重口味SM

Two drugs commonly used in heart surgery interfere with a naturally occurring anticonvulsant in the brain, researchers say (photo courtesy of University Health Network)

Seizures linked to drugs used in surgery

Anesthetics can reduce risk, U of T team finds

Two drugs commonly given during cardiac surgery can lead to convulsive seizures, but anesthetics can help cut the risk, say researchers from the Faculty of Medicine at the 重口味SM.

Patients undergoing complex heart operations or trauma surgery are often given tranexamic acid (TXA) and aminocaproic acid (EACA) to reduce blood loss. But new research shows these drugs are associated with a four- to six-fold increase in post-operative seizures.

The risk is highest for cardiac surgery patients 鈥 between three and seven and a half per cent have seizures after arriving in the intensive care unit.

鈥淢any Canadians are treated with these drugs, particularly TXA, each year to decrease bleeding and help patients avoid blood transfusions," said Beverley Orser, Professor of Physiology and Anesthesiology at the 重口味SM and Canada Research Chair. "Surgeons and anesthesiologists need to be mindful that these drugs can be pro-convulsants.鈥

However, anesthetics can reduce the risk, Orser said.

鈥淭o decrease a patient鈥檚 risk of seizure, it鈥檚 critical to adjust the dose of TXA and EACA. In some cases where the risk of seizures is high, it is advisable to maintain a certain level of anesthetic sedation until the drugs wear off,鈥 said Orser, a staff anesthesiologist at Sunnybrook Health Sciences Centre.

Seizures can cause long-term, permanent neurological problems, increase the risk of stroke and prolong a patient鈥檚 recovery time. 

Clinicians had long been perplexed as to the cause of seizures associated with the use of TXA and EACA.  Irene Lecker, a PhD candidate in Orser鈥檚 laboratory, discovered that these drugs interfere with a naturally occurring anticonvulsant in the brain, glycine, and that widely used anesthetics reverse this interfering effect.

David Mazer, Professor and Vice-Chair of Research in the Department of Anesthesia at 重口味SM and co-investigator on the study, says this research will change the way these drugs are used around the world.

鈥淣ow that we understand what鈥檚 happening inside the brain and the mechanism behind the seizures, we can treat patients better,鈥 he says.

Dr. Orser is using these findings, now published in Journal of Clinical Investigation, to work with the Sunnybrook Health Sciences Centre team to develop a new practice of drug administration during and after surgery.

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