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August 03, 2010

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Repeated anesthesia may affect kids’ learning

March 11, 2010
Courtesy University of Gothenburg
and World Science staff

A study with young ro­dents shows re­peat­ed an­es­the­sia wipes out mem­o­ry-forming brain cells, sci­en­tists say.

The re­sults sug­gest chil­dren may al­so suf­fer learn­ing and mem­o­ry im­pair­ments after re­peat­edly be­ing put out of con­scious­ness to un­dergo surg­eries, ac­cord­ing to the re­search­ers. But plen­ty of ex­er­cise may help un­do the dam­age, they not­ed.

Adult an­i­mals weren’t found to suf­fer long-term im­pair­ment from an­es­the­sia.

The stu­dy, from the Uni­vers­ity of Goth­en­burg, Swe­den, is pub­lished in the Jour­nal of Cer­e­bral Blood Flow & Me­tab­o­lism.

Anes­thet­ics are typ­ic­ally ad­min­is­tered to pa­tients by in­hala­t­ion, in­jec­tion or both be­fore sig­nifi­cant sur­geries. Pa­tients then fall asleep, re­lax their mus­cles and feel no pain. Of­ten sev­er­al dif­fer­ent drugs are giv­en at once; they take about 15 to 20 sec­onds to work, de­pend­ing on when the an­es­thet­ic reaches the brain.

“Pe­di­atric anes­thetists have long sus­pected that chil­dren who are anes­thetised re­peat­edly over the course of just a few years may suf­fer from im­paired mem­o­ry and learn­ing,” said Goth­en­burg re­search­er Klas Blom­gren.

His re­search team ac­ci­den­tally disco­vered a link be­tween re­peat­ed an­es­the­sia and loss of key stem cells that ma­ture in­to mem­o­ry-forming cells. The group was stu­dying what hap­pens to stem cells ex­posed to strong mag­net­ic fields, as dur­ing a brain scan. 

It turned out mag­net­ic fields had no tan­gi­ble ef­fects, but re­peat­ed an­es­the­sia did. It “wiped out a large por­tion of the stem cells in the hip­po­cam­pus, an ar­ea of the brain that is im­por­tant for mem­o­ry,” said Blom­gren. “The stem cells in the hip­po­cam­pus can form new nerve and gli­al cells, and the forma­t­ion of nerve cells is con­sid­ered im­por­tant for our mem­o­ry func­tion.” The ef­fect was ev­i­dent only in young rats or mice, pos­sibly be­cause stem cells are more sen­si­tive in an imma­ture brain, he spec­u­lat­ed.

“We have not been able to un­der­stand ex­actly what hap­pens when the stem cells are wiped out,” he added. “We could­n’t see any signs of in­creased cell death, but are spec­u­lat­ing that the stem cells lose their abil­ity to di­vide.”

An­oth­er treat­ment that de­stroys stem cells in the brain is ra­dia­tion therapy, used on can­cer pa­tients. Blom­gren and his re­search team have used an­i­mal stud­ies to show that phys­i­cal ac­ti­vity af­ter ra­dia­tion therapy can re­sult in a great­er num­ber of new stem cells and partly re­place those that have been lost. “What’s more, the new nerve cells seem to work bet­ter in an­i­mals that ex­er­cise. Now that we know this, we can come up with treat­ments,” Blom­gren said.

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A study with young rodents indicates repeated anesthesia wipes out memory-forming brain cells, scientists say. The results suggest children may also suffer memory impairment as a result of repeatedly being put out of consciousness to undergo surgeries, according to the researchers. But plenty of exercise may help undo the damage, they noted. Adult animals weren’t found to suffer long-term impairment from anesthesia. The study, from the University of Gothenburg, Sweden, is published in the Journal of Cerebral Blood Flow & Metabolism. Anesthetics are typically administered to patients by inhalation, injection or both before surgical procedures. Patients then fall asleep, relax their muscles and feel no pain. Often several different drugs are given at once; they take about 15 to 20 seconds to work, depending on when the anaesthetic reaches the brain. “Pediatric anesthetists have long suspected that children who are anesthetised repeatedly over the course of just a few years may suffer from impaired memory and learning,” said Gothenburg researcher Klas Blomgren. His research team accidentally discovered a link between repeated anaesthesia and loss of key stem cells that mature into memory-forming cells. They were studying what happens to stem cells exposed to strong magnetic fields, as during a brain scan. It turned out magnetic fields had no tangible effects, but repeated anaesthesia did. It “wiped out a large portion of the stem cells in the hippocampus, an area of the brain that is important for memory,” said Blomgren. “The stem cells in the hippocampus can form new nerve and glial cells, and the formation of nerve cells is considered important for our memory function.” The effect was evident only in young rats or mice, possibly because stem cells are more sensitive in an immature brain, he speculated. “We have not been able to understand exactly what happens when the stem cells are wiped out,” he added. “We couldn’t see any signs of increased cell death, but are speculating that the stem cells lose their ability to divide.” Another treatment that destroys stem cells in the brain is radiotherapy, used on cancer patients. Blomgren and his research team have previously used animal studies to show that physical activity after radiotherapy can result in a greater number of new stem cells and partly replace those that have been lost. “What’s more, the new nerve cells seem to work better in animals that exercise. Now that we know this, we can come up with treatments,” Blomgren said.