Media Releases

University of Toronto researchers discover why anesthetics cause prolonged memory loss

November 3, 2014

Toron­to, ON — Researchers at the Uni­ver­si­ty of Toronto’s Temer­ty Temer­ty Fac­ul­ty of Med­i­cine have shown why anes­thet­ics can cause long-term mem­o­ry loss, a dis­cov­ery that can have seri­ous impli­ca­tions for post-oper­a­tive patients.

Until now, sci­en­tists haven’t under­stood why about a third of patients who under­go anes­the­sia and surgery expe­ri­ence some kind of cog­ni­tive impairment—such as mem­o­ry loss—at hos­pi­tal dis­charge. One-tenth of patients still suf­fer cog­ni­tive impair­ments three months lat­er.

Anes­thet­ics acti­vate mem­o­ry-loss recep­tors in the brain, ensur­ing that patients don’t remem­ber trau­mat­ic events dur­ing surgery. Pro­fes­sor Bev­er­ley Ors­er and her team found that the activ­i­ty of mem­o­ry loss recep­tors remains high long after the drugs have left the patient’s sys­tem, some­times for days on end.

Ani­mal stud­ies showed this chain reac­tion has long-term effects on the per­for­mance of mem­o­ry-relat­ed tasks.

“Patients — and even many doc­tors — think anes­thet­ics don’t have long-term con­se­quences. Our research shows that our fun­da­men­tal assump­tion about how these drugs work is wrong,” says Ors­er, a Pro­fes­sor in the Depart­ments of Anes­the­sia and Phys­i­ol­o­gy, and anes­the­si­ol­o­gist at Sun­ny­brook Health Sci­ences Cen­tre.

In the study — led by PhD can­di­date Agnes Zurek — the team gave healthy male mice a low dose of anes­thet­ic for just 20 min­utes and found that recep­tor activ­i­ty was increased for a week after­wards. These results sug­gest the same effect can impact a patient’s learn­ing and mem­o­ry dur­ing a time when they are receiv­ing crit­i­cal infor­ma­tion about their care.

“There’s a lot going on after surgery, which can alter our abil­i­ty to think clear­ly. Loss of sleep, new envi­ron­ments and med­ica­tions can all impact a patient’s men­tal func­tion. Anes­thet­ics like­ly com­pound these issues,” says Ors­er.

She rec­om­mends physi­cians and fam­i­ly mem­bers care­ful­ly mon­i­tor patients after surgery for any signs of mem­o­ry loss. “Patients should write every­thing down or have a sec­ond pair of ears with them after surgery. For high-risk groups, physi­cians need to inform patients about these pos­si­ble side effects and help man­age the impact on recov­ery and over­all health,” says Ors­er.

The like­li­hood of a patient expe­ri­enc­ing cog­ni­tive impair­ment depends on their age, health, type of surgery and the anes­thet­ic, with chances increas­ing for more intri­cate pro­ce­dures. The inci­dence is high­est in the elder­ly or those under­go­ing major surgery such as car­diopul­monary bypass.

“Anes­thet­ics don’t put you to sleep—they induce a phar­ma­co­log­i­cal coma. We shouldn’t take these drugs light­ly,” Prof. Ors­er cau­tions.

Ors­er and her team are look­ing at drugs that can stop the recep­tors and restore mem­o­ry loss. While they are still in the ear­ly stages of research, they say some of the drugs show very promis­ing results in ani­mal stud­ies.

The study was pub­lished today in theJour­nal of Clin­i­cal Inves­ti­ga­tion.


For more infor­ma­tion, please con­tact:

Hei­di Singer
Com­mu­ni­ca­tions and Media Rela­tions Spe­cial­ist
Office of Strat­e­gy, Com­mu­ni­ca­tions and Exter­nal Rela­tions
Temer­ty Temer­ty Fac­ul­ty of Med­i­cine
Uni­ver­si­ty of Toron­to
416 978 5811