Microalbuminuria assessment after thoracic surgery: Early identification of complication risks

Microalbuminuria (MA) is considered a reflection of systemic capillary leak and an early marker of acute stress reaction to the surgical insult, proportional to the severity of the initiating condition and predictive of the individual response to surgical stress.

We conducted a prospective study to assess for the variation of MA within 4 days after thoracic surgery. We correlated observed MA levels with both their respective PaO₂ /FiO₂ respiratory ratio and the onset of postoperative complications.

This single-centre study enrolled 255 consecutive patients having an American Society of Anaesthesiologists (ASA) score ≤ 3. The mean age was 62 years with 67% male. All patients were scheduled for elective pulmonary resection. MA was measured in urine samples as the albumin-to-creatinine ratio (A/C), prior to, at and after extubation up to 96 hours. PaO₂ /FiO₂ was measured at extubation and on the first postoperative day.

Overall, preoperative A/C levels resulted normal, with a significant average increase at extubation which peaked 6 hours later (P < 0.001). Larger postoperative A/C increases were observed in patients who developed postoperative complications, compared to those without these complications (P < 0.019). Moreover, patients undergoing major open pulmonary resections had larger postoperative A/C increases, compared to those undergoing minor video-assisted thoracic surgery resections (P < 0.006). At the time of extubation, A/C was inversely related to the PaO₂ /FiO₂ ratio (r = -0.25; P = 0.038). Peak A/C > 61 mg/g (P = 0.0003) was associated with postoperative cardio-pulmonary complications (OR 3.85; P = 0.003).

Within 6 hours after extubation, MA assessment may be a rapid and relatively inexpensive method for better predicting perioperative risk in an ASA score ≤ 3 population.