At the end of his patients

ON a chilly Wednesday night in late April, Noah Wyle stood before a mirror on a Warner Bros. soundstage and spoke what are among his last lines as Dr. John Carter, the “ER” physician he’s played since the show began over a decade ago. “It’s been 11 years,” he said. “And I feel like I pretty much grew up with all of you guys.”

It’s a sentiment that resonates beyond the script for Wyle’s last episode, which airs Thursday on NBC. “Before that script came out I was thinking of using that line myself,” Wyle said about the real-life party his cast mates are planning for him. “It’s always easier to say the lines that are written for me than to come up with my own.”

For all its incarnations, most viewers still associate “ER” with its original cast, which, along with Wyle, included George Clooney, Anthony Edwards, Eriq La Salle, Julianna Margulies and Sherry Stringfield. “I don’t think I would have been successful or been able to deal with the success I had if I hadn’t had those role models around me consistently,” said Wyle, who was just 21 when he began the show. “I feel very fortunate to have started exactly when I did in the company of those actors. They taught me an incredible amount.”

The last remaining original cast member to leave the show (Stringfield rejoined the cast in 2001 after a five-year absence), Wyle has admitted to some exhaustion at the hands of Dr. Carter, who even by television standards experienced more in his 20s and early 30s than most of us do in a lifetime. From hapless medical student to seasoned physician, he survived medical residency, the pressures of his enormously wealthy family, a nearly fatal stabbing by a schizophrenic patient followed by drug addiction and rehab and, most notably, a life-changing volunteer stint as a doctor in war-torn Africa where he treated AIDS, polio and whooping cough and was nearly executed by guerrilla soldiers. Along the way, he fell in love with a Parisian clinic worker played by Thandie Newton and suffered the loss of their child.

“The character was originally conceived as a kind of comic relief,” said executive producer John Wells, who directed Wyle’s final episode. “But Noah brought an innocence and intelligence to the character that went beyond those elements. I remember in the beginning, on the first day of dailies, Rod Holcomb, who directed the pilot, said ‘Keep an eye on this guy. He’s going to end up being so much more than the buffoon.’ ”

Last season’s Africa story line represented a departure for both Wyle and the series. In a show known for its frenetic pace and almost nonlinear storytelling -- Wells says he always thought of it as “pointillist; a lot of small moments that come together if you step back far enough” -- the episodes set in the Congo were inspired in part by Wyle’s involvement with Doctors of the World, the American arm of Doctors Without Borders. During the war in Kosovo, Wyle, who already had a long-standing relationship with groups such as Human Rights Watch, traveled to Macedonia with his wife and his mother (who, as it happens, spent 20 years as a nurse at Kaiser Hospital) to observe doctors working in refugee camps.

“It was pretty intense,” Wyle said. “We saw 80-year-old women who’d been shot, who’d been forced at the end of a gun to pack up every belonging they had and march for two hours out of their country. I remember a busload of refugees pulled up, and we were running and pulling people off the bus and getting them in medical tents. I did some simple stuff like taking blood pressure. But even then I think I screwed it up on a couple people.”

Wyle and his wife, Tracy, a makeup artist whom he met on the set of the 1997 film “The Myth of Fingerprints,” have a 2-year-old son and are expecting a second child in October. Since beginning “ER,” he’s appeared in films such as “Donnie Darko,” “White Oleander” and “Enough,” but unlike Clooney, who left the show to pursue a movie career, and Edwards, who moved to New York to get involved in producing and directing projects, Wyle says his decision to leave the show has less to do with film aspirations than fatherhood.

“The producers were extremely courteous to me about giving me time off when my wife was pregnant, and I did take a little paternity-leave stint at the beginning of the 10th season,” he says. “But when my son was born I hated the fact that we brought him home from the hospital on a Sunday and I was back to work on Monday and I worked 12 hours that day and 14 the next. Ultimately, that’s not the kind of parent I want to be. But I’ve always said about our show that there’s really no point in leaving unless you’re ready to change your life. You can’t find better material or work with nicer people or a better crew.”

This summer, Wyle plans to shoot a sequel to the last year’s TNT movie “The Librarian,” and though he says he’s open to television projects, his main priority is spending time with his family. They have a farm in the Santa Ynez Valley, and when he’s home he spends most of his free time in Griffith Park riding the train with his locomotive-obsessed son.

As Wyle ate a blueberry muffin and sipped black coffee, a tall man with a white beard approached his booth and extended a hand.

“Mr. Wyle, congratulations,” he said. “I guest-starred with you guys back in Season 5. I came into the ER. I had a dead brother.”

Wyle said this happens a lot. “It helps if they describe their wound,” he said. “That usually jogs my memory.”

He also still gets squeamish in real-life hospitals. And despite how many patients Dr. Carter has treated, Wyle isn’t one to confuse being a real doctor with playing one on TV.

“I can honestly say that anytime I’ve ever been around a physician or nurse while they’re plying their trade, I’ve always been really gratified how little it means to them that I’m there in the face of what they have to do,” he said. “That’s a sensibility we’ve tried to employ when we play these people. Doctors are beset often by bureaucratic pressures and personal problems. But you check all that baggage at the door and just take care of the person in front of you. It’s the last unassailable profession.”