Prospective evaluation after thoracic surgery of microalbuminuria and Pa02/Fi02 ratio

PROSPECTIVE EVALUATION AFTER THORACIC SURGERY OF MICROALBUMINURIA AND PaO2/FiO2 RATIO; BACKGROUND and OBJECTIVE There is increasing evidence that microalbuminuria (MA) reflects systemic vascular endothelial dysfunction. Transient MA occurs within an hour from trauma, burn injury, or elective surgery and it is proportional to the magnitude of the insult. MA is higher in patients later developing complications, thus suggesting that MA is a sign of increased systemic vascular permeability and may predict complications. MA has been associated with alterations of the respiratory ratio PaO2/FiO2 and later organ function, suggesting that this index may also reflect changes of capillary permeability in the lungs. That implies that MA may have a role in early identification of surgical patients at risk of systemic inflammatory response syndrome (SIRS) and multiple organ failure. Little is known about MA and its potential implication after thoracic surgery. We therefore performed a prospective study to serially assess MA in patients undergoing elective thoracic surgery. METHODS Design: short-term prospective observational study. Setting: thoracic surgery unit. Patients: 225 consecutive patients;. Outcome measures: MA in first-void urine samples expressed as urine albumin:creatinine ratio, (M:Cr) was measured before surgery (Tp), at extubation time (T0), 6 hours following extubation (T6) and in postoperative day 1 (T24) and 3 (T72). Pa/FiO2 was measured at extubation and at T24 RESULTS Mean age was 63 years [60 to 65], 67% were male, and the most common comorbidities were COPD (115), hypertension (103), and diabetes (28). Sixty-four patients underwent standard thoracic surgery (150 lobectomies, 14 pneumonectomies) and 61 VATS resections. Preoperative MA level was normal, mean 0.61 mg/dl ([0.48 to 0.79]) while increased significantly (P<0.01) at T0 and the levels returned to normal within T72 . We found significant MA differences between categories defined by type of surgery (standard vs. VATS) and co-morbidities. At T0 comparison of Ma values with the PaO2/FiO2 ratio showed a significant inverse relationship r = -0.28; p=0.03. CONCLUSIONS Our study showed that MA might be and early marker of increased vascular permeability in thoracic surgery patients. As expected a larger increase was observed in diabetics and hypertensives. MA assessed at T0 was significantly higher in patients submitted to major thoracic procedure and also showed an inverse relationship with the PaO2/FiO2 ratio. However, MA did not discriminate the risk of developing postoperative complications. Further studies are required to evaluate the prognostic value of this test for postoperative patients with risk of respiratory failure.