Supplemental oxygen for prevention of nausea and vomiting after breast surgery

S. Purhonen*,1, M. Niskanen1, M. Wüstefeld1, P. Mustonen2 and M. Hynynen3

1 Department of Anaesthesiology and Intensive Care, and 2 Department of Surgery, Kuopio University Hospital, PO Box 1777, FIN-70211 Kuopio, Finland. 3 Department of Anaesthesia and Intensive Care, Helsinki University Central Hospital, Jorvi Hospital, FIN-02740 Espoo, Finland

Corresponding author. E-mail: sinikka.purhonen@kuh.fi

Accepted for publication: April 12, 2003


    Abstract
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 Abstract
 Introduction
 Methods and results
 Comment
 References
 
Background. Administration of supplemental oxygen 80% has been shown to halve the incidence of postoperative nausea and vomiting (PONV). We tested the efficacy of supplemental oxygen 50% in decreasing the incidence of PONV after breast surgery.

Methods. One hundred patients receiving standardized sevoflurane anaesthesia were randomly assigned to two groups: oxygen 30% administration (Group 30); and oxygen 50% administration (Group 50). Oxygen was administered during surgery and for 2 h from the end of surgery.

Results. The incidence of PONV over 24 h after surgery showed no difference between the groups: 82% in Group 30 and 89% in Group 50. However, during the postoperative oxygen administration, eight patients vomited in Group 30, compared with none in Group 50 (P<0.05). After oxygen therapy ceased, there was no difference in the incidence of vomiting between the groups. Nausea and need for rescue antiemetics did not differ between the groups.

Conclusion. The incidence of vomiting decreased during the short postoperative administration of supplemental oxygen 50%. However, perioperative oxygen 50% administration did not prevent PONV over the 24-h follow-up period in patients undergoing breast surgery performed under general anaesthesia.

Br J Anaesth 2003; 91: 284–7

Keywords: anaesthesia, general; oxygen, supplemental; surgery, breast; vomiting, nausea, postoperative


    Introduction
 Top
 Abstract
 Introduction
 Methods and results
 Comment
 References
 
The optimal strategy for prevention of postoperative nausea and vomiting (PONV) is still unresolved.1 Pharmacological prophylaxis may increase costs and predispose to adverse events.2 Supplemental oxygen is inexpensive and a potential alternative to prevention of PONV. The incidence of PONV was halved in patients receiving 80% compared with oxygen 30% inspired during laparotomy and for 2 h after surgery.3 However, administration of oxygen 80% during the postoperative period requires a special mask.3 4 A lower concentration of oxygen, for example 50%, could be administered with a routine mask. In addition, high concentrations of oxygen may cause undesirable effects.5 6 We designed this prospective randomized study to test the hypothesis that perioperative supplemental oxygen 50% administration would reduce the incidence of PONV in women undergoing breast surgery performed under general anaesthesia.


    Methods and results
 Top
 Abstract
 Introduction
 Methods and results
 Comment
 References
 
Following approval by the hospital ethics committee, written informed consent was obtained from 100 female patients (ASA I–III) scheduled for breast surgery. All patients received oral diazepam 10–15 mg 1 h before surgery. Anaesthesia was induced with fentanyl 2 µg kg–1 and propofol 2–2.5 mg kg–1. Patients were ventilated with oxygen 100% by mask until tracheal intubation, which was facilitated with rocuronium 0.5 mg kg–1. Anaesthesia was maintained with sevoflurane.

Patients were randomly assigned to two groups: patients in Group 30 breathed oxygen 30%, in nitrogen (not nitrous oxide), while patients in Group 50 breathed supplemental oxygen 50%, in nitrogen. Patients’ lungs were mechanically ventilated with a positive end-expiratory pressure (PEEP) of 6 mm Hg. Fentanyl 1 µg kg–1 was given before the skin incision, and every 45 min during surgery. At the end of surgery, neuromuscular block was antagonized with neostigmine 2.5 mg and glycopyrrolate 0.5 mg i.v.

After surgery, patients breathed either oxygen 30% or 50% for 2 h from the end of surgery. The specified oxygen concentration was mixed with the oxygen blender of the ventilator (Servo, Siemens-Elema AB, Solna, Sweden) and given at a rate of 20 litre min–1. To prevent dilution of the gas composition with air, patients breathed through an adhesive continuous positive air pressure mask (Vital Signs, Totowa, NJ, USA) without a PEEP valve. A 40-cm piece of breathing tube was joined with a Y-connector to the mask to form the oxygen reserve. The fraction of inspired oxygen was measured under the mask at the beginning of postoperative oxygen administration and once more 1 h later. The anaesthetists were aware of the administered oxygen concentration. Patients and the nurses reporting PONV were blinded.

Rescue antiemetic treatment was provided with ondansetron 1 mg i.v. twice and thereafter with droperidol 10 µg kg–1 i.v. once. Pain was treated with oxycodone 0.1 mg kg–1 i.m. or half of the dose i.v. Propacetamol 2 g was infused immediately postoperatively, and thereafter oral acetaminophen 1 g every 8 h was given for pain. PONV assessments were performed at 1, 2, 6 and 24 h after surgery. Nausea and pain were scored using a linear scale from 0 to 10 (0=no nausea or no pain; 10=nausea or pain ‘extreme’). Each episode of vomiting was recorded. Patients experiencing retching were included in the vomiting category.

