During the last two weeks, about 50,000 Washington area residents opened their mailboxes to find a residents page newsletter sent to them unsolicited by the Washington Hospital Center.

The latest issue of "For Your Good Health" contains information about diabetes, over-the-counter drugs, Parkinson's disease and sunburn. And it contains one more bit of vital information: the name and address of the hospital center.

The hospital center's mailing - which was targeted in part to the higher income neighborhoods of upper Northwest Washington - is but a single, low-key example of the growing willingness of American hospitals to reach into their communities for potential patients, using techniques ranging from the educational to the hard sell.

While nearly every hospital for years has employed a public relations director to help smooth potential rough spots between the institution and the public, the growing national trend, hospital officials say, is toward a much more aggressive, sales-oriented approach, including in some cases outright hucksterism.

During the last four years, Sunrise Medical Center in Las Vegas has at various times lured patients with everything from cash rebates to Mediterranean cruises.

Fast-pitch television commercials plug the Sunrise hospital's special services, and one surgery spot even takes the viewer into an open chest cavity for a close-up of a beating heart.

According to a spokeswoman for the Chicago-based American Hospital Association, few of AHA's 6,200 members have gone as far as Sunrise in their pursuit of filled beds.

However, more and more hospitals, AHA officials, say, have come to view themselves as businesses competing in a tightly regulated industry for a limited number of customers.

"Traditionally, hospital advertising and public relations has been: 'Here we are, here's how good we are, come and use our facilities,'" said Dunlop Eckert, president of Washington's Greater Southeast Community Hospital.

"This new term and discipline that's now getting into hospitals - marketing - says, 'Let's see what the community thinks it needs and wants, and then see how we can tailor our facilities and programs to meet those needs.'"

Greater Southeast, for example, has had to become more competitive recently because of the presence of nearby Southern Maryland Medical Center in Prince George's County.

"For years, we were the only ones out here, othe than Hadley (Memorial Hospital)," said Eckert, "and we didn't have to worry about this kind of stuff. We were jammed. Now we're not the only show in town.There's a new hospital down the road, and we have to deal with it."

Greater Southeast's obstetric and gynecology business has dropped about 10 percent since Southern Maryland Opened.

The hospital is now thinking about advertising a maternity tour for prospective mothers, says hospital public relations director Stephanie McNeil. "What we're considering . . . is an ad saying, 'If you're considering having a baby, if you want to come in and see what a typical delivery room looks like, we offer evening tours for the working mother.'"

McNeil said her hospital's board of directors rejected an earlier advertising proposal she made, but "If you're asking, 'are certain hospitals thinking about doing things like that', yes, we certainly are," she said.

In Glenbrook and Evanston, Ill., hospital boards appear less conservative.

For a six week period this spring, newly opened Glenbrook Hospital, an affiliate of Evanston Hospital, ran one full-page newspaper advertisement each week in suburban and Chicago newspapers.

"There are three things to look for when you're choosing an emergency room," read the headline of one of the ads. "How long will it take to get there? How good is the staff? How complete is the equipment?"

The body of the ad, said Barbata Traeger, director of marketing and public relations for the two hospitals, consists of a large photograph of the emergency room director, quotes from him about the emergency services, and gives the hospital's logo and phone number and a map showing its location.

The hospital ran the advertisement, said Traeger, after conducting "a market study to find out the public's perception of the hospital and its services.

"We feel the advertising was necessary because the perceptions of the hospital weren't clear and we weren't being understood through routine public relations methods," said Traeger. "We thought we'd try these means and they're working very well." Physician referrals, she said , have gone from "two or three a day to nine or ten."

Traeger said she received "a little flak from some physicians" for advertising, "but not nearly as much flak as I thought we'd get. We're looking at budgets for next year, and I'm putting in money for additional advertising campaigns." The latest campaign, she said, cost about $20,000.

Jane Snyder, public relations director for the Washington Hospital Center, and a member of the American Hospital Association committee that drew up advertising guidelines for AHA members, says she doesn't believe her hospital is "marketing" at all.

"What we're doing is public information, and it's something we've been doing for years," she said.

"it's true we're reaching the public with more information than anyone around," said Snyder, "but we've always been doing that."

The 50,000 copies of the health newsletter, however, were not all mailed to residents in the immediate area of the hospital.

Instead, the newsletter was selectively mailed, reaching upper-middle-class residents of upper Northwest Washington, most of whom are closer to Sibley Memorial and Georgetown University Hospitals than the hospital center. Also reached were residents of the Takoma Park, Md., area, who live virtually on the doorstep of Washington Adventist Hospital.

The mailing did not go to the closer Capitol Hill area, where an occupant mailing might reach lower income persons without health insurance.

Snyder said the newsletter was not mailed to Capitol Hill because the hospital center does not consider that neighborhood in its service area, despite its physical proximity. It did go to many homes in the Adams-Morgan area, she said which has a comparable economic mix.

Snyder denied that mailings from the Washington Hospital Center have ever been designed to attract patients to the area's largest private hospital. Rather she said, they are designed to fulfill the hospital's social obligation to provide health education.

In Las Vegas, however, hospital officials say quite candidly, the name of the game is filling beds.

In 1975, said Jim Joyce, director of Sunrise Medical Center's advertising agency, the hospital decided it had to attack a problem which plagues almost all hospitals patients check in Sunday for tests or operations early in the week, but Friday and Saturday much of the hospital's equipment and facilities go unused.

First, said Rena Ruby, the hospital's public relations director, came the rebate program. "We offered patients a 5.25 percent cash rebate on their bills if they came in on a Friday or Saturday. But that was a problem with the insurance companies. They wanted the money Sunrise was giving directly to the patients. That program, she said, died in court.

"Then we went to a recooperative cruise. If you came in on a Friday or Saturday morning, every Monday morning we gave away a $4,000 recooperative cruise. It worked so well that we had to stop it," she said. So many patients thronged the hospital "we had to do emergency admissions only."

Since the hospital stopped giving away cruises, Joyce said, weekend admissions have dropped off, but they have remained well above the old levels, he said.

The hospital then went to "an Insta-Care program. We guaranteed that if a person entered Sunrise Hospital's Emergency Room, within 60 seconds of the time they entered the door they'd be in the system. A nurse would be there to get them into the appropriate room. We always met the guarantee."

Although the hospital pays about $200,000 a year for television and print advertising, Ruby and other officials deny such costs are passed on to the patients. More efficient use of facilities, she said, has meant lower medical bills. Private rooms at Sunrise, she said, cost less than a ward room at the local county hospital.

One of the main television campaigns, said Joyce, "focused on the fact that . . . a lot of people didn't realize the sophistication we have in Las Vegas.

"So we stressed our cancer and open heart surgery facilities. Even to the point of showing a heart operation, showing the heart removed and pulsating on camera," said Jim Joyce. "It was tastefully done."

Greater Southeast Washington's McNeil says she can see her hospital advertising in the not too distant future, but she rules out open heart surgery in living color.

"That's getting on the quack side," she said with a grimace. "It's like those ads for quicky plastic surgery in California."