Multicenter Clinical Study Affirms Safety of Deep General Anesthesia: Key Findings and Impact

A new study published on June 10 in the Journal of the American Medical Association (JAMA) supports previous research findings, indicating thatAnesthesia is not more dangerous for the brain at higher doses than at lower doses, according to researchers. A new study has revealed the results of a large clinical trial involving over 1,000 elderly patients who had cardiac surgery at four hospitals in Canada. The researchers, along with colleagues at Washington University School of Medicine in St. Louis, discovered that the quantity of anesthesia administered during surgery did not impact the likelihood of postoperative delirium, which could potentially lead to long-term cognitive decline. There has been concern that general anesthesia may harm the brain and cause both short-term and permanent cognitive impairment.Postoperative cognitive disorders are a significant reason why older adults put off or avoid important medical procedures,” explained Michael S. Avidan, MBBCh, the Dr. Seymour and Rose T. Brown Professor of Anesthesiology and head of the Department of Anesthesiology at Washington University. “Our recent study adds to the growing evidence that higher doses of general anesthesia do not have harmful effects on the brain. By dispelling the common misconception that general anesthesia causes cognitive disorders, we can have a positive impact on public health by empowering older adults to make informed decisions about necessary surgeries, ultimately improving and maintaining their well-being.In the past, the amount of anesthesia given has been carefully balanced to avoid giving too little or too much. Not enough anesthesia can put patients at risk of being aware during surgery without being able to move or show their distress. Despite improvements in anesthesia care, around 1 in 1,000 people still experience unintended waking during surgery, which can lead to long-lasting emotional trauma. However, the good news is that there are more reliable ways to prevent this distressing complication, according to Avidan, the senior author of the study.Clinicians can now administer a safe dose of general anesthesia without worrying about risking their patients’ brains. The practice of general anesthesia should evolve based on new evidence. Previous studies have indicated that excessive anesthesia could contribute to postoperative delirium, which is a neurological issue affecting about 25% of older patients after major surgeries and causing symptoms such as confusion, altered attention, paranoia, memory loss, hallucinations, and delusions.Delirium can cause distress for patients and their families. Although it is usually temporary, it has been associated with longer stays in the intensive care unit and the hospital, as well as other medical complications, persistent cognitive decline, and a higher risk of death.

To examine the effects of reducing anesthesia on postoperative delirium, Avidan and his team previously carried out a similar clinical study involving over 1,200 older surgical patients at Barnes-Jewish Hospital in St. Louis. The researchers utilized an electroencephalogram (EEG) to monitor the brain’s electrical activity in patients during major surgery and adjusted the anesthesia accordingly.esia levels to avoid brain function suppression, which is a sign of too much anesthesia. The study showed that reducing anesthesia did not prevent postoperative delirium.

To further investigate the findings from their trial at one hospital, Avidan worked with Alain Deschamps, MD, PhD, an anesthesiology professor at Universitè de Montreal, and a group of Canadian clinical researchers. They conducted a multicenter trial with patients at four hospitals in Canada – Montreal, Kingston, Winnipeg, and Toronto.

This clinical trial included 1,140 patients who were undergoing cardiac surgery.The study involved high-risk procedures with a high rate of postoperative complications. About half of the patients had their anesthesia adjusted based on electrical activity in the brain, while the other group received the usual care without EEG monitoring. The group with adjusted anesthesia received almost 20% less anesthesia and also had 66% less time with suppressed electrical brain activity. However, both groups had 18% of the patients experience delirium in the first five days after surgery. There were no significant differences in the length of hospital stays, the incidence of medical complications, and the risk of death up to one year postoperatively between the two groups.The two study groups showed different results among patients. The group that received less anesthesia had almost 60% more patients experiencing undesirable movements during surgery, which could have had a negative impact on the surgeries. Dr. Avidan stated that there has been a belief that deep general anesthesia can excessively suppress brain activity and lead to postoperative delirium. However, the two clinical trials conducted on nearly 2,400 older surgical patients at five hospitals in the United States and Canada have shown that higher general anesthetic dosing does not incur a neurotoxic cost. This dispels the concern that was previously held.It is believed that postoperative delirium may be the result of factors unrelated to general anesthesia, like the pain and swelling after surgery. There is a need for further research to investigate other ways to avoid postoperative delirium. However, we can now assure our patients that they can ask for and anticipate being unconscious, unable to move, and free from pain during surgery, without being concerned about general anesthesia causing harm to their brains.”