The glow on the screen was unmistakable.
It showed a green dye injected into Jim Harrington's bloodstream flowing through the vessels in his right hand, signaling success for the surgery to reattach his thumb, nearly severed in a car accident.
It was a relief for Harrington, whose left hand was disabled earlier from a stroke, and for doctors, who felt confident enough in the tissue's health that they discharged him after one night in the hospital.
"I told the doctors I really needed to keep this thumb," said the 51-year-old from Milton, Del. "I'm not a doctor, but even I could see right away there was blood flow."
Doctors have used the real-time dye tracking technology for decades to show proper circulation, mostly during heart and eye procedures, and more recently in breast reconstruction and other plastic surgery. Now researchers at MedStar Union Memorial Hospital's Curtis National Hand Center want to show it can replace less sensitive, or more expensive and potentially harmful, diagnostic tools in working with hands damaged by accident or extreme cold.
Many hospitals already have the machinery to perform what is known as indocyanine green, or ICG, laser angiography in their operating rooms, and Union Memorial doctors said it would be easy to wheel it into emergency rooms or a doctor's office when patients arrive with damaged hands.
ICG images and software analysis could offer doctors a better idea whether blood flow is cut off in fingers and thumbs than a clinical exam or a Doppler test using sound waves, or from imaging that uses contrast dye that could damage the kidneys and expose patients to higher radiation doses.
The green ICG dye is cheap and believed to be safe for most people, largely dissipating from the body in about five minutes, and it quickly and easily glows when held up to a camera attached to the angiography machine, said Dr. Chris Forthman, Harrington's hand surgeon.
Better diagnostic information from the technology could mean less waiting and guesswork, reduced patient harm and cost, and maybe even fewer amputations, he said.
For example, "with frostbite, it is tough to know what tissue will live or die. We usually take a wait-and-see approach," Forthman said. "With this technology, we'd probably know long before the body would tell us."
When someone has frostbite, blood flow to fingers, toes, noses and ears is reduced when they are frozen, but they can recover fully if the vessels aren't damaged. Severe frostbite can lead to amputation.
Harrington and about 20 other patients with trauma and disease are being studied at Union Memorial to determine the best candidates for the technology. Patients will return after one and two weeks and again after two months to allow doctors to track their blood flow.
No cases of frostbite have been included in the study so far, mainly because there aren't many in the region. So far this winter, 31 people have gone to emergency departments in Baltimore City complaining of possible frostbite, the same as all of last winter and many times the complaints in the previous three, according to the city health department.
There are, however, many more cases of Raynaud's phenomenon, a cold-related disorder in which spasms restrict blood flow to fingers, toes and other extremities. The Raynaud's Association reports it affects 28 million Americans.
And the cold will continue this week as temperatures are forecast to dip into the 20s on Thursday with lows in the teens Thursday night and single digits on Friday night. The city declared a Code Blue alert through Saturday, expanding homeless services.
Doctors at other hospitals locally and across the country say they are interested in the study's results. However, they cautioned, the images may not provide all the answers, particularly with frostbite.
The body's reaction is often unpredictable and early images may not show what tissue will ultimately die or regenerate, said Dr. Kurtis Kim, a vascular surgeon at Mercy Medical Center.
Also, it's not clear exactly how much blood flow is needed to stave off complications such as extreme cold sensitivity, healing problems and a repeat of frostbite, said Dr. Jaimie Shores, clinical director of the hand/arm transplant program at the Johns Hopkins Comprehensive Transplant Center.
He said Hopkins does not regularly use such imaging now in replanting fingers or assessing damage from cold. While the technology is FDA-approved, it's not marketed for this and insurance companies often won't cover uses not specifically studied for effectiveness and safety. The machine is also expensive and not all hospitals own one.
But there could be clinical and financial value in such a test if it offers quantitative value, said Shores, also an assistant professor of plastic and reconstructive surgery in Hopkins' school of medicine.
"It's tough to gather enough cases where we can make meaningful conclusions from the data," he said. "There will be benefit from the Curtis Hand Center studying this, even if we don't end up changing treatments."
Dr. Vishal D. Thanik, a hand surgeon and assistant professor of plastic surgery at NYU Langone Medical Center, agreed the technology could be valuable in regularly assessing progress, specifically with replants and Raynaud's, without fear of harm to patients or even having to move them because the machine is portable.
"There's a lot of Raynaud's, and often the efficacy of treatments is based on symptoms," he said. "Invasive tests such as angiography aren't used a lot. But you could do this relatively frequently. And there would be no downside."
For his part, Harrington is glad to be part of the investigation.
Two months ago he was a passenger in a car driven by his mother, who failed to negotiate an odd turn and crashed into another car. He instinctively reached for the handle above the window as the air bag curtain deployed downward.
The bag hit his thumb like a gunshot. The Delaware hospital where he was taken wrapped his hand and sent him two hours by ambulance to Union Memorial, one of the largest hand centers in the country.
Doctors detected no circulation with the Doppler test and assumed all vessels in Harrington's thumb were severed. Surgeons spent more than seven hours reattaching bone, muscle and tendons and grafting a piece of vein from his arm into the thumb.
The next day, the doctors used the imaging to check blood flow from the new vein, but discovered another vessel had not been completely severed. Had they used the imaging before the surgery, they might not have done the graft, said Dr. Helen Hui-Chou, a hand surgery fellow who initiated the study.
After both veins glowed on the screen, Harrington was discharged, rather than waiting the standard five days to ensure circulation continued.
At his last follow-up two months after surgery, Harrington watched the screen light up even brighter. He said he was glad that he'd soon be stringing beads with his 4-year-old daughter.
"He's on his way to recovery and full use of his thumb," Hui-Chou said.