Safety and Efficacy of Using SightSaver Visual Evoked Potential (VEP) for VEP Monitoring in Prone Spine Surgery

Ischemic Optic Neuropathy Clinical Trial

— SightSaver  

Official title:

A Pilot Study to Determine the Efficacy and Safety of Detecting Subtle Visual Changes During Visual Evoked Potential (VEP) Monitoring Using SightSaver ™ Flash Visual Evoked Potential Stimulator in Spine Prone Surgery

Clinical Trial Details — Status: Active, not recruiting

Administrative data

• NCT number: NCT02643615
• Other study ID #: 2014H0208
• Status: Active, not recruiting
• Phase: N/A
• First received: December 11, 2015
• Last updated: December 28, 2015
• Start date: September 2014
• Est. completion date: September 2016

Study information

• Verified date: December 2015
• Source: Ohio State University
• Contact: n/a
• Is FDA regulated: No
• Health authority: United States: Institutional Review BoardUnited States: Food and Drug Administration
• Study type: Interventional

Clinical Trial Summary

Post-operative visual loss (POVL) following non-ocular surgical procedures is an infrequent but severe complication. Little is understood about this complication, but most cases seem to result from loss of blood flow to the optic nerve. This is a pilot, single center, prospective, randomized, two-arm study involving 20 subjects at The Ohio State University Wexner Medical Center who are scheduled to undergo spine surgery that requires prone position and at least two hours of general anesthesia or total intravenous anesthesia (TIVA) and intraoperative neurophysiological monitoring. Patients will be randomized to either general anesthesia or TIVA, and wear the SightSaver device to monitor visual evoked potentials (VEPs) during surgery in order to detect possible changes in optic nerve function that may lead to POVL. We hypothesize that this new, flexible, disposable device will yield better results and more patient satisfaction than devices currently used for visual monitoring during prone spine surgeries.

Description:

The exact mechanism underlying POVL is poorly understood, but nearly all cases seem to involve ischemic optic neuropathy (ION). Posterior ION is more commonly the result of spinal procedures. The spine surgery associated risk factors include: prone position, Trendelenburg positioning, blood loss, prolonged procedure, use of vasoconstriction agents to correct blood pressure, direct ocular compression, and hypotension [1,2]. Given the fact that the suspected mechanism is a gradual infarction of the optic nerve, POVL could theoretically be prevented based on early detection of reversible optic nerve dysfunction. Visual evoked potentials (VEP) are a highly sensitive method for detecting optic nerve dysfunction, including ischemia.

During IONM, an emitted light passes through the lens, reaching the retina and causing hyperpolarization. The signal generated by the retina in response to a flash of light is known as the electroretinogram (ERG). This response may be recorded using conventional neurophysiological equipment and reflects overall retinal function. The VEP peaks are generated during the passage of electrical signal from the retina via the optic pathways to the primary visual cortex, and can also be registered during IONM. Measurements of VEP peaks under anesthesia can vary depending on type of anesthetic regimen, some producing more interference with the electrical impulses than others.

The problems encountered during VEP monitoring are numerous: a reusable device must be cleaned in between patients, tightly fitting goggles pose a risk of damaging the eyes, goggles may fall off or move intraoperatively and be difficult to reposition once the procedure is underway. Also, the light emitting diodes tend to be too weak to produce an adequate stimulus. This pilot study presents a new different approach from current methods. The SightSaverTM visual stimulator design consists of the following key advantages over the current technologies: hygienically superior to re-usable goggles, provides physical protection to the ocular region, use of higher intensity diodes and adhesive foam padding shaped to contours of periocular region.

This pilot, single center, prospective, randomized, two-arm study will involve 20 subjects at The Ohio State University Wexner Medical Center who are scheduled to undergo spine surgery that requires prone position and at least two hours of general anesthesia or TIVA and intraoperative neurophysiological monitoring. Eligible subjects that provide voluntary and written informed consent will be included in the study with a 1:1 randomization ratio of two arms, n=10 patients per each of two anesthesia regimen groups: general anesthesia and TIVA. All patients will wear the SightSaverTM visual stimulator. IONM of VEP with include insertion of half-inch needle electrodes placed just under the skin on either side of the eye, at the top of the forehead and three along the back of the head. Flashes of light, delivered at continuous intervals, will be emitted from diodes mounted in the SightSaverTM visual stimulator. After the baseline VEP is established for the patient, monitoring of VEP will occur at every 30 minutes during surgery. If during the monitoring process, a significant VEP waveform change has occurred, an alert will trigger the surgical staff to check four different parameters: technical issues with goggles, anesthetic changes, significant blood loss or a blood pressure change. Analysis of data collected will be used to evaluate the efficacy of SightSaverTM visual stimulator for intraoperative VEP-based detection of significant visual changes during prone spine surgeries.

