Dexmedetomidine on Intraoperative Somatosensory and Motor Evoked Potential Monitoring During Neurosurgery in Pediatric Patients

Dexmedetomidine on Intraoperative Somatosensory and Motor Evoked Potential Monitoring During Neurosurgery in Pediatric Patients

Measuring the Effects of Dexmedetomidine on Somatosensory Evoked and Muscular Evoked Potential During Neurosurgery in Pediatric Patients

The investigators want to know if using the study drug dexmedetomidine will improve nerve wave readings during neurosurgery. These readings are done many times during surgery while the patient is asleep. The readings look at how nerves are working and let the operating team know if nerves are hurt during surgery. If the readings tell that nerves are not working correctly, the surgeons can help while changing the way of operating. The study drug will be used in addition to the general anesthesia that a patient is given. The nerve readings that the investigators get while using the study drug will be compared with nerve readings that the investigators get while not using the study drug. The study hypothesis is that dexmedetomidine does not change nerve readings.

Somatosensory evoked potential (SSEP) and motor evoked potential (MEP) have become an integral component in intraoperative care of patients and have resulted in a high degree of sensitivity in predicting neurologic outcomes. According to Padberg, Nuwer and Ecker ,SSEP and MEP monitoring allows surgical interventions to occur early and thus decreases the incidence of postoperative neurologic deficits. These measurements are done during surgery under general anesthesia and it is known that anesthetic agents have a dose-dependent adverse effect on the ability to record evoked potential responses. All anesthesia agents seem to interfere with the measurements especially in higher doses. In 1999, dexmedetomidine, a highly specific and selective alpha-2-adrenergic agonist with sedative, anxiolytic and analgesic effects, got FDA approved for adult patients for sedation. Since then, it has also been widely used off-label in various settings; it is described as a successful adjunct for surgical procedures in adolescents and adult populations where SSEP/ MEP monitoring is beneficial. Several small and retrospective studies have shown that dexmedetomidine does not appear to interfere with neurophysiological monitoring when used in FDA approved doses. In pediatric patients, dexmedetomidine is also used off-label and has been shown to be beneficial. In fact, at Doernbecher Childen's Hospital, the use of dexmedetomidine has become a standard in pediatric procedures involving SSEP and MEP measurements. To the best of our knowledge, prospective studies in pediatric patients with SSEP monitoring while using dexmedetomidine have not been completed. If dexmedetomidine does not interfere the SSEP/MEP reading, it might be an advantageous adjunct to use in these settings. Propofol has a small risk of a serious side effect called propofol infusion syndrome. Propofol infusion syndrome is potentially life threatening, with the development of a profound lactate acidosis. It is seen when large doses of propofol (usually from a prolonged infusion) are given in the pediatric population.

Our trial will examine the changes in latency and amplitude of SSEP and changes in amplitude and morphology of MEP while using different anesthetic combinations including isoflurane, proposal and dexmedetomidine. Monitoring teams will document any changes throughout the surgery and communicate with the team about those changes. The design of the study will be a prospective AB design.

We will include following general anesthesia techniques: Fentanyl 1 - 2 mcg/kg/hr, Propofol 150 - 250 mcg/kg/min, Isoflurane 0.6% expiratory With this general anesthesia technique we will do our first SSEP/MEP measurements after 30 minutes. After 30 minutes we will stop isoflurane and will wash out the inhalational anesthetic with high flow air/oxygen and provide: Fentanyl 1 - 2 mcg/kg/hr, Propofol 150 - 250mcg/kg/min. This technique will be held for 30 minutes. SSEP/ MEP measurements will be done after 30 minutes. After the measurements dexmedetomidine will be added with a loading dose of 0.5 mcg/kg over 10 minutes and continuous infusion of 0.5 mcg/kg/hr for 30 minutes. Fentanyl 1 -2 mcg/kg/hr, Propofol 100 - 250mcg/kg/min, Dexmedetomidine 0.5 mcg/kg/hr.

Significant improvement of MEP and SSEP readings during neurosurgery for pediatric patients while using dexmedetomidine as an adjunct to general anesthesia and therefore improvement in clinical decision making.

Changes in latency and amplitude of SSEP and changes in amplitude and morphology of MEP while using different anesthetic combinations including isoflurane, propofol and dexmedetomidine.

Inclusion Criteria: Pediatric patients between 2 and 12 years old Undergoing neurosurgery and Requiring SSEP/ MEP measurements Exclusion Criteria: Patients younger than 2 and older than 12 years Patients with known bradyarrhythmias Patients with severe liver disease Conditions that may alter reading, e.g. neuromuscular diseases

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