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

Abstract

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 oximetrycorrected 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 pCO 2 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.