Our primary efficacy variable was the incidence of nausea, vomiting, or both over the initial 24 h after surgery. The sample size of the study (49 patients in each group) was estimated by using a 2-sided {alpha}-level of 0.05 and a power of 0.80. The incidence of PONV was assumed to be 60% after oxygen 30% administration and 30% after oxygen 50% administration during the first 24 h after surgery. Comparisons between the groups were performed with the {chi}2-test for categorical data and Mann–Whitney U-test for continuous data. Nausea and pain scores were analysed by using the Mann–Whitney U-test with Bonferroni’s correction, and the highest scores during the first 2-h period after surgery were used in the analysis. Risk scores for PONV were calculated according to Apfel and colleagues.7 All tests were performed using SPSS 10.0 for windows software (SPSS, Inc., Chicago, IL, USA). The level of significance was P<0.05.

Three women in Group 50 dropped out because they felt the oxygen mask uncomfortable, and one patient in Group 30 because of further surgery for bleeding. There were no differences with respect to the calculated risk scores for PONV between the groups. The overall incidences of PONV over the first 24 h after surgery did not differ between the groups (Table 1). However, during the first 2 h after surgery, eight patients in Group 30 vomited, whereas none did in Group 50. Nausea, the need for rescue antiemetics, and the median times from the end of surgery to the first symptom of PONV, and to the first dose of ondansetron did not differ between the groups. There were no differences between the groups in pain scores, in postoperative oxycodone administration, or in adverse events.


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Table 1 Incidences of PONV. Values are expressed as numbers of patients (%) and medians (interquartile range). *P<0.05 vs Group 30. Group 30=oxygen 30%; Group 50=oxygen 50%
 

    Comment
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 Abstract
 Introduction
 Methods and results
 Comment
 References
 
We found that supplemental perioperative oxygen 50% did not reduce the incidence of PONV compared with oxygen 30% in patients undergoing breast surgery performed under general anaesthesia. We found only a brief beneficial effect on the incidence of vomiting, but not on nausea, during the postoperative administration of oxygen 50%. Greif and colleagues3 found that the incidence of PONV decreased from 30% to 17% when oxygen 80% vs oxygen 30% was administered during colorectal surgery and for 2 h afterwards. Goll and colleagues8 found that supplemental oxygen 80%, when administered intra-operatively during gynaecological laparoscopy, halved the incidence of PONV from 44% to 22% compared with oxygen 30%. The divergent results between these two studies3 8 and the present trial might be attributable to the lower concentration of supplemental oxygen used in our study. On the other hand, our finding is in agreement with our recent observation of no effect of oxygen 80% on PONV after ambulatory gynaecological laparoscopy.4

The beneficial effect of supplemental oxygen in preventing PONV after laparotomy3 and laparoscopy8 has been speculated to result from amelioration of regional intestinal hypoxia. After breast surgery, amelioration of hypoxia in tissues other than intestinal tract, as well as factors other than tissue hypoxia, might be important in prevention of PONV. In contrast to the present study, the rescue antiemetic therapy was not standardized by Greif and colleagues.3 Nor did they specify the distribution of risk factors for PONV between the groups, such as a history of motion sickness. In the study of Goll and colleagues,8 there tended to be fewer risk factors for PONV (higher alcohol intakes, more current smokers, fewer patients with a history of PONV or motion sickness, and less use of postoperative opioids) in the oxygen 80% group than in the oxygen 30% group. Although none of these risk factors was alone significant, they may have combined to form a clinically significant difference in the different baseline risk.9 In our study groups the calculated risk scores for PONV did not differ.7

In conclusion, perioperative supplemental oxygen 50% decreased vomiting for a short period during the immediate postoperative phase. However, it did not reduce PONV over the 24-h follow-up period after surgery.


    References
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 Abstract
 Introduction
 Methods and results
 Comment
 References
 
1 Watcha MF. The cost-effective management of postoperative nausea and vomiting. Anesthesiology 2000; 92: 931–3[ISI][Medline]

2 Tramer MR. A rational approach to the control of postoperative nausea and vomiting: evidence from systematic reviews. Part I. Efficacy and harm of antiemetic interventions, and methodological issues. Acta Anaesthesiol Scand 2001; 45: 4–13[CrossRef][ISI][Medline]

3 Greif R, Laciny S, Raph B, Hickle RS, Sessler DI. Supplemental oxygen reduces the incidence of postoperative nausea and vomiting. Anesthesiology 1999; 91: 1246–52[ISI][Medline]

4 Purhonen S, Turunen M, Ruohoaho UM, Niskanen M, Hynynen M. Supplemental oxygen does not reduce the incidence of postoperative nausea and vomiting after ambulatory gynecologic laparoscopy. Anesth Analg 2003; 96: 91–6[Abstract/Free Full Text]

5 de Richemond AL, Bruley ME. Insidious iatrogenic oxygen-enriched atmospheres as a cause of surgical fires. In: Stoltzfus JM, Benz F, Stradling J, eds. Flammability and Sensitivity of Materials in Oxygen-enriched Atmospheres, 6th Edn. Philadelphia: American Society for Testing and Materials, 1989; 392–404

6 Reber A, Enberg G, Wegenius G, Hedenstierna G. Lung Aeration. The effect on pre-oxygenation and hyperoxygenation during total intravenous anaesthesia. Anaesthesia 1996; 51: 733–7[ISI][Medline]

7 Apfel CC, Läärä E, Koivuranta M, Greim C-A, Roewer N. A simplified risk score for predicting postoperative nausea and vomiting. Anesthesiology 1999; 91: 693–700[ISI][Medline]

8 Goll V, Akca O, Greif R, et al. Ondansetron is no more effective than supplemental intraoperative oxygen for prevention of postoperative nausea and vomiting. Anesth Analg 2001; 92: 112–17[Abstract/Free Full Text]

9 Apfel CC, Kranke P, Greim C-A, Roewer N. What can be expected from risk scores for predicting postoperative nausea and vomiting? Br J Anaesth 2001; 86: 822–7[Abstract/Free Full Text]