Out of sci-fi and into the OR

Photos: Webb Chappell

by Marty Downs

At first glance it would be easy to mistake Children's Hospital Boston cardiac surgeon Pedro del Nido, MD, for a racecar enthusiast working the controls of an arcade game. A binocular display immerses him in the scene before him and his hands disappear into the maw of the huge console at which he sits. But no thumping arcade music or flashing lights threaten to distract him. The sounds of the operating room are hushed, broken only by occasional subdued question or command, as del Nido concentrates on closing an errant artery in 6-year-old Tessa Greenhalgh's tiny heart—from across the room.

Sitting at the console of the da Vinci robotic surgical system, del Nido views a three-dimensional, magnified display of Tessa's heart. It appears just as clear and present as if he had opened her chest and were standing at her side, but the image is produced by two lenses at the end of a finger-thick wand inserted into Tessa's chest through a small incision. The two controls in his deft grasp operate instruments at the ends of two other wands. Between del Nido and his young patient, 20 feet of cables, half a ton of robot, and a mountain of computer processing power translate his hand and finger movements into the movements of surgical forceps, scalpels and clips inside Tessa's chest. The translation provides an opportunity to scale down the surgeon's movement, if needed, and to filter out the slightest tremor, making the robot even more precise than a surgeon operating directly.

The absolute calm and confidence that del Nido displays in the operating room and with patients is what brought Tessa's parents to Children's. In October 2003, when their nurse practitioner heard a mechanical-sounding murmur in Tessa's neck, she sent them to their local hospital for an evaluation. The cardiologist there diagnosed her with a congenital heart defect called patent ductus arteriosus. An artery that bypasses the undeveloped lungs in fetuses should have closed when she was born, but never did. Her heart was working too hard to recycle blood that should have been on its way to the rest of her body. The doctor recommended a surgery that would have left Tessa with a 10-inch scar and kept her out of school for weeks, so a family friend who is a physician recommended they try Children's for a second opinion. The family left their first visit with del Nido "feeling no doubt" about what the surgeon was capable of, says Tessa's mother Tina Craig. "He was able to put our minds at rest."

That feeling of support followed them through the whole procedure. When Tessa checked in on Monday for her Tuesday morning surgery, nurses brought picture books and took the time to answer every question she had, including the big one, "will I have to get any shots?"

Above, while the main surgeon controls the robot's surgical arms from a console across the room, the other surgeons and operating room nurses are at the patient's bedside, and can view the surgery's progress on a TV monitor.

Reach in and touch
In the late 1980s, minimally invasive surgery became commonplace for many straightforward procedures. The video-endoscope lets surgeons see into the chest or abdomen through a small incision, and similarly inserted long-handled instruments can be used to cut or reposition tissue. Patients are often back at work (or play) in days rather than the weeks it takes to recover from conventional abdominal or chest surgery. But the straight handles and fixed instruments provide little dexterity for the complex work of cardiac reconstruction. Because the instruments pivot where they enter the chest or abdominal wall, moving an instrument to the right requires moving the handle to the left. It takes a little time to adjust to the backwards movements, like learning to steer a boat with a rudder.

The da Vinci system has changed all that. The system's instruments flex in a wrist-like movement near the surgical site, precisely emulating the hand and finger movements of the surgeon at the console, so surgeons can function in the same way they always have, rather than learning to reverse years of training. With more flexibility inside the patient, the tools also let them work in tighter spaces and put less strain on the tissues around the openings.

The next generation
Seeing the system's potential for use with children, del Nido began working with the company and with engineers at Harvard and Boston University to develop the next generation of robotic tools. "We wanted to start with the technology, figure out the problems, then convert it for pediatric use," he says. Del Nido's efforts have already paid off. The instruments originally designed by da Vinci's creator, Intuitive Surgical, are eight millimeters in diameter, which is fine for adults, but often too big for children. So del Nido worked with Intuitive to develop a new set of five-millimeter tools that are much more appropriate for younger patients, and in early 2004 became the first surgeon in the world to use the instruments on a pediatric patient.

Now that some of the technical hurdles have been cleared, del Nido says the smaller instruments are sure to become popular with surgeons who operate on adults. "If the idea is to be minimally invasive," says del Nido, "then the smaller the better." He's also a lead investigator on a $5 million partnership grant from the National Institutes of Health to develop three-dimensional ultrasound technology that will allow surgeons to see inside a beating heart in real time.

Luckily, Tessa's heart could be repaired from the outside, where there is enough space to see and move instruments. Surgery on the valves and muscles inside the heart still requires bypass, in which a machine takes over the work of the heart and lungs while a surgeon works on the still and empty heart. Shutting down the heart and lungs, even for a short time, poses certain risks, including greater chance of clotting and stroke, as well as further injury to the heart itself.

If we can operate inside the chest without opening it up, what's keeping us from working inside a beating heart, wondered del Nido. A lot, it turns out, but that hasn't daunted him or his colleagues on the partnership grant, Pierre Dupont at Boston University and Robert Howe at Harvard's Biorobotics Laboratory. One of the first problems is seeing through the continuous rush of blood in the heart. Three-dimensional ultrasound has been used to image heart valves and other soft tissues for several years, but never in real time. Working with Philips Medical Systems, they were able to speed image processing enough to get a three-dimensional view of a working heart valve at 30 frames per second.

The robotic surgical unit is covered in plastic to ensure sterility. Here the surgeons and nurses are closing the patient's incisions after the operation.

Challenges to spare
Sound waves reflect very differently from metal surfaces than from soft tissue, so del Nido and his colleagues soon found that when they introduced instruments into the ultrasound field, they either distorted the whole image or the instruments just disappeared. Dupont describes the effect like looking at a bright light reflected in a mirror. If you look straight at it, you're blinded, but if it reflects in another direction, you can't see it at all. Dupont's group of graduate students is exploring several approaches to this problem, including using non-metallic instruments or coatings and equipping the instruments with electromagnetic beacons, providing a sort of "you are here" sign in the ultrasound image.

Other challenges include keeping the surgeon oriented within the less-familiar ultrasound view, finding the safest locations to enter the heart and the quickest, simplest ways to close the holes behind them. For fine work, as is needed to repair a mitral valve, surgeons can't work on a constantly moving surface. It's like trying to thread a needle on the heaving deck of a boat. For such situations, the team is devising a way to synchronize heart, image and instruments so the image will appear still, even as the heart beats on.

The new prototypes won't be available next year, or even the year after, but ultimately the efforts will pay off in surgical tools and methods that are truly appropriate for children and even for fetal surgery. Meanwhile even with today's instruments, Tessa was back in school a week to the day after her surgery, far sooner than she would have been just a few years ago.