Effects of balanced and unbalanced colloid and crystalloid solutions on renal oxygenation in a rat model of hemorrhagic shock and resuscitation

Introduction

Hydroxyethyl starch (HES, 130 kD) dissolved either in saline (Voluven^®) or in a balanced Ringer's acetate solution (PlasmaVolume Redibag^®, PVR) and Ringer's acetate (RA) and 0.9% NaCl (NaCl) were investigated as regards their efficacy in restoring renal oxygenation in a rat model of hemorrhagic shock and resuscitation.

Methods

In 22 anesthetized, mechanically ventilated rats, hemorrhagic shock was induced by withdrawing blood volume from the femoral artery until the mean arterial pressure (MAP mmHg) was reduced to 40 mmHg. One hour after reaching a MAP of 40 mmHg, animals were resuscitated with either Voluven^® (n = 5), PVR (n = 6), RA (n = 5), or NaCl (n = 6) until a target MAP of 80 mmHg was reached. Oxygen tension in the renal cortex (CμPO₂ mmHg), outer medulla (MμPO₂ mmHg), and renal vein were measured using oxygen-dependent quenched phosphorescent lifetimes of Oxyphor G2. Renal artery blood flow (RBF ml/minute) was measured. Renal oxygen delivery and renal oxygen consumption (DO₂ and VO₂ ml·minute/g) were calculated.

Results

During hemorrhagic shock, CμPO₂, MμPO₂, RBF, DO₂, and VO₂ decreased and O₂ER increased. During resuscitation, CμPO₂ and MμPO₂ were increased in all groups (P < 0.001) although least prominent in the NaCl group. RBF was significantly increased during resuscitation in all groups (PVR; 5.1 ± 0.2 P < 0.001, RA; 3.5 ± 0.4 P < 0.001, Voluven^®; 3.4 ± 0.4 P < 0.01), except for the NaCl group, and DO₂ was significantly increased in the PVR group (0.20 ± 0.02 vs 0.39 ± 0.06; P < 0.01) and RA group (0.22 ± 0.03 vs 0.41 ± 0.06; P < 0.01), while this remained low in the other two groups. Fluid resuscitation was not able to restore VO₂. After 1 hour of resuscitation CμPO₂ was significantly higher in the PVR group (49.9 ± 2.4 P < 0.01) and the Voluven^® group (45.3 ± 5.1 P < 0.05) but not in the RA group (40.6 ± 2.2 P > 0.05) compared with the NaCl group (32.1 ± 2.55). Furthermore, RBF was significantly higher in the PVR group (5.1 ± 0.2 P < 0.01) compared with the NaCl group (2.4 ± 0.5) after 1 hour of resuscitation.

Conclusions

Our results suggest that both colloid solutions (Voluven^® and PlasmaVolume Redibag^®) are preferred resuscitation fluids with respect to crystalloid solutions. Moreover, the balanced colloid solution (PVR) appears to restore renal blood flow and oxygenation more than the crystalloids or unbalanced colloids do in this rat model of hemorrhagic shock and resuscitation.