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Introduction: Open surgical repair of aortic aneurysm and aortoiliac occlusive disease is associated with prolonged lengths of stay compared to less invasive endovascular therapies, in part due to post-operative ileus. Alvimopan, a peripherally acting mu-opioid antagonist, has been shown to produce quicker return of gastrointestinal function after elective open colonic resections. The purpose of this study was to evaluate the efficacy of alvimopan as an adjunct to reduce the impact of post-operative ileus on patients undergoing open aortic surgery.
Methods: The study group was compromised of patients administered a 12mg dose of alvimopan prior to undergoing elective open aortic infrarenal replacement, and then continued post-operatively with 12mg twice a day dosing. Treatment was continued until complete return of bowel function was achieved, followed by termination of therapy. The control cohort was identified using a database of patients undergoing elective open aortic surgery and did not receive alvimopan. Study endpoints were time to complete return of bowel function and length of hospital stay.
Results: A total of 40 patients were included in the study, 20 patients in both the study and control groups. The populations were well matched in regard to demographics, operative variables, and medication profiles. The time to complete return of bowel function was decreased in the study population (3.1 ± 1.1 vs. 4.5 ± 1.7 days, P<0.01). Likewise, length of hospital stay was significantly less in the study cohort (5.1 ± 1.1 vs 6.8 ± 2.0 days, P<0.01) (Table). There were no untoward events in the study population resulting from the administration of alvimopan. Furthermore, use of this mu-opioid receptor antagonist did not affect post-operative analgesic requirements, with the two populations having comparable morphine-equivalent use (74.0 ± 32.3 vs. 63.6 ± 35.3 mg/d, P = 0.33). Subgroup analysis of the transperitoneal (n=31) and retroperitoneal patients (n=9) showed divergent results. The transperitoneal group had 16 patients in the study group and 15 in the control group, with the study group having significant shorter time to bowel function and hospital stay (3.2 ± 1.1 vs. 4.9 ± 1.7 days, P<0.01 and 5.3 ± 1.0 vs. 7.5 ± 1.8 days, P<0.01, respectively). The retroperitoneal group had 4 patients in the study group and 5 in the control group. The populations were well matched among all variables, and there was no significant difference between study and control groups when evaluating the study endpoints.
Conclusions: These data demonstrate that perioperative alvimopan can safely be administered to hasten the time to return of complete bowel function and decrease the length of hospital stay in open aortic surgery patients, specifically when a transperitoneal approach is employed. Further investigation via a prospective, randomized pharmacoeconomic endpoint trial is warranted given the improved resource utilization demonstrated in this series.

	All patients (n = 40)		Transperitoneal (n=31)		Retroperitoneal (n = 9)
	Study	Control	Study	Control	Study	Control
Age (years)	64.3 ± 10.1	67.0 ±7.2	65.8 ± 10.0	66.2 ± 7.6	58.5 ± 9.3	69.4 ± 6.1
Gender (male)	65.0%	85.0%	62.5%	80.0%	75.0%	100%
Aneurysm size (cm)	5.7 ± 0.7	5.5 ±1.0	5.7 ±0.7	5.2 ± 0.7	5.8 ± 0.3	6.1 ± 1.4
Operative time (min)	157.9 ± 37.7	144.6 ± 42.1	161.3 ± 40.6	144± 44.8	145.5 ±23.6	146.2 ± 37.7
Aortic clamp time (min)	49.2 ± 22.8	39.3 ±11.2	49.3 ± 24.7	37.5 ±10.3	48.8 ±15.2	44.6 ±13.3
Estimated blood loss (cc)	691.3 ± 250.2	905.0 ± 574.4	701.6 ± 278.8	886.7 ± 582.0	650.0 ± 70.7	960.0 ± 613.8
Post-operative MSO4-equiv use (mg/day)	74.0 ± 32.3	63.6 ± 35.3	75.7 ± 34.9	59.1 ± 36.4	67.6 ± 21.2	77.0 ± 31.2
Time to bowel movement (d)	3.1 ± 1.1*	4.5 ± 1.7	3.2 ±1.1*	4.9 ±1.7	2.75 ± 1.3	3.2 ± 0.8
Length of stay (d)	5.1 ± 1.1*	6.8 ± 2.0	5.3 ± 1.0*	7.5 ± 1.8	4.0 ± 1.2	4.8 ± 1.1

* = P < 0.05 versus control; MSO₄-equiv = Morphine equivalent