Background: Surgery, causing inflammation, disrupts endothelial permeability leading to movement of fluids and albumin across the vascular barrier. Fluid therapy for restoring circulatory homeostasis may lead to positive fluid balance which has been shown to increase morbidity and mortality in surgical patients. The current investigation aims to describe physio-pathological changes in circulating albumin, fluid and electrolyte balance, and acid-base equilibrium in a cohort of patients undergoing laparoscopic surgery under general anesthesia.
Methods: Single-center prospective observational study. Patients undergoing laparoscopic colorectal surgery were screened for eligibility. Before surgery, the baseline fasting conditions were homogenized. Hemoglobin, urinary and plasmatic were collected before surgery and then at pre-defined timepoints. Albumin/creatinine ratio was measured before and after surgery. Expected and actual circulating Sodium concentrations were compared according to a physiological theoretical model. Assessment and quantification of changes in major electrolytes, albumin and acid-base balance was defined as the primary outcome of the study.
Results: Thirty-eight patients were enrolled in the protocol. Patients had a positive electrolytes (Na+ 295 [244-375] mmol, Cl- 234 [195-295] mmol, K+ 16.8 [12.0-21.4] mmol) and fluid balance (2165 [1727-2728] mL). The positive fluid balance was associated with stable chloride (105 [103-107], end study vs. 103 [102-106] mmol/L, baseline, P not significant) and potassium (4.2 [3.8-4.4], end study vs. 4.1 [3.6-4.4] mmol/L, baseline, P not significant) levels, but sodium concentrations decreased over time (138 [137-140], end study vs. 139 [138-141] mmol/L, baseline, P<0.05). The albumin/creatinine ratio was higher at the end of surgery 134 [61-267] vs. 7 [4-14], P<0.001).
Conclusions: Data from patients undergoing colorectal laparoscopic surgery showed a positive fluid balance, decreased circulating albumin and increased albuminuria. A positive sodium balance was not always associated with an increase in sodium plasma concentration.