BALTIMORE – Hypoalbuminemia was identified as a significant risk factor for increased mortality and morbidity in obese patients undergoing elective general surgery, in a large study of patients from the ACS National Surgical Quality Improvement Program (NSQIP) database, Dr. Zachary C. Dietch reported at the annual meeting of the Surgical Infection Society.
The results suggest that surgeons may need to be more careful in evaluating protein deficiency in obese patients before surgery, said Dr. Dietch, a surgical resident at the University of Virginia, Charlottesville.
Protein-calorie deficiency is a well-known risk factor for complications, including infections and other surgical complications, but the risks of protein deficiency in different weight classes have not been well described. And while serum albumin is commonly used as an index for nutritional status and is known to correlate with adverse surgical outcomes, its use "as an index for nutrition status remains controversial," he noted.
But based on the results, "We feel that these risks likely reflect protein deficiency, and we feel that serum albumin appropriately reflects protein status in this population," he commented.
To evaluate the association of preoperative serum albumin and surgical complications by weight class, Dr. Dietch and his associates evaluated 240,000 general elective surgery patients, from the 2011 NSQIP database who had an elective procedure. After excluding certain groups of patients including those with systemic infections, cirrhosis, as well as those who were pregnant and those who had no preoperative albumin results available, they were left with about 86,000 patients.
Of these patients, 2,088 (about 2.4%) had a low serum albumin (below 3.0 g/dL); these patients tended to be older and tended to be in lower weight categories. Of those with hypoalbuminemia, 6.2% had a body mass index of 40 kg/m2 and greater and almost 22% had a BMI between 30-39 (a BMI of 30 and greater falls in the obese category), and they had higher rates of comorbidities.
After controlling for factors that included comorbidities, surgical wound classification, operation type and complexity, the interaction of hypoalbuminemia and BMI conferred a statistically significant increase in the risk of mortality among those with a BMI of 40 and above, with an odds ratio of 18.98; and among those with a BMI between 30 and 39, with an odds ratio of 3.14 – when compared with patients in lower weight categories, who had low serum albumin, Dr. Dietch said.
Among those with a BMI of 40 and greater who had hypoalbuminemia, the risk of all complications was significantly increased (OR, 3.13) and the risk of all infectious complications was significantly increased (2.59). The risk of all complications was not significantly increased among those with a BMI of 30-39.
"The impact of protein deficiency on outcomes among patients may not be appreciated by surgeons," he concluded. This was a hypothesis-generating study and future studies "should prospectively investigate preoperative nutritional interventions in at-risk patients regardless of BMI," he added, noting that the next step would be a pilot study.
The limitations of the study included the possibility that the NSQIP data did not capture confounding disease states, and no causal relationship between protein status and surgical complications could be established because of the observational nature of the study, he noted.
In response to an audience member’s comment that a low albumin can be a reflection of a proinflammatory state, Dr. Dietch said that he and his coinvestigators recognized this and attempted to eliminate patients with proinflammatory states, such as those with systemic infections and those with systemic inflammatory response syndrome.
The study was funded by a National Institutes of Health training grant. Dr. Dietch had no disclosures