Research suggests that surgical operations involving general anaesthetic may damage mental ability by starving the brain of oxygen. We all know that the oxygen saturation falls as we go up an altitude. Using this principle tests were conducted on climbers as they scaled Mount Everest. The landmark study which monitored 198 climbers who scaled Everest, where there is only one third of the oxygen as at sea level, found significant cognitive decline after the teams descended from the peak.

It is reported that one fifth of patients develop hypoxia after surgery which can lead to confusion, high blood pressure, heart failure or even death. We all know that elderly patients are often confused after surgery involving a general anaesthetic. New research from University College London suggests that the condition can also have a significant impact on brain function, with the effects lasting for at least 11 days after oxygen deprivation.

In particular, tasks associated with speech and language, learning, planning, focussing and organising were severely impacted, with performance falling by nearly 20 per cent on tests taken before and after the ascent. And the effects were still present when the climbers returned to Kathmandu, 11 days later.

Asked whether the same impact might be seen after surgery, study leader Professor Stanton Newman, Dean of the School of Health Sciences at City, said: “Absolutely. What we found is that there was a clear relationship between levels of hypoxia and brain function which has not been established before.

“It was possible to group people into three groups, some of whom had mild effects, and some whom it was significant. We noticed that it was worse for older people. “We know that a number of people who go back to work after surgery and find that they have cognitive problems but it was unclear what was causing it.

“We also noticed that the declines happened even when people were given oxygen and their oxygen levels returned to normal.”

Similar levels of oxygen deprivation are encountered by Everest climbers as patients in a state of hypoxia.
Participants received a series of neuropsychological tests assessing memory, language, attention, and executive function using standardised and commonly used assessments in clinical and research settings.

These were administered at sea level in London,11,400ft (3,500m) at Namche Bazaar in Nepal, and at (17,000ft ) 5,300m at Everest Base Camp. Tests were also conducted upon return to 4200ft (1,300m) in Kathmandu. This group was also compared with a control group.
They found that the greatest decline was in older adults suggesting that cognitive recovery from surgery may take longer in older people.

The research was published in the journal PLOS One.