Scientists in Massachusetts, Italy, and elsewhere are experimenting with a familiar medical treatment for the new problem of covid-19. They’ve begun clinical trials meant to find out whether inhaled nitric oxide can save people who are severely sick from the new coronavirus. This treatment might even be used preventatively to keep health care workers infection-free.
Nitric oxide, or NO, is a key part of our biology (and not to be confused with nitrous oxide, aka N2O or laughing gas). It helps our blood vessels dilate, speeding up blood and oxygen flow around the body. For decades, nitric oxide has also been repurposed by doctors to relieve blood pressure in the pulmonary arteries of oxygen-deprived patients whose lungs have failed. These clotted arteries make it harder for the lungs to process oxygen, even when it’s being supplied by a ventilator. This use of nitric oxide was first tested out in blue-faced newborns in the 1990s, becoming an FDA-approved therapy in 1999; it’s since been expanded to other groups of patients.
“About a half-million Americans have breathed in NO. Mainly adults with cardiac surgery and various things and, of course, 30,000 babies a year,” Warren Zapol, the emeritus anesthetist-in-chief at Massachusetts General Hospital and a professor at Harvard Medical School, told Gizmodo by phone this week.
Many people who contract covid-19 suffer no more than a bad cold, but severe cases can develop acute respiratory distress syndrome (ARDS), a frightening and deadly condition. The lungs of people with ARDS become flooded with leaked bodily fluid, cutting off their oxygen supply and effectively drowning them. Though interventions like invasive ventilation can save someone with ARDS, it remains a grim prognosis, as septic shock and organ failure often follow. ARDS isn’t just risky for covid-19 patients, either—the needed life-saving interventions can expose health care workers to concentrated, aerosolised doses of virus from a patient.
“This is primarily, first, a lung injury. We all know that. But if you don’t stop it, it will get to your heart, your liver, the rest of your organs, and kill you,” said Zapol.
Nitric oxide is already used as a “rescue therapy” for ARDS cases where people are unable to get enough oxygen through a ventilator. So Zapol and his colleagues reason that NO could be used for difficult covid-19 cases, too. But it’s not just the crucial boost to lung function that has Zapol and his colleagues interested in this treatment.
Nearly two decades ago, scientists in China found evidence that suggested the gas itself could kill or inhibit the growth of the SARS coronavirus in patients, while other scientists found the same pattern in the lab. Because covid-19 is caused by a coronavirus closely related to SARS, called appropriately SARS-COV-2, they’re hoping this same trick will work against it.
Zapol and colleagues have begun at least two randomised, controlled clinical trials at Massachusetts General Hospital. One will involve covid-19 patients already dealing with severe respiratory distress; the other will involve patients with mild to moderate covid-19. In both trials, the hope is that nitric oxide can stop things from getting worse.
Another trial they hope to get approved and underway would actually test whether nitric oxide can help protect the medical staff treating these patients. Zapol’s team theorizes that you can dose health care workers with nitric oxide before and after their shifts so that the virus has a harder time infecting them. Though they would temporarily have lower oxygen levels as a result, in theory they should be able to function and work normally.
“I hate seeing doctors and nurses becoming covid-19 positive. I hate it,” Zapol said. “So we’ll hopefully see if we can prevent health care workers from going positive.”
Any potential treatment for covid-19, no matter how it’s useful it’s been for other conditions, will have to go through the ringer of clinical trials before it should be widely used. But Zapol’s team is already working with researchers in Italy and China to test out nitric oxide in patients there, as part of a longstanding collaboration between the groups. So if it does work, we’ll have more than one line of evidence to prove it.