Susceptibility of Motor-Evoked Potentials to Varying Targeted Blood Levels of Dexmedetomidine
Susceptibility of Motor-Evoked Potentials to Varying Targeted Blood Levels of Dexmedetomidine
Reduction of the spinal cord injuries during scoliosis surgery is a major goal of the
 anesthesia and surgical team. Despite improvement in scoliosis surgery over the years, the
 development of neurological deficits remains the most feared complication of spine surgery.
 During scoliosis surgery it is very important to monitor the spinal cord to detect spinal
 cord injury with surgical manipulation. Continuous or intermittent intraoperative
 electrophysiological monitoring (neuron-monitoring) is used routinely during these procedures
 to provide the surgeon with information concerning the integrity of neurological structures
 at risk. All neuron-monitoring modalities are affected by the anesthetic regimen used. Of the
 various intravenous anesthetic drugs, the combination of propofol, remifentanil and
 dexmedetomidine appear to impact neuron-monitoring the least. The current anesthetic practice
 is to use the three drugs in combination at doses that do not depress the signals but there
 is no data relating targeted dexmedetomidine and propofol blood levels to neuron-monitoring
 signals. The lack of data results in wide variability in dosing with consequent variability
 in patient response.

 Hypothesis: Clinically relevant blood levels of dexmedetomidine will affect the amplitude of
 transcranial motor-evoked potentials (TcMEP) either independently or by interaction with
 propofol in a dose dependent manner.
Inclusion Criteria:

 -  Subjects must be 10 to 25 years of age

 -  Diagnosis of idiopathic scoliosis is established

 -  Subject's legal authorized representative has given written, informed consent to
 participate in the study and, where appropriate, the subject has given assent to
 participate

 -  American society of Anesthesiology physical status one/two

 -  Patients scheduled for posterior spinal fusion only

 Exclusion Criteria:

 -  • Patients with neuromuscular scoliosis and patients with motor or sensory deficit in
 the lower extremities

 -  Patients with allergy to, or contraindication for the drugs or techniques used in
 the study

 -  Morbid obesity (Body mass index higher than 40)

 -  History of malignant hyperthermia

 -  Patient with severe cardiopulmonary disease (pulmonary hypertension,
 cardiomyopathy, mechanical ventilation)