Conditions: Scoliosis
Keywords: dexmedetomidine neuromonitoring spine procedures safe dose 1- safe dose of dexmedetomidine when used in total intravenous anesthesia for procedures require neuromonitoring 2- safe dose of propofol when uses in comination with dexmedetomidine in neuromontoring 3effect of dexmedetomidine on somatosensory evoked potential and motor evoked potentials
Allocation: RANDOMIZED | Intervention model: FACTORIAL
Enrollment: 44
Healthy volunteers: no

Brief summary:
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.

Detailed description:

Arms:
arm 1: Dexmedetomidine low infusion, Propofol low infusion arm 2: Dexmedetomidine high infusion, Propofol low infusion arm 3: Dexmedetomidine high infusion, Propofol high infusion arm 4: Dexmedetomidine intermediate infusion, Propofol intermediate infusion arm 5: Dexmedetomidine low infusion, Propofol high infusion

Interventions: intervention 1: low dexmedetomidine, low propofol intervention 2: high dexmedetomidine, low propofol intervention 3: Dexmedetomidine intervention 4: Dexmedetomidin intervention 5: Dexmedetomidine
Intervention descriptions: intervention 1: Dexmedetomidine loading dose 0.6 MCG/KG,Propofol infusion 100 MCG/KG/M intervention 2: Dexmedetomidine loading dose 1.1 MCG/KG ,Propofol infusion 100 MCG/KG/M intervention 3: Dexmedetomidine loading dose 0.6 MCG/KG,Propofol infusion 200 MCG/KG/M intervention 4: Dexmedetomidine loading dose 1.1 MCG/KG.Propofol infusion 200 MCG/KG/M intervention 5: Dexmedetomidine loading dose 0.9 mcg/kg,Propofol infusion 140 mcg/kg/min

Protocol document: