Intraocular Pressure During Abdominal Aortic Aneurysm (AAA) Repair

• Sponsor: University of Manitoba (Other)
• Overall Status: Completed
• CT.gov ID: NCT00450294
• Collaborator: (none)
• Enrollment: 10
• Location: 1
• Duration (Months): 5
• Patients Per Site Per Month: 2

Study Details

Study Description

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 patient's 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.

Condition or Disease	Intervention/Treatment	Phase
Problem With Vision Blindness; Intraocular Pressure; Ischemic Optic Neuropathy

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 0.002% and 0.0008% (1,2). However, retrospective reviews in spinal and cardiac surgery demonstrated higher rates of perioperative blindness; that is, between 0.2% and 0.06% respectively (3,4). 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 (5,6,7). 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 (8,9). Surgery specific factors involve profound blood loss, anemia, hypotension, prone positioning and duration of surgery (5,6,7,10). 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) and/or 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 (12,13,14). 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 Design

• Study Type: Observational
• Actual Enrollment: 10 participants
• Time Perspective: Prospective
• Official Title: The Effect of Aortic Infrarenal Clamping and Unclamping On Intraocular Pressure During Abdominal Aortic Aneurysm (AAA) Repair
• Study Start Date: Mar 1, 2007
• Actual Study Completion Date: Aug 1, 2007

Outcome Measures

Primary Outcome Measures

1. Right Intraocular Pressure During Various Event Intervals in Open Abdominal Aortic Aneurysm Surgery. [Measurements made at baseline, post induction preincision, 1 min post clamp, 5 min post clamp, 1 min pre unclamp, 1 min post unclamp, 5 min post unclamp, skin closure]

   Intraocular pressure measurements were made with a tonometer. These measurements were recorded and kept blinded from the clinicians.

2. Left Intraocular Pressure [Measurements made at baseline, post induction preincision, 1 min post clamp, 5 min post clamp, 1 min pre unclamp, 1 min post unclamp, 5 min post unclamp, skin closure]

   Intraocular pressure measurements were made with a tonometer. These measurements were recorded and kept blinded from the clinicians.

Eligibility Criteria

Criteria

• Ages Eligible for Study: 18 Years and Older
• Sexes Eligible for Study: All
• Accepts Healthy Volunteers: Yes

Inclusion Criteria:

• All patients presenting to St. Boniface General Hospital for elective AAA repair requiring an arterial line, central line and general anesthesia will be eligible for inclusion in this study.

Exclusion Criteria:

• . The exclusion criteria for this study are:

1. Patients with a history of acute or chronic eye disease

2. Allergy to topical ophthalmologic anesthesia

3. Patients receiving nitrous oxide, ketamine or succinylcholine during anesthesia

4. If the surgical procedure will require the aorta to be re-clamped following unclamping, those patients will also be excluded

5. Patients that are VRE+ or MRSA+ will be excluded for infection control purposes

Contacts and Locations

Locations

	Site	City	State	Country	Postal Code
1	St. Boniface General Hospital	Winnipeg	Manitoba	Canada	R2H 2A6

Sponsors and Collaborators

• University of Manitoba

Investigators

• Principal Investigator: Amit Chopra, M.D., University of Manitoba, Department Of Anesthesiology, Faculty of Medicine

Study Documents (Full-Text)

None provided.

More Information

Publications

• 13 Kayacan N, Gulbin A, Akar M, Karsli B. The effect of pneumoperitoneum and head-down position on intraocular pressure. Gynaecological Endoscopy 2002;11:383-87.
• Beck RW, Servais GE, Hayreh SS. Anterior ischemic optic neuropathy. IX. Cup-to-disc ratio and its role in pathogenesis. Ophthalmology. 1987 Nov;94(11):1503-8.
• Brown RH, Schauble JF, Miller NR. Anemia and hypotension as contributors to perioperative loss of vision. Anesthesiology. 1994 Jan;80(1):222-6.
• Cheng MA, Todorov A, Tempelhoff R, McHugh T, Crowder CM, Lauryssen C. The effect of prone positioning on intraocular pressure in anesthetized patients. Anesthesiology. 2001 Dec;95(6):1351-5.
• Gelman S. The pathophysiology of aortic cross-clamping and unclamping. Anesthesiology. 1995 Apr;82(4):1026-60. Review.
• Hayreh SS, Jonas JB. Optic disc morphology after arteritic anterior ischemic optic neuropathy. Ophthalmology. 2001 Sep;108(9):1586-94.
• Hayreh SS. Anterior ischemic optic neuropathy. Clin Neurosci. 1997;4(5):251-63. Review.
• Larkin DF, Connolly P, Magner JB, Wood AE, Eustace P. Intraocular pressure during cardiopulmonary bypass. Br J Ophthalmol. 1987 Mar;71(3):177-80.
• Lee LA, Roth S, Posner KL, Cheney FW, Caplan RA, Newman NJ, Domino KB. The American Society of Anesthesiologists Postoperative Visual Loss Registry: analysis of 93 spine surgery cases with postoperative visual loss. Anesthesiology. 2006 Oct;105(4):652-9; quiz 867-8.
• Murphy DF. Anesthesia and intraocular pressure. Anesth Analg. 1985 May;64(5):520-30.
• Myers MA, Hamilton SR, Bogosian AJ, Smith CH, Wagner TA. Visual loss as a complication of spine surgery. A review of 37 cases. Spine (Phila Pa 1976). 1997 Jun 15;22(12):1325-9.
• Nuttall GA, Garrity JA, Dearani JA, Abel MD, Schroeder DR, Mullany CJ. Risk factors for ischemic optic neuropathy after cardiopulmonary bypass: a matched case/control study. Anesth Analg. 2001 Dec;93(6):1410-6, table of contents.
• Roth S, Thisted RA, Erickson JP, Black S, Schreider BD. Eye injuries after nonocular surgery. A study of 60,965 anesthetics from 1988 to 1992. Anesthesiology. 1996 Nov;85(5):1020-7.
• Stevens WR, Glazer PA, Kelley SD, Lietman TM, Bradford DS. Ophthalmic complications after spinal surgery. Spine (Phila Pa 1976). 1997 Jun 15;22(12):1319-24.
• Warner ME, Warner MA, Garrity JA, MacKenzie RA, Warner DO. The frequency of perioperative vision loss. Anesth Analg. 2001 Dec;93(6):1417-21, table of contents.
• Williams EL, Hart WM Jr, Tempelhoff R. Postoperative ischemic optic neuropathy. Anesth Analg. 1995 May;80(5):1018-29. Review.

• Responsible Party: Amit Chopra, Assistant Professor, University of Manitoba
• ClinicalTrials.gov Identifier: NCT00450294
• Other Study ID Numbers: B2006:180
• First Posted: Mar 22, 2007
• Last Update Posted: Mar 31, 2014
• Last Verified: Feb 1, 2014

• Additional relevant MeSH terms: Optic Nerve Diseases; Blindness; Optic Neuropathy, Ischemic; Aneurysm; Aortic Aneurysm; Aortic Aneurysm, Abdominal

Study Results

Participant Flow

Recruitment Details	Ten patients were recruited into the study after informed consent at the preoperative anesthetic clinic during a twelve month period.
Pre-assignment Detail	Because this is a purely OBSERVATIONAL STUDY, there was no group assignment. All patients enrolled in the study were assigned to one group, that is, all patients had intraocular pressure measurements performed.

Arm/Group Title	Longitudinal Study Group
Arm/Group Description	This study is an OBSERVATIONAL STUDY. Ten patients were enrolled to determine what happens to eye pressure during surgery for abdominal aortic aneurysm repair. Therefore, all ten patients had intraocular pressure measurements made at different event intervals to determine if there was a change in intraocular pressure compared to their baseline intraocular pressure that was taken before surgery. No active intervention was performed to the patients based on intraocular pressure as clinicians were blinded to the intraocular pressure values.Measurement of Central venous pressure at event intervals during abdominal aortic aneurysm repair. Data are presented as mean +/- standard error.
Period Title: Overall Study
STARTED	10
COMPLETED	10
NOT COMPLETED	0

Baseline Characteristics

Arm/Group Title	Longitudinal Group
Arm/Group Description	This study is an observational longitudinal design. Ten patients were enrolled to determine what happens to eye pressure during surgery for abdominal aortic aneurysm repair. Therefore, all ten patients had intraocular pressure measurements made at different event intervals to determine if there was a change in intraocular pressure compared to their baseline intraocular pressure that was taken before surgery. No active intervention was performed to the patients based on intraocular pressure as clinicians were blinded to the intraocular pressure values.
Overall Participants	10
Age (Count of Participants)
<=18 years	0 0%
Between 18 and 65 years	3 30%
>=65 years	7 70%
Age (years) [Mean (Standard Deviation) ]
Mean (Standard Deviation) [years]	68.5 (11.2)
Sex: Female, Male (Count of Participants)
Female	0 0%
Male	10 100%
Region of Enrollment (participants) [Number]
Canada	10 100%
Cross Clamp Duration (min) [Mean (Standard Deviation) ]
Mean (Standard Deviation) [min]	58 (15.3)
Preop Right Intraocular Pressure (mm Hg) [Mean (Standard Deviation) ]
Mean (Standard Deviation) [mm Hg]	16.9 (2.6)
Preop Left Intraocular Pressure (mm HG) [Mean (Standard Deviation) ]
Mean (Standard Deviation) [mm HG]	16.7 (2.7)
Body mass index (kg/m2) [Mean (Standard Deviation) ]
Mean (Standard Deviation) [kg/m2]	27.3 (3.4)
Abdominal Aortic Aneurysm Size (cm) [Mean (Standard Deviation) ]
Mean (Standard Deviation) [cm]	5.7 (0.5)
Cerebrovascular Accident (CVA) (participants) [Number]
HAS CVA	4 40%
No CVA	6 60%
Diabetes mellitus (participants) [Number]
HAS DM	10 100%
NO DM	0 0%
Hypertension (participants) [Number]
HAS HTN	10 100%
NO HTN	0 0%
Hyperlipidemia (participants) [Number]
HAS Hyperlipidemia	10 100%
NO Hyperlipidemia	0 0%
Epidural (participants) [Number]
Epidural	10 100%
NO Epidural	0 0%
Cumulative Crystalloid (L) [Mean (Standard Deviation) ]
Mean (Standard Deviation) [L]	2.84 (0.13)
Vasopressor infusion (participants) [Number]
Vasopressor Infusion	10 100%
NO vasopressor infusion	0 0%
Mannitol (participants) [Number]
Received Mannitol	10 100%
N) Mannitol	0 0%
ASA Physical Status (participants) [Number]
ASA I (healthy person)	0 0%
ASA II (mild systemic disease)	0 0%
AASA III (Severe systemic disease)	10 100%
ASA IV (Severe systemic disease, constant threat)	0 0%
ASA V (moribund person)	0 0%

Outcome Measures

1. Primary Outcome

Title	Right Intraocular Pressure During Various Event Intervals in Open Abdominal Aortic Aneurysm Surgery.
Description	Intraocular pressure measurements were made with a tonometer. These measurements were recorded and kept blinded from the clinicians.
Time Frame	Measurements made at baseline, post induction preincision, 1 min post clamp, 5 min post clamp, 1 min pre unclamp, 1 min post unclamp, 5 min post unclamp, skin closure

Outcome Measure Data

Analysis Population Description

The analysis was per protocol.

