Intraocular Pressure During Prone Spinal Surgery

This study has been terminated.
(Principal Investigator is leaving the UMDNJ)
Sponsor:
Collaborators:
Foundation for Anesthesia Education and Research
New Jersey Eye Institute
Information provided by:
Rutgers, The State University of New Jersey
ClinicalTrials.gov Identifier:
NCT00176722
First received: September 13, 2005
Last updated: May 6, 2010
Last verified: May 2010
  Purpose

Postoperative visual loss resulting from surgical procedures not performed on the eye is a devastating outcome for the patient and poorly understood by the medical community. It is potentially a preventable complication. Diminished blood supply to the optic nerve, affecting both the anterior or posterior portions of the optic nerve, is the most common cause of postoperative visual loss. Other, less common causes include occlusion of the retinal artery and vein, a retinal embolism and cortical blindness. The incidence of postoperative visual loss increases in patients undergoing cardiopulmonary bypass and prone spinal surgery. Although the etiology of postoperative visual loss is unknown, it is thought to be multifactorial, and several potential risk factors have been identified, including degree of low blood pressure, preoperative hematocrit, external compression of the eye, amount of blood loss, prolonged duration of surgical time and lying in the face down position. The investigators believe this study is a unique opportunity to examine the mechanisms responsible for the antecedents to postoperative visual loss (POVL) and ischemic optic neuropathy (ION), a devastating complication of (usually) an elective surgical procedure. The purpose of this research is to try and determine the potential variables responsible for postoperative visual loss which will assist the medical community in devising methods for its prevention.


Condition Intervention Phase
Spine Surgery
Vision Impairment
Other: table tilt
Phase 2

Study Type: Observational
Study Design: Time Perspective: Prospective
Official Title: The Effect of Table Position on Intraocular Pressure (IOP) and Ocular Perfusion Pressure (OPP) During Prone Spine Surgery

Further study details as provided by Rutgers, The State University of New Jersey:

Primary Outcome Measures:
  • changes in intraocular pressure and retinal oximetry [ Time Frame: over introperative time ] [ Designated as safety issue: No ]

Enrollment: 7
Study Start Date: June 2006
Estimated Study Completion Date: January 2012
Estimated Primary Completion Date: October 2011 (Final data collection date for primary outcome measure)
Groups/Cohorts Assigned Interventions
surgical
males & females undergoing spine surgery in the prone position
Other: table tilt
One group randomized to table tilt. One group will be flat.

Detailed Description:

Postoperative permanent visual loss is a rare but devastating complication of surgery estimated to occur after approximately 1/60,000 anesthetics. After procedures involving cardiopulmonary bypass and prone spinal surgery, the estimates are higher, 1/1600 to 1/1100, respectively and have led to the formation in July of 1999 of the Postoperative Visual Loss (POVL) Registry under the auspices of the American Society of Anesthesia (ASA) Committee on Professional Liability. The majority of reported cases as of early 2003 were associated with spine surgery (67%).

Of the spine cases, the majority were due to ischemic optic neuropathy (ION) (81%) followed by central retinal artery occlusion (13%) and unknown diagnosis (6%). Central retinal artery occlusion is characterized by periorbital edema, a cherry red spot at the fovea and monocular blindness. It is thought to be due to direct prolonged extraocular pressure on the globe and thus is preventable. Direct pressure on the eye is the etiology most often mentioned by spine surgeons in an attempt to explain all forms of postoperative visual loss.

Post anesthetic ION, affecting both the anterior and posterior portions of the optic nerve, however, is the more common diagnosis. The etiology is unclear but hypo perfusion of the optic nerve has been associated with multiple risk factors. The four patient factors are obesity, hypertension, diabetes and low preoperative hematocrit. There are five surgical factors, which include an operation of long duration, large blood loss, prone position, deliberate hypotension, and blood replacement strategies which increase the tissue fluid compartment while decreasing the hematocrit. ION occurs in patients who had their heads suspended in Mayfield tongs (18% of ION cases), virtually eliminating any source of external pressure. In addition, 58% of these patients had bilateral disease, making direct pressure less likely.

