- Researchers reported a novel "total artificial lung" approach to extracorporeal support for a patient who needed bilateral lung transplantation due to infection.
- Similar cases have been reported with different methodology for handling hemodynamic load.
- This case involved use of a flow-adaptive shunt between the right pulmonary artery and right atrium to act as an effective surrogate for the lost pulmonary vascular capacitance.
In a patient whose lungs liquefied due to infection, a novel "total artificial lung" approach provided extracorporeal support until donor organs became available for bilateral lung transplantation, researchers reported.
The 33-year-old man developed acute respiratory distress syndrome (ARDS) triggered by the flu. Over the next 6 weeks, pneumonia caused by carbapenem-resistant Pseudomonas aeruginosa progressively necrotized his lungs.
Despite broad-spectrum antimicrobial therapy, efforts to control the infection source, and full venoarterial extracorporeal membrane oxygenation (ECMO) support, the man repeatedly went into cardiac arrest, "reflecting refractory septic shock and the inability of conventional support to stabilize his cardiopulmonary physiology," Ankit Bharat, MD, of the Canning Thoracic Institute at Northwestern University in Chicago, and colleagues wrote in Med.
"When the infection is so severe that the lungs are melting, they're irrecoverably damaged," Bharat said in a statement.
To allow a chance for survival, that source of infection had to go. Both lungs were removed and the patient switched to ECMO with a flow-adaptive shunt between the right pulmonary artery and right atrium for 48 hours until lungs became available for transplantation.
"In my practice, young patients die almost every week because no one realized that transplantation was an option," Bharat noted.
"Conventionally, lung transplant is reserved for patients who have chronic conditions like interstitial lung disease or cystic fibrosis," he added. "Currently, people think if you get severe ARDS, you keep supporting them and ultimately the lungs will get better."
However, "for severe lung damage caused by respiratory viruses or infections, even in acute settings, a lung transplant can be lifesaving," he said.
At least three other similar cases have previously been published, noted Stephanie Chang, MD, surgical director of lung transplantation at the NYU Langone Transplant Institute in New York City, who was not involved in the study.
"Thankfully, this is a very rare situation, but for these patients who would otherwise die, it's reassuring that there are these techniques ... and that other centers have done this as well," she said. "Centers with experience with ECMO and experience with lung transplant can utilize techniques like this to help save patients' lives and get them to lung transplant."
Bharat and colleagues emphasized the novelty of their approach in addressing the hemodynamics of blood after lung explant.
Conventional ECMO "remains dependent on the capacitance and buffering properties of the pulmonary circulation," they wrote. "After bilateral pneumonectomy, the loss of this large vascular reservoir exposes the right ventricle to abrupt increases in venous return, while outflow obstruction at the level of the pulmonary artery stump predisposes to dangerous pressure elevations."
When patients are in a hyperdynamic septic state, they are especially at risk of right ventricular distension or pulmonary artery stump disruption, they noted.
Their use of a flow-adaptive shunt (a percutaneously placed Protek-Duo cannula) between the right pulmonary artery and right atrium provided an alternative low-resistance pathway for excess right ventricular output, recirculated blood according to pressure differentials, and functioned as an effective surrogate for the lost pulmonary vascular capacitance, they explained.
"We suggest that this is safer than creating a pulmonary artery to left atrial shunt, utilized in a previously [reported publication], which would risk causing systemic embolism," they added.
Although Chang acknowledged that the other published cases didn't use the same strategy to try to recreate pulmonary vascular resistance, "I don't know if it was necessary, because the three other places that published didn't do that and their patients did just fine and took longer than 2 days to make it to transplantation."
The patient in this case survived to 2 years with "excellent" cardiopulmonary function, Bharat and team said.
The explanted lungs showed extensive necrosis and fibrosis with homogeneous immune cell infiltration across all sampled regions, with "widespread collagen deposition that resembled end-stage fibrotic lung disease seen in COVID-19 ARDS," unlike the typical heterogeneous involvement seen in ARDS from which patients can recover, they noted. There were very few alveolar type 2 cells that are needed to regenerate alveolar structures, and molecular signatures matched progressive fibrosis rather than resolution. Tissue architecture showed complete effacement across all analyzed regions.
"For the first time, biologically, we are giving molecular proof that some patients will need a double lung transplant, otherwise they will not survive," Bharat said.
He and his colleagues acknowledged that larger studies are needed to determine if specific transcriptional or spatial signatures can reliably distinguish irreversible injury from potentially recoverable ARDS.
"Such markers could have important clinical implications, as delayed recognition of nonrecoverable lung injury is associated with high mortality and remains a central obstacle to timely transplant referral," they wrote.
Disclosures
The researchers reported support from the NIH.
Chang disclosed no conflicts of interest.
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