Hopefully dispelling the myth that surgical anesthesia won’t do permanent damage to young brains, a new study from Cornell University and the University of California, San Diego, suggests any molecular breakdown between the brain’s neurons is purely temporary in nature.
Each year, an estimated six million kids undergo surgery in the United States, including one and a half million infants, requiring general anesthesia. While the evidence is typically seen as mixed regarding the potential for harm in the brain, the latest researchers suggest most cases can be traced back to other causes, such as the surgery itself, post-op care, medications, stress, or any combination of the four.
Anesthesia, they are finding, plays a far smaller, if negligible, role in causing young brains to endure persistent trauma. "Because the clinical studies haven't been completed, preclinical studies, such as ours, are needed to define the effects of various anesthetics on brain structure and function,” said Shelley Halpain, co-researcher and professor of biology at UC San Diego, in a statement.
The team relied on a once-popular anesthetic called isoflurane. Unfortunately, even the most sophisticated technology still can’t examine the brain’s natural processes on a molecular level. Researching rodent brains is only marginally less difficult. Instead, they used a cultured sample of rats’ brain cells, administering the anesthesia and closely observing how long it took to shrink the connections between axons and dendrites — two structures involved in sending and receiving neural signals. More important, they observed how long these structures took to reestablish.
"We observed detectable decreases in dendritic spine numbers and shape within as little as 10 minutes," said Halpain, referring to the expected decrease in neuronal connections. "However this spine loss and shrinkage was reversible after the anesthetic was washed out of the culture."
Halpain and her colleagues concede the findings aren’t wholly conclusive, at least not in the sense that all questions have been answered. Translating cultured tests into live rodent brains is already hard enough, let alone making the leap from cultured tests to live human cognition. The study acts as more of a proof of principle, showing that isoflurane acts as it’s intended for clinical use.
"Our study was reassuring in the sense that the effects are not irreversible and this fits in with known clinical effects," said Hugh Hemmings Jr., chair of anesthesiology at Weill Cornell and the study's co-senior author.
Other anesthetics, such as sevoflurane, desflurane, and the commonly used intravenous drug, propofol, must also be tested before the team can draw hardline conclusions. In future, follow-up tests the team will probe cell cultures with these alternative anesthetics. By and large, the study may have produced more questions than answers, Hemmings said. "Connecting what we found to the cognitive effects of isoflurane will require much more detailed analysis."
Source: Platholi J, Herold K, Hemmings H, Halpain S. Isoflurane Reversibly Destabilizes Hippocampal Dendritic Spines by an Actin-Dependent Mechanism. PLOS ONE. 2014.