One of the most feared complications of surgery is said to be losing one’s memory. A number of patients undergoing a major surgery with general anaesthesia were involved in a survey where they indicated they were most concerned about brain damage and memory loss. These participants in the survey, and many others, have this fear and for good reason. In recent research that was published in the British medical journal called The Lancet, ‘a surprisingly high’ number of people, 1 in 14 over the age of 65 undergoing major noncardiac surgery, will suffer minor strokes and more delirium following their operations.
The “NeuroVISION” trial, the largest international clinical trial of its type, followed more than 1000 patients across 12 academic centres in nine countries, to determine the relationship between covert stroke (strokes that can only been detected through brain imaging) and cognitive decline in patients aged 65 years or older, one year after surgery. The study was built upon earlier work by Professor Alan Barber in cardiac surgery patients. At the time, most anaesthetists and surgeons thought of stroke as a severe, but rare complication of surgery. Dr Douglas Campbell, an Auckland Hospital specialist anaesthetist and one of the lead researchers for the NeuroVISION trial, says that the possibility that small, covert strokes could contribute to postoperative delirium and cognitive dysfunction was not even contemplated. This study, which was partly funded by the Neurological Foundation, discovered that following low-risk surgery, several patients have been having these covert strokes. These patients have a high risk of developing dementia or cognitive decline and are at risk of having a subsequent stroke.
“This study, which was partly funded by the Neurological Foundation, discovered that following low-risk surgery, several patients have been having these covert strokes. These patients have a high risk of developing dementia or cognitive decline and are at risk of having a subsequent stroke.”
The trial started prior to surgery, where participants underwent cognitive testing. During the first 72 hours after surgery, patients were screened for delirium twice each day. Between two and nine days after surgery, the researchers used Magnetic Resonance Imaging (MRI) scanning to detect any blocked blood vessels. Patients were followed up throughout their hospital stay and contacted 30 days after surgery. Then cognitive testing was done again at the one year follow-up.
Dr Campbell was surprised by the number of people suffering these small strokes as it was ‘surprisingly high’. “Seven percent of patients suffered what are called ‘covert’ strokes that might not be picked up usually because of all the other things going on after an operation – sedation, pain, and being bed-ridden”. If you suffer from these covert strokes, you are twice as likely to suffer delirium following the operation and it could impact on your cognitive abilities a year down the track explained Dr Campbell.
However, the trial discovered another surprising figure. Twenty-eight percent of patients who hadn’t had covert strokes still suffered cognitive decline a year later, and that figure rose to 42 percent if they had suffered from the covert strokes.
“So, an unexpected number of elderly patients are showing cognitive decline a year after surgery without the added complication of covert strokes. We aren’t sure why that is so high; whether its age, illness or a result of the surgery,” says Dr Campbell.”
Due to the achievement of the first study, the researchers have decided another trial is needed. That is why the researchers are planning NeuroVISION 2, which will compare the results with those who are not having surgery but are still experiencing cognitive decline. This trial will look at changes in blood pressure, heart rhythm and other issues that could be the cause of the mini strokes. This may uncover ways to prevent these events and ultimately prevent cognitive decline.
In the meantime, Dr Campbell says it is a matter of clinicians and patients over the age of 65 adding the possibility of small strokes to the list of potential complications when they weigh up the risks and benefits of major surgery.
As an anaesthetist, Dr Campbell did not foresee that stroke research would become his main area of interest when he first applied for a Neurological Foundation Project Grant for NeuroVISION. It was his first successful large grant application and he says it has opened up a whole new avenue of future research for him. He is now the Principal Investigator on MASTERSTROKE, a large randomised controlled trial of two blood pressure targets during clot retrieval for stroke, which is also funded by a Neurological Foundation Project Grant. There is now a group of Auckland Hospital and University researchers collaborating on stroke research, first in man device trials, randomised controlled trials, animal models of stroke, and effects of anaesthesia drugs and physiological interventions. Dr Campbell says that it is a very exciting field and that they have future plans for other avenues of research aiming to improve the clinical care of this devastating disease.
Dr Douglas Campbell is an Anaesthetic Specialist in the Department of Anaesthesia and Perioperative Medicine at Auckland City Hospital. He is the Principal Investigator for the New Zealand arm of the international multicentre NeuroVISION study as well as the principle investigator on the MASTERSTROKE trial. Both studies are funded by Neurological Foundation project grants.