Caleb Scharf discusses Earth’s place in the cosmos; Karlheinz Meier describes his quest to simulate the human brain
A patient lies motionless on an operating table at Yale-New Haven Hospital in Connecticut. His heart is completely still. He’s being kept alive by a heart-lung machine that pumps blood through his body.
“Turn the pump off,” says surgeon John Elefteriades. At that moment, monitors around the theatre flatline. The 50-year-old patient has no pulse and is showing no signs of brain activity. He is dead. Everything is going as Elefteriades planned. On a wall, facing the operating table, are two large digital clocks. One is stopped at 11.25am, the very moment the patient dies, while the other continues to run. Despite the patient’s apparent demise, the surgical team continues to work, completely unphased by what’s just happened. And now the atmosphere is getting decidedly chilly – in a very literal sense. In fact, it’s getting so cold that nurses pull sterile smocks over their scrubs to keep themselves warm as the temperature in the room falls.
The patient’s head is also wrapped in bandages and then covered in ice. By anyone’s standards, deliberately stopping a patient’s circulation as he lies on the operating table is a pretty drastic course of action. But it’s necessary. The patient has an aortic aneurysm. The aorta is the vital vessel that carries blood away from the heart before it moves throughout the body, providing the tissues with oxygen. Usually, it’s the width of a garden hose. In our patient, it’s swelled to the size of a tennis ball. In such a worryingly stretched state, it’s weak and vulnerable. Without treatment, the bulging aorta could burst open at any minute and the patient could die almost instantly.
The first part of the surgery was simple; simple in heart surgery terms that is. The aneurism was caused by a defective heart valve. “Do you know who first drew one of these?” Elefteriades asks, pointing out the faulty valve. “Leonardo da Vinci.” He replaces the defective tissue with an animal valve.
Clamps stopped the flow of blood to the heart itself, and a heart-lung machine pumped oxygenated blood throughout the rest of the body. But the anatomy of the aortic arch, where this aneurysm is located, makes it impossible to separate it from the circulatory system with clamps. So there’s only one way Elefteriades can do the necessary plumbing work and replace the dodgy pipework: shut off the circulation entirely. And that’s where all that ice comes in.
Usually, when the brain is starved of oxygen, cells start to die within four minutes. After five minutes, there’s a good chance of permanent brain damage. Minutes later, the brain will be so damaged that death is a real possibility. But Elefteraides plans to keep his patient ‘dead’ for at least 20 minutes, if not longer. In fact, he’s confident he’s got up to an hour to do his work. And it’s all down to the cooling – cooling from the chilly room, but mostly from the heart-lung machine. Before it was switched off, bags of ice had been loaded into its heat exchanger to cool the blood.
As the patient’s body temperature drops from around 37°C to just 19°C, the chemical processes in his brain are slowed. They’re slowed so much that the brain cells can be left without oxygen for a long time – long enough for the surgeon to do his work. Lying on an operating table in the middle of a high-tech operating theatre, our patient has gone into hibernation. What stands Elefteraides out from the surgical crowd is the way he does this operation.
Many surgeons supply the brain with blood during the procedure – cerebral perfusion in surgical parlance. But Elefteriades cuts circulation to the brain entirely, saying there are problems maintaining the exact flow of blood that’s required, so the brain could swell dangerously. He says cooling the brain protects it just as well as pumping blood around it and he’s done extensive studies to prove it.
The technique Elefteraides is using is called Deep Hypothermic Circulatory Arrest (DHCA) and during it the patients are clinically dead – they have stopped breathing and don’t have a circulation. During their trip to the other side, some patients even have the classic near-death experiences of seeing light-filled tunnels and departed relatives. “In a lot of theatres, DHCA is a time of high anxiety,” says Elefteriades as he cuts away the damaged tissue. “But we do it every day. It’s a very controlled procedure.” He’s right, there are no panicked orders or anxious glances here. “It’s the first 15 minutes,” an assistant announces at 11.40am. Elefteriades has removed a piece of stretched aortic tissue about twice the size of a credit card. “We’d have had to leave that behind [without the DCHA],” he says. At 11.46am, Elefteriades calls across the theatre to the perfusionist managing the heart-lung machine. “Now, Sam, I’d like you to start a very, very small flow. Very slow.” The surgeon is not asking for circulation to resume. He wants merely a trickle of blood to refill the aorta as he prepares to finish his work.
At 11.52am, Elefteriades asks for the heart-lung machine to be restarted. Almost immediately, the patient’s lungs start to move. Warm air is blown around the patient’s head and legs, and the heart-lung machine’s heat exchanger that was filled with ice earlier is now gradually warming the blood. Blood contains protein that will solidify if heated too rapidly, creating the equivalent of scrambled eggs in the veins. The slow pace of the warming is actually hard on the surgical team, who’ve spent the past half hour working hard. “It’s very difficult for us to make that transition,” says Elefteriades, finally stepping back from the patient for a moment.
Eventually, the patient’s heart begins to beat independently – he’s back after being in suspended animation for 27 minutes. “It’s a good thing,” the surgeon says as he looks down at the beating heart. He laces the patient’s sternum together with wires and goes to record his observations in the patient’s chart. In just a few hours, the patient is up and walking around the hospital’s intensive care unit chatting with his nurses. Later, sitting on his bed, he recounts his experience. “I woke up totally aware – unfortunately,” he quips, remembering the sore throat he got from his breathing tube. “I feel great,” he says, relieved. But doesn’t hesitate to call his experience a “high-anxiety” procedure. Our patient’s memories stopped as the anaesthesia took effect and resumed when he awoke – there’s no near-death experience here. Still just hours after lying in an operating theatre dead, he knows he is a 50-year-old stock analyst from Connecticut. He knows the code to his voicemail. And, thankfully, he knows the concerned woman at his bedside is his wife.
“Yes, he’s the same guy,” she says, smiling at him over a cup of coffee. It’s what Elefteriades expected, having seen so many patients thrive after the procedure. Take Dr Daniel Slatkin. Slatkin knows death, having spent his career performing autopsies. The 75-year-old was in DHCA for 29 minutes in 2005 while Elefteriades operated on him. “I was dead,” says Slatkin. “Although dead is a misnomer in my case. I was no more dead than a hibernating squirrel.”
Reminded that hibernating animals still have a circulation and continue to breathe, albeit at a very reduced rate, he sticks by his conclusion. The deep chill he experienced wasn’t a death because it wasn’t “irreversible,” he says. Clearly brain damage is the biggest risk of stopping the flow of blood to a patient’s head. But Elefteriades, a professor at Yale School of Medicine, has studied a group of his own patients who’d been through DHCA. He singled out people with intellectually demanding jobs – a CEO, several doctors, an artist and so forth – and looked for subtle changes to their cognitive ability following their excursions to the other side. He didn’t find any problems.
In fact, the study showed a slight improvement in intellectual tasks, though not enough to be statistically significant. “Our residents joke that they’re smarter when they’re done than when we started,” says Elefteriades. “But why do these patients do so well after I’ve wiped their hard drives?” asks Elefteriades. The preservation of their memories, personalities and abilities suggests to him that these essential, defining elements of our selves are ‘hard-wired’ in the brain. If medicine could extend the period people can stay in deep hypothermia while protecting that ‘wiring’, the applications would be astounding – from buying time for patients awaiting organ donation to preventing fatal blood loss on the battlefield.
Elefteriades believes deep hypothermia promises dramatic changes to medicine in the future. “There may be vistas there that we haven’t realised,” he says. “It changes the whole concept of death.”
Colleen Shaddox is a freelance journalist based in the US