Oxygen Counters Nausea, Vomiting After Surgery

Nov. 5, 1999 (Atlanta) -- New research shows that oxygen may be a simple way to curb uncomfortable and potentially dangerous postoperative nausea and vomiting. Despite the development of new anesthetic drugs and medications to combat nausea and vomiting following surgery, as many as 70% of patients experience these complications after an operation.

The study, which appears in the November issue of Anesthesiology, involved 231 patients at a hospital in Vienna, Austria, all of whom were undergoing colon surgery scheduled to last at least two hours.

The patients were anesthetized using a set of drugs that included isoflurane -- which is delivered in a gaseous mixture of nitrogen and oxygen. About half the patients got the isoflurane mixed with 30% oxygen; the other half got isoflurane mixed with 80% oxygen. The patients continued to inhale these oxygen concentrations for two hours after surgery -- not knowing to which category they'd been assigned. Attending nurses and surgeons were also unaware of which patients were receiving the higher dose of oxygen.

Nausea and vomiting evaluations began once patients reached the recovery room, and continued at six-hour intervals for 24 hours. The authors found a marked difference between the two groups. About 30% of the patients inhaling the lower concentration of oxygen developed nausea during the 24 hours after surgery -- with seven actually vomiting. Just 17% of the 'high-oxygen' group reported symptoms of nausea, and only two vomited.

While the researchers regard these differences as clinically significant, they're puzzled as to what high-concentration oxygen does to curb nausea and vomiting. One possibility is that as a consequence of inhaling the low-oxygen mixture, patients took in a higher amount of nitrogen -- which can cause the bowel to expand. That, in turn, stimulates the release of a chemical called serotonin, which can trigger nausea and vomiting.

One of the study's researchers says that the big question is whether supplemental oxygen would work as well after other types of surgeries. Preliminary data from unpublished studies has suggested that the answer is yes.

"We have since done a study of 300 patients undergoing laparoscopy," says Daniel Sessler, MD, a professor of anesthesia at the University of California at San Francisco. "The results were essentially identical." Laparoscopy is a procedure during which surgery is performed through several small holes in the abdomen.

About half as many patients inhaling high-concentration oxygen experienced nausea and vomiting after laparoscopy. Sessler also says that "very preliminary data" shows that oxygen administered by paramedics may counter vomiting caused by motion sickness -- specifically, that experienced by sick patients taking turbulent ambulance rides. And he adds that using oxygen to prevent nausea and vomiting is "risk-free."

What may be especially attractive about these findings from a hospital standpoint is that money could be saved. "Oxygen costs a few cents per patient ... ondansetron [Zofran] costs thirty dollars," Sessler says, referring to one popular anti-vomiting drug. He adds that nausea and vomiting can add substantial costs to an otherwise simple hospital visit when, for example, a day surgery patient becomes so ill they have to be hospitalized because they can't keep anything down.

And there's also the issue of patient comfort. "It's a good-sized problem," says Ellen Sullivan, RN, the nurse in charge of the post-anesthesia care unit at Brigham and Women's Hospital in Boston. "It's one of those things that makes the patient most uncomfortable ... and one of the things that would delay discharge."

Sessler says that when he questions patients after surgery, many point to nausea and vomiting as the low-point in the experience -- even more so than the pain.