Patients given extra oxygen during surgery have less nausea

The incidence of nausea after a general anaesthetic can be reduced by half simply by giving patients more oxygen during and after surgery, according to a study in the November issue of Anesthesiology (1999;91:1246-52). The study involved researchers at the University of California, San Francisco, and in Vienna, Austria.

About half of 231 patients undergoing colon surgery at Donauspital, Vienna, and Vienna General Hospital received the conventional 30% oxygen in their anaesthetic gas and for two hours during recovery, while the other half received a mixture containing 80% oxygen.

Another study, published in the October issue of Anesthesiology, confirmed that the procedure was safe (1999;91:991-8)

Not only did the procedure dramatically reduce the incidence of nausea, but it was also cost effective, because while antinausea drugs cost $30 (£18.75) per dose, the extra oxygen costs almost nothing.

Moreover, even the most effective drugs, given after patients experience nausea, only have a 50-50 chance of working, said Dr Daniel Sessler, professor of anaesthesiology and postoperative care at the University of California, senior author and designer of both studies.

The authors do not know why the extra oxygen works, but they suggest that during abdominal surgery the intestines do not get the usual amount of oxygen because of cutting or temporary misplacement. It is known that tissues starved of oxygen release chemical messengers that trigger nausea and vomiting, presumably to rid the body of toxic contents.

The research is part of continuing studies by an international team called the Outcomes Research Group, which examines accepted practice in anaesthesiology to determine if simple improvements can produce major benefits.