Nitrous Oxide Added at the End of Sevoflurane Anesthesia and Recovery
Condition: Elective Surgical Procedures; Laparoscopy; Laparotomy; Anesthesia, General; Anesthesia Recovery Period
MeSH terms: Postoperative Nausea and Vomiting
Study type: Interventional

Summary: 
      Addition of nitrous oxide N2O towards the end of prolonged isoflurane anesthesia hastens
      patients recovery. The hypothesis is that the addition of N2O at the end of prolonged
      sevoflurane anaesthesia also hastens early recovery without increasing the frequencies and
      intensity of PONV and improves quality of recovery.
    

Detailed description: 
      The investigators will include 100 adult patients, American Society of Anesthesiologists
      (ASA) physical status I-III, who will be scheduled for elective laparotomies or laparoscopic
      surgeries under sevoflurane anesthesia lasting 120 minutes or longer. After written informed
      consent participants will be randomized into two groups: GO2 - air in 30% oxygen and GN2O -
      the same mixture until the last 30 minutes of surgery when 70% N2O in 30% oxygen will be
      used. General anesthesia will be performed with propofol and fentanyl for anesthesia
      induction, rocuronium for muscle relaxation and volatile anesthetic sevoflurane for
      maintenance. The participants will be extubated in the operation room (OR) after they open
      their eyes and follow commands. Postanesthetic recovery score by Aldrete, Ramsay sedation
      scale (RSS), and Simplified postoperative nausea and vomiting impact scale score by Myles
      (PONV ISS) will be used to assess recovery in PACU and surgical ward. Modified Aldrete score
      assigns a score of 0, 1, or 2 to activity, respiration, circulation, consciousness, and
      color, giving a maximal score of 10 ( score of 9 indicates recovery sufficient for the
      patient to be transferred from the PACU). RSS [score 1-6] consists of six levels of sedation
      [Awake levels: 1, anxious and agitated or restless or both; 2, co-operative, orientated, and
      tranquil; 3,responds to commands only. Asleep levels are dependent on the response to a light
      glabellar tap or loud auditory stimulus: 4, a brisk response; 5, a sluggish response; 6, no
      response]. PONV ISS is the sum of the numerical responses to questions Q1 and Q2 ( Q1: The
      vomiting or dry-retching count? 0 - 2 or 3 (three or more times); Q2: Severity of nausea -
      interference with activities of daily living: score 0-3 [0 - not at all, 1-sometimes, 2-
      often or most of the time, 3 - all of the time] and score ≥5 defines clinically important
      PONV. Quality of Recovery questionnaire (QoR-40) on the first, second and third postoperative
      days will be used for assessment of postoperative quality of recovery.The QoR-40 consists of
      five clinically relevant dimensions: (i) physical comfort (12 items), (ii) emotional state (9
      items), (iii) physical independence (5 items), (iv) psychological support (7 items), and (v)
      pain (7 items). Each item is rated on a five-point Likert scale. The QoR-40 score ranges from
      40 (extremely poor quality of recovery) to 200 (excellent quality of recovery). A 100 mm
      visual analogue scale (VAS) [0= no pain, 10= maximal pain] and the use of postoperative
      analgesics (opioids/non-opioids: yes or no, quantity in milligrams) shall be used for pain
      assessment during the first 24 postoperative hours.The sample size for early recovery time
      (primary endpoint) is based on the results of our recent study. The sample size was
      calculated on the assumption that 15 (SD 7) min would be needed for early recovery for the
      GO2 patients and that the GN2O patients would require four minutes less time (11 [SD 5] min).
      We would need 38 participants in each group for the primary outcome to have a power of 0.8
      and an alpha level of 0.05.
    

Intervention name(s): Nitrous Oxide
Intervention type(s): Drug
Intervention description(s): The nitrous oxide group (GN2O) will receive 70% N2O in 30% O2 at the end of surgery.
Intervention MeSH terms: Nitrous Oxide
Allocation: Randomized
Intervention model: Parallel Assignment
Intervention model description: Intervention Model: Parallel Assignment
Masking: Double (Participant, Outcomes Assessor)
Primary purpose: Treatment
Keywords: Anesthetics, Inhalation; Anesthesia Recovery Period; Postoperative Nausea and Vomiting; Pain, Postoperative