Louisville, Kentucky (CNN)Ben Neal's laptop lights up with emergency calls. A paramedic and supervisor with Louisville Metro Emergency Medical Services, Neal activates the siren on his silver SUV and races off, weaving his way through Sunday traffic.
Someone is in cardiac arrest and needs immediate attention.
Neal pulls into a neighborhood dotted with family homes and playsets in the backyards. A church sits on the corner. The sign out front reads "Heroin is a Sickness, and Jesus is the Cure."
The call, it turns out, isn't a cardiac arrest but another overdose -- part of the growing opioid epidemic taking hold of this Kentucky city of 766,000 people. And this has been an especially busy few days already, with 118 overdose calls over a 72-hour period beginning Thursday.
Neal gets out of his truck and points to a group of people standing on the porch of a home, talking to EMS and police officers. First responders already administered a dose of naloxone, the opioid blocker known for reviving people on the brink of death.
When someone is saved from an overdose, authorities offer to take them to a hospital. It can get tense. Some run off, fearing arrest. Others get violent. Today, the person simply refuses. The ambulance leaves without a patient.
Neal shakes his head.
"It's one of the ones that's going to stick in the back of your mind," Neal says. "Granted, I can't take them against their will, but I'm leaving them in that same environment that they literally almost died in."
CNN rode along with Neal for three hours, from 4 to 7 p.m. Sunday, to get a glimpse of what first responders are facing amid this wave of overdoses. It's grueling, exhausting work that ensnares the city's emergency crews. For every overdose, police, fire and EMS crews respond.
During the three hours CNN visited, Neal's crews responded to nine overdoses, many of them probably caused by heroin. When he arrived at one scene and began talking with firefighters, there was suddenly another radio call: another overdose.
The relentless pace of responding to the opioid crisis both exhausts and gives a sense of purpose to first responders like Neal.
"You hear some of the stories of, 'Man, we used all our naloxone. We ran out of our bag valve masks. We've had so many overdoses, we had to go back to the station and pick up more,' " Neal says. "It does take a toll."
By the end of Sunday, Louisville emergency crews responded to 151 calls about overdoses over a four-day span, a blistering pace that stretched and strained resources. Not every call was necessarily a heroin overdose, authorities said. Some could've involved prescription drugs, alcohol, narcotics or a combination.
One person using heroin was killed while riding in a car that crashed, authorities said; the driver of the car had used heroin but survived.
The overdoses seemingly happened everywhere. Homes. Restaurants. Parking lots. People slumped in cars at stop lights.
"It can be anywhere," says Jody Meiman, the executive director for Louisville Metro EMS. "Unfortunately, we've had to respond to all those locations."
Armed with vials of naloxone, the city's first responders revive person after person, oftentimes multiple people in an hour. And, Neal says, he's seeing the need to use increased doses. EMS workers normally give one dose to an overdosing patient -- but, he says, one patient was recently administered as many as seven doses of the antidote.
"That could mean people's tolerance levels are going up or, you know, the heroin itself is becoming more and more potent," Neal says.
In one 911 call, the caller says a 40-year-old man has overdosed on heroin. The dispatcher calmly tells the caller to create an airway so he can breathe better. "Listen to me. Here's what I want you to do," the dispatcher says. "I want you to take one hand and put it on his forehead, the other hand under his neck and tilt his head back. OK?"
The caller says the man is breathing better, but within moments, everything changes. "He's blue. He's getting a bluish color to him," the caller said. "He's snorting. He's not really breathing."
The dispatcher reassures him crews are on the way.
Two weeks ago, Louisville Mayor Greg Fischer sought to reassure the public in his state of the city address that the city is fighting the epidemic, saying that 150 more police officers are being hired and that the city is working with federal authorities to get "heroin dealers off our streets."
Neal and Meiman said heroin overdoses began increasing about two years ago, but there's been a major upswing in the past two months. In January, EMS crews responded to an average of 22 overdose calls a day -- 33% more than this time last year.
The situation appears to be worsening. The four-day spike that began Thursday amounted to an average of 38 overdoses a day, almost double last month's average.
"We saw a big push to eliminate prescription opioids just a couple years ago," Meiman says. "Where that was a huge success, now people are starting to get addicted to heroin. It's easy to get. It's cheap."
A lack of detox beds only complicates the matter. "There's not enough places for people to go right now to get the help that they need," Meiman adds.
Not far from the parking lot where Louisville Metro EMS ambulances park is a public health building. For a few hours on Monday, a steady stream of people walk into a conference room and sit down in front of Sonia Rudolph for instructions on how to use naloxone.
Rudolph is a nurse practitioner with a 22-year-old son who overdosed four times last January but is clean now. His mother gives back by sharing what she's learned as a volunteer with the Kentucky Harm Reduction Coalition.
"The one thing I want families to know when they come in is that you are not alone, that there are those of us out here that are going through what you're going through," Rudolph says. "Knowing this training and having the ability to help in emergency situations does give you a little bit more of a sense of control over the situation. It gives you some relief in knowing that if this happens and you're there, you can at least keep them alive until EMS can get there."
Dozens in attendance nod along as she shows them how to give rescue breaths before giving the naloxone, which looks like nasal spray. There's even a more expensive version of the drug in packaging that talks you through each step.
Rudolph looks choked up as she recites one fact: It takes only four minutes without oxygen to the brain for someone to start dying. You can see that she's thinking of her own son's multiple overdoses.
"I know that no ambulance can get anywhere in four minutes, even the best ones," Rudolph says.
Not everyone in these groups has a family member who uses heroin. Some are active users. Others don't know anyone who uses heroin but want to be prepared should they ever come across an overdose.
Kristina Blizzard comes to the training session with her teenage son. They both volunteer with a local charity that feeds those in need. Sometimes, she says, the people who seek their help struggle with opioid addiction.
"I would hate to not have myself prepared in case we came across a situation where we could make a difference," Blizzard says.
This day, volunteers with the Kentucky Harm Reduction Coalition manage to train and hand out naloxone kits to 80 people. One member of the group, Russ Read, says he often hears criticism that handing out naloxone enables more heroin use. His response is terse.
"We are enablers," Read declares. "We enable people to live another day."