Recruitment information / eligibility

• Status: Active, not recruiting
• Enrollment: 20
• Est. completion date: September 2016
• Est. primary completion date: December 2015
• Accepts healthy volunteers: No
• Gender: Both
• Age group: 18 Years and older

Eligibility

Inclusion Criteria:

• Male or Female older than 18 years of age

• ASA status of I to IV and scheduled to undergo elective spinal prone position procedures under general anesthesia or TIVA only with intraoperative neurophysiological monitoring with an expected duration of surgery to be at least 2 hours

• If female, have been surgically sterilized or are postmenopausal; if of child-bearing potential, must have a negative serum pregnancy test the day of surgery

• Ability and willingness to sign informed consent

• Literate in the English language

Exclusion Criteria:

• Prisoner status

• Women who are pregnant or lactating/breast feeding

• Patients with a history of contact allergies to foam and/or plastic devices

• Any condition, which, in the opinion of the investigator, would make the subject ineligible for participation in the study, such as a history of unstable cardiovascular, pulmonary, renal, hepatic, neurologic (seizures), hematologic or endocrine abnormality (hyperthyroidism, unstable Diabetes type I/II)

Study Design

Allocation: Randomized, Endpoint Classification: Safety/Efficacy Study, Intervention Model: Parallel Assignment, Masking: Open Label, Primary Purpose: Prevention

Related Conditions & MeSH terms

• Ischemic Optic Neuropathy
• Optic Nerve Diseases
• Optic Neuropathy, Ischemic

Intervention

Device:
• VEP under TIVA
Propofol will be administered for anesthesia maintenance in patients randomized to the TIVA arm of the study. In order to record the VEPs, standard half-inch sub-dermal needle electrodes will be inserted subcutaneously around the visual area and the SightSaverTM visual stimulator will be placed to monitor VEP during surgery.
• VEP under balanced anesth.
Balanced general anesthesia with desflurane will be administered for anesthesia maintenance in patients randomized to the blanced general anesthesia arm of the study, In order to record the VEPs, standard half-inch sub-dermal needle electrodes will be inserted subcutaneously around the visual area and the SightSaverTM visual stimulator will be placed to monitor VEP during surgery.

Drug:
• Propofol
Propofol will be administered for anesthesia maintenance in patients randomized to the TIVA arm of the study. In order to record the VEPs, standard half-inch sub-dermal needle electrodes will be inserted subcutaneously around the visual area and the SightSaverTM visual stimulator will be placed to monitor VEP during surgery.
• Desflurane
Balanced general anesthesia with desflurane will be administered for anesthesia maintenance in patients randomized to the blanced general anesthesia arm of the study, In order to record the VEPs, standard half-inch sub-dermal needle electrodes will be ins

Locations

Country	Name	City	State
United States	The Ohio State University Wexner Medical Center	Columbus	Ohio

Sponsors (1)

Lead Sponsor	Collaborator
Ohio State University

Country where clinical trial is conducted

United States, 

Outcome

Type	Measure	Description	Time frame	Safety issue
Primary	Efficacy in detencting subtle intraoperative VEP changes using Sighsaver visual stimulator during spine prone surgeries under balanced general anesthesia versus TIVA.	VEP waveforms were analyzed by experienced neurophysiologists in real time and any significant changes during surgery were analyzed immediately and triggered an alert to the surgeon and anesthesia care providers as needed.	Intraoperative monitoring during the length of surgery	Yes
Secondary	The difference in VEP changes with a single and double stimuli using the Sightsaver visual stimulator		Intraoperative monitoring during the length of surgery	No
Secondary	The diiference in number of VEP alerts using Sighsaver visual stimulator during spine prone surgeries under balanced general anesthesia versus TIVA.	Comparing the rate of VEP alerts during spine prone surgeries under general anesthesia versus TIVA	Intraoperative monitoring during the length of surgery	No
Secondary	Safety of using using Sighsaver visual stimulator during spine prone surgeries under balanced general anesthesia versus TIVA (number of adverse events)	The number of adverse events related with the use of the Sightsaver visual stimulator will be collected	Intraoperative monitoring during the length of surgery	Yes