The purpose of this study is to characterize the effects of intravenous lidocaine on pain processing and cognitive function. Functional magnetic resonance imaging will be used to identify the neural correlates of these phenomena. The study will consist of 1 visit and involves no long-term follow up.
This is an observational cohort study of volunteer subjects, which will employ neuroimaging and behavioral measures to characterize the effects of intravenous lidocaine on pain processing and cognitive function. A steady-state effect-site concentration of lidocaine will be achieved, and a short battery of cognitive behavioral tasks will be employed. At the dose target, pain task functional MRI and resting-state connectivity will be determined. This work will use a systems neuroscience approach to fill an important knowledge gap about the central effects of intravenous lidocaine, a commonly-used opioid alternative analgesic agent. Aim1: Determine cognitive behavioral effects of a steady-state dose of IV lidocaine using a short battery of tasks. The investigators hypothesize that the administration of lidocaine will correlate to decreased pain ratings, slowed psychomotor response, and decreased memory encoding. Aim2: Determine the neural effects of a steady-state dose of IV lidocaine in response to acute pain, and on resting connectivity. The investigators hypothesize that pain task-related activation will decrease in the insula and anterior cingulate, corresponding to decreased ratings of pain intensity and unpleasantness. Additionally, the investigators expect widespread decreases in long-range functional connectivity between brain areas know to be involved in these two areas and other known to be involved in pain processing.
Study Type
INTERVENTIONAL
Allocation
NA
Purpose
BASIC_SCIENCE
Masking
NONE
Enrollment
30
Experimental acute pain stimulus will be delivered using an electric nerve stimulator.
Subjects will receive an intravenous infusion of lidocaine for about 30 minutes.
University of Pittsburgh Medical Center
Pittsburgh, Pennsylvania, United States
Brain Activation to Painful Stimulation Difference: Drug-free Condition Minus Lidocaine Condition
The Z-score is calculated by linear regression of the task timing against the MRI signal time-course (MRI data is in arbitrary units with no maximum or minimum) at each voxel (single data point in brain). Primary outcome is listed for the Right insula, but similar scores are calculated throughout the brain. Z-score of 0 indicates no task-related changes. Z-scores further from zero indicate stronger correlation between functional MRI signal change and the task timing, with positive values indicating increases in fMRI signal and negative Z-scores indicating decreases. Practically, higher positive Z-scores indicate increased brain activity and larger negative Z-scores indicate decreased brain activity. This outcome is reported as a number, as it is calculated using all the data across subjects combined into one statistical measure for the overall strength of difference in MRI signal change between two groups of data. Dispersion measures cannot be calculated for the summary Z-score.
Time frame: 4.5 minutes
Resting-state Functional Connectivity Difference: Drug-free Minus Lidocaine
Functional connectivity (FC) measures the correlation of MRI signal time-series between brain regions. Changes in FC reflect differences in brain state, in this case between drug-free and lidocaine conditions. The reported value is the FC change between the right insula and anterior cingulate. A T-statistic of 0 indicates no change; more positive scores mean stronger connectivity in the drug-free condition, and more negative scores mean stronger connectivity with lidocaine. This outcome is a number reflecting the overall magnitude of difference between two datasets, calculated in one summary statistic. Dispersion measures cannot be calculated for the T-statistic in this analysis framework.
Time frame: 8 minutes
Pain Intensity Score Difference, Drug-free Condition Minus Lidocaine Condition
Numerical rating scale (0-10) pain score difference, comparing drug-free to the steady-state dose of lidocaine. Higher pain scores indicate more pain; a positive difference between pain score during the drug-free condition minus the value during the lidocaine condition indicates pain reduction (a better outcome).
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Time frame: 12 minutes
Memory Performance Difference, Drug-free Minus Lidocaine Condition
Performance on a short computer-based test of memory for visual pictures will be quantified using signal detection metric d-prime, reflecting ability (in standard deviation units) to detect previously-seen images from the background "noise" of previously un-seen images. Differences will be determined between the drug-free condition and the lidocaine condition. Higher values of d-prime indicate stronger memory performance; a positive difference for drug-free minus lidocaine condition would indicate the expected decrease in memory performance.
Time frame: 3 minutes
Motor Response Time Differences
Response times (in ms) after hearing a tone will be recorded and compared between the drug-free and Lidocaine condition, with the calculated difference in response times reported. Higher values will reflect slower responses, which are expected under the lidocaine condition.
Time frame: 1 minute