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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.
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
Allocation: Randomized, Control: Dose Comparison, Endpoint Classification: Efficacy Study, Intervention Model: Parallel Assignment, Masking: Double Blind (Subject, Caregiver, Investigator, Outcomes Assessor), Primary Purpose: Treatment
Skull Pin Insertion
Toronto Western Hospital
University Health Network, Toronto
Published on BioPortfolio: 2014-07-23T21:11:00-0400
Skull pins are used to immobilize the head during craniotomy. Fixation of skull pins causes acute hemodynamic changes which may affect cerebral autoregulation and hence cerebral blood flow...
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Fractures of the skull which may result from penetrating or nonpenetrating head injuries or rarely BONE DISEASES (see also FRACTURES, SPONTANEOUS). Skull fractures may be classified by location (e.g., SKULL FRACTURE, BASILAR), radiographic appearance (e.g., linear), or based upon cranial integrity (e.g., SKULL FRACTURE, DEPRESSED).
Neoplasms of the base of the skull specifically, differentiated from neoplasms of unspecified sites or bones of the skull (SKULL NEOPLASMS).
A skull fracture characterized by inward depression of a fragment or section of cranial bone, often compressing the underlying dura mater and brain. Depressed cranial fractures which feature open skin wounds that communicate with skull fragments are referred to as compound depressed skull fractures.
A mutation named with the blend of insertion and deletion. It refers to a length difference between two ALLELES where it is unknowable if the difference was originally caused by a SEQUENCE INSERTION or by a SEQUENCE DELETION. If the number of nucleotides in the insertion/deletion is not divisible by three, and it occurs in a protein coding region, it is also a FRAMESHIFT MUTATION.
The inferior region of the skull consisting of an internal (cerebral), and an external (basilar) surface.
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