Effect of Remifentanil Boluses on Hemodynamics in Skull Pin Insertion
Condition: Skull Pin Insertion; Short Duration Analgesia
Study type: Interventional

Summary: 
      Skull pin insertion during craniotomies is a brief, intensely stimulating, painful stimuli
      occurring during the conduct of a neurosurgical or spine anesthetic. Remifentanil is an ultra
      short acting opioid that has been successfully used to blunt hemodynamic responses in a wide
      variety of clinical scenarios. It is our intention to ascertain the optimal dose for blunting
      the hemodynamic response to skull pin insertion using remifentanil.
    

Detailed description: 
      Skull pin insertion is commonly required for craniotomies and cervical spine surgery. It is a
      brief but highly stimulating maneuver performed following induction, during a period of light
      anesthesia, and may cause significant rise in blood pressure, heart rate and intracranial
      pressure if not anticipated and treated.

      A wide variety of methods have been shown to be effective at blunting this hypertensive
      response. These include intravenous agents such as fentanyl, sufentanil, clonidine, ketamine
      and magnesium sulphate, local anesthetic methods such as injection at pin sites or full scalp
      blocks, deepening the volatile agent, oral premedication or a combination of these methods.
      There is no consensus on which of these methods is the best. Many anesthesiologists simply
      use boluses of propofol - a reliable way of accomplishing this effect with a familiar drug.
      It is also very common for anesthesiologists to use remifentanil, by increasing the infusion
      rate and or bolusing.

      Remifentanil is an ultra-short acting opiate with such rapid onset and offset, that it is
      most easily and safely delivered by infusion. Increasingly in the literature, however, are
      reports of remifentanil administered as boluses rather than infusions. Boluses may be ideal
      for very short stimulating procedures such as intubation and skull pin fixation where a quick
      onset and offset are desired. Although the safety of bolusing remifentanil has been
      established in many studies , some authors are still apprehensive . Care must be taken to
      avoid bolusing with greater doses than required since this may lead to bradycardia and
      hypotension. In non-ventilated patients, respiratory depression is common and chest wall
      rigidity may occur at doses larger than 4ug/kg9.

      Different bolus dose-effect studies have recommended the following for remifentanil in a
      variety of clinical settings:

        -  3-5ug/kg with propofol 2mg/kg for intubation without muscle relaxants ,

        -  2ug/kg with propofol TCI (>4ug/ml) and cisatracurium for intubation (no additional
           hemodynamic benefit using 4ug/kg)

        -  1-1.25ug/kg for rapid sequence intubation with thiopentone 5-7mg/kg and succinylcholine
           1mg/kg

        -  ED50 of 1.7ug/kg and ED95 of 2.88ug/kg for good to excellent intubating conditions in
           both infants and children (when used with 10ug/kg glycopyrrolate and 4mg/kg propofol)

        -  3ug/kg (plus 4mg/kg propofol) provides similar intubating conditions when used in place
           of succinylcholine 2mg/kg for intubation in infants8

      Remifentanil is not currently recommended for the following settings:

        -  As a sole agent for loss of consciousness with a high ED50 of 12ug/kg, lack of
           reliability and muscle rigidity common at such high doses

        -  Wide interindividual variability limit its use for labor analgesia (0.2-0.8ug/kg, median
           dose of 0.4ug/kg)

      In neurosurgery, it is common to administer remifentanil as an infusion. Optimal infusion
      rates have already been investigated for intracranial surgery . However it is increasingly
      common to administer remifentanil as a bolus particularly during skull pin fixation, due to
      the desirable quick onset and offset, and there are no studies at present that have
      investigated optimal dose requirements for boluses in this setting.

      At our institution we commonly administer remifentanil as a bolus during skull pin fixation
      and are interested in determining which bolus doses are safe and effective
    

Intervention name(s): Remifentanil
Intervention type(s): Drug
Intervention description(s): A single bolus dose of Remifentanil will be administered at the time of skull pin insertion
Intervention MeSH terms: Remifentanil
Allocation: Randomized
Intervention model: Parallel Assignment
Masking: Quadruple (Participant, Care Provider, Investigator, Outcomes Assessor)
Primary purpose: Treatment
Keywords: skull pin insertion; remifentanil; short acting opioid; craniotomy; cervical spine surgery; hemodynamic changes; dose requirement; age related