back, into a kidney.

A few days later, the resident caring for the patient neared the teaching hospital’s witching hour: whether or not his work was done, he had to leave at 6 P.M. That’s because, a decade ago, largely in response to widespread concerns that tired residents were making too many errors, the Accreditation Council for Graduate Medical Education enacted nationwide rules that limited the number of consecutive hours residents can work. Five years later, a review of the data suggested that, on average, the rules had failed to make our nation’s teaching hospitals any safer. Proponents of the reforms argued that the rules had neither gone far enough nor been properly enforced. Accordingly, in 2011, first-year residents were limited even more—to sixteen-hour shifts, rather than the thirty hours previously allowed. Training programs scrambled to comply.

To facilitate the marked increase in transfers of care, known as handoffs, trainees now rely on electronic to-do lists describing the necessary tasks for any one patient (for example: “Check P.M. electrolytes. Call patient’s son in Minnesota and do NOT mention that he signed a do-not-resuscitate order.”) And for the resident caring for the bowel-surgery patient—a resident who had been occupied all day with small emergencies and urgent paperwork—the to-do item he had not yet completed was “Pull abdominal drain.”

Because patient care is now so dependent on these handoffs, at 5:45 P.M., when the resident had to choose between pulling the drain and updating the handoff list with the day’s events and overnight tasks, he knew that skipping the update would be crippling to the overnight resident. So when she arrived, he handed her a fresh list, which now included an instruction to pull the abdominal drain.

A few hours later, the resident entered the patient’s room, saw the kidney drain coming from the patient’s back, and assumed it was the one to pull. When she was done, she checked off the box, looked down at the many remaining to-do items for the patients she was covering, and wondered how she would possibly get through it all before the morning team arrived.

Overnight, urine once again filled the patient’s abdomen, but the patient did not complain—she wanted to avoid another uncomfortable drain insertion. When the morning team found her at 6 A.M., writhing in pain, another drain was urgently placed. The patient recovered uneventfully, but everyone involved in her care felt terrible. No one was tired, yet the mistake had still happened. So who, or what, was to blame?

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The data evaluating the impact of the 2003 reforms suggest that, when it comes to patient safety, little has changed in teaching hospitals. But when it comes to preparing young doctors to manage disease, the training environment has been completely transformed. Take heart failure—the most common reason for admission to the hospital in the United States—and a problem that I, as a cardiologist, deal with often. In a sense, heart failure is simple: the heart fails to pump blood forward, so fluid backs up. But that’s about where the simplicity ends.

Treatment begins with a diuretic to help the kidneys clear the fluid, but sometimes, if you give the patient too much diuretic, the kidneys fail, and even more fluid accumulates. Then again, if the kidneys do fail, it’s possible that the problem is too little diuretic. Suppose the patient soon has a fever. You order a chest X-ray, and the abnormality you see would normally indicate pneumonia—but it also looks identical to a heart-failure image. With heart failure, you take fluids away; with pneumonia, you give fluids. Then you realize the patient’s heart is beating a hundred and twenty-five times per minute. Is the rapid rate helping the heart pump more blood, or is it making the heart failure worse?

For a young doctor, the right course of action isn’t always clear. Acquiring the necessary knowledge and experience requires feedback, which strengthens one’s ability to anticipate how the many variables and small decisions might affect the patient. What’s more, learning how to manage illness demands infinite tweaking; each patient is unique.

But now, residents spend less time directly caring for patients than they once did, and the feedback inherent in the hours once spent with more seasoned physicians has also diminished. In the earlier years of my training, morning rounds were a sacred time. The whole team would gather to learn about the patients who came in overnight, and discuss patients already in our care. We would hear their stories, examine them, review data, and then, together, make decisions about their care for the day. Now, however, the scheduling is such that overnight residents often have to leave before rounds, and the daily ritual has morphed into a race against the clock. Instead of beginning by asking who the sickest patient is, we now ask which resident needs to leave.

The stories of our patients, which we used to own, now come in fits and spurts, passed along via an unending game of telephone. “Anyone know why the heart failure patient’s diuretic was held?” the team leader might ask. “Anyone?” With the resident who made the decision often gone, a mad shuffling of pages invariably ensues, as trainees flip through their lists until someone finds the patient and utters the six saddest words of the shift-limit era: “I don’t know. I’m just covering.”

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As we seek to understand what this new training system means for the future of health care, the ease of monitoring certain outcomes sometimes keeps us from understanding equally important but little-studied factors. Rivka Galchen describes this challenge in her recent essay about the legendary Elmhurst Hospital physician and clinical educator Dr. Joseph Lieber: “The field of medicine has advanced through measuring: weight, blood pressure, dosage, cost, days until discharge, years until death… But sometimes the medical field makes the mistake of valuing most what is most easily measured.”

Our approach to duty-hour limits for residents has been no exception. Everyone knows how it feels to be tired, and there is nothing easier to count than hours worked or slept. I have lost count of the number of conversations I’ve had with non-doctor friends that have begun, “You do realize sleep deprivation is akin to being drunk?” This sentiment is echoed in a recently published survey of U.S. citizens that found that eighty per cent of people would prefer a different doctor if they knew theirs had been working more than twenty-four hours. This conviction—that a rested doctor who doesn’t know you would be better than a tired doctor who does—fueled the 2003 and 2011 reforms.

This is not to suggest that we shouldn’t measure everything we can. But the most important things to quantify are hard to measure: outcomes relating to quality and education. And although it will be a while before we can really understand the effect of the 2011 reforms, two recently published studies suggest that, right now, both quality of care and quality of education are suffering.