Arellano 2000.

Methods	Study design: Randomized controlled trial Study grouping: Parallel group
Participants	Baseline Characteristics Nitrous oxide‐free – A Number randomized: 740 Number analysed: 310 Age (mean): NR for subsample with outcome % male: 0 Type of surgery: Outcome data ‐ 231 terminations of pregnancy: 79 laparoscopy Nitrous oxide‐based – A Number randomized: 750 Number analysed: 307 Age (mean): NR for subsample with outcome % male: 0 Type of surgery: Outcome data ‐ 235 terminations of pregnancy: 72 laparoscopy Included criteria: Women undergoing termination of pregnancy (TOP) or ambulatory gynaecologic laparoscopy (LAP). ASA status I or II, between 18 and 55 yrs of age, all day‐surgery patients Excluded criteria: Patients undergoing other ambulatory gynaecologic procedures were not studied, to reduce heterogeneity in study population; history of psychiatric disease, narcotic/sedative use, drug abuse, or morbid obesity (30% above ideal body weight)
Interventions	Intervention Characteristics Nitrous oxide‐free – A Name: Propofol + 100% O₂ Induction: TOP: IV fentanyl 0.7 mcg/kg. 20 mg lidocaine and 2.0 mg/kg propofol IV over 40 secs, further propofol titrated to loss of lid reflex LAP: Fentanyl 1.5 mcg/kg and d‐tubocurare 3 mg IV. 20 mg lidocaine and 2.0 mg/kg propofol IV over 40 secs, further propofol titrated to loss of lid reflex. Succinylcholine 1.5 mg/kg IV, oral intubation. After induction, 0.075 – 0.1 mg/kg vecuronium IV Maintenance: TOP: 100% O₂. Intermittent bolus doses of 20 mg propofol in response to clinical signs of light anaesthesia (movement, laccrymation, or phonation in response to surgical stimuli, or increases in blood pressure, pulse rate, or respiratory rate of ≥ 20%) LAP: 100% O₂. Infusion of propofol 100 – 200 mcg/kg/min supplemented by intermittent bolus doses of 20 mg propofol in response to clinical signs of light anaesthesia (movement, laccrymation in response to surgical stimuli or increases in blood pressure, or pulse rate of ≥20%) Recovery: At the end of surgery, neuromuscular blockade was reversed with atropine 0.02 mg/kg and neostigmine 0.04 mg/kg. In all participants, propofol and N₂O were discontinued when the dressing was applied at the end of surgery Other drugs used: NR Premedication: No premedication was given Duration of anaesthesia (min): NR Nitrous oxide‐based – A Name: Propofol + 65% N₂O Induction: TOP: Fentanyl 0.7 mcg/kg IV. 20 mg lidocaine and 2.0 mg/kg propofol IV over 40 secs, further increments of propofol titrated to loss of lid reflex LAP: Fentanyl 1.5 mcg/kg and d‐tubocurare 3 mg IV. 20 mg lidocaine and 2.0 mg/kg propofol IV over 40 secs, further increments of propofol titrated to loss of lid reflex. Succinylcholine 1.5 mg/kg IV and oral intubation. After induction, 0.075 – 0.1 mg/kg vecuronium IV Maintenance: TOP: N₂O and O₂ FiO₂ 35% administered by mask. Intermittent bolus doses of 20 mg propofol in response to clinical signs of light anaesthesia (movement, laccrymation, or phonation in response to surgical stimuli, or increases in blood pressure, pulse rate, or respiratory rate of ≥ 20%) LAP: N₂O and O₂ FiO₂ 35%. Anaesthesia maintained with an infusion of propofol 100 – 200 mcg/kg/min supplemented by intermittent bolus doses of 20 mg propofol in response to clinical signs of light anaesthesia (movement or laccrymation in response to surgical stimuli or increases in blood pressure, or pulse rate of ≥ 20%) Recovery: At the end of surgery, neuromuscular blockade was reversed with atropine 0.02 mg/kg and neostigmine 0.04 mg/kg. In all participants, propofol and N₂O were discontinued when the dressing was applied at the end of surgery Other drugs used: NR Premedication: No premedication was given Duration of anaesthesia (min): NR Monitoring: Clinical signs as described above
Outcomes	Accidental awareness The incidence of perioperative dreaming and awareness during anaesthesia was assessed in 649 participants 1 hr and 24 hrs after surgery, face‐to‐face or telephone interview using a questionnaire. No reason given why only in subsample and not clear whether based on 1‐ or 24‐hr interview. Only 1 participant in this study reported intraoperative awareness (laparoscopy, N₂O group). The attending anaesthesiologist noted that "this event was likely caused by a kinked IV line that interrupted the flow of propofol for a short period"
Identification	Country: Canada Setting: 4 hospitals in Ontario Authors name: Ramiro J. Arellano Institution: Department of Anesthesia, University of Toronto Email: arellano@is.dal.ca Address: Department of Anesthesia,Queen Elizabeth II Health Sciences Center, Halifax Infirmary, 1796 Summer Street, Halifax, Nova Scotia, Canada, B3H 3A7
Aim of study	This study in women undergoing ambulatory gynaecologic surgery compares outcomes in participants administered total intravenous anaesthesia with propofol versus the propofol plus N₂O. The primary outcome was the time to home readiness. Secondary outcomes included the incidence of postanaesthetic adverse events
Notes	"Six hundred forty‐nine patients were questioned postoperatively about perioperative dreams." Numbers in relevant table (table 5 of paper) do not add up to 649 for either 1‐hr or 24‐hr column. We have used the 24‐hr column numbers. Numbers randomized: propofol: 497 TOP: 243 lap; propofol +N₂O 503 TOP: 247 lap Sponsorship source: Supported by a grant from Physicians Services Incorporated Foundation, Toronto, Ontario, Canada
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	Quote: "randomly allocated by computer‐generated random numbers in blocks of four to receive either total intravenous anesthesia with propofol (TIVA group) or propofol and N₂O (N₂O group). Stratification by hospital site and surgical procedure ensured that roughly equal numbers of subjects within both treatment groups were enrolled at each site"
Allocation concealment (selection bias)	Low risk	Quote: "Patients were allocated to either the TIVA or N₂O group when the anesthesiologist opened the sealed opaque envelopes at induction of anesthesia"
Blinding of participants and personnel (performance bias) All outcomes	High risk	Quote: "anesthesiologists were not blinded to treatment allocation to ensure safe anesthetic care. Biased administration of the anesthetics and unblinding of the research assistants were prevented by the following: (1) pre‐enrollment training of anesthesiologists to standardize anesthetic administration; (2) random visits by the principal investigator to discuss the anesthetic protocol with the anesthesiologists; (3) ongoing review of the anesthetic study sheets by the principal investigator; (4) restricting the research assistants from access to the operating rooms or patients’ charts" Comment: No mention of participant blinding
Blinding of outcome assessment (detection bias) All outcomes	Low risk	Quote: "Four research assistants blinded to treatment allocation enrolled patients into the study, obtained demographic and baseline information, and collected postoperative data" Comment: No mention of participant blinding
Incomplete outcome data (attrition bias) All outcomes	High risk	Quote: "Six hundred forty‐nine patients were questioned post‐ operatively about perioperative dreams" Comment: Only 617/1490 participants had outcome data. No reason given
Selective reporting (reporting bias)	Low risk	Comment: All relevant outcomes described in Methods reported
Other bias	Low risk	Comment: None identified