Anesthesia is not an area of medicine most folks profess to understand. As one anesthesiologist put it: “The lay public has the notion that we knock people on the head and they go to sleep, and then we knock them on the head again and they wake up.”
But today, even doctors are realizing how little they know about the effects of heavy sedation.
Since the beginning of modern medicine, doctors who administer anesthesia have largely confined their worries to the period beginning when patients are sedated and ending when they’re fully awakened. Now, two startling studies suggest that the effects of anesthesia linger for a year or longer, increasing the risk of death long after the surgery is over and the obvious wounds have healed.
“We don’t know whether the things we do really have an effect that lasts out to a very long period of time, but there is enough evidence to suggest it might,” says Dr. David Gaba, a professor of anesthesiology at Stanford University School of Medicine. “Even if it’s a subtle and fairly uncommon phenomenon, it could affect an awful lot of people.”
About 20 million Americans undergo surgery with general anesthesia each year.
Worries about the long-term effect of anesthesia -- and the demands for additional studies -- began to emerge recently when two research groups published papers linking deep sedation and an increased risk of death in the year or two after surgery.
One study, presented last fall at the American Society of Anesthesiologists annual meeting by Swedish researchers, showed that the duration spent under deep anesthesia is a significant risk factor for predicting death up to two years after surgery. Although the patients in the study were undergoing non-cardiac surgery, most deaths resulted from heart attacks or cancer.
The other study, published in the journal Anesthesia & Analgesia in January by Duke University researchers, found that longer amounts of time spent under deep sedation increased the risk of death in the year following surgery. The patients in the Duke study underwent major, non-cardiac surgery with general anesthesia, and again, deaths in the first year after surgery were primarily from heart attacks or cancer.
“The idea that what we do in the operating room may impact outcomes in our patients weeks, months or years down the road is exciting,” says Dr. Steffen E. Meiler, vice chairman for research in the department of anesthesiology and perioperative medicine at the Medical College of Georgia.
Surgery experts and anesthesiologists met in Washington, D.C., last fall and at smaller regional meetings since then to discuss the findings and plan research that could answer their questions. So far, doctors seem to agree that the long-term effects of surgery and anesthesia can lead to deaths. But they don’t agree on the precise cause.
Some experts suggest that anesthesia and surgery may ignite a cascade of inflammation in the body that can aggravate heart, respiratory, cancer conditions or dementia.
According to the leading theory -- just a hypothesis for now -- surgery and anesthesia trigger the release of stress hormones, such as norepinephrine, that in turn activate inflammatory responses in the body and undermine the workings of the immune system. Inflammation is known to worsen many diseases, including heart disease, cancer, even dementia.
Since the first studies were published, newer research has suggested that non-cardiac surgery with anesthesia also can cause a cognitive decline in some elderly people up to two years after the surgery, says Dr. Terri G. Monk, a professor of anesthesiology at Duke who led the study. That data was presented last fall at the American Society of Anesthesiologists annual meeting.
“Neither surgery nor anesthesia is a natural thing,” Gaba says. “What some people suspect -- but there is still not much evidence for -- is there could be people whose inflammation processes don’t come back to normal after surgery but stay revved up for a very long time.”
Surgery itself causes pain, stress and anxiety, Meiler notes. Then there’s the anesthesia, perhaps blood transfusions, and usually hypothermia (low body temperature) during surgery -- all of which can rattle the immune system in a profound way.
Sicker, older and obese people may be at more risk for death longer after surgery.
“What we’re now starting to learn is maybe there is a zone that we’ve always accepted as fine before that may have some subtle effects that we didn’t know about before,” Gaba says.
Although doctors must be able to blunt pain, keep a patient from moving and block awareness and memory during surgery, they also must be able to awaken the patient soon after the surgery. If the new findings hold up, they’ll have even more reasons to give patients as little anesthesia as necessary -- and to take additional measures to protect patients.
Newer monitors that precisely gauge a patient’s sedation level could help improve safety, says Dr. Michael Lew, chairman of anesthesiology at City of Hope National Medical Center in Duarte. Accounts of patients waking up during surgery had spurred the development of the sophisticated monitors, but even with the monitors, doctors face a balancing act.
“What has evolved is a feeling that maybe, at times, anesthesia is not deep enough and that we need better monitors to look at the depth of anesthesia,” Lew says. “On the other hand, Monk’s study is saying if you run them too deep, you increase mortality.”
Doctors also say that giving patients certain drugs before surgery can offset the risks of death later. For example, beta-blockers, drugs that control hypertension, are recommended for many patients before non-cardiac surgery to reduce the risk of postoperative death. Beta blockers can relieve stress on the heart during surgery. A 2004 study, however, showed that only about 40% of the suitable candidates for the prevention measure received it.
Two recent studies, Meiler says, show that statins given to patients undergoing major vascular surgery could protect against death after surgery by improving the patient’s cholesterol levels and stabilizing plaque in the arteries’ walls to avoid rupture.
Preoperative visits between the patient and anesthesiologist increasingly may include discussions about minimizing the long-term risks of surgery. Certain patients may be safer with a particular type of anesthesia, for example.
With continuing research, Meiler says, “The preoperative visit is going to reach a new level of sophistication.”