December 12, 2008

The Impact of Obesity on Perioperative Outcomes of Open and Endovascular Abdominal Aortic Aneurysm Repair from the National Surgical Quality Improvement Program

Kristina A. Giles, M.D., Frank B. Pomposelli, Jr., M.D., Allen D. Hamdan, M.D., Mark C. Wyers, M.D., Marc L. Schermerhorn, M.D..
Beth Israel Deaconess Medical Center, Boston, MA, USA.

OBJECTIVES:
Obesity and morbid obesity have been shown to increase wound infections and mortality after many surgical procedures. Little is know about the relative impact of obesity on these outcomes after open and endovascular abdominal aortic aneurysm (AAA) repair (EVAR).
METHODS:
The 2005-2006 National Surgical Quality Improvement Program (NSQIP), a multi-institutional risk-adjusted database, was retrospectively queried to compare perioperative mortality (in-hospital or 30-day) and postoperative surgical site infections (SSI) after open repair and EVAR. Patient demographics, comorbidities, and operative details were analyzed. Body mass index (BMI) was calculated from height and weight variables and definitions of obesity and morbid obesity were defined as BMI >30kg/m² and BMI >40kg/m² respectively. Student’s T-test, Chi-square and multivariate logistic regression were used to compare outcomes.
RESULTS:
There were 977 open repairs and 1,318 EVAR. Open repair patients were younger (71.6 vs. 74.1 years, P<.05), less likely male (74% vs. 82%, P<.001), and less likely to be obese (26% vs. 31%, P<.05). Obese patients had a statistically higher rate of SSI after open repair (6.3% vs. 1.5%, P<.001) and a trend toward more SSIs after EVAR (3.2% vs. 1.8%, P<.09). In all patients, mortality was 4.1% vs. 1.1% after open vs. EVAR respectively (RR 3.9, P<.001). Obese patients had a mortality of 5.1% after open repair vs. 0.7% after EVAR (RR 6.8, P<.001) while morbidly obese patients had a mortality of 13.3% versus 1.8% (RR 7.5, P<.05). Obesity was an independent predictor of both mortality and SSI after open but not EVAR (Table).
CONCLUSIONS:
Obesity confers a worse outcome for mortality and infectious complications than EVAR. The relative risk of mortality between open repair and EVAR increases with increasing BMI. Obese patients and particularly morbidly obese patients should be treated with EVAR when anatomically feasible.



*Multivariate Predictors of Mortality After Open AAA Repair*				*Multivariate Predictors of Mortality After Endovascular AAA Repair*
	OR	95% CI	P Value		OR	95% CI	P Value
Age	1.1	1.01- 1.1	< .05	Age	1.1	1.01- 1.2	< .05
Current Dialysis or Cr >1.8mg/dL	2.3	1.01- 5.2	< .05	Poor Pre-op Functional Status	7.3	2.2 -24.4	< .01
Angina	4.8	1.4 -15.8	< .05	Current Dialysis	9.4	1.6 -54.7	< .01
Ventilator dependence	20.4	5.1 -81.9	< .001	Weight Loss	7.3	1.9 -32.9	< .01
Morbid Obesity: BMI > 40 kg/m²	3.6	1.3 - 9.7	< .05
*Multivariate Predictors of SSI After Open AAA Repair*				*Multivariate Predictors of SSI After Endovascular AAA Repair*
	OR	95% CI	P Value		OR	95% CI	P Value
Female Gender	2.4	1.1 - 5.2	< .05	Female Gender	2.3	1.1 - 5.1	< .05
Current Smoker	2.5	1.1 - 5.6	< .05	Current Dialysis	11.6	3.0 -44.4	< .001
Obesity: BMI > 30 kg/m²	5.2	2.3 -11.7	< .001
Current Dialysis or Cr >1.8mg/dL	2.7	1.03- 7.1	< .05

Cr: Creatinine, BMI: Body Mass Index

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