Loss of protein, immunoglobulins, and electrolytes in exudates from negative pressure wound therapy

Background: A relatively new technology in wound care, negative pressure wound therapy (NPWT), has become widely used for the management of open abdomens and soft tissue wounds and provides a means to collect wound exudate to quantify protein loss. Methods: A prospective observational study was conducted in surgical, trauma, or burn patients (8 patients with open abdomens and 9 patients with acute soft tissue wounds on NPWT). NPWT exudate was collected and assayed to characterize loss of protein, electrolyte, and immunoglobulins over multiple days of NPWT. Results: Total protein was present in open abdomen NPWT exudate, 2.9 ± 0.9 g/dL. In the soft tissue wound exudate, a similar mean concentration was found, 2.59 ± 0.6 g/dL (P =.34). Exudate concentrations of albumin, urea nitrogen, immunoglobulins, and electrolytes between wound types were also not significantly different. There were significant (P =.03) differences in the median volume of exudate, 1031 mL/d for open abdomens in contrast to 245 mL/d soft tissue wounds. Therefore, 24-hour losses of proteins and electrolytes were greater in patients with open abdomens than soft tissue wounds. Mean total protein loss was 25 ± 17 g/d for open abdomens and 8 ± 5 g/d for soft tissue wounds. Conclusion: There are significant losses of proteins in wound exudate. As there is no significant difference in the concentration of total protein between wound type, the rate of loss may be calculated as 2.9 g/dL times the volume of wound exudate. The rate of protein loss from wounds is similar to the presently assumed insensible loss rate of 12-25 g/d.