The effect of body mass index on major outcomes after vascular surgery

Abstract

Objective: Obesity has been associated with an increased risk for cardiovascular morbidity and mortality, although pooled evidence in patients undergoing vascular surgery are lacking. The aim of this systematic review was to evaluate the effect of body mass index (BMI) on major postoperative outcomes in patients undergoing vascular surgery.

Methods: A systematic literature review conforming to established criteria to identify eligible articles published before May 2016 was conducted. Eligible studies evaluated major postoperative outcomes in vascular surgery patients of different BMI groups according to the weight classification of the National Institutes of Health criteria: underweight (UW), BMI ≤18.5 kg/m²; normal weight (NW), BMI of 18.6 to 24.9 kg/m²; overweight (OW), BMI of 25 to 29.9 kg/m²; and obese (OB), BMI ≥30 kg/m². Major outcomes included 30-day mortality, cardiac complications, and respiratory complications. Secondary outcomes included wound and cerebrovascular complications, renal complications, deep venous thrombosis/pulmonary embolism, and other complications.

Results: Overall, eight retrospective studies were eligible including a total of 92,525 vascular surgery patients (2223 UW patients, 29,727 NW patients, 34,517 OW patients, and 26,058 OB patients). Pooled data were as follows: mortality rate, 2.5%; cardiac events, 2.1%; respiratory events, 8.6%; wound complications, 6.4%; cerebrovascular events, 6.4%; renal complications, 3.9%; other infections, 5.3%; deep venous thrombosis/pulmonary embolism, 1.2%; and other complications, 3.7%. Meta-analysis showed that OB patients were associated with lower mortality (odds ratio [OR], 0.64; 95% confidence interval [CI], 0.541-0.757; P < .0001), cardiac morbidity (OR, 0.81; 95% CI, 0.708-0.938; P = .004), and respiratory morbidity (OR, 0.87; 95% CI, 0.802-0.941; P = .0006) after vascular surgery compared with NW patients. However, OB patients were associated with a higher wound complication rate (OR, 2.39; 95% CI, 1.777-3.211; P < .0001) compared with NW patients. In contrast, UW patients were associated with a higher mortality (OR, 1.71; 95% CI, 1.177-2.505; P = .005) and respiratory morbidity (OR, 1.84; 95% CI, 1.554-2.166; P < .0001) compared with NW patients.

Conclusions: The "obesity paradox" does exist in patients undergoing vascular surgery. This paradox refers not only to 30-day overall mortality but also to 30-day cardiac and respiratory complications. However, obesity seems to be associated with more wound complications. Surprisingly, UW patients are associated with higher mortality as well as respiratory events postoperatively.