CHICAGO — George Vander Linde tapped a code into the emergency room’s automated medicine cabinet. A drawer slid open and he flipped the lid, but found nothing inside.

Vander Linde, a nurse, tried three other compartments that would normally contain morphine or another painkiller, hydromorphone. Empty.

The staff was bracing for a busy weekend. Temperatures were forecast for the 90s, and summer is a busy time for emergency departments — the time of year when injuries rise from bike accidents, broken bottles, and gunshots.

At Norwegian American Hospital and other emergency departments, doctors and nurses have been struggling for months without crucial drugs like morphine, used to ease the pain of injuries like broken bones, and diltiazem, a heart drug. Norwegian has been out of morphine since March. The shortages are part of a nagging problem that has intensified this year as a rash of decades-old staples became scarce.

Hospitals small and large have been scrambling to come up with alternatives, with doctors and nurses dismayed to find some patients must suffer through pain or risk unusual reactions to alternative drugs that are not the best option.

“So many substances are short, and we’re dancing every shift,’’ said Dr. James Augustine, a doctor in Cincinnati who works for US Acute Care Solutions, a company that employs doctors who work in emergency departments for hospitals around the country.

One of the main companies that makes the drugs, Pfizer, has warned that manufacturing problems at some of its plants will lower supplies of many of its products until next year.

For years, drug shortages have created a behind-the-scenes scramble as pharmacists, doctors, and nurses cobble together fixes that are often invisible to patients. But doctors around the country say the latest shortages are more directly affecting patient care.

A survey in May of emergency doctors by their professional association, the American College of Emergency Physicians, found that 9 of 10 said they did not have access to critical medicines, and nearly 4 in 10 said that patients had been negatively affected.

“The lack of pain medications is a huge issue,’’ said Dr. Benjamin Savitch, who oversees the emergency room at Norwegian American for US Acute Care Solutions. He said that it can be difficult to explain to patients what is happening. “They are often disappointed and frustrated that the system is not functioning at the level it should,’’ he said.

Like so much else in health care, the roots of the drug shortage are complex and seemingly without a simple fix. The vast majority of the products in question are sterile injectable drugs, hospital workhorses that are cheaply priced even though they can be difficult to make. These low margins have led some companies to stop making the drugs, while others have failed to invest in older facilities, leading to a host of quality problems, recalls, and plant shutdowns.

The periodic problems were compounded last fall when Hurricane Maria hit Puerto ­Rico, a major center of pharmaceutical manufacturing, causing a shortage of small saline bags that are a mainstay in hospitals and worsening a yearslong problem with keeping intravenous fluids in stock.

But even as that crisis subsided, hospitals began grappling with the aftermath of another industry cataclysm: serious manufacturing problems at Pfizer, the nation’s largest maker of generic injectable drugs.

In February of last year, the Food and Drug Administration issued a warning letter to the company for problems at its plant in McPherson, Kan., one of several factories Pfizer took over after it acquired the injectable maker Hospira in 2015.

The agency described the plant’s manufacturing process as “out of control’’ and, among other problems, said Pfizer had not properly investigated complaints about vials that contained particles later identified as bits of cardboard. If injected, the agency said, the contaminated vials could pose a “significant risk’’ to patients.

Pfizer executives said that while the company regretted the effect the shortages were having on patients, it was investing significant resources to get the plants up to par after taking them over from Hospira. It plans to spend $800 million by year’s end and has pledged to invest at least $1.3 billion over the next five years.

“We are completely aware of the essential nature of our portfolio,’’ said Navin Katyal, general manager for the Pfizer Injectables unit in the United States. “The patient is truly our North Star. It’s driving our urgency to recover.’’

Katyal also said that while many supplies will not return to normal until next year, Pfizer is continuing its manufacturing — albeit at a slower pace — while the plants are being fixed and some of the most critical shortages are expected to be eased by the end of the year.

By the numbers, the current state of drug shortages does not look that bad. According to a recent FDA report, the agency tracked just 39 new product shortages in 2017, compared with a peak of 251 in 2011. And while the FDA described 2017 as a “challenging year,’’ it said it successfully prevented shortages of 145 products by taking actions such as allowing imports of certain products.

But Erin Fox at the University of Utah, who tracks shortages, said the figures do not reflect the intensity of the gaps in supplies. “We’ve had all of these shortages before at different times, but what’s harder about it right now is that it’s all at once,’’ she said.

Dr. Scott Gottlieb, the FDA commissioner, acknowledged that while it has made progress, it has not solved the underlying problem of slim profit margins on products that are difficult to produce.

Gottlieb said he planned to act soon on a recent request by members of Congress to look more broadly at the issue. One action, he said, could involve imposing more requirements on manufacturers, while at the same time working with programs like Medicare to increase reimbursements for certain drugs, as when they are used in outpatient clinics.

“Today it’s one drug, tomorrow is going to be another drug,’’ Gottlieb said. “We’ve got to think of something more holistic and comprehensive.’’