A terrorist attack similar to the 2004 commuter train bombings in Madrid would be even more catastrophic in Los Angeles or Washington, D.C., because the injured would overwhelm strained emergency services, experts told a congressional hearing Monday.

"It is irrational to believe that an emergency system that is already overwhelmed by the day-to-day volume of acutely ill patients would be able to expand its capacity on short notice," said Dr. Roger J. Lewis, a professor in the Department of Emergency Medicine at Harbor-UCLA Medical Center.

The bombings in Madrid, on the eve of a national election, killed 177 and injured 2,000. Almost 1,000 of the injured were taken to 15 hospitals. One hospital alone received 270 patients in less than three hours.

The House Committee on Oversight and Government Reform examined conditions at 34 hospitals in seven cities on an arbitrarily chosen date and time -- March 25 at 4:30 p.m. -- to gauge how they could have handled such an influx of patients. The survey focused on hospitals with level 1 trauma centers, which handle the most serious injuries.

None of the hospitals surveyed in New York City, Chicago, Houston, Denver and Minneapolis had enough ER beds, intensive-care beds and regular beds to treat the number of patients that arrived at Madrid hospitals. But Los Angeles and Washington, D.C., had the most acute shortages.

The emergency rooms at three of the five Los Angeles County hospitals surveyed were on diversion that afternoon, meaning that they were turning away ambulances because there was no place to put new patients. In the other two hospitals combined, just six ER beds were available.

Two of the five hospitals had no intensive care beds available. On average, each had fewer than 30 regular beds free.

mary.engel@latimes.com