Volume kinetics of Ringer's lactate solution in acute inflammatory disease.

Background: Little is known about the turnover of crystalloid fluids infused in patients with acute systemic inflammation. We hypothesised that systemic inflammation would be associated with altered distribution and elimination of Ringer's lactate solution (volume kinetics).

Methods: Ringer's lactate solution (15 ml kg) was infused intravenously over 35 min in patients undergoing cholecystectomy (n=20) or appendectomy (n=20) starting before induction of general anaesthesia. Blood samples and urine were collected over the following 2 h. Plasma concentrations of inflammatory (tumour necrosis factor-α, interleukin-10, and C-reactive protein) and endothelial damage (syndecan-1) biomarkers were quantified by enzyme-linked immunosorbent assay. The volume kinetics was studied using mixed-effect modelling.

Results: Ongoing surgery (duration: 30-45 min) increased the rate constant for fluid transfer from the plasma to the extravascular space (k; from 32 to 57×10 min; P<0.001), and decreased the elimination rate constant (k; from 5.3 to 0.6×10 min; P<0.001). A lower mean arterial pressure was associated with reduced elimination, independent of conscious/anaesthetised state. The redistribution of fluid back to the plasma occurred more slowly in the group with appendicitis (P<0.02), in whom higher plasma concentrations of C-reactive protein were measured [median: 38.1 (range 1.8-143.6) vs 1.3 (0.1-159.0) μg ml; P<0.001]. However, no biomarkers for inflammation or endothelial damage were significantly associated covariates in the kinetic model.

Conclusions: No association was found between the volume kinetics of Ringer's lactate solution and the degree of inflammation as indicated by established biomarkers in patients with cholecystitis or appendicitis. However, the rate of elimination was greatly retarded by general anaesthesia in both groups.

Clinical Trial Registration: ChiCTR-IOR-15006063.