A new Brazilian study has found that two relatively simple measures can help reduce the incidence of post-operative cognitive dysfunction (POCD): administering a small dose of the anti-inflammatory drug dexamethasone right before an operation and avoiding profound anesthesia during the operation.
POCD is a condition characterized by impaired memory and concentration following surgery under general anesthesia. It may be temporary or permanent, mild or debilitating, and is mostly observed in older patients.
The problem has worsened as the population ages and a growing number of older adults undergo surgical procedures made possible by advanced medical technology. Research has suggested a rise in mortality from POCD in the first year after surgery under general anesthesia.
There is some debate regarding the adequate depth of anesthesia and the risks of very profound anesthesia. Excessively superficial anesthesia is known to raise the risk of patient recall of the procedure, which is undesirable.
“Our findings confirm recent evidence that the deeper the anesthesia-induced hypnosis, the higher the incidence of POCD,” said lead researcher Dr. Maria José Carvalho Carmona, a professor of anesthesiology at the University of São Paulo’s Medical School (FM-USP).
“The literature points to a link with the systemic inflammatory response induced by surgical trauma, damaging the central nervous system. If so, the use of an anti-inflammatory drug may have a protective effect.”
For the study, the researchers assessed 140 patients between the ages of 60 and 87 who underwent surgery under propofol-induced general anesthesia at the Central Institute of Hospital das Clínicas, FM-USP’s teaching hospital, in most cases for removal of gallstones.
Before the surgery, the patients received a battery of tests to measure mental and cognitive status. Patients who failed to achieve a cutoff score were excluded from the study. The remaining subjects were divided randomly into four groups.
In the operating room, deep anesthesia typical of major surgical procedures was induced in the first and third groups, and more superficial anesthesia in the second and fourth. Only the third and fourth groups received dexamethasone.
The depth of anesthesia was monitored using bispectral index (BIS) technology, which processes electroencephalogram signals to measure drug-induced unconsciousness. The researchers classified a BIS of 35-45 as deep anesthesia and a BIS of 46-55 as superficial anesthesia.
In the fourth group (superficial anesthesia with dexamethasone), 15.3 percent of the patients developed POCD immediately after surgery, but after six months the pre-operative cognitive status was restored in all patients.
“The results reinforce recent evidence of the importance of avoiding deep anesthesia,” Carmona said. “With regard to the use of dexamethasone, more research is needed to confirm our finding, preferably in multicenter trials, but there are strong indications that it can be beneficial in many cases.”
This type of research is relatively new. Before the 1950s, older patients were rarely subjected to major surgery, and significant research in this field has only been conducted for approximately 15-20 years.
“The causes of and risk factors for POCD are still being discussed,” she said. “Little is said about rehabilitation or ways of helping patients recover pre-operative cognitive function.”
One of the obstacles to reliable diagnosis and rehabilitation is a lack of practical and secure instruments for pre- and post-operative cognitive assessment.
“The tests available today are either too time-consuming or quick but unreliable,” Carmona said. “This makes it hard to follow up on patients.”
The findings are published in the journal PLoS One.