An hour of intravenous anesthetic during surgery can shave a day off the hospital stay and decrease the risk of postoperative complications for some patients, according to Dr. Marcel Durieux.
Intravenous anesthetics (for example, lidocaine) exert surprising effects on recovery from some – but not all – major abdominal surgeries. They’re associated with decreased postoperative pain, quicker return of bowel function, and a shorter length of stay. But they don’t help in all surgeries – not even in all abdominal surgeries – and the way they work is still something of a mystery, he said.
The well-documented systemic benefits of surgical epidurals got anesthesiologists thinking about intravenous agents, said Dr. Durieux, professor of anesthesiology at the University of Virginia, Charlottesville. Epidurals provide excellent postoperative pain control, but it was obvious that their effects spread much farther.
"Even if the local anesthetic goes away, its beneficial effect does not."
"They do much more than just help pain," he said in an interview. "They have significant effects on surgical outcomes that can’t be explained simply by blocking sodium channels in nerves."
Because the effects span several systems, they are probably due to systemic absorption of the anesthetic agent, he said. "If improved outcomes have little to do with blocking nerves, there is no special reason to give an anesthetic near those nerves. You should be able to give it intravenously at doses that lead to blood levels similar to what we get with an epidural."
Researchers have been looking at the issue for more than a decade, and are now honing in on inflammation as the root of these postoperative problems.
A hyperinflammatory response to surgical trauma is probably the root of many postoperative problems, including pain and thrombosis, Dr. Durieux said. "The response develops during the case and lasts into the postoperative period. If it continues, it can lead to a lot of negative effects – increased cardiac strain, impaired respiratory function that can lead to respiratory distress syndrome, nausea and ileus, and a procoagulatory state."
Intravenous local anesthetics seem to suppress that response before it explodes. The drugs likely target neutrophils and the two pathways in which they respond to a bodily injury: priming and activation.
In normal activation, a neutrophil senses bacteria and generates superoxide that kills the invader, leading to the normal inflammatory response seen with an illness. But a wound, including a surgical wound, primes the neutrophils for a superresponse. "Subsequently, when they encounter bacteria, they generate 10 times the amount of superoxide, actually damaging the body," Dr. Durieux said.
In some yet-unknown way, local anesthetics appear to inhibit neutrophilic priming. "There is no other drug around that selectively blocks priming. And if you don’t prime these neutrophils during surgery, you won’t have them there 2 days after surgery causing problems. Even if the local anesthetic goes away, its beneficial effect does not."
Recognition of this prolonged anti-inflammatory effect may eventually shape the administration of intraoperative local anesthetics. Because there is no data-driven protocol, some anesthesiologists give the drug for an hour during surgery, some continue it in the recovery room, and a few want to continue it on the surgical floor.
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Cardiovascular Disease