MY FIRST BODY came on my first shift. It was a Friday night, dark and cold, the wind whipping across the empty fields. We were at a rollover on a country road. Someone had drifted too far into the snow on the shoulder and gone into a ditch. There had been two occupants, but somehow they were fine, not a scratch on them. On the way back to the ambulance—paramedics here in Canada call them trucks—we were talking about how lucky the people were when the radio squawked.

Serving a region with a population of just over 1 million, the Ottawa Paramedic Service answered more than 103,000 calls last year. The calls come over the radio in bunches. In my first five minutes inside the truck, there were calls for a woman having a seizure in a grocery store, an 8-week-old boy choking, a homeless man found unconscious in an alley, a possible heart attack in a chicken restaurant. If you just sat inside that ambulance listening to the radio, you’d believe the world was falling apart. It’s madness. But even in the midst of all that screaming and chaos, there are calls that stand out. A Code 4 is a life-threatening emergency, lights and sirens. A Code 4 VSA—vital signs absent—is lights and sirens and a little bit more. This call was a VSA, a woman stretched out in the darkness to our west. Darryl and I jumped into the ambulance and bucked it.

Darryl Wilton was my mentor and partner. He’s 36, tall, with a shaved head. If you could request a particular paramedic when you dialed 911, you would ask for him. He’s been in the truck for 12 years, and he has seen a lot of things. As part of my training, he showed me photographs from some recent calls to make sure I had the stomach for the work. He didn’t want to have to treat me, too. (“The barrel-over-the-falls effect,” he called the bilious up-rush that rookies suffer.)

I understood there would be my life before I spent time in the truck and my life after. As we raced through the night, I tried to prepare myself. Darryl prepared, too, but in a different way. He switched his brain into its most methodical gear. It was almost as though he were treating patients in advance of seeing them. “Time is tissue,” he said. With every minute that passes before treatment, more body parts that should be pink turn white or blue, and white or blue equals death. As we listened to updates on the radio, he’d ask me what I thought about what was coming, and he would gently guide me toward the likely reality. Code 4s that came in just after snowstorms were often heart attacks—someone goes out to shovel and his heart can’t handle the exertion. VSAs early in the morning were often unworkable, because chances were that the victim had died in the night, hours before he was discovered. Then the Code 4 would become a Code 5—what Darryl calls “obviously dead.”

We knew this woman was elderly and laid out in her garage. It was a little after 7 p.m., which gave us a few possibilities. It had been snowing pretty hard, so maybe she had a shovel in her hands. Or maybe she fell on a patch of ice and hit her head. Darryl worried that she might have gone down sometime in the afternoon and not been found until someone returned home from work. We both reached into the box between us and pulled out blue nitrile gloves. It turns out the lights and sirens clear minds as well as traffic, the way boxers use entrance music. When the voice on the radio came on again to say that we were likely heading into a Code 5, I was ready.

She was lying on the cement on her back, folded up impossibly small. Her knee was blown out, and she had thrown a slipper. Her face was waxy white, whiter than even her hair. Her eyes were closed, but her mouth open. She was also frozen nearly through.

Back in the truck, we speculated about what had happened to the woman. Only now, none of the possibilities was good. “It’s hard to know which came first, the fracture or the fall,” Darryl said. We both hoped out loud that she had gone quickly, but we both knew she probably hadn’t. We fell silent, needing the radio to spark us back to life.

IN SOME WAYS, the human body is a simple machine: Air needs to go in and out, and blood needs to go around and around. Anything that interrupts those two processes is bad and must be corrected quickly. I was told again and again to remember the ABCs: airway, breathing, circulation. That’s the essence of emergency medicine. The problem is, there are hundreds of reasons why the ABCs stop working.

Take the heart. It’s a pump. A heart attack stops it from pumping, which means blood isn’t carrying oxygen to the brain, which means the brain dies, and the brain can’t repair itself or be brought back to life. It’s pretty simple math. But there are several types of cardiac arrest, and each needs to be treated differently. Some cause the heart to flat-line, like we’ve all seen on TV. We’ve also seen the TV doctors shock a flat-lining patient with paddles, but that’s not the way it works. In reality, the paddles are used when someone’s heart is beating too fast or fibrillating and needs to be shocked into a normal rhythm. CPR won’t restart a heart, either. CPR saves lives because pumping on someone’s chest will generate enough blood flow to keep the brain alive until help arrives. But only seriously toxic medications such as epinephrine, atropine, and dopamine will coax a chugging heart to start beating properly again.

