Effect of Remifentanil on the Recovery Profile After Prolonged Head and Neck Surgery
Condition: Pain; Head and Neck Disorder
Study type: Observational

Summary: 
      Opioid tolerance in the perioperative period is inevitable especially with ultra-short acting
      agents such as remifentanil. Existing evidence had shown that opioid induced hyperalgesia due
      to neuroplastic changes in the central as well as peripheral nervous system leads to
      sensitization of pro-nociceptive pathways. However there has been a controversy of occurrence
      of such tolerance following the use of remifentanil and the quality of recovery as compared
      to conventional opioids. The investigators evaluated the occurrence of opioid tolerance and
      other significant adverse effects with remifentanil in subjects undergoing head and neck
      surgeries. The investigators studied ASA physical status I and II adult subjects undergoing
      elective head and neck procedures, under general anesthesia with minimum expected duration of
      2 hours. The remifentanil infusion was used in one group and intermittent boluses of morphine
      or fentanyl administered in another group. They were evaluated for immediate post-operative
      pain by using numerical rating scale (NRS), the opioid consumption, post-operative nausea,
      vomiting, other significant adverse effects of remifentanil and the time to discharge from
      PACU.
    

Detailed description: 
      We have studied 222 of you between the age of 21 and 80 years, over a period of 2 years at
      Singapore General Hospital, Singapore. All of you were ASA I to II and scheduled for elective
      head and neck surgery with minimum expected duration of 2 hours, requiring general
      anesthesia. The methodology of this observational study was approved by the International
      review Board at Singapore General Hospital, Singapore. Informed consent was obtained from you
      prior to the procedure. If you had previous history of either drug or alcohol abuse, have
      been using opioids for long term, mental disorder with difficult to understand pain scoring
      system, ASA physical status of III and above, your surgical procedure warranting elective
      postoperative ventilation you would have been excluded from this study. The study was not
      randomized and the choice of intra-operative opioids were left to the discretion of
      anesthesiologist attending you.

      You were not premedicated and instructed about 11 point numerical rating score after reaching
      induction room. Upon arrival in the operating room, you were monitored with EKG, non-invasive
      arterial pressure and pulse oxymetry. The attending anesthesiologist gave you either
      Remifentanil or conventional opioids at standard doses from the induction of anesthesia to
      end of surgery. Sevoflurane, desflurane or isoflurane with oxygen air mixture were utilized
      to maintain anesthesia at the minimum alveolar concentration of 0.8 to 1.2 . Choice of
      opioid, volatile agent, muscle relaxants, airway was left to the discretion of the
      anesthesiologist attending the patient. Parameters including type of volatile anesthetic
      agent, method of air way establishment, the duration of surgery, the remifentanil used
      (microgram.kg-1 ) and amount of morphine or fentanyl (microgram.kg-1) were documented. Upon
      arrival to the PACU you were assessed for the pain.

      For the first 15 minutes behavioral score (0 - calm patient with no verbal or behavioral
      manifestation of pain, 1 - behavioral or verbal expression of pain, and 2 - intense
      behavioral or verbal manifestation [crying or extreme agitation]) were utilized and
      subsequently numerical rating scale (NRS) was used for every 5 minutes until discharge from
      the PACU.

      Intravenous morphine or fentanyl was used to treat immediate post-operative pain in PACU till
      the NRS is less than or equal to 3 as per PACU acute pain management protocol. Maximum NRS of
      pain, amount of morphine or fentanyl used for rescue analgesia, occurrence of either nausea
      or vomiting and the antiemetic used was gathered every 15 minutes. Upon discharge from the
      PACU, total opioids consumed, duration of the PACU (defined by time since admission to
      decision made for discharge by PACU anesthesiologists, to rule out the prolong PACU stay from
      other reasons) and occurrence of other potential side effects that affect the quality of
      recovery such as drowsy, nausea, vomiting, shivering and evidence of respiratory suppression
      ( desaturation or bradypnea ) were documented.

      Our primary outcome was amount of opioids used in PACU and the secondary outcomes were the
      duration of PACU stay and the adverse effects of remifentanil that influence the recovery as
      stated above.
    

Intervention name(s): Remifentanil; choice of intra-operative opioids were left to the discretion of anesthesiologist
Intervention type(s): Drug; Drug
Intervention description(s): The remifentanil infusion was used intra operatively in remifentanil group and intermittent boluses of morphine or fentanyl administered for conventional opioid group
Intervention MeSH terms: Remifentanil
Observational model: Case-Control
Time perspective: Prospective
Sampling method: Non-Probability Sample
Study population: 
        We studied 222 adult subjects between 21 and 80 years, over two years at Singapore General
        Hospital, Singapore. All subjects were ASA I to II and scheduled for elective head and neck
        surgery with minimum expected duration of 2 hours, requiring general anesthesia.
      
Keywords: remifentanil; head and neck surgery; recovery pofile; Opioid induced hyperalgesia; post operative pain