Effects of different fluid transfusion regimens on glycocalyx in patients undergoing thoracic surgery

Background: Endothelial Glycocalyx (EG) composing of proteoglycans heparan sulfate (HS), Syndecan-1, and plasma proteins forms a physiologically active surface layer on the vascular endothelium, regulates oncotic pressure. We aimed to compare the effects of two different fluid transfusion regimens on EG. Methods : 41 patients with ASA I-III physical status were included in this prospective, randomized controlled study. We collected blood samples before anesthesia induction and after surgery to measure hemoglobin-hematocrit levels and biochemical parameters. Hemodynamic parameters were recorded every 15 minutes perioperatively. We divided the patients into two groups: Group R received 3 ml/kg/h, and Group L received 8 ml/kg/h of Ringer's lactate infusion. To assess endothelial damage, HS and Syndecan-1 levels, blood samples were taken after anesthesia induction(T1), after pneumonectomy or lobectomy(T2), and at the end of surgery(T3). Results : Demographic characteristics, blood loss, and urine output were similar between the groups(p>0.05). Preoperative and postoperative hemodynamic parameters, hemoglobin/hematocrit levels, BUN, and creatinine values were also similar (p>0.05) but the amount of fluid administered was significantly different(p<0.001). Syndecan-1 and HS levels were showed no significant differences(p>0.05). Similarly, intra-group analysis of Syndecan-1 and HS levels at T1-T2, T2-T3, and T1-T3 showed no significant differences(p>0.05). Conclusions: Syndecan-1 and HS levels were similar between the groups supporting that both fluid regimens have similar effects on EG. Considering the preservation of biochemical parameters including renal function tests of the patients and the possible complications of hypervolemia such as anastomotic leakage, pulmonary edema, pneumonia, and wound infection after surgery, we believe that 3ml/kg/hr fluid administration may be more advantageous. Trial Registration : ClinicalTrials.gov (NCT07192523): Registered on 10 June 2025 (retrospectively).