Ignite Creation Date:
2024-05-05 @ 11:55 AM
Last Modification Date:
2024-10-26 @ 9:16 AM
Study NCT ID:
NCT00176722
Status:
TERMINATED
Last Update Posted:
2015-04-24
First Post:
2005-09-13
Brief Title:
Intraocular Pressure During Prone Spinal Surgery
Sponsor:
University of Medicine and Dentistry of New Jersey
Organization:
Rutgers The State University of New Jersey
Study Overview
Official Title:
The Effect of Table Position on Intraocular Pressure IOP and Ocular Perfusion Pressure OPP During Prone Spine Surgery
Status:
TERMINATED
Status Verified Date:
2015-04
Last Known Status:
None
Delayed Posting:
No
If Stopped, Why?:
Principal Investigator is leaving the UMDNJ
Has Expanded Access:
False
If Expanded Access, NCT#:
N/A
Has Expanded Access, NCT# Status:
N/A
Acronym:
None
Brief Summary:
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
Detailed Description:
Postoperative permanent visual loss is a rare but devastating complication of surgery estimated to occur after approximately 160000 anesthetics After procedures involving cardiopulmonary bypass and prone spinal surgery the estimates are higher 11600 to 11100 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 andor 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
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 andor 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
Study Oversight
Has Oversight DMC:
None
Is a FDA Regulated Drug?:
None
Is a FDA Regulated Device?:
None
Is an Unapproved Device?:
None
Is a PPSD?:
None
Is a US Export?:
None
Is an FDA AA801 Violation?:
None