A fleeting look of consternation passed across Dr. Peter Bourne's face as he sat in his cramped, windowless basement office in the West Wing of the White House. He had just been asked, whatever became of Peter Bourne?

It is axiomatic in Washington that when people start asking whatever became of you, it is time to wonder where your career is carrying you.

And Bourne, after all, had a hand in convincing Jimmy Carter to enter the 1976 presidential sweepstakes. Early on, he suggested in a memo to the then obscure former Georgia governor that he seek the highest office in the land.

What's more, Bourne was the man - and his wife, Mary King, was the woman - who acted as the point team for the Carters in Washington, long before anybody took their ambitions seriously.

For three years they infiltrated the social and political inner sanctums of the federal city, courting the press and working the cocktail and dinner party circuit, first as visionaries and later like a rhetorical antidote the Carter's populist-tinged remonstrances about Establishment Washington.

"They know and understand the interrelationships between people in Washington," a grateful candidate Carter said in July 1976.

Clearly, Bourne and King were going places.

And they did.

Mary King, who during the campaign served as Carter's chief adviser on women and who was adoringly described as being in the center of the Carter "brain trust" - on the same level as foreign policy adviser Zbigniew Brzezinski - was given a $50,000-a-year post as deputy director of Action, the volunteer service agency.

Although feminist groups howled doublecross and charged that Carter reneged on a promise to appoint King director of the agency, White House press secretary Jody Powell said later he had checked with Carter and was told that the president never had intended to appoint her to a top position.

King is sharp, Powell said at the time, but she did not have adequate experience to run a large government operation.

As for Bourne, the urbane, British-born Atlantan who wrote the original memo urging Carter to run for the presidency, the small basement office would seem, at least, to suggest that he became lost in a rush for power during the administration's frenetic transition phase.

Amid reports that he lost some of his influence when Hamilton Jordan began flexing his muscles at the White House, Bourne ended up with the title "special assistant for mental health."

"It never really was a formal title. People just started calling me that," Bourne explained in an interview.

He also reached back to an old field of expertise - drug abuse prevention - which he had polished in the Nixon White House as assistant director of the Office for Drug Abuse Prevention.

In his first six months in the Carter White House, Bourne compiled a record of bold drug policy - urging decriminalization of marijuana and initiating experimental heroin use in alleviating pain in terminally ill patients - but his efforts seemed anonymous as narcotics began to fade from the public spotlight.

Now, Bourne is busy at the task of broadening his influence once more, and he has quietly involved himself in tasks that bear little resemblance to the title he began with.

"I deal in human concerns. My role now really encompasses all humanitarian issues, particularly in the international area," said Bourne, with no discernible timidity and not sounding particularly like an exile.

"All humanitarian issues," in this case, involve an array of management activities:

He is active in behind-the-scenes development of a national health insurance policy, an undertaking he says will become increasingly time-consuming in the month ahead.

He is establishing two commissions, one on world hunger and one that will govern the International Year of the Child.

He also is White House liaison to a jumble of United Nations organizations, including the World Health Organization, the High Commission for Refugees, the Disaster Relief Organization, UNICEF and the World Intellectual Properties Organization, which polices international patent and copyright agreements.

In response to reports that all this activity is leading to suggestions in some departments - particularly State and Health, Education and Welfare - that he is becoming "meddlesome," Bourne said, "Oh, sure, people feel we're meddling, but that's always the way it is. In some areas they like our presence, in some there's competitiveness. That's the way it is."

And if Bourne feels he has achieved something less than he envisioned in those lonely years before Carter's nomination, he doesn't show it.

"Right after the election, the president asked me to write what I'd like to do, and I said there are four areas I wanted to involve myself," Bourne said. He ticked them off: Establishing a President's Commission on Mental Health (which he did), being a "focal point" on a federal drug policy, working with "basic international human needs" and working in the general area of health.

"I have a four-year investment with him in national health insurance," Bourne said, alluding to Carter's early backing of such a plan."I plan to contribute to it now."

Bourne said he sees Carter "as much as I need to," but he conceded, "Mostly, what I do now is my memo. There are memos every day.

"This is entirely of my own choosing. I'm doing exactly what I asked to do," Bourne said, adding he was not unaware of the rumors that he has been, in effect, shelved in the administration.

"I've never cared to get into the internal battles that some people do who see their total role as dependent upon winning or losing those battles. Those of us from Georgia have a kind of longevity that is secure. His [Carter's] commitment to Bert Lance, even in adversity, reflects that," Bourne said.

Bourne said he "could have gone to some agency and left a mark on some specific undertaking," but he said he now feels more comfortable "touching a maximum number of lives around the world."

"I've never felt power was a motivating factor for me. If you can send one memo to the president that says 'Here's something you can do or say while visiting a foreign country,' then that one memo can have more impact on a great number of people than doing a lot of other things," Bourne said.