The drugs were in the big blue bag. It’s the portable pharmacy in the portable emergency room, and it came in with us on every call. Before my first shift, I worked my way through the blue bag and a few others with a paramedic named Suzanne Noël. It was impossible to cover everything that might happen on a given shift—broken bones, strokes, childbirth, heart failure, gunshot wounds. The job requires a free kind of spirit, and like most paramedics I met, Suzanne was bright-eyed and quick to smile.

It was one of the great lessons of the truck. I expected to find a bunch of burnouts dragging through the graveyard shift. But paramedics are a surprisingly sunny bunch. They understand that it’s all so much randomness. Like a passenger who walks away from a fatal highway accident, they know the out-of-body feeling that follows the cheating of death, the feeling that every day between that day and their last will be a gift that so easily could have gone unopened.

THE CALLS NEVER let up, and they were never the same thing twice. Darryl has answered thousands of calls in his career. Some have been burned into his memory by the noise and blood. I learned soon enough that certain routine calls could, for whatever reason, keep me awake for hours.

The call I remember most came on my final shift. We were at an asthma call on a relatively slow Monday morning when we heard a Code 4 VSA crackle: an old man found by his son on his living-room floor. Darryl and I hopped into the truck and began pushing through the awakening streets. I remembered what Darryl had told me about early-morning VSA calls, and I reached again for the blue nitrile gloves.

The GPS brought us to a stretch of attached homes, small and a little run-down. Another paramedic team, Marc and Pierre-Paul, had just beaten us to the address. The man’s son was at the open door, standing in the cold. Inside, the house was still dark, the curtains drawn, but it smelled like sickness—like vinegar, and urine, plus dog kibble, plus cheese. It hits you as soon as you walk through the door.

He was stretched out on the brown carpet. There were lots of certificates and awards on the walls. There were some new ones on the couch, framed but waiting to be hung—won by his children, maybe grandchildren. The man was barefoot, shirtless, and cold to the touch. He had been there for a while. He had crept downstairs in the middle of the night for a glass of water or to take a leak and here he was, stopped in his tracks. He looked Code 5.

Yet suddenly, a pulse. Marc and Pierre-Paul had poured the epinephrine, atropine, and dopamine into him, and now a heart that wasn’t really beating had started up again, however faintly. Trauma patients are rushed to the hospital, but every other patient has to be stabilized before transport. So we kept working on the man, watched over our shoulders by his son.

The defibrillator was fired up, the ECG leads attached to the old man’s chest and—sure as hell, beep beep beep. Now the blood was going around, but the air still wasn’t going in and out, so we worked an intubation tube down his throat. A bag valve was attached to the tube. It looks like a clear plastic football and has to be squeezed manually every four or five seconds to push in the air. It’s a strange sensation, knowing the only thing keeping a man alive is your blue hands and a piece of plastic.

At last the old man was not only alive but stable. We covered him with a blanket and moved him into the ambulance, still squeezing the football, still watched by the son. We worked all the way to the hospital, shouting over the sirens, and we worked as we wheeled him into the operating room, where the doctors were waiting. We gave the old man to them, and we went outside and shivered for a second before we went to the next call.

I came home after, and I was supercharged. My wife asked me what we had done, and I told her. We turned a man’s heart back into a pump and his lungs back into oxygen tanks. He should have been another body on another floor, but instead we watched him turn from white to pink in front of us, and then we watched some very small things happen, the things my time in the truck taught me never to take for granted: He swallowed, he turned his head, and then finally he opened his eyes and looked straight at me. His eyes were blue, like mine, and they were wet in the bright light in the back of the truck. And then, talking to my wife, my eyes were wet, too. I am a father and a son, and that day, we had given a son back his father.

“Today we saved a life,” I said.

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