Long after power is restored from Sandy, the effect of another more-precarious outage is still taking shape: Some of the largest hospitals in lower Manhattan remain shuttered. Other hospitals are scrambling to fill the gap, and concern is rising that the patchwork system can't last for long.

NYU Langone Medical Center and Bellevue Hospital, the flagship of the city's public hospital system, were forced to evacuate due to loss of electricity and damage from Sandy. The Manhattan Veterans Affairs Medical Center evacuated patients before the storm and has not reopened.

There is no firm timetable on the hospitals' return. A spokesman for the city agency that runs Bellevue said that the hospital will likely be out for at least several weeks. NYU's outpatient clinics have reopened but the hospital itself remains closed.

"This is not a tenable situation," said Bellevue's director of emergency medicine, Dr. Lewis Goldfrank, who holds a similar title at NYU. "There's just too many people. You can't dump this level of patients out on the open market."

Bellevue's emergency room treated more than 100,000 patients last year, and its physicians and outpatient clinics handled more than a half million patient visits, according to state Department of Health data. It is also a large provider of psychiatric services and a hub for treating patients in police custody.

Beyond the huge daily patient load it handles, Bellevue is also a key piece of the city's crisis response system as the only high-level trauma center near the lower section of Manhattan. Trauma centers handle the most serious cases, including victims of gunshots, stabbings, auto accidents, falls and terrorist attacks.

Now, the nearest Level One trauma centers for residents of lower Manhattan aren't all that close: New York Presbyterian/Weill Cornell Medical Center is on the Upper East Side at East 68th Street and St. Luke's/Roosevelt Hospital is on the Upper West Side.

Officials say there's no reason to think that, for now, trauma victims in lower Manhattan will be any worse off than those in other parts of the city. The response speed is still acceptable, they say. And if a trauma victim is in an immediately life-threatening situation, such as a traumatic cardiac arrest, ambulances bring them to the closest hospital, regardless of whether it's a trauma center.

But the fear is that there won't be enough surge capacity at other hospitals if there is a major disaster, or that overworked staff at other hospitals will grow fatigued under the load and patient care could suffer.

"All systems can work at above capacity for some time without significant detriment," wrote Dr. Ronald Simon, director of trauma at Bellevue, in an email to ProPublica.

"But, with time, people will tire, over-worked systems will fail, and patients will suffer," wrote Simon, who is also chairman of the state health department's regional trauma advisory committee. "No question in my mind that the current status of care in Manhattan is not sustainable for any length of time."

The longer Bellevue and the others are closed, the more worrisome it becomes.

It "leaves a whole blank spot in the lower part of Manhattan," said Dr. Amesh Adalja, an associate of the Center for Biosecurity of the University of Pittsburgh Medical Center.

Below is a map of Level One trauma centers in New York City. Click on an icon for more information.

Adalja studied the 2010 closure of downtown Manhattan's St. Vincent's Hospital when doctors feared that the system wouldn't be able to absorb the patients. Four hospitals—Bellevue, NYU, Beth Israel and New York Downtown Hospital—stepped in and expanded their services.

Two of those four are now out of service.

Bellevue's staff has been shifted to other public hospitals and clinics, which are coordinating to minimize the impact, said Goldfrank, the hospital's emergency medicine director. Goldfrank said he is particularly concerned about what will happen to patients with chronic conditions, such as heart disease and diabetes, who depend on regular care to keep them out of the hospital.

Beth Israel Medical Center, located in lower Manhattan at 1st Avenue and 16th Street, has seen its ambulance traffic increase by 70 percent since before the storm. It currently receives about 135 patients a day by ambulance, compared to an average of 84 before the storm, said Dr. Gregg Husk, chairman of emergency medicine there.

"For us, this is Guinness Book of Records territory," Husk said, noting that his ER had its highest-ever days in terms of overall volume, ambulance volume and admissions from the ER to the hospital.

The hospital has increased its staffing so wait times have not been effected, Husk said.

Other hospitals around the city have stepped in. Mount Sinai Hospital on the Upper East Side accepted patients evacuated from NYU and Bellevue last week. Wayne E. Keathley, the hospital's president, said the hospital is prepared to do even more. "We're very much now in the moment-by-moment planning phase."

Ian Michaels, a spokesman for New York's Health and Hospitals Corporation, which runs the city's public hospitals including Bellevue, said the agency is still trying to figure out how quickly the hospital can get back online. "The assessment is ongoing," he said late Tuesday. "We'll know more soon."

Michaels disputed a report on the New York Times website Tuesday that said Bellevue was in lock-down mode "because of possible structural damage from the storm."

"We don't suspect that there are any structural issues," Michaels said.

In addition to Bellevue, Coney Island Hospital in Brooklyn was also evacuated and is not back in service. That leaves nine functioning public acute-care hospitals, Michaels said, "operating very near capacity. There are very few beds available within the HHC system right now."

A spokesman for the New York State Department of Health, Bill Schwarz, said in an e-mail that "the handling of trauma calls in Lower Manhattan has run smoothly."

"Patients are being transported to appropriate facilities based on their medical needs and services required," Schwarz wrote. "Response times for life-threatening emergencies in Manhattan are meeting FDNY Bureau of EMS goals. Turnaround times at Emergency Departments at Manhattan hospitals have remained steady, with no noticeable increases as a result of the storm impact."

An FDNY spokesman said response times for ambulances to get to patients in life-threatening situations "have been under our targeted goal of 7 minutes since the storm. No delays have been reported."

For the moment, doctors said, trauma calls have been way down since the storm.

"With the hurricane and with the bad weather, a lot of people are staying off the streets," said Simon, Bellevue's trauma director. "It's not uncommon after natural disasters for trauma in the immediate wake of it to go down."

Simon said he believes the existing trauma centers can probably pick up the added load and have "surge capacity" in the event of another disaster or a mass-casualty event. "If something did happen, all of the hospitals would still be able to take the additional patients that that would provide. Would they all have to travel a little farther? Yes. Would that mean anything as far as life and limb is concerned? Probably not."

Jennifer LaFleur contributed to this report.