Hypoalbuminemia is disproportionately associated with adverse outcomes in obese elective surgical patients

Abstract

Background: Protein deficiency (PD) is a known risk factor for surgical complications; however, the risks of PD by weight class have not been well described. It was hypothesized that the combination of obesity and PD is associated with increased surgical complications compared with normal weight and normoalbuminemic patients.

Methods: A total of 85,833 general surgery patients undergoing elective operations within the 2011 National Surgical Quality Improvement Program were analyzed. Patients with conditions that could potentially confound serum albumin (SA) were excluded. Patients were stratified by normal (>3.0 g/dL) versus low (<3.0 g/dL) SA. The relative impact of SA and body mass index (BMI) (as individual and as combined variables) on surgical morbidity and mortality were assessed. Multivariate analyses were performed to identify independent risk factors for morbidity and mortality.

Results: Overall, 2,088 (2.43%) patients had low preoperative SA. 587 (28.1%) patients with low preoperative SA were obese (BMI>30), versus 39,299 (46.9%) with normal preoperative SA. Importantly, the interaction of hypoalbuminemia and BMI was independently associated with all complications among hypoalbuminemic patients with BMI>40, and mortality for patients with BMI>30 after controlling for appropriate demographic characteristics, co-morbidities, surgical wound classification, operation type, and complexity (c-statistic: .803 and .874 respectively).

Conclusion: PD and obesity appear to synergistically increase the risk of surgical complications. Paradoxically, malnutrition may be less easily recognized in obese individuals and surgeons may need to more carefully evaluate this population before surgery. Future studies should investigate therapy to correct PD specifically among obese patients before surgery.

Keywords: Hypoalbuminemia; Malnutrition; Mortality; National Surgical Quality Improvement Program; Nutrition assessment; Nutrition status; Obesity; Postoperative complications; Protein deficiency; Protein-energy malnutrition.