Impact of saline-based tetrastarch vs balanced tetrastarch and crystalloid solutions on hyperchloraemic acidosis in endotoxaemic sheep

Introduction

Septic shock is frequently associated with metabolic acidosis derived from increased lactic acid production and infusion of sodium chloride-based resuscitation fluids. Although the impact of hyperchloraemic acidosis on outcome is still not fully understood, avoiding such a condition is desirable. The hypothesis of the present study was that resuscitation with saline-based tetrastarch solutions results in higher plasma chloride and lower base excess levels as compared with either balanced tetrastarch or crystalloid solutions in ovine endotoxaemic shock.

Methods

Thirty-one awake healthy ewes received a continuous infusion of Salmonella typhosa endotoxin started at 5 ng/kg/minute, which was doubled every hour until the mean arterial pressure (MAP) fell below 65 mmHg. Thereafter, sheep were randomized to receive either balanced 6% HES 130/0.4; saline-based 6% HES 130/0.4 (both HES solutions were infused up to 50 ml/kg); balanced crystalloids; or no fluids. Fluid resuscitation was guided to optimize central venous pressure (8 to 12 mmHg), pulmonary arterial occlusion pressure (12 to 15 mmHg) and mixed-venous oxygen saturation (≥65%). Norepinephrine was infused to establish a MAP of 70 ± 5 mmHg, if necessary. Haemodynamic variables and blood gas analyses were determined hourly throughout the study period. Animals surviving the 12-hour intervention period were deeply anaesthetized and killed.

Results

Haemodynamic variables were comparable between groups. Plasma chloride concentrations were significantly higher, and oximetry-corrected base excess was lower in the saline-based tetrastarch group as compared with the balanced tetrastarch or balanced crystalloid group over the whole interventional period (each P < 0.05). Whereas arterial pCO₂ was lowest in the saline-based tetrastarch group (each P < 0.05), there were no differences between treatment groups in arterial pH.

Conclusions

As compared with balanced tetrastarch or crystalloid solutions, saline-based tetrastarch infusion is associated with hyperchloraemic acidosis, which is compensated by hyperventilation in awake, endotoxaemic sheep.