Arm/Group Title	Longitudinal Group
Arm/Group Description	This study is an OBSERVATIONAL STUDY. Ten patients were enrolled to determine what happens to eye pressure during surgery for abdominal aortic aneurysm repair. Therefore, all ten patients had intraocular pressure measurements made at different event intervals to determine if there was a change in intraocular pressure compared to their baseline intraocular pressure that was taken before surgery. No active intervention was performed to the patients based on intraocular pressure as clinicians were blinded to the intraocular pressure values.
Measure Participants	10
Preoperative	16.9 (0.75)
Pre-induction	13.8 (0.75)
1 min post clamp	14.6 (0.75)
5 min post clamp	13.5 (0.75)
1 min before unclamp	14.1 (0.75)
1 min following unclamp	14.4 (0.75)
5 min following unclamp	15 (0.75)
Skin closure	14.1 (0.75)

Statistical Analysis 1

Statistical Analysis Overview	Comparison Group Selection	Longitudinal Group
	Comments	Repeated measures anova with post hoc t-tests using tukey's correction.
	Type of Statistical Test	Superiority or Other
	Comments
Statistical Test of Hypothesis	p-Value	<0.001
	Comments	That the means at the different timepoints would not all be equal.
	Method	ANOVA
	Comments

2. Primary Outcome

Title	Left Intraocular Pressure
Description	Intraocular pressure measurements were made with a tonometer. These measurements were recorded and kept blinded from the clinicians.
Time Frame	Measurements made at baseline, post induction preincision, 1 min post clamp, 5 min post clamp, 1 min pre unclamp, 1 min post unclamp, 5 min post unclamp, skin closure

Outcome Measure Data

Analysis Population Description

[Not Specified]

Arm/Group Title	Longitudinal Study Group
Arm/Group Description	This study is an observational longitudinal design. Ten patients were enrolled to determine what happens to eye pressure during surgery for abdominal aortic aneurysm repair.
Measure Participants	10
Preoperative	16.7 (0.57)
Pre-incision	15 (0.57)
1 min post clamp	14.7 (0.57)
5 min post clamp	13.7 (0.57)
1 min before unclamp	14.6 (0.57)
1 min following unclamp	15.1 (0.57)
5 min following unclamp	15.3 (0.57)
Skin closure	14.7 (0.57)

Statistical Analysis 1

Statistical Analysis Overview	Comparison Group Selection	Longitudinal Group
	Comments	Repeated measures anova with post hoc t-tests using tukey's correction.
	Type of Statistical Test	Superiority or Other
	Comments
Statistical Test of Hypothesis	p-Value	<0.001
	Comments	That the means at the different timepoints would not all be equal.
	Method	ANOVA
	Comments

Adverse Events

Arm/Group Title	Longitudinal Group
Arm/Group Description	This study is an OBSERVATIONAL STUDY. Ten patients were enrolled to determine what happens to eye pressure during surgery for abdominal aortic aneurysm repair. Therefore, all ten patients had intraocular pressure measurements made at different event intervals to determine if there was a change in intraocular pressure compared to their baseline intraocular pressure that was taken before surgery. No active intervention was performed to the patients based on intraocular pressure as clinicians were blinded to the intraocular pressure values.
All Cause Mortality
	Longitudinal Group
	Affected / at Risk (%)	# Events
Total	/ (NaN)
Serious Adverse Events
	Longitudinal Group
	Affected / at Risk (%)	# Events
Total	0/10 (0%)
Other (Not Including Serious) Adverse Events
	Longitudinal Group
	Affected / at Risk (%)	# Events
Total	0/10 (0%)

Limitations/Caveats

There were no limitations to trial during course of study.

More Information

Certain Agreements

Principal Investigators are NOT employed by the organization sponsoring the study.

There is NOT an agreement between Principal Investigators and the Sponsor (or its agents) that restricts the PI's rights to discuss or publish trial results after the trial is completed.