Dexmedetomidine vs Propofol on the Recordings of Deep Brain Activity Measured Through Implanted Stimulators (DEXPROPAR)

Dexmedetomidine vs Propofol on the Recordings of Deep Brain Activity Measured Through Implanted Stimulators

Effects of Dexmedetomidine vs Propofol on the Recordings of Deep Brain Activity (Local Field Potentials) Measured Through Implanted Stimulators

This clinical trial has been designed to study and compare changes in deep brain activity (field potentials) in Parkinson's disease (PD) patients while awake, and during sedation with dexmedetomidine or propofol. The recording is made through a deep brain stimulation (DBS) electrode implanted for PD management. The investigators hypothesize that dexmedetomidine produces fewer changes as compared to propofol, and that those changes are consistent and recognizable when compared to activity in patients not exposed to any sedation. Typification of those changes would in the future allow for patients to undergo this surgery comfortably while not compromising the quality of the recording and of the final clinical outcome. The principal variable analyzed is the signal's power in each of the frequency bands, absolute and relative. The analysis will include usual clinical methods such as rapid Fourier transform (FFT) and window fast Fourier transform (WFFT), wavelet analysis, Gabor, and coherence.

Comparative clinical trial, non blinded, controlled and sequential, evaluating the effects of propofol and dexmedetomidine in the basal ganglia of PD patients through a DBS electrode. It is a phase IV clinical trial evaluating the effects of a drug outside the approved. The study takes part in three phases: DBS placement under sedation with dexmedetomidine at 0.2 μg/kg/h. This will be called "dexmedetomidine record". Four days later and with no sedation, a recording will be registered in one of the specialized electrically isolated rooms at the Neurophysiology Department. This will be dubbed "basal recording". The equipment used is also the standard one used for routine postoperative recordings. 5 days after the initial surgery, and following the protocol in place for these procedures, the tunnelization and battery placement will take place. This is done under general anaesthesia. During anaesthetic induction, the patient is exposed to incremental doses of propofol. Different plasmatic concentrations will be targeted using the mathematical model in the target controlled infusion (TCI) pump. These recordings will be called "propofol at a 0.5, 1, 1.5, 2, 2.5 μg/mL".

Recording registered through the deep brain stimulation electrodes with dexmedetomidine at 0.2 μg/kg/h.

Recording registered through the deep brain stimulation electrodes with propofol at plasmatic levels of 0.5, 1, 1.5, 2, 2.5 μg/mL.

Patients will receive a loading dose of 1 µg/kg in 10 min before starting the surgery. The maintenance dose will be 0.2-1 µg/kg/h for a Ramsey Sedation Score of 3-4 during the surgery´s preparation. It will be reduced to 0.2 µg/kg/h 15 min before starting the microelectrode recording for a Ramsey Sedation Score of 2. After the placement of the deep brain stimulator we will record the local field potentials activity. In addition, the subscales of rigidity, tremor and bradykinesia of the Unified Parkinson's Disease Rating Scale (UPDRS-III) score will be evaluated. Once the deep brain stimulator recording and neurologic exploration will be over patients will receive a maintenance dose 0.2-1 µg/kg/h until the end of the surgery. It will be stopped to transfer the patient to the ICU.

The target doses are 0.5, 1, 1.5, 2 and 2.5 µg/kg. For its administration we will use the TCI (target controlled infusion) system. After programming each dose we will wait until the plasma and brain concentration of propofol are stabilized in this target and then we will record the local field potentials activity through the DBS. In addition, the subscales of rigidity, tremor and bradykinesia of the UPDRS-III score will be evaluated.

Signal power separated in bandwidth (theta, slow beta, fast beta, gamma, high frequency); absolute and relative. The comparison will be made between the different measurements: dexmedetomidine, basal and propofol.

Inclusion Criteria: Capacity to understand, consent and commit for the three phases of the study. Older than 18 years old. The patient is scheduled for DBS electrode placement for PD treatment by his neurologist. Exclusion Criteria: Allergy or hypersensibility to dexmedetomidine or propofol Cardiac blockade (types 2 and 3) without an implanted pacemaker Low blood pressure (mean < 60 mmHg) or symptoms of low cardiac output. Severe cerebrovascular disease. Pregnancy or nursing mothers.

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