Postoperative Serum Albumin as Predictors of Surgical Outcomes: Insights into Capillary Permeability and Inflammation

Sir, The reduction in plasma albumin concentration after major surgical trauma is well recognised, although the precise timing and detailed mechanisms remain insufficiently characterised. This exploratory study sought to evaluate changes in albumin synthesis and the transcapillary escape rate (TER) during the postoperative period, particularly when inflammatory markers typically reach their peak levels. While it is well known that albumin concentrations fall significantly after surgery, the interplay between increased leakage and altered synthesis during this period is not clearly defined. By examining these components during the height of inflammation, this study aims to determine whether elevated TER, reduced synthesis, or a combination of both mechanisms explains the postoperative hypoalbuminemia commonly observed following major surgical procedures. Concerns about the harmful effects of starch-based colloids in critically ill patients1,2 and the lack of demonstrable perioperative benefit3,4 have shifted attention toward albumin as a preferred colloid for intravenous therapy. Albumin administration during surgery may help maintain colloid osmotic pressure and reduce intestinal edema,3 although postoperative albumin (P-Alb) infusions have not consistently shown clinical benefit. The clinical significance of low P-Alb remains somewhat unclear; however, levels below 25 g/L on the first postoperative day predict major complications such as pancreatic fistula after pancreaticoduodenectomy.5 The timing of capillary leakage after surgery is poorly described but may mirror the postoperative inflammatory response, as C-reactive protein levels typically peak between the first and third postoperative days in major abdominal surgeries. Albumin synthesis during surgical stress and inflammation has not been comprehensively studied, with findings differing depending on the postoperative timing of observation. In our data, increases in patient body weight and fluid balance, along with a measurable reduction in intravascular albumin mass, suggest significant albumin leakage through the capillary barrier. By the second postoperative day, we speculate that the TER elevated by surgical trauma may begin returning to baseline, making continued leakage harder to detect. This shift may reflect a reduced concentration gradient between plasma and extravascular compartments. Limited information exists on extracellular albumin concentrations in surgical patients, though studies in healthy volunteers report lymphatic levels of 5-25 g/L2 and skeletal muscle microdialysis levels near 13.2 g/L, suggesting a narrow gradient relative to postoperative plasma values. Plasma C-reactive protein levels on postoperative day 2 ranged widely between 24 and 234 mg/L in patients undergoing pancreaticoduodenectomy, indicating substantial variability in the inflammatory response. This variability may explain why capillary leakage in our cohort did not match the increased leakage observed after thoracic surgery.1 Plasma volume estimates derived using anthropometric equations6 and corrected hematocrit values closely matched measured values, supporting the reliability of our calculations. The marked decline in P-Alb appears partly attributable to extravasation, as approximately 19 ± 12 g of albumin could not be accounted for when comparing intravascular albumin loss with albumin administered and measured. Similar perioperative protein losses have been reported in gynecologic surgeries,2 and factors such as starch administration and fluid overload may have further influenced albumin distribution. The prognostic importance of hypoalbuminemia has been well documented, with strong associations between low albumin and increased mortality in chronic illness and critical care settings.1,2,6 Preoperative hypoalbuminemia is also consistently linked to poorer surgical outcomes. Its repeated correlation with complications across diverse surgical and medical contexts suggests that serum albumin is a valuable and cost-effective biomarker for perioperative risk assessment. Because albumin testing is simple and routinely performed, it provides a practical means of evaluating patient status prior to surgery. In our study, individuals with preoperative hypoalbuminemia demonstrated higher rates of adverse outcomes within 30 days across eight surgical specialties, aligning with the observations of Gibbs et al.4 Patients with disseminated cancer exhibited even greater risks, including increased postoperative mortality. Further analysis of P-Alb concentrations and postoperative outcomes revealed natural inflection points in adverse event rates corresponding to the lower and upper limits of normal albumin levels. These findings indicate that deviations from the normal albumin range – even within its higher or lower bounds – may carry meaningful clinical implications. The data reinforce the role of preoperative serum albumin as an independent predictor of short-term surgical risk. The heightened impact observed among patients with widespread malignancy illustrates the interplay between systemic disease burden, inflammation, nutritional status, and surgical recovery. Overall, our results support the integration of albumin measurement into standard preoperative risk stratification models, as it effectively reflects metabolic and inflammatory states that influence postoperative morbidity and mortality. Financial support and sponsorship Nil. Conflicts of interest There are no conflicts of interest.