Ignite Creation Date:
2024-05-05 @ 5:26 PM
Last Modification Date:
2024-10-26 @ 9:31 AM
Study NCT ID:
NCT00450294
Status:
COMPLETED
Last Update Posted:
2014-03-31
First Post:
2007-03-21
Brief Title:
Intraocular Pressure During Abdominal Aortic Aneurysm AAA Repair
Sponsor:
University of Manitoba
Organization:
University of Manitoba
Study Overview
Official Title:
The Effect of Aortic Infrarenal Clamping and Unclamping On Intraocular Pressure During Abdominal Aortic Aneurysm AAA Repair
Status:
COMPLETED
Status Verified Date:
2014-02
Last Known Status:
None
Delayed Posting:
No
If Stopped, Why?:
Not Stopped
Has Expanded Access:
False
If Expanded Access, NCT#:
N/A
Has Expanded Access, NCT# Status:
N/A
Acronym:
None
Brief Summary:
The objective of this study will be to answer a clinical question that has not already been investigated that is what are the effects of aortic infra-renal clamping and unclamping on intraocular pressure during Abdominal Aortic Aneurysm AAA repair Depending on the results this study may raise or alleviate concern that vascular surgery for abdominal aortic aneurysm could contribute to early perioperative exacerbation of pre-existing eye disease and increase a patients vulnerability to developing a type of blindness known as ischemic optic neuropathy The purpose of this observational study is to evaluate whether intraocular pressure measurements with a handheld tonometer will detect changes in intraocular pressure related to intraoperative events during aortic cross clamping and unclamping that may provide information on causes of perioperative blindness
Detailed Description:
Perioperative blindness in nonocular surgery has gained significant clinical interest as an overwhelming complication with an increasing incidence Initial published studies suggested a rare occurrence with an estimated postoperative visual loss of 0002 and 00008 12 However retrospective reviews in spinal and cardiac surgery demonstrated higher rates of perioperative blindness that is between 02 and 006 respectively 34 The difference in published reports suggests that the true incidence is likely underestimated because of fears regarding litigation ineffective means of reporting and extra work involved Fortunately numerous case reports and series in the middle to late 1990s were published prompting the American Society of Anesthesiologists ASA Committee on Professional Liability to establish the ASA Postoperative Visual Loss Registry POVL in 1999 as a medium to collect confidential comprehensive perioperative data on patients developing postoperative blindness
The POVL registry along with other case series has demonstrated that the most common cause of visual loss is non-arteritic ischemic optic neuropathy 567 Perioperative non-arteritic ischemic optic neuropathy ION is a consequence of patient and surgery specific factors that results from hypoperfusion and infarction of the optic nerve head 8 Anatomical factors such as variation in the number of short posterior ciliary arteries sPCA supplying the optic nerve head location of sPCA watershed zone and small optic cup to disk ratio increase susceptibility to optic nerve ischemia 89 Surgery specific factors involve profound blood loss anemia hypotension prone positioning and duration of surgery 56710 The interaction of these surgical variables and patient specific anatomical factors can decrease ocular perfusion pressure the difference between mean arterial pressure and intraocular pressure and result in ION 11
Based on the determinants of ocular perfusion pressure OPP low mean arterial pressure MAP andor high intraocular pressure IOP can decrease OPP and lead to ION Therefore it is necessary to investigate changes in IOP incurred from different types of surgery that may increase vulnerability to developing ION Normal IOP is between 12 - 20 mm Hg Studies have been published assessing intraocular changes with prone positioning laparoscopic surgery and cardiopulmonary bypass 121314 However there has been no literature evaluating intraocular pressure during abdominal aortic aneurysm AAA repair AAA repair is a high-risk surgery associated with blood loss hypotension and has been reported in a case series associated with ION 6 The surgery involves clamping and unclamping of the aorta to facilitate excision of the aneurysm and graft repair Aortic cross clamping and unclamping is an intense physiologic insult affecting venous return systemic vascular resistance cardiac output and acid base status These physiologic changes are further pronounced with more proximal cross-clamping and longer duration Because infrarenal abdominal aortic aneurysms are the most common type of AAA repair we will be assessing IOP with patients undergoing elective infrarenal abdominal aortic reconstruction
Infrarenal aortic cross clamping is associated with increases in venous return central venous pressure and arterial blood pressure 15 The hemodynamic changes with infrarenal unclamping entail decreases in venous return central venous pressure and arterial blood pressure 15 The determinants of intraocular pressure involve extraocular muscle tone aqueous flow choroidal blood volume and central venous pressure 16 The volume redistribution proximal to the aortic cross-clamp should cause a rise in venous pressure increase resistance to aqueous drainage and increase choroidal blood volume thereby increasing intraocular pressure However after aortic unclamping choroidal blood volume and IOP should decrease as venous return and central venous pressure decline Therefore our hypothesis is that IOP will be increased during aortic cross clamping and decreased following aortic unclamping
The POVL registry along with other case series has demonstrated that the most common cause of visual loss is non-arteritic ischemic optic neuropathy 567 Perioperative non-arteritic ischemic optic neuropathy ION is a consequence of patient and surgery specific factors that results from hypoperfusion and infarction of the optic nerve head 8 Anatomical factors such as variation in the number of short posterior ciliary arteries sPCA supplying the optic nerve head location of sPCA watershed zone and small optic cup to disk ratio increase susceptibility to optic nerve ischemia 89 Surgery specific factors involve profound blood loss anemia hypotension prone positioning and duration of surgery 56710 The interaction of these surgical variables and patient specific anatomical factors can decrease ocular perfusion pressure the difference between mean arterial pressure and intraocular pressure and result in ION 11
Based on the determinants of ocular perfusion pressure OPP low mean arterial pressure MAP andor high intraocular pressure IOP can decrease OPP and lead to ION Therefore it is necessary to investigate changes in IOP incurred from different types of surgery that may increase vulnerability to developing ION Normal IOP is between 12 - 20 mm Hg Studies have been published assessing intraocular changes with prone positioning laparoscopic surgery and cardiopulmonary bypass 121314 However there has been no literature evaluating intraocular pressure during abdominal aortic aneurysm AAA repair AAA repair is a high-risk surgery associated with blood loss hypotension and has been reported in a case series associated with ION 6 The surgery involves clamping and unclamping of the aorta to facilitate excision of the aneurysm and graft repair Aortic cross clamping and unclamping is an intense physiologic insult affecting venous return systemic vascular resistance cardiac output and acid base status These physiologic changes are further pronounced with more proximal cross-clamping and longer duration Because infrarenal abdominal aortic aneurysms are the most common type of AAA repair we will be assessing IOP with patients undergoing elective infrarenal abdominal aortic reconstruction
Infrarenal aortic cross clamping is associated with increases in venous return central venous pressure and arterial blood pressure 15 The hemodynamic changes with infrarenal unclamping entail decreases in venous return central venous pressure and arterial blood pressure 15 The determinants of intraocular pressure involve extraocular muscle tone aqueous flow choroidal blood volume and central venous pressure 16 The volume redistribution proximal to the aortic cross-clamp should cause a rise in venous pressure increase resistance to aqueous drainage and increase choroidal blood volume thereby increasing intraocular pressure However after aortic unclamping choroidal blood volume and IOP should decrease as venous return and central venous pressure decline Therefore our hypothesis is that IOP will be increased during aortic cross clamping and decreased following aortic unclamping
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