Anaesth Intens Care (1990),
18, 58-61
Gastric Aspiration at the End of Anaesthesia Does Not Decrease Postoperative Nausea and Vomiting J. HOVORKA,* K. KORTTILAt AND O. ERKOLA* Department of Anaesthesia, Women's Clinics, Helsinki University Central Hospital, Helsinki, Finland
SUMMARY Two hundred and one women undergoing elective abdominal hysterectomy were anaesthetised with isoflurane in nitrous oxide and oxygen. At the end ofanaesthesia the stomach was aspirated in half of the patients, selected in random order. In the other half no aspiration was performed. Incidence and severity ofemesis (none, nausea, retching or vomiting) was assessed during the first 24 hours after operation. Emesis was similar after the operation regardless of aspiration of the stomach (overall emesis 79% and 70%for those whose stomach had and had not been aspirated, respectively). The incidence at all times during the 24 hours was similar in both groups. The results suggest that gastric aspiration at the end of anaesthesia has no major effect on the incidence or severity of postoperative emesis in patients undergoing abdominal hysterectomy. Key Words: ANAESTHESIA, ANESTHESIA, GENERAL: isoflurane, gastric aspiration; COMPLICATIONS: nausea, vomiting Postoperative nausea and vomiting are among the most common complications of general anaesthesia and continue to be common, despite advances in the techniques used in general anaesthesia. In our previous studies we have attempted to decrease the incidence of postoperative nausea and vomiting but without complete success. 1-4 Factors stretching the stomach or gut wall may cause postoperative emesis by slowing down the motion of the intestine or stimulating the emetic centre directly.5,6 To our knowledge, however, properly controlled studies on the effect of gastric emptying on postoperative emesis, using the same anaesthetic techniques and with the same surgical operation, have not been carried out. ·M.D., Senior Staff Specialist. tM.D., Ph. D., Associate Professor. tM.D., Senior Staff Specialist. Address for Reprints: Dr. J. Hovorka, Department of Anaesthesia, Women's Clinics, Helsinki University Central Hospital, Haartmaninkatu 2, SF-00290 Helsinki, Finland Accepted for publication September 22, 1989
The aim of the present study was to find out whether gastric aspiration at the end of operation offers any advantages as far as postoperative nausea and vomiting are concerned. Abdominal hysterectomy was chosen as the surgical procedure because the surgical trauma and the duration of anaesthesia are similar in all patients. PATIENTS AND METHODS Two hundred and one patients scheduled for abdominal hysterectomy were enrolled. The study protocol was accepted by the institutional ethics committee and informed consent was obtained from each patient. Only patients in ASA group I or 11 and between the ages of 35 and 55 years were studied. Patients were randomised according to the date of birth to group A (even day): gastric aspiration performed at the end of anaesthesia, or to group B (uneven day): no gastric aspiration. All patients were premedicated with pethidine 1 mg/kg IM 40 to 60 minutes before anaesthesia. After insertion of an IV cannula Anaesthesia and Intensive Care, Vol. 18, No. 1, February, 1990
GASTRIC ASPIRATION AND POSTOPERATIVE EMESIS
and starting an infusion of Ringer's solution, alcuronium chloride 1.5 mg, glycopyrrolate 0.2 mg and fentanyl 0.1 mg were administered. Anaesthesia was induced with thiopentone 4 mg/kg. Before tracheal intubation patients were ventilated trying to avoid the passage of gases into the stomach. Oral tracheal intubation was facilitated with suxamethonium 1.5 mg/kg and anaesthesia was maintained with isoflurane in combination with nitrous oxide and oxygen (30%). The initial vaporiser setting for isoflurane was 1%, and thereafter the concentration of isoflurane was adjusted with a goal of administering the least isoflurane possible, according to the clinical need. The concentration was changed if the systolic blood pressure or heart rate changed more than 25% from the baseline. The inspired and expired concentrations of isoflurane were monitored with an anaesthetic agent monitor. Patients were also given fentanyl as an adjunct in a standardised way (0.05 mg every 45 minutes). Alcuronium was used to maintain neuromuscular blockade, 20-25% of the patient's muscle power being maintained as assessed using a nerve stimulator. 