Effects of balanced and unbalanced colloid and crystalloid solutions on renal microvascular perfusion in endotoxemic rats

Introduction

In this study we investigated the effects on renal micro-circulatory perfusion of resuscitation with hydroxyethyl starch (HES 130/0.42) dissolved in a balanced Ringer's acetate salt solution (Plasma Volume Redibag^®, HES-RA) or hydroxyethyl starch (HES 130/0.4) dissolved in saline (Voluven^®, HES-NaCl) and compared this with resuscitation with saline solution (0.9% NaCl, NaCl) in an LPS-induced septic shock model in the rat.

Methods

In 20 anesthetized, mechanically ventilated rats, endotoxic shock was induced by infusion of LPS (10 mg/kg over 30 minutes). When the mean arterial pressure (MAP) was decreased to 40 mmHg, fluid resuscitation was started in three groups of five rats each, and in one five-rat group no fluids were given. Renal cortical microvascular perfusion (RMP) was assessed at high temporal and spatial resolution using laser speckle imaging. Additional measurements included systemic hemodynamics, renal artery blood flow (RBF), blood gas analysis, creatinine clearance, and plasma ions and calculated renal oxygen delivery (DO₂). Time points were: baseline, during septic shock at a MAP of 40 mmHg, and at 30 minutes of resuscitation.

Results

LPS infusion decreased MAP and RMP in all rats. Resuscitation with NaCl did not improve MAP (P > 0.05) and appeared to increase RMP heterogeneity (0.95 ± 0.08 AU vs 1.83 ± 0.13 AU; P < 0.001), metabolic acidosis (7.1 ± 0.06 vs 6.93 ± 0.05 pH; P < 0.05 and 11.36 ± 1.1 vs 15.9 ± 1.4 mmol/l base excess; P < 0.05), and plasma chloride ion levels (110.3 ± 0.7 vs 116.2 ± 1.7 mmol/l; P < 0.05). Fluid resuscitation did not affect systemic oxygenation parameters (sO₂, pO₂, O₂Hb) and renal DO₂. Resuscitation with NaCl increased plasma levels of Na⁺, tubular reabsorption of Na⁺, and creatinine clearance compared with resuscitation with the two colloid solutions. HES-NaCl and HES-RA provided similar effects on systemic and regional hemodynamic parameters. However, while HES-RA improved RBF (2.3 ± 0.4 vs 5.7 ± 0.2), HES-NaCl did not. NaCl resuscitation worsened the metabolic acidosis, which was not affected by the two colloid solutions. The plasma HCO₃^- level was increased by HES-RA resuscitation (13.18 ± 2.1 vs 19.56 ± 1 mmol/l; P < 0.01), whereas it was stable in the other groups.

Conclusions

Balanced HES preparation (HES-RA, PlasmaVolume Redibag^®) in endotoxemic rats showed acute beneficial effects on kidney microcirculation and on kidney function via bicarbonate balance whereas the NaCl treatment was harmful compared with both HES groups.