In a randomized controlled clinical trial, 14 patients requiring resection of
tumors were divided in two groups: one group was anesthetized with
nitrous oxide [67% N2O-33% O2 (vol/vol)] and the other with
propofol. Two other groups of subjects were studied: a group of patients that was undergoing
orthopedic procedures and was anesthetized with
nitrous oxide [67% N2O-33% O2 (vol/vol)] and a control group (fasted for 10 hrs and no
anesthesia). In patients requiring resection of
tumors, the blood
L-methionine concentration was significantly lower and the blood
amino acid pattern was significantly affected after the administration of
nitrous oxide (120-310 mins) compared with values after the induction of
anesthesia and before surgery. The administration of
propofol (120-240 mins) did not produce any of these changes. No patients required
blood transfusion during surgery, and the patients had not previously been treated with
cancer chemotherapeutic agents. The administration of
nitrous oxide (60-150 mins) to patients undergoing
orthopedic procedures did not affect blood
L-methionine. It is concluded that the administration of
nitrous oxide to
cancer-bearing patients, but not to those undergoing
orthopedic surgery, produced major changes in
amino acid metabolism; therefore, consideration should be given to the avoidance of exposure of
cancer patients to
nitrous oxide.