Optical Tissue Stylet - descriptive observational study into paravertebral space detection in humans

For effective regional anesthesia and interventional pain treatments, correct
needle (and catheter) placement is crucial. Currently, needle placement is done
under image guidance. However, accuracy of needle placement could still be
improved if information would be available that would complement the current
imaging and electrical stimulation methods. We have developed a system based on
optical spectroscopy that has the potential to provide such complementary
information.

This study will be an observational study in a limited number of subjects to
investigate if the method can reliably identify the paravertebral space.
Detection of the paravertebral space is of particular relevance to the fields
of regional anesthesia and interventional pain treatment.

Subjects will be recruited via the preoperative screening clinic. Under general
anesthesia a thoracic paravertebral block at 3 levels, consisting of 2 single
shot blocks and 1 continuous block, will be performed which is a standard
anesthesia procedure for these types of surgery. Both the single injection
thoracic paravertebral blocks in each subject will be evaluated in this study.
A needle containing an optical stylet will be inserted towards the sonographic
endpoint in the paravertebral space; during needle advancement data will be
collected with the optical tissue stylet system. The position of the needle tip
during advancement and at the endpoint will be confirmed by real-time
ultrasound imaging. A testdose of local anesthetic with epinephrine is
administered in order to exclude vascular needle placement. Methylene blue
will be injected after the administration of local anesthetic. Subsequently, an
additional confirmation of correct needle placement within the paravertebral
space will be obtained by direct visual observation of the dye in the thoracic
paravertebral space by the thoracic surgeron during surgery. After the
measurements, the needle and optical stylet will be withdrawn and disposed of.
Off-line,data analysis of the optical spectra will be performed, to investigate
the potential of the optical tissue stylet technology to reliably discriminate
the paravertebral space from other tissues encountered during needle
advancement.

In case of positive results additional studies will be set up, for instance to
explore the potential of the optical tissue stylet technology to detect
epidural acces, and accidental needle insertion into epidural veins. At a later
stage, one could envision studies investigating if providing the optical tissue
stylet data to the physician during a procedure results in improved procedure
success rates. For more information see pages 10, 11 and 12 of the
corresponding protocol.

The primary objective of the trial is to investigate if the optical tissue
stylet technology can reliably identify the thoracic paravertebral space.
Diffuse reflectance spectra will be acquired during needle advancement, with
custom-made needle stylets that contain optical fibers.

This is a non-randomized descriptive observational study.

The procedure of inserting the needle and collecting the data will take about
20 minutes. This is about 5 minutes longer than the standard procedure.
Subjects will not experience any discomfort as the needle punctures will be
performed under general anesthesia, which is common practice in these surgical
procedures. Methylene blue is a commonly used dye in patients during medical
(diagnostic) procedures. It is used for example in endoscopic polypectomy,
chromo-endoscopy and sentinel lymph node dissections. It can also be
administered intravenously, to treat methemoglobinaemie, for example as the
result of use of prilocaine. Apart from discoloration of urine, side effects
are infrequent.
There is no direct benefit for the group of subjects; however, the results of
this investigation may in future assist the improvement of regional anesthesia
and interventional pain procedures.