Supplemental oxygen reduces the incidence of postoperative nausea and vomiting.

BACKGROUND: Despite new anesthetic drugs and antiemetics, particularly 5-hydroxytryptamines, the incidence of postoperative nausea or vomiting remains between 20% and 70%. The authors tested the hypothesis that supplemental perioperative oxygen administration reduces the incidence of postoperative nausea or vomiting. METHODS: Patients undergoing colon resection were anesthetized with fentanyl and isoflurane. During and for 2 h after surgery they were randomly assigned to (1) 30% oxygen, balance nitrogen (n = 119); or (2) 80% oxygen, balance nitrogen (n = 112). The incidence of nausea or vomiting during the first 24 postoperative hours was evaluated by nurses blinded to group assignment and oxygen concentration. Data were analyzed with unpaired t or Mann-Whitney U tests. Results are presented as means +/- SD; P < 0.05 was considered significant. RESULTS: Factors known to influence nausea and vomiting were comparable in the two groups. Perioperative oxygen saturation was well within normal limits in each treatment group; saturations the first postoperative morning were comparable in each group. Supplemental oxygen reduced the incidence of postoperative nausea or vomiting from 30% in the patients given 30% oxygen to 17% in those given 80% oxygen (P = 0.027). CONCLUSIONS: Supplemental oxygen reduced the incidence of postoperative nausea or vomiting nearly twofold after colorectal surgery. The mechanism by which oxygen administration reduces the incidence of these postoperative sequelae remains unknown but may be related to subtle intestinal ischemia. Because oxygen is inexpensive and essentially risk-free, supplemental oxygen appears to be an effective method of reducing postoperative nausea and vomiting.

Onset time, recovery duration, and drug cost with four different methods of inducing general anesthesia.

UNLABELLED: We compared two conventional induction techniques (thiopental and propofol), an inhaled induction with sevoflurane using a circle system, and a rebreathing method. Fentanyl 1 microg/kg was given to women undergoing 10- to 20-min procedures. Anesthesia was induced (n = 20 each) with one of the following: 1) sevoflurane and N2O from a rebreathing bag (Sevo/Bag). A 5-L bag was prefilled with a mixture of sevoflurane 7% and N2O 60% in oxygen. The bag was connected between the normal circle system, separated by a spring-loaded valve; 2) sevoflurane 8% and N2O 60% from a circle system on a conventional anesthesia machine with a total fresh gas flow of 6 L/min (Sevo/Circle); 3) propofol 3 mg/kg as an i.v. bolus; 4) thiopental sodium 5 mg/kg as an i.v. bolus. Postoperative nausea and vomiting was treated with ondansetron. Induction times were comparable with each method. Recovery duration was shortest with sevoflurane, intermediate with propofol, and longest with thiopental. Induction drug costs were lowest with Sevo/Bag and thiopental, intermediate with Sevo/Circle, and highest with propofol. However, sevoflurane (by either method) caused considerable nausea and vomiting that required treatment. Consequently, total drug cost was least with thiopental, intermediate with Sevo/Bag and propofol, and greatest with Sevo/Circle. Thus, no single technique was clearly superior. IMPLICATIONS: Anesthetic induction techniques influence awakening time, recovery duration, and drug costs. We tested two i.v. methods and two inhaled techniques. However, none of the four tested methods was clearly superior to the others.