Some of the inhaled anesthetics that made modern surgery possible may soon become weapons to combat viral and bacterial infections in the lungs, like influenza and pneumonia.
New experiments have added to the evidence that certain so-called “volatile” anesthetics, like nitrous oxide and halothane, have powerful effects on the immune system. Those anesthetics have been in use for more than a century and are common in modern operating rooms.
The findings suggest that volatile anesthetics may someday be helpful against seasonal and pandemic flu, particularly when there are flu vaccine shortages or limitations.
Study co-leader Krishnan Chakravarthy says:
“A therapy based on these inhaled drugs may help deal with new viral and bacterial strains that are resistant to conventional vaccines and treatments and could be a game changer in terms of our preparedness for future pandemics and seasonal flu outbreaks, because it’s focusing on host immunity. We hope our study opens the door to the development of new drugs and therapies that could change the infectious disease landscape.”
Mice and the Flu
The research team built experiments on previous research in which children with upper viral respiratory tract infections who were exposed to halothane during minor surgical procedures had significantly fewer respiratory symptoms and shorter illnesses than patients who were not.
To examine just how some inhaled anesthetic drugs affect viral and bacterial infections, Chakravarthy, a faculty member at the Johns Hopkins University Institute for NanoBioTechnology and a resident physician in anesthesiology, and Paul Knight, professor of anesthesiology at the University at Buffalo, exposed mice to both influenza virus and Streptococcus pneumoniae bacteria.
Giving the animals volatile anesthetics, such as halothane, led to decreased bacterial burden and lung injury following infection, the researchers discovered. The anesthetics augmented the anti-bacterial immune response after influenza viral infection by blocking chemical signaling that involves type I interferon, a group of proteins that help regulate the activity of the immune system.
450-fold Fewer Viable Bacteria
The researchers found that animals exposed to halothane had 450-fold fewer viable bacteria compared with those who were not. Astoundingly, the treated mice appeared as if they had never even been infected with influenza virus.
Symptoms such as involuntary bristling of hairs of the skin, hunched posture, impaired gait, labored breathing, lethargy, and major weight loss were significantly less in infected mice exposed to halothane.
“Our study is giving us more information about how volatile anesthetics work with respect to the immune system,” Chakravarthy says. “Given that these drugs are the most common anesthetics used in the operating room, there is a serious need to understand how they work and how we can use their immune effects to our advantage.”
Halothane Modulates the Type I Interferon Response to Influenza and Minimizes the Risk of Secondary Bacterial Pneumonia through Maintenance of Neutrophil Recruitment in an Animal Model
Brian A. MacDonald, B.S.; Krishnan V. Chakravarthy, M.D., Ph.D.; Bruce A. Davidson, Ph.D.; Barbara A. Mullan, M.S.; Ravi Alluri, M.D.; Anders P. Hakansson, Ph.D.; Paul R. Knight, M.D., Ph.D.
Anesthesiology. 2015; 123(3):590-602. doi: 10.1097/ALN.0000000000000766