7 End-tidal C02 was measured continuously with a capnometer and maintained at 5 to 5.5%. At the end of anaesthesia, glycopyrrolate 0.4 mg and neostigmine 2.0 mg were given IV. Before that an orogastric tube was passed into stomach and spontaneous expulsion of air was observed by placing the end of the tube under the water and watching air bubbles. After this the remaining gastric contents were aspirated with a 50 ml syringe with the patient lying on her back. After several attempts to aspirate, the tube was removed before waking up the patient. The volumes of air and the liquid aspirated were small, usually less than 30 ml. Oxycodone chloride was used to relieve postoperative pain. It was administered IV in the postanaesthesia care unit in 4 mg increments and thereafter IM in the ward, at a dose of 0.13 mg/kg. ASSESSMENT OF EMESIS
The incidence of nausea and vomiting was determined at intervals during the first 24 hours after the operation; from 0-2,2-6,6-12, 12-18 and 18-24 hours, as in our previous Anaesthesia and Intensive Care, Vol. 18, No. I, February, 1990
59
studies. '-4 At the end of each interval a trained nurse, being unaware concerning details of gastric aspiration, recorded whether nausea, retching or vomiting had occurred. The results were scored, in a manner similar to that of Bellville et al., g as none, nausea, retching or vomiting. Droperidol 1.25 mg was administered once during each period if prolonged nausea or vomiting occurred. If a patient experienced more than one symptom, for example both nausea and vomiting, she was listed as having vomited; each patient was assessed five times during the 24-hour period. STATISTICS
Analysis of variance was used for comparisons of the patients' characteristics. The chi-square test was used to compare the incidence of emesis. A P-value less than 0.05 was considered statistically significant. Statistical power,9 i.e. the adequacy of our sample size and chances of finding a difference between the two groups, was estimated according to Fleiss. 10 RESULTS
There were 100 patients in group A (stomach aspirated) and 101 patients in group B (stomach not aspirated). The two groups (A and B) were similar with regard to age, weight, duration of anaesthesia as well as with regard to history of nausea and vomiting after previous anaesthetics and the drugs used during the present anaesthesia (Table 1). Table 2 shows that the incidence and severity of emesis at any time during the 24-hour-period was similar in groups A and B. Similarly, the overall incidence of nausea, retching and vomiting did not differ between the groups when assessed for the whole 24-hour follow-up period. The overall incidence of emesis (either nausea, retching or vomiting) during 24 hours was 79% and 70% in the group A and B, respectively. Emesis was not severe after 12 hours, and nearly disappeared by 24 hours after anaesthesia. There was no significant difference between the study groups A and B during any of the studied intervals. DISCUSSION
We found that gastric aspiration at the end of anaesthesia did not decrease the incidence of postoperative nausea and vomiting. Even
J. HOVORKA ET AL.
60 TABLE
I
Characteristics of the test groups. Mean (SD)
N Age (yr) Weight (kg) Duration of anaesthesia (min) Isoflurane concentration (%) Inspired Expired Alcuronium (mg) Oxycodone for postoperative pain (total mg) Droperidol for postoperative emesis total (mg) range (mg) number of patients
Group A Stomach aspirated
Group B Stomach not aspirated
lOO 43 (5) 64 (9)
101 43 (5) 65 (11 )
94
96 (30)
(25)
1.1 (0.2) 0.9 (0.2) 16.4 (2.8)
56
(14)
1.2 0-7.5 61
1.1 (0.2) 0.8 (0.2) 16.9 (3.5) 56
(16)
1.2 0-6.25 62
TABLE 2 Percentage incidence of emesis (nausea. retching or vomiting) in two groups. Group A - stomach aspirated and Group B - stomach not aspirated, in women undergoing abdominal hysterectomy under isojlurane anaesthesia.
Assessment Emesis (overall) 0-24 hrs after anaesthesia Emesis 0-2 hrs None Nausea Retching Vomiting Emesis 2-6 hrs after anaesthesia None Nausea Retching Vomiting Emesis 6-12 hrs after anaesthesia None Nausea Retching Vomiting Emesis 12-18 hrs after anaesthesia None Nausea Retching Vomiting Emesis 18-24 after anaesthesia None Nausea Retching Vomiting
Group A (n = lOO) Stomach aspirated
Group B (n=IOI) Stomach not aspirated
79
70
46 31 16 7
59 24 13 4
63 24 11 2
65 21 10 4
72 60 in the immediate postoperative phase (0-2 19 18 and 2-6 hours periods), which would have 7 18 been the most likely time period to be altered, 3 3 no difference was noted between the groups. The trial design and scoring system used for 81 83 nausea and vomiting in this study have been 13 9 used by our group before and proved useful 4 3 and sensitive in comparing anti-emetic drugs 5 2 given before, during and after general anaesthesia l •3,11 and in studying the influence 78 83 of nitrous oxide on postoperative emesis. 4,12 A 13 12 comparison of emesis is justified in the 2 I present investigation, since the variables 3 8 which most affect the incidence of nausea and vomiting l3 (i.e. age, sex, type and duration of operation, amount of narcotics given) were the meticulous nature of the follow-up of all similar in both groups. Although the patients, when even minor, short-lasting administration of opioid analgesics may cause nausea had been noted. Similar figures have nausea and vomiting, we chose to use been reported in our previous studies. 4,11 Loss pethidine for premedication and a small dose of the childbearing organ and fear of losing of fentanyl during the operation, as pain after normal female feelings could have the operation has also been implicated as a contributed to the high incidence of nausea major cause of postoperative nausea and and vomiting in this study.15 Power analysis 9 ,1O indicated that we had an vomiting. 14 The overall incidence of nausea and vomiting in this study (79% in group A 80% chance of finding an effect (at P < 0.05) and 70% in group B) is rather high. The high that stomach emptying decreased the overall incidences are mainly due to nausea, incidence of emesis by 20% (from 70% to rather than vomiting, being common. The 50%). To demonstrate smaller differences high incidence of nausea can be explained by would require investigation of more patients. Anaesthesia and Intensive Care. Vol. 18. No. I. February, 1990
GASTRIC Asp IRA nON AND POSTOPERATIVE EMESIS
In conclusion, we could not confirm the generally accepted theory that gastric emptying at the end of operation reduces the incidence of nausea and vomiting after general anaesthesia in patients undergoing abdominal hysterectomy.
REFERENCES I. Korttila K, Kauste A, Auvinen J. Comparison of
2.
3.
4.
5.
domperidone, droperidol and metoclopramide in the prevention and treatment of nausea and vomiting after balanced general anesthesia. Anesth Analg 1979; 58:396-400. Korttila K, Kauste A, Tuominen M, Salo H. Droperidol prevents and treats nausea and vomiting after enflurane anaesthesia. Eur J Anaesth 1986; 2:379-85. Kauste A, Tuominen M, Heikkinen H, Gordin A, Korttila K. Droperidol, alitsapride and metoclopramide in prevention and treatment of postoperative emetic sequelae. Eur J Anaesth 1986; 3: 1-9. Korttila K, Hovorka J, Erkola O. Nitrous oxide does not increase the incidence of nausea and vomiting after isoflurane anesthesia. Anesth Analg 1987; 66:761-5. Collins VJ. Principles of Anesthesiology. 2nd ed. Lea & Febiger Philadelphia 1976: p. 160 I.
Anaesthesia and Intensive Care. Vol. 18. No. I. February, 1990
61
6. Editorial: Nausea and vomiting after general anaesthesia. Lancet 1989; i:651-2. 7. Ali HH, Savarese JJ. Monitoring of neuromuscular function. Anesthesiology 1976; 45:216-22. 8. Bellville JW, Bross IDJ, Howland WS. A method for the clinical evaluation of antiemetic agents. Anesthesiology 1959; 20:753-60. 9. Altman DG. Statistics and ethics in medical research. III How large a sample. Br Med J 1980, 281: 1336-8. 10. Fleiss JL. Statistical methods for rates and proportions. 2nd ed. John Wiley and Sons New York 1981: pp.258-80. 11. Hovorka J, Korttila K, Erkola O. Nausea and vomiting after general anaesthesia with isoflurane, enflurane or fentanyl in combination with nitrous oxide and oxygen. Eur J Anaesth 1988; 5: 177-82. 12. Hovorka J, Korttila K, Erkola O. Nitrous oxide does not increase nausea and vomiting following gynaecological laparoscopy. Can J Anaesth 1989; 36: 145-148. 13. Muir JJ, Warner MA, Offort KP, Buck CV, Harper JV, Kunkel SE. Role of nitrous oxide and other factors in postoperative nausea and vomiting: A randomised and blinded prospective study. Anesthesiology 1987; 66:513-18. 14. Anderson R, Krogh K. Pain as a major cause of postoperative nausea. Can J Anaesth 1976; 23:366-9. 15. Held R. La psychologie affective de la relation medecin maiM en anesthesiologie. Cah d' Anesth 1961; 8:677-702.
18, 58-61
Gastric Aspiration at the End of Anaesthesia Does Not Decrease Postoperative Nausea and Vomiting J. HOVORKA,* K. KORTTILAt AND O. ERKOLA* Department of Anaesthesia, Women's Clinics, Helsinki University Central Hospital, Helsinki, Finland
SUMMARY Two hundred and one women undergoing elective abdominal hysterectomy were anaesthetised with isoflurane in nitrous oxide and oxygen. At the end ofanaesthesia the stomach was aspirated in half of the patients, selected in random order. In the other half no aspiration was performed. Incidence and severity ofemesis (none, nausea, retching or vomiting) was assessed during the first 24 hours after operation. Emesis was similar after the operation regardless of aspiration of the stomach (overall emesis 79% and 70%for those whose stomach had and had not been aspirated, respectively). The incidence at all times during the 24 hours was similar in both groups. The results suggest that gastric aspiration at the end of anaesthesia has no major effect on the incidence or severity of postoperative emesis in patients undergoing abdominal hysterectomy. Key Words: ANAESTHESIA, ANESTHESIA, GENERAL: isoflurane, gastric aspiration; COMPLICATIONS: nausea, vomiting Postoperative nausea and vomiting are among the most common complications of general anaesthesia and continue to be common, despite advances in the techniques used in general anaesthesia. In our previous studies we have attempted to decrease the incidence of postoperative nausea and vomiting but without complete success. 1-4 Factors stretching the stomach or gut wall may cause postoperative emesis by slowing down the motion of the intestine or stimulating the emetic centre directly.5,6 To our knowledge, however, properly controlled studies on the effect of gastric emptying on postoperative emesis, using the same anaesthetic techniques and with the same surgical operation, have not been carried out. ·M.D., Senior Staff Specialist. tM.D., Ph. D., Associate Professor. tM.D., Senior Staff Specialist. Address for Reprints: Dr. J. Hovorka, Department of Anaesthesia, Women's Clinics, Helsinki University Central Hospital, Haartmaninkatu 2, SF-00290 Helsinki, Finland Accepted for publication September 22, 1989
The aim of the present study was to find out whether gastric aspiration at the end of operation offers any advantages as far as postoperative nausea and vomiting are concerned. Abdominal hysterectomy was chosen as the surgical procedure because the surgical trauma and the duration of anaesthesia are similar in all patients. PATIENTS AND METHODS Two hundred and one patients scheduled for abdominal hysterectomy were enrolled. The study protocol was accepted by the institutional ethics committee and informed consent was obtained from each patient. Only patients in ASA group I or 11 and between the ages of 35 and 55 years were studied. Patients were randomised according to the date of birth to group A (even day): gastric aspiration performed at the end of anaesthesia, or to group B (uneven day): no gastric aspiration. All patients were premedicated with pethidine 1 mg/kg IM 40 to 60 minutes before anaesthesia. After insertion of an IV cannula Anaesthesia and Intensive Care, Vol. 18, No. 1, February, 1990
GASTRIC ASPIRATION AND POSTOPERATIVE EMESIS
and starting an infusion of Ringer's solution, alcuronium chloride 1.5 mg, glycopyrrolate 0.2 mg and fentanyl 0.1 mg were administered. Anaesthesia was induced with thiopentone 4 mg/kg. Before tracheal intubation patients were ventilated trying to avoid the passage of gases into the stomach. Oral tracheal intubation was facilitated with suxamethonium 1.5 mg/kg and anaesthesia was maintained with isoflurane in combination with nitrous oxide and oxygen (30%). The initial vaporiser setting for isoflurane was 1%, and thereafter the concentration of isoflurane was adjusted with a goal of administering the least isoflurane possible, according to the clinical need. The concentration was changed if the systolic blood pressure or heart rate changed more than 25% from the baseline. The inspired and expired concentrations of isoflurane were monitored with an anaesthetic agent monitor. Patients were also given fentanyl as an adjunct in a standardised way (0.05 mg every 45 minutes). Alcuronium was used to maintain neuromuscular blockade, 20-25% of the patient's muscle power being maintained as assessed using a nerve stimulator. 7 End-tidal C02 was measured continuously with a capnometer and maintained at 5 to 5.5%. At the end of anaesthesia, glycopyrrolate 0.4 mg and neostigmine 2.0 mg were given IV. Before that an orogastric tube was passed into stomach and spontaneous expulsion of air was observed by placing the end of the tube under the water and watching air bubbles. After this the remaining gastric contents were aspirated with a 50 ml syringe with the patient lying on her back. After several attempts to aspirate, the tube was removed before waking up the patient. The volumes of air and the liquid aspirated were small, usually less than 30 ml. Oxycodone chloride was used to relieve postoperative pain. It was administered IV in the postanaesthesia care unit in 4 mg increments and thereafter IM in the ward, at a dose of 0.13 mg/kg. ASSESSMENT OF EMESIS
The incidence of nausea and vomiting was determined at intervals during the first 24 hours after the operation; from 0-2,2-6,6-12, 12-18 and 18-24 hours, as in our previous Anaesthesia and Intensive Care, Vol. 18, No. I, February, 1990
59
studies. '-4 At the end of each interval a trained nurse, being unaware concerning details of gastric aspiration, recorded whether nausea, retching or vomiting had occurred. The results were scored, in a manner similar to that of Bellville et al., g as none, nausea, retching or vomiting. Droperidol 1.25 mg was administered once during each period if prolonged nausea or vomiting occurred. If a patient experienced more than one symptom, for example both nausea and vomiting, she was listed as having vomited; each patient was assessed five times during the 24-hour period. STATISTICS
Analysis of variance was used for comparisons of the patients' characteristics. The chi-square test was used to compare the incidence of emesis. A P-value less than 0.05 was considered statistically significant. Statistical power,9 i.e. the adequacy of our sample size and chances of finding a difference between the two groups, was estimated according to Fleiss. 10 RESULTS
There were 100 patients in group A (stomach aspirated) and 101 patients in group B (stomach not aspirated). The two groups (A and B) were similar with regard to age, weight, duration of anaesthesia as well as with regard to history of nausea and vomiting after previous anaesthetics and the drugs used during the present anaesthesia (Table 1). Table 2 shows that the incidence and severity of emesis at any time during the 24-hour-period was similar in groups A and B. Similarly, the overall incidence of nausea, retching and vomiting did not differ between the groups when assessed for the whole 24-hour follow-up period. The overall incidence of emesis (either nausea, retching or vomiting) during 24 hours was 79% and 70% in the group A and B, respectively. Emesis was not severe after 12 hours, and nearly disappeared by 24 hours after anaesthesia. There was no significant difference between the study groups A and B during any of the studied intervals. DISCUSSION
We found that gastric aspiration at the end of anaesthesia did not decrease the incidence of postoperative nausea and vomiting. Even
J. HOVORKA ET AL.
60 TABLE
I
Characteristics of the test groups. Mean (SD)
N Age (yr) Weight (kg) Duration of anaesthesia (min) Isoflurane concentration (%) Inspired Expired Alcuronium (mg) Oxycodone for postoperative pain (total mg) Droperidol for postoperative emesis total (mg) range (mg) number of patients
Group A Stomach aspirated
Group B Stomach not aspirated
lOO 43 (5) 64 (9)
101 43 (5) 65 (11 )
94
96 (30)
(25)
1.1 (0.2) 0.9 (0.2) 16.4 (2.8)
56
(14)
1.2 0-7.5 61
1.1 (0.2) 0.8 (0.2) 16.9 (3.5) 56
(16)
1.2 0-6.25 62
TABLE 2 Percentage incidence of emesis (nausea. retching or vomiting) in two groups. Group A - stomach aspirated and Group B - stomach not aspirated, in women undergoing abdominal hysterectomy under isojlurane anaesthesia.
Assessment Emesis (overall) 0-24 hrs after anaesthesia Emesis 0-2 hrs None Nausea Retching Vomiting Emesis 2-6 hrs after anaesthesia None Nausea Retching Vomiting Emesis 6-12 hrs after anaesthesia None Nausea Retching Vomiting Emesis 12-18 hrs after anaesthesia None Nausea Retching Vomiting Emesis 18-24 after anaesthesia None Nausea Retching Vomiting
Group A (n = lOO) Stomach aspirated
Group B (n=IOI) Stomach not aspirated
79
70
46 31 16 7
59 24 13 4
63 24 11 2
65 21 10 4
72 60 in the immediate postoperative phase (0-2 19 18 and 2-6 hours periods), which would have 7 18 been the most likely time period to be altered, 3 3 no difference was noted between the groups. The trial design and scoring system used for 81 83 nausea and vomiting in this study have been 13 9 used by our group before and proved useful 4 3 and sensitive in comparing anti-emetic drugs 5 2 given before, during and after general anaesthesia l •3,11 and in studying the influence 78 83 of nitrous oxide on postoperative emesis. 4,12 A 13 12 comparison of emesis is justified in the 2 I present investigation, since the variables 3 8 which most affect the incidence of nausea and vomiting l3 (i.e. age, sex, type and duration of operation, amount of narcotics given) were the meticulous nature of the follow-up of all similar in both groups. Although the patients, when even minor, short-lasting administration of opioid analgesics may cause nausea had been noted. Similar figures have nausea and vomiting, we chose to use been reported in our previous studies. 4,11 Loss pethidine for premedication and a small dose of the childbearing organ and fear of losing of fentanyl during the operation, as pain after normal female feelings could have the operation has also been implicated as a contributed to the high incidence of nausea major cause of postoperative nausea and and vomiting in this study.15 Power analysis 9 ,1O indicated that we had an vomiting. 14 The overall incidence of nausea and vomiting in this study (79% in group A 80% chance of finding an effect (at P < 0.05) and 70% in group B) is rather high. The high that stomach emptying decreased the overall incidences are mainly due to nausea, incidence of emesis by 20% (from 70% to rather than vomiting, being common. The 50%). To demonstrate smaller differences high incidence of nausea can be explained by would require investigation of more patients. Anaesthesia and Intensive Care. Vol. 18. No. I. February, 1990
GASTRIC Asp IRA nON AND POSTOPERATIVE EMESIS
In conclusion, we could not confirm the generally accepted theory that gastric emptying at the end of operation reduces the incidence of nausea and vomiting after general anaesthesia in patients undergoing abdominal hysterectomy.
REFERENCES I. Korttila K, Kauste A, Auvinen J. Comparison of
2.
3.
4.
5.
domperidone, droperidol and metoclopramide in the prevention and treatment of nausea and vomiting after balanced general anesthesia. Anesth Analg 1979; 58:396-400. Korttila K, Kauste A, Tuominen M, Salo H. Droperidol prevents and treats nausea and vomiting after enflurane anaesthesia. Eur J Anaesth 1986; 2:379-85. Kauste A, Tuominen M, Heikkinen H, Gordin A, Korttila K. Droperidol, alitsapride and metoclopramide in prevention and treatment of postoperative emetic sequelae. Eur J Anaesth 1986; 3: 1-9. Korttila K, Hovorka J, Erkola O. Nitrous oxide does not increase the incidence of nausea and vomiting after isoflurane anesthesia. Anesth Analg 1987; 66:761-5. Collins VJ. Principles of Anesthesiology. 2nd ed. Lea & Febiger Philadelphia 1976: p. 160 I.
Anaesthesia and Intensive Care. Vol. 18. No. I. February, 1990
61
6. Editorial: Nausea and vomiting after general anaesthesia. Lancet 1989; i:651-2. 7. Ali HH, Savarese JJ. Monitoring of neuromuscular function. Anesthesiology 1976; 45:216-22. 8. Bellville JW, Bross IDJ, Howland WS. A method for the clinical evaluation of antiemetic agents. Anesthesiology 1959; 20:753-60. 9. Altman DG. Statistics and ethics in medical research. III How large a sample. Br Med J 1980, 281: 1336-8. 10. Fleiss JL. Statistical methods for rates and proportions. 2nd ed. John Wiley and Sons New York 1981: pp.258-80. 11. Hovorka J, Korttila K, Erkola O. Nausea and vomiting after general anaesthesia with isoflurane, enflurane or fentanyl in combination with nitrous oxide and oxygen. Eur J Anaesth 1988; 5: 177-82. 12. Hovorka J, Korttila K, Erkola O. Nitrous oxide does not increase nausea and vomiting following gynaecological laparoscopy. Can J Anaesth 1989; 36: 145-148. 13. Muir JJ, Warner MA, Offort KP, Buck CV, Harper JV, Kunkel SE. Role of nitrous oxide and other factors in postoperative nausea and vomiting: A randomised and blinded prospective study. Anesthesiology 1987; 66:513-18. 14. Anderson R, Krogh K. Pain as a major cause of postoperative nausea. Can J Anaesth 1976; 23:366-9. 15. Held R. La psychologie affective de la relation medecin maiM en anesthesiologie. Cah d' Anesth 1961; 8:677-702.