Thus, most POVL cases appear to be directly related to a change in retinal and/or optic nerve perfusion. The visual loss associated with anterior ION is caused by infarction in the watershed zones between the areas supplied by the posterior ciliary arteries, which are end arteries without anastomosis. Posterior optic neuropathy is thought to be caused by decreased oxygen delivery to the posterior portion of the optic nerve between the orbital apex and the entrance of the central retinal artery.

Critical to any discussion of perfusion to the eye is the concept of ocular perfusion pressure (OPP), defined as the difference between the mean arterial pressure (MAP) and the intraocular pressure (IOP). Unopposed decreases in MAP, increases in IOP or a combination of the two may result in hypo perfusion of the eye and can cause an ocular infarction at the level of the retina or optic nerve, leading to varying degrees of visual loss which is frequently bilateral and irreversible.

Animal data indicate that IOP increases with downward head tilting in the supine position, possibly due to increased episcleral venous pressure. Limited data for awake human volunteers indicate that IOP increases with supine positioning and is further elevated with head down tilting and prone positioning again possibly due to a rise in episcleral venous pressure.

This is a randomized prospective study examining the effect of the table position on intraocular pressure and ocular perfusion pressure during spine surgery.

Subjects will be recruited following the preoperative visit to the Neurosurgical office. An informed consent will be obtained after the consent for surgery is signed. A visual acuity exam will be performed with one of the study team members with the subject wearing corrective lenses on the morning of the surgery. The reactivity of the pupil will also be assessed via a penlight.

  Eligibility

Ages Eligible for Study:   18 Years to 65 Years
Genders Eligible for Study:   Both
Accepts Healthy Volunteers:   No
Sampling Method:   Probability Sample
Study Population

Subjects undergoing spine surgery in the prone position.

Criteria

Inclusion Criteria:

  • Men and women between the ages of 18 and 65 years of age who are mentally capable of providing an informed consent.
  • Planned elective spinal surgery in which the modified Jackson table will be used.

Exclusion Criteria:

  • Failure to provide an informed consent
  • History of stroke
  • Known history of corneal disease
  • Known history of carotid disease
  • Known history of sensitivity to cyclogyl and/or proparacaine HCL 0.5%
  Contacts and Locations
Choosing to participate in a study is an important personal decision. Talk with your doctor and family members or friends about deciding to join a study. To learn more about this study, you or your doctor may contact the study research staff using the Contacts provided below. For general information, see Learn About Clinical Studies.

Please refer to this study by its ClinicalTrials.gov identifier: NCT00176722

Locations
United States, New Jersey
University of Medicine & Dentistry - New Jersey Medical School
Newark, New Jersey, United States, 07101
University of Medicine & Dentistry of NJ
Newark, New Jersey, United States, 07101
Sponsors and Collaborators
University of Medicine and Dentistry of New Jersey
Foundation for Anesthesia Education and Research
New Jersey Eye Institute
Investigators
Principal Investigator: Geordie Grant, MD Rutgers, The State University of New Jersey
  More Information

No publications provided

Responsible Party: Geordie P. Grant, MD, UMDNJ
ClinicalTrials.gov Identifier: NCT00176722     History of Changes
Other Study ID Numbers: 0120040320
Study First Received: September 13, 2005
Last Updated: May 6, 2010
Health Authority: United States: Institutional Review Board

Keywords provided by Rutgers, The State University of New Jersey:
Spine Surgery
Intraocular Pressure
lumbar or thoracic Spine Surgery in the prone position
and its association with visual change

Additional relevant MeSH terms:
Vision, Low
Vision Disorders
Sensation Disorders
Neurologic Manifestations
Nervous System Diseases
Eye Diseases
Signs and Symptoms

ClinicalTrials.gov processed this record on July 20, 2014