Effects of fluid resuscitation with 0.9% saline versus a balanced electrolyte solution on acute kidney injury in a rat model of sepsis*

Abstract

Objective: To compare the acute effects of 0.9% saline versus a balanced electrolyte solution on acute kidney injury in a rat model of sepsis.

Design: Controlled laboratory experiment.

Setting: University laboratory.

Subjects: Sixty adult, male Sprague-Dawley rats.

Interventions: We induced sepsis by cecal ligation and puncture and randomized animals to receive fluid resuscitation with either 0.9% saline or Plasma-Lyte solution for 4 hours after 18 hours of cecal ligation and puncture (10 mL/kg in the first hour and 5 mL/kg in the next 3 hr). Blood and urine specimens were obtained from baseline, 18 hours after cecal ligation and puncture, immediately after 4 hours fluid resuscitation, and 24 hours later. We measured blood gas, plasma electrolytes, creatinine, interleukin-6, cystatin C, and neutrophil gelatinase-associated lipocalin concentrations. We also analyzed urine for cystatin C and neutrophil gelatinase-associated lipocalin. We used Risk, Injury, Failure, Loss and End-stage criteria for creatinine to assess severity of acute kidney injury. We observed all animals for survival up to 1 day after resuscitation. Surviving animals were killed for kidney histology. Finally, we carried out an identical study in 12 healthy animals.

Measurements and main results: Compared with Plasma-Lyte, 0.9% saline resuscitation resulted in significantly greater blood chloride concentrations (p < 0.05) and significantly decreased pH and base excess. Acute kidney injury severity measured by RIFLE criteria was increased with 0.9% saline compared with Plasma-Lyte resuscitation (p < 0.05), and these results were consistent with kidney histology and biomarkers of acute kidney injury. Twenty-four-hour survival favored Plasma-Lyte resuscitation (76.6% vs 53.3%; p = 0.03). Finally, in healthy animals, we found no differences between fluids and no evidence of acute kidney injury.

Conclusion: Volume resuscitation with Plasma-Lyte resulted in less acidosis and less kidney injury and improved short-term survival when compared with 0.9% saline in this experimental animal model of sepsis.

Figure 1

Effects of resuscitation fluids on electrolytes and acid-base status in septic rats. Data are expressed as medians and interquartile range. All animals contributed data to the first 3 time points; 16 animals in the saline group and 23 in the Plasma-Lyte (PL) group contributed data to the 24-hr time point. Dashed line: Animals with cecal ligation and puncture (CLP) treated with 0.9% saline. Solid line: Animals with CLP treated with PL. *p < 0.05, versus baseline in the same group; #p < 0.05, comparison between groups at the same time point; &p < 0.05, versus the values before fluid resuscitation in the same group. A, Whole blood chloride concentrations (mmol/L). B, Whole blood potassium concentrations (mmol/L). C, Arterial blood pH. D, Arterial base excess (mmol/L). NS = 0.9% saline.

Figure 2

Effects of resuscitation fluids on renal function in septic rats. Data are expressed as medians and interquartile range for A and B; 16 animals in the saline group and 23 in the Plasma-Lyte (PL) group contributed data to the 24-hr time point. Dashed line: Animals with cecal ligation and puncture (CLP) treated with 0.9% saline. Solid line: Animals with CLP treated with PL. *p < 0.05, versus baseline in the same group; #p < 0.05, comparison between groups at the same time point; &p < 0.05, versus the values before fluid resuscitation in the same group. A, Plasma creatinine concentration (mg/dL). B, Blood urea concentration (mg/dL). C, Percentage of different severity of acute kidney injury (AKI) measured by RIFLE categories. R, I, F = AKI RIFLE classes Risk (creatinine change, 150–199%), Injury (creatinine change, 200–299%), and Failure (creatinine change, ≥ 300%). Saline resulted in significantly greater rates of AKI and severe (I or F) AKI (p < 0.001). NS = 0.9% saline.

Figure 3

Effects of resuscitation fluids on biomarkers of acute kidney injury in septic rats. Data are expressed as medians and interquartile range. Sixteen animals in the saline group and 23 in the Plasma-Lyte (PL) group were alive at 24 hr. Dashed line: Animals with cecal ligation and puncture (CLP) treated with 0.9% saline. Solid line: Animals with CLP treated with PL. *p < 0.05, versus baseline in the same group; #p < 0.05, comparison between groups at the same time point; &p < 0.05, versus the values before fluid resuscitation in the same group. A, Plasma neutrophil gelatinase-associated lipocalin (NGAL) (IU/mL). B, Plasma cystatin C (IU/mL). C, Urine NGAL (IU/mL). D, Urine cystatin C (IU/mL). NS = 0.9% saline.

Figure 4

Effects of resuscitation fluids on kidney histopathology in septic rats. Kidney tissues were collected 24 hr after fluid resuscitation (46 hr after cecal ligation and puncture [CLP]). Histological sections (5 μm) of kidney were stained with hematoxylin and eosin and periodic acid Schiff. NS: Animals with CLP treated with 0.9% saline; Plasma-Lyte (PL): Animals with CLP treated with PL. Saline-treated rats showed significant loss of brush border and vacuolization in tubules, these changes in PL-treated rats are milder.

Figure 5

Effects of resuscitation fluids on plasma interleukin (IL)-6 in septic rats. Data are expressed as mean and SE after log transformation (log pg/mL). Sixteen animals in the saline (NS) group and 23 in Plasma-Lyte (PL) group were alive at 24 hr. Dashed line: Animals with CLP treated with 0.9% saline. Solid line: Animals with CLP treated with PL. *p < 0.05, versus baseline in the same group; #p < 0.05, comparison between groups at the same time point; &p < 0.05, versus the values before fluid resuscitation in the same group.

Figure 6

Association between interleukin (IL)-6 and acute kidney injury (AKI). A, IL-6 levels in the different severity of AKI in all animals (data are expressed as mean and SE after log transformed, log pg/mL). *p < 0.05. B, Blood IL-6 and urine neutrophil gelatinase-associated lipocalin (NGAL) levels with time in all animals (data were expressed as median, IL-6: pg/mL; NGAL: IU/mL). RIFLE = Risk, Injury, Failure, Loss and End-stage.

Figure 7

Effects of resuscitation fluids on short-term survival in septic rats. Dashed line: Animals with cecal ligation and puncture (CLP) treated using 0.9% saline. Solid line: Animals with CLP treated using Plasma-Lyte (n = 30 each). Fluid resuscitation began 18 hr after CLP and continued for 4 hr. Animals were followed for survival for an additional 24 hr (46 hr after CLP).