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Development of assessment techniques for methadone dependent patients

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Patil, SG 2010 , 'Development of assessment techniques for methadone dependent patients', PhD thesis, University of Tasmania.

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Abstract

Background:
During the past decades, use of urine testing, methadone plasma concentration (MPC), pupillometry and to some extent Reaction Time Test (RTT) has been use for assessment of opioid dependent patients (ODP). Urine and blood testing techniques have been traditionally used while others are still widely been investigated. Pupillometry and RTT techniques provide a direct measurement of the of the patients level of intoxication. However, pupillometry still requires a better understanding of the pupil characterization, eye safety standards, accommodation effects, and understanding consensual response of pupil, discretely. In addition, a systematically designed multifunctional pupillometer is required to gather all the above information and test its usefulness in clinical settings. RTT has been used in the past to some extent however its usability as an assessment tool is still under investigation.

Objectives:
A novel multifunctional pupillometry goggles was developed and used for pupil characterization measurement. We also developed a Simple Visual RTT (SVRTT) for the assessment of methadone patients. In addition, blood testing was conducted to investigate its relationship with pupillometry and SVRTT. Lastly, an arousal index was developed, that can be potentially used by physicians in clinical settings.

Material and Methods:
The pupillomety system consisted of a personal computer, goggles and a control unit. The system, capable of recoding pupil images at 10f/s for 140 seconds in one single test, was used for ipsi-lateral (IPL) and contra-lateral (COL) measurements. Pupillary characterization was studied using varied light intensities. Furthermore, SVRTT consisted of a personal computer and a mouse. The patient clicked the mouse button when visual stimulus was displayed on the computer monitor and RT was automatically recorded. Blood samples were collected for 6hrs (duration of the test) at an interval of one hour.

Results:
High correlation was obtained between MPC-Pupillometry, MPC-SVRTT, and Pupillometry-SVRTT. Pupil characterization parameter (Constriction Amplitude, Constriction Velocity, Redilation Amplitude, Redilation Velocity, Relaxation Standard Deviation) were measured and high correlations were obtained when compared with MPC and SVRTT. No significant effect was obtained in accommodation response. Differences were obtained between IPL and COL results however the differences were constant. Pupil measurements were best obtained at higher light intensity (lOOlux). Based on the data an Arousal Index (Al) was developed which correlated highly with MPC.

Discussion and Conclusion:
This work is significant advancement in understanding pupillometry characteristics discretely. The results revealed that pupil characterization can be indicative of methadone metabolism and absorption and has the potential to be used in clinical settings. It is concluded that COL and IPL measurements showed significant differences, however the differences were approximately constant and pupil response was similar in both measurements. The safety of eye while conducting pupillomety test is important, especially
when IR light or higher intensity visual light is used. SVRTT for the first time, has shown, it's potential to be used along with pupillometry in clinical settings in controlled environment. These findings, built on a sound experimental design and development, can be seen as a step towards establishing pupillometry and SVRTT as clinical assessment tool. An arousal index was developed based on the pupil measurements which can be used to predict MPC of patients during methadone absorption and metabolism.

Item Type: Thesis - PhD
Authors/Creators:Patil, SG
Keywords: pupillometry, pupillometry characterization, methadone dependent patients, reaction time test, eye safety
Copyright Information:

Copyright 2010 the author - The University is continuing to endeavour to trace the copyright owner(s) and in the meantime this item has been reproduced here in good faith. We would be pleased to hear from the copyright owner(s).

Additional Information:

Thesis (PhD)--University of Tasmania, 2010

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