It’s a constant part of the cacophony of city life: the blare of ambulance sirens. We pull our cars over, wait dutifully, then drive on, almost never knowing who’s inside that ambulance, what put them there or their fate.

On Sept. 30, 2016, the person inside was 6-year-old Zachery Vines. He had been climbing on a wet bar when it toppled onto him, the protruding bar top crushing his midsection. In a flash, what had been a typically hectic Friday afternoon became the worst day of his family’s life.

Fortunately, Dr. Peggy Knudson was waiting for him. The longest-serving trauma surgeon at San Francisco General Hospital — she started working there 28 years ago — knew instantly the pale, sweaty, nonresponsive boy taken from that ambulance was in deep trouble and whisked him into surgery. His liver had been wrecked.

“I can remember my feelings in the operating room, just like, ‘Oh my God, we’ve got to save this kid,’” Knudson recalled.

She did save that kid. And now the athletic, energetic boy with the quintessential gap-toothed grin of a 6-year-old is back in kindergarten, back to wrestling with his two older brothers and back to health. On Thursday, his family honored Knudson on the field of AT&T Park at the San Francisco General Hospital Foundation’s annual Heroes & Hearts awards luncheon.

In a culture that considers sports stars and celebrities its heroes, it can be easy to forget there are real, everyday heroes among us. And in a whirring world where so much seems to go wrong, it can be easy to forget to stop and savor the small bits of good news that are everywhere.

This happy story seemed anything but on that late Friday afternoon.

Like any family of five, the Vines family, who live in Midtown Terrace, had to divide and conquer. Kristin Vines, the director of human resources for a tech company, was with her middle son, Jacob, 9, at a sports practice at Golden Gate Park. Her husband, Jason, an engineer for a biotech company, was out and about with Zachery and their oldest son, Nathan, 11. All three boys are students at Notre Dame des Victoires, a private school at the foot of Nob Hill.

At a business Vines didn’t want to name because nobody was at fault and there are no lawsuits, Zachery was climbing on a wet bar when it fell over. Her husband called 911 and then called her.

“He said, ‘Zachery’s hurt bad.’ All I knew was the tone of his voice was not normal,” Vines, 44, recalled. “He sounded scared, and I got scared, and he said, ‘You’ve got to come to the hospital now.’”

They knew when the paramedics decided to take Zachery to San Francisco General, the city’s only Level 1 Trauma Center, that the injuries were grave. The trauma surgeons there treat 2,000 patients a year who have been seriously injured — struck by cars, shot, stabbed, burned, crushed or who have fallen off ladders or roofs.

Knudson was the trauma surgeon on duty when Zachery’s ambulance arrived, a lucky break for the Vines family. The 66-year-old Los Altos Hills resident had treated victims of the 2010 earthquake in Haiti and the 2013 Asiana Airlines crash at San Francisco International Airport, as well as soldiers injured on the battlefield in Iraq. U.S. News and World Report named her to its Top Doctors list, among its top 1 percent of surgeons in the country.

Knudson said that when she saw Zachery for the first time, it appeared he was in shock and in danger of slipping into a coma. She took him immediately into surgery, opening up his chest and abdomen. She found his crushed liver, an organ that if damaged can cause the patient to bleed to death very quickly.

“The injuries were so severe,” Knudson said. “I thought, ‘Oh, I don’t know if this kid is going to make it.’ Everybody in the operating room was really pulling for him. We pull for everybody, but kids are special. ... It’s a special thing to be able to have people trust you with their child’s life.”

Meanwhile, the Vineses sat in the waiting room for the two hours that surely felt like 20.

“I can say as a mom it was the scariest moment of my life not knowing if he was going to live,” Kristin Vines said, remembering that Knudson came into the waiting room after the surgery to tell them he had survived the operation, but now they would have to take it “moment by moment.”

Zachery remained in the hospital’s intensive care unit for a month, undergoing several more surgeries and nearly dying again after getting a stomach infection. Meanwhile, his mother stayed in his room around the clock, except for a few quick trips home to pick up clean clothes, and his father was there most of the time, too.

The boys’ grandmothers took care of Zachery’s brothers and kept the household running. The family’s friends rallied around to help.

After a month, Zachery was able to leave the hospital. He has some scars on his belly and is a little clingier than before. But he’s 100 percent recovered medically and is back at school and on his sports teams, an outcome Knudson described as “remarkable.”

She is adamant, though, that while she is the one who received the award, Zachery wouldn’t have made it without a big team of people.

“To have a successful outcome takes a huge group of people — it takes everybody from the paramedics who got this child to the right hospital at the right time, the people who work in the emergency room, the blood bank, anesthesia, every nurse, every nurse practitioner,” Knudson said. “Even once he started to get better, trying to get him to eat (was hard), and the cafeteria staff would come in and fix him special meals.”

Kristin Vines said her family is still recovering from the ordeal but is slowly getting back to normal.

“It’s what you would imagine a household of boys to be — the wrestling, the running around, the nonstop noise,” she said. Part of that nonstop noise is Zachery calling, “Mommy, I love you!” 20 times a day, she said.

Vines said she nominated Knudson for the award because so many San Franciscans take San Francisco General for granted, until that one horrible day when they need it.

“I don’t know how you thank someone,” she said, pausing as her voice wavered. “How you thank someone for saving your son’s life?”

San Francisco Chronicle columnist Heather Knight appears Tuesday and Friday. Email: hknight@sfchronicle.com, Twitter: @